ISSN

Japanese

Joumalof

TropicalMedicineandO304−2146

Hygiene平成元年6月15日

第17巻第2号

日本熱帯医学会雑誌表紙デザイン・装丁・学会シンボルマーク等について
第31回日本熱帯医学会総会御案内

容

内
総

説
The

原

present

statusandfutureprospects ofmalaria control

一Norman

G．Gratz

131−147

著

エクアドルにおける人吸血性サシチョウバエ7種の卵巣付属腺による穎粒分
泌と経産歴との関係（英文）…高岡宏行，Eduardo

A．Gomez

L．JohnB．Alexander，橋口義久

149−155

英毅

157−173……………一一・…一…Vanida
Waterdemand and schistosomiasis amongthe Gumau people of

Kerdpibule

175−183

BauchiB．Akogun185−189

カダヤシとメダカにおける脳炎媒介蚊の駆除，および両種の蚊幼虫捕食能と競争に関する生態学的研究（英文）……・……・・…・……………・…・…………佐藤A field
againsttest of2一［1−methy1−2一（4−phenoxyphenoxy）ethoxy］pyridine
principal

vectors

State7Nigeria

ofmalariainfoot−hill

area

in

Thailand…………一・……………一…・……………Oladele

エクアドルのアンデス高地で見いだされたE漉吻π偽跳亜属の1新種ブユの記載（英文）…・…………………一一……・…・………Sixto

Coscar6n，高岡宏行

191−196

ガストログラフィンによる広節裂頭条虫，無鉤条虫，大複殖門条虫の駆虫効果（英文）一西山利正，古木 純子，八木

荒木

恒治，天野

純，和田 輝夫，
197−203博之，辻井正

ナイジェリア，プラトー州ジャラワ漢谷におけるオンコセルカ症の流行状況（英文）…Bertram E．B．Nwoke，Celestine O．E．Onwuliri，塩飽邦憲，

Gad会

O．Ufomadu，多田

功，高橋

弘

205−211報

第13回日本熱帯医学会九州支部大会講演213

日本熱帯医学会九州支部ニュース

213−214

………

投稿規定

日熱医会誌

Japan．」．TrOP．

Med．Hyg．

日本熱

帯医学会

Japan. J. Trop. Med. Hyg., Vol. 17, No. 2 1989 pp 131 147

131

Review

THE PRESENT STATUS AND FUTURE PROSPECTS
OF MALARIA CONTROLNORMAN G. GRATZ
Received February 22 1989/Accepted April 10 1989

INTRODUCTION
Malaria remains a major public health problem in most of the almost 100 countries or
territories in which it is still endemic. It has been estimated that the number of new clinicalcases is on the order of 100 million annually (WHO, 1987). While in many of the endemic
countries the epidemiological situation has remained static, in others it has worsened andthere have been a number of countries in which a serious recrudesence has occurred within
the last few years, among them Sri Lanka and Brazil. There are many different reasons forthis complex situation and some of them will be touched upon below, following a generalreview of the current epidemiological situation.

THE GLOBAL MALARIA SITUATION
Of a total world population of some 5.000 million people, more than 2,000 million live inareas where malaria has either never existed, has disappeared spontaneously following socialand economic development, has been eradicated or where the risk of infection has been
eliminated through improved health and economic conditions.
In areas where some 2,500 million people live (50% of the world's population) , efforts arebeing made to reduce or control transmission through the application of antimalaria mea‑sures of one type or another; these inculde the majority of malarious countries of Asia andthe Americas. However, the health services in many of the countries of these regions are notsufiiciently developed to maintain the reduced level of transmission that some of them wereable to achieve through concerted malaria control programmes and as many are now facedby economic and social difnculties, their malaria situation may grow worse and transmission
periodically intensifies.

In the remaining malaria endemic areas of the world where more than 400 million people
live, no specific measures are undertaken to control the transmission of malaria and, in theseareas (for the most part Africa south of the Sahara) , the prevalence of malaria remains

unchanged.
The following section will review the malaria situation by region and sub‑region.

c/o Malaria Action Programme World Health Organization, Geneva, Switzerland

132

AFRICA NoRTH OF THE SAHARA
The total population of this sub‑region is over 100 million people and ' imost 80 millionof them live in areas that were at one time malarious. Libya and Tunisia have only reported
imported cases of malaria while but a small number of indigenous cases now occur in Algeria.

Malaria is of low intensity in Egypt and transmission occurs only in limited areas. In
Morocco, however, transmission has increased in recent years. The malaria control pro‑gramme is attempting to deal with this increase which in any event is limited in nature andthe total number of cases annually is less than a thousand.

AFRICA SOUTH OF THE SAHARA
Of the more than 450 million people who live in this region, only 53 million live in areas
where malaria has either never existed, such as in most of South Africa and Lesotho, or inthose limited areas from where it has been eradicated. In the remaining areas, however, theendemicity of malaria has remained virtually unchanged over the years.
While most countries of this region had developed strategies for the control of malaria
in the past, a reduction of malaria prevalence, especially in their rural areas, is not feasible.
The reasons are technical, operational, administrative and financial; Iittle, in fact, can be doneother than reduce mortality and morbidity through the improvement of diagnostic andtreatment services and through the more appropriate use of antimalaria drugs, especially inlimited target groups such as pregnant women and children. Even this restrained objective
is often difficult to meet due to shortages of drugs and to the poorly developed primary healthcare systems which can not always ensure the prompt diagnosis and treatment of clinicalmalaria; the spread of chloroquine resistant strains of Plasmodium falciparum in Africa has
made therapy more difficult. Nevertheless, there are some areas where mortality frommalaria alone is lower today than was previously the case, even among infants (Carnavale
and Vaugelade, 1987) ; this change has been attributed principally to the easy availability of

the antimalaria drugs (WHO, 1986a) which at least commercially, are widely available.
Unfortunately antimalarial drugs are very frequently used incorrectly by populations whotake inadequate dosages of the drugs for periods of time too short to achieve a radical cure.

As noted above, the appearance of resistance may also reduce their broad efficacy.
There are certain situations usually associated with major ecological or socio‑economicchanges which have resulted in a focal worsening of the situation; an example of such asituation is the displacement of populations with limited levels of immunity into areas of hightransmission that occurred as a result of the Sahel drought. Currently a very severe malaria

epidemic is taking place on the plateau region of Madagascar due primarily, apparently, toa poor economic situation which badly hampered the continuing implementation of malaria
control measures. Transmission on the plateau is by Anopheles funestus which has reinvaded
the high plateau region of the island after being absent from the area for many years(Fontenille and Rakotoarivony, 1988) .
Broadly speaking, vector control is of limited efiicacy in this region. The principal vector

species freely feed and rest both indoors and outdoors and thus the application of residual
insecticides to the interior of houses has only a limited effect on the transmission of malaria

despite the high level control which is frequently achieved of house entering mosquitoes.

133

W* hile indoor resting densities may be reduced, malaria transmission is likely to continue atmuch the same rate. There are also many other difnculties associated with vector control
including the problem and great cost of achieving coverage of all the dwellings in the endemic

rural and peri‑urban areas and the focal occurrence of insecticide resistance. Neverthelessconsiderable interest is being expressed in the use of insecticide impregnated bednets,
curtains and screens which may at least reduce the frequency of infections by malaria.
Insecticide resistance to the chlorinated hydrocarbon insecticides DDT, dieldrin and HCH is

widespread and the limited number of urban and peri‑urban vector control programmes
making use of residual insecticides must apply OP, carbamate or pyrethroids whose cost is
considerably greater than that of the chlorinated hydrocarbons such as DDT. In a numberof countries efforts are being made to at least improve the control of malaria in peri‑urban

areas and, as an example, a Japanese sponsored urban malaria control programme in
Tanzania will make use of the OP insecticide fenitrothion for indoor residual applications

along with other methods against the malaria vectors in Dar‑es‑Salaam and Tanga.
One of the most serious constraints to effective malaria control in the Africa region is thelack of trained personnel for the planning, organization, implementation, monitoring andevaluation of malaria control programmes. This shortage exists at every level, whether for
personnel to carry out epidemiological or entomological surveillance, do research, clinicalmanagement of cases or the administration and supervision of control operations. The
training of personnel should, therefore, have a high priority. A number of international
training courses on basic malariology and malaria control have recently been sponsored bydonor governments, among them Italy, France and the USSR as well as by internationalorganizations such as the WHO and UNDP and other such courses are planned for the future.

The UNDP/World BankIWHO Special Programme for Research and Training in
Tropical Diseases has supported MSc courses in medical entomology and vector control inthree centres in Africa in Bouake, Cote d'lvoire, Jos, Nigeria and Nairobi, Kenya as relatively

few African scientists have been previously trained in this discipline.

THE AMERICAS
It is estimated that the population at risk of contracting malaria in the America region

has increased from 143.6 (30%) million in 1960 to 263.4 million (39%) in 1986. 950,471 casesof malaria were registered in the region in 1986 which was an increase of 57,236 cases over1985 and the highest figure registered since 1958. Morbidity per 100,000 population in themalaria endemic areas rose from 164.95 in 1985 to 360.89 in 1986; almost 20 million people in
the Region received no protection at all against malaria; it is of concern to note that the twomost frequent reasons for such a lack of protective programmes were lack of resources in
58.1% of the cases and socio‑political problems in 14.9% (PAHO, 1988).
The increase occurred in 12 countries in which control activities are being carried out
i,e. Argentina, Bolivia, Brazil, Colombia, Costa Rica, Dominican Republic, French Guiana,

Guyana, Mexico, Nicaragua, Panama and Peru.
In Mexico which reported 13.8% of all the cases in the Region, there was a 14.4% increaseover the number in 1985. Fortunately, the proportion of cases of P. falciparum fell by 30%
during the same period.
The malaria problem in Brazil which has 46.7% of the cases in the Region is associated134with a great human migration into the Amazon region of the country which in itself accounts
for 96.3% of the cases of the disease in Brazil; 70% of these cases were registered in the twd

states of Para and Rondonia. Considerable efforts are underway to control the transmissionof the disease in this geographical area including insecticide application and selective

chemotherapy. The problem of controlling malaria in the Amazon and in forest areas
contiguous to areas of human settlement is common to several countries in this part of SouthAmerica.
The human population covered by intradomiciliary spraying in the Americas is some 25
and a half million. Despite the spread of DDT resistance in Anopheles species, especially inpopulations of An. albimanus. DDT still represents 89.3% of the insecticides applied, while

fenitrothion is 5.1%, propoxur 2.0%, bendiocarb 1.0%, deltamethrin 0.6% and malathion andall others together 2.0%. Field trials of new insecticides continue in the Region to ensure thecontinuing availability of effective compounds for use where the development of vector
resistance necessitates change to an alternative compound. As will be shown later, contami‑
nation of mosquito larval habitats by the agricultural use of insecticides both in the Americas
and in other rural areas where malaria is present, is a major factor in selecting for insecticide

resistance in mosquito populations even before the compounds have been used in publichealth.

The extent of development of P. falciparum strains resistant to chloroquine is very
serious problem in South America and particularly in Brazil and Colombia. The necessity touse more expensive, alternative drugs in the areas where the use of chloroquine is to a great

extent precluded adds to the cost of malaria treatment.
The situation in Guyana is serious; the index of parasitemia for the population of themalarious areas was 20.6 per thousand in 1986, the highest for the Region and, even more
seriously, 56.6% of the infections were attributed to P. falciparum.

By contrast the number of cases of malaria in Guatemala has dropped substantially.
Ninety‑seven per cent of the cases in the country are due to P. vivax with most of the cases

occurring in the northern part of the country. An even greater drop in the number of newmalaria cases has been registered in Haiti where the number of new cases in 1984 was 69,863
and had fallen to 14,363 by 1986. The present status of control operations in the country is
uncertain due to economic di i:culties.

ASIA WEST OF INDIA
The total population of this region is 222 million people of which 186 million live in areas

which were originally malarious. Fifteen million live in areas which have been freed from thedisease, 35 million in areas of limited risk and some 4 million in areas where there are no
antimalaria measures being carried out. Despite a high number of imported cases, Bahrain,

Cyprus, Israel, Kuwait, Lebanon and Qatar all continue to be free from indigenous malaria.
In 1986, increases in malaria were recorded from Afghanistan, Iran, Pakistan, Yemen and

Democratic Yemen, and the United Arab Emirates. The number of cases reported from lraq,
Syria and Saudi Arabia declined sowewhat from the previous year. The malaria control
situation in Afghanistan has deteriorated greatly and the number of cases reported may
probably an underestimate. One hundred and fifty‑six thausand cases were reported in 1984and more than 228,000 in 1985.

135

Malaria has traditionally been a major public health problem in what is now Pakistan
and is still an important problem in part of Pakistan's population of 97.5 million. Epidemics

frequently occur in the irrigated plains of the Punjab and Sind which are the most densely
populated parts of the country. While most of the population of the country and most of themalaria transmission is rural, persistent urban malaria transmission in some urban areas has
necessitated that malaria control be carried out in the cities as well. The main rural vector
is An. culiclfacies and in the urban areas it is An. stephensi.

A malaria eradication programme was started in Pakistan in 1960 with a good deal of
initial success. However, the poor participation of the general health services, a reliance onhouse spraying as the sole control measure, the development of resistance to DDT and HCH,
and economic difficulties led to a very serious recrudescence of the disease in the early 1970s

with an estimated 10 million cases having occurred in 1972 (AID Report, 1987) (though theofficial figure was but 642,958 microscopically confirmed cases; EMRO, 1987). A number of
improvements were introduced into the programme in 1975 including the replacement of theorganochlorine insecticides by malathion, the inclusion of urban areas in control and various
administrative changes. While the situation improved until 1980, many difficulties are stillfacing the programme and the number of cases rose from 17,707 in 1980 to the 90,393 cases
reported in 1986 (AID Report, 1987) . Furthermore chloroquine resistant P. falciparum strains

have also appeared in Pakistan. Even more seriously the proportion of P. falciparum has
risen from 13.32% to 33.39% of the total positive slides (Report of External Evaluation
Group, 1985) .

While it had been thought that the presence of large numbers of Afghan refugees inPakistan lead to a worsening of the malaria situation by bringing a heavy load of malaria
with them, investigation showed that in actuality the refugees themselves faced a high riskof malaria infection on their arrival in Pakistan (Suleman, 1988) .

THE INDIAN SUBCONTINENT AND ISLANDS OF THE INDIAN OCEAN
Of the total population of 884 million people in this area some 96% or 850 million are
exposed to malaria risk to varying degrees. Most of the original malarious areas must still

remain under some type or another of malaria control.
Numerous problems exist in the region of a technical, financial, operational and manage‑
rial nature. Resistance to insecticides in vector species and resistance to drugs of P.
falciparum are both wide spread; resistance to fansidar has also appeared in Bangladesh. As
regards the number of reported cases, there has not been a serious general worsening of thesituation in any area other than in Nepal in the last year or two; however, on the other hand,relatively little progress is being made and the overall situation in the region appears to havestabilized at the existing level of transmission. But in view of the spread of drug resistantstrains of P. falciparum and the continued spread of resistance to insecticides in important
species of vectors, such a stabilization cannot be considered a satisfactory situation.
In Bangladesh, the entire population of the country lives in areas where malaria transmis‑
sion occurs; residual insecticide applications are carried out in areas where 2.3 million people

live. Sixty per cent of all malaria cases and 93% of all P. falciparum cases are now reported
from districts in the eastern border area of the country. Though the number of reported casesof malaria remains more or less the same, the proportion of the cases due to P. falciparum has

136

risen from 40% in 1983 to 45% in 1984 and 49% in 1985. Although the number of individual
reports of chloroquine resistance is rising, most of them are still restricted to forested areasof the east and north‑east of the country.
Malaria transmission in Bhutan has stabilized or declined somewhat but the chloroquine‑

resistant strains of P. falciparum apparently imported from India have established local
transmission of such strains in the country.
Of the population of more than 750 million people in India, at least 728 million people live

in areas where malaria transmission continues and at least half this number live in areas ofhigh transmission. Some 100 million people are covered by the P. falciparum Containment
Programme which is itself part of the National Malaria Eradication Programme. More than
63 million people in urban areas are covered by programmes based essentially on antilarvalmeasures. Urban malaria transmission remains a serious problem as the larviciding on which
it is based does very little to permanently ameliorate the transmission by An. stephensi(Hyma et al.. 1984). Sharma and Mehrotra (1986) believe that the resurgence of malaria in
India preceded the true problem of insecticide resistance and that the malaria resurgenceoccurred in towns where control measures were non‑insecticidal and in regions which were
not under the infiuence of transmission by insecticide‑resistant vectors.
Throughout the country the number of new cases every year has stabilized at a reported

figure of about 2 million and the increase in percentage of cases due to P. falciparum seems

to have peaked at 29% in 1984 as compared to 9.7% in 1977 (WHO, 1987) . On the other handresistance to chloroquine continues to spread as does Anopheles resistance to insecticides.
Resistance to the organochlorines and, increasingly, to malathion, continues to intensify
among populations of An. culiclfacies and both An. stephensi and An. annularis have shown
resistance to DDT and HCH. In some areas the level of resistance to DDT, HCH and, to alesser extent, malathion in A n. culiclfacies populations is high enough to prevent interruptionof transmission by use of these insecticides (Vittal et al.. 1982) . This necessitates a continued

search for new compounds that can be used as replacements for those to which resistance hasdeveloped for use in indoor residual spray programmes. The alternative would be to abandon

residual spray programmes but this might well have serious consequences in a number ofareas.

The number of new cases of malaria in Nepal has been steadily rising from 17,000 casesin 1983 to 42,000 cases in 1985. Economic constraints are a problem in the purchase of
insecticides and part of the country remains without any antimalaria protection at all. The

malaria programme already consumes 20% of the national health budget (Najera, J.A.,
personal communication) .
Out of a population of about 16 million people in Sri Lanka, at least 12 million live inareas where malaria transmission continues. The malaria control situation in the country has
continued to deteriorate for several reasons. Part of this is obviously due to the politicalsituation which renders control activities difiicult to implement in certain areas. However,in very many areas the problem involves a poor level of management and operational
supervision of the programme along with a lack of supplies including transport and petrol.
The difiiculties are increased by the rapid spread of resistance to DDT in the only vector, An.

culiclfacies and the appearance and spread of resistance to malathion despite a considerable

effort which had been made to avert it. As control depends on insecticide coverage in areas
where some 4 million people live, this is a serious development. Moreover, after several years

137

of an increase in the proportion of cases due to P. falciparum (from 2% of the cases in 1982

to 20% in 1986, Samarasinghe, 1986), chloroquine resistant strains of the parasite haveappeared and have become well established. Improvement is badly needed in the manage‑
ment and supervision of the programme lest the numbers of cases egin to rise even more
steeply as has occurred in the past in Sri Lanka. As it is, the number of new cases increased
from 38,566 in 1982 to 149,470 in 1984, decreased to 117,816 in 1985 and, in 1986, has risen toalmost 420,000. Furthermore, malaria is appearing in new areas of the country, around thecity of Kandy specifically, and the incidence is increasing in the areas of water development

schemes such as in the Mahaweli development area (Wiejesundera, 1988) . As water develop‑
ment schemes grown in number and in area, the spread of malaria as a result could becomea major threat (2nd Independent Assessment of the Intensive Malaria Control Programme,
Anti‑malaria Campaign, 1984) .

EASTERN AslA, THE WESTERN PACIFIC AND OCEANIAIn this vast area of 1,670 million people, 1,324 million live in originally malarious areas.

Malaria has been eradicated from areas where 244 million live and the risk is consideredlimited in areas with a population of 531 million.

Australia, Brunei Darussalam, North and South Korea, Hong Kong, Japan. Macao,
Mongolia. Singapore and large areas of China are considered to be free of malaria (WHO,1987) .

The number of reported cases in China has been steadily declining and is now on theorder of 500,000 a year. The well supervised and intensive control work being carried out,
integrated with the health services, should reduce the endemicity even further. One of the
problem areas which remains is Hainan Island where the malaria is endemic in the mountain‑
ous and hilly areas. Chloroquine resistance in P. falciparum is a problem mainly in Hainan
Island, and in some focal areas of the south of China.
Malaria is considered the leadiing public health problem in Burma and has been accorded
the top priority in the national health plan for 1986‑1990. Out of an estimated population ofsome 36 million, 22.1% Iive in areas where control is based on the government making
antimalarial drugs available, 13.6% in areas covered by indoor residual spraying with DDT,
41.9% in surveillance areas, 13.9% in vigilance areas and 8.5% in non‑malarious areas(Kondrashin, 1986). The resistance of P. falciparum to chloroquine is a serious and wide‑

spread problem in the country. Resistance has also been found to sulfadoxine/pyrimethamineand has been spreading rapidly. Among the vectors, An. annularis is resistant to DDT in thenorth‑west part of the country where it is a vector in the coastal areas, and there are some
reports of resistance from other areas and from other species. No alternative insecticides arein operational use or under field trials in Burma.
The programme in Burma is faced by many difficulties including difficult access to many
border areas, a shortage of insecticide and transport and the still growing problem of drug
resistance.

A population of some 46 to 47 million people in Thailand is considered at some risk tomalaria. Of this number some 11 million live in areas where they are protected by control

operations and 35 million in areas where malaria transmission has been reported as having
been interrupted. In most of the latter area, the malaria services have now been integrated

138

with the general health services. Three million people live in areas where indoor residual

insecticide spraying continues to be applied. The incidence of malaria has been greatly
reduced throughout the country in the last three decades though some serious problems
persist such as the increase in the proportion of P. falciparum from the early 1980s and a
spread of drug resistance in this species. The control of exophilic vectors An. minimus. An.
balabacensis and An. dirus in the forested, mountainous parts of the country is a problem forthe control organization as is the control of malaria in and around the refugee camps in theborder areas with Kampuchea and Vietnam. Most of areas covered by residual spraying still
make use of DDT though large areas have been sprayed by fenitrothion as well.
Malaria is well controlled in Peninsular Malaysia and Sarawak with only some 10,000
and 1,000 cases a year respectively recently recorded. More than 90% of the total population
live in ares freed from malaria transmission and most of the remaining transmission is in
hilly, undeveloped areas on the peninsula and in the border areas of Sarawak. In Sabah,
where most of the cases are caused by P. falciparum, resistance to chloroquine is widespreadand the disease remains a serious problem; the number of cases has recently increased
considerably. Integrated malaria control is carried out by the health services by spraying,
drug distribution and increased surveillance as appropriate to the various endemic areas.

Some years ago, it was estimated that 83% of the total area of Kampuchea wasmalarious and that 35% of the total population were living in malarious areas (Harinasuta
et al., 1982) . Because of the political situation within the country, Iittle accurate information

is available on the incidence of malaria. Antimalaria measures have begun again recently
though of a limited nature. Transmission will probably continue within Kampuchea until agreater degree of stability is achieved in the country.

In the refugee camps on and near the Thai‑Kampuchean border malaria is reported as
the most serious communicable disease problem (Meek, 1988) , especially where inhabitants
are exposed to An. dirus populations in forested areas. Most of the transmission is due toP. falciparum especially in those camps with the most malaria transmission; the strains of P.
falciparum in this areas are, for the most part, also resistant to chloroquine and fansidar.

Malaria also remains a major public health problem in the Lao People's Democratic
Republic and antimalaria activities are very limited in scope, probably only to insecticide

spraying in certain areas. The parasite rate for the entire country is estimated at 10‑12%(WHO, 1987) and most of the country's population of 3.2 million is at risk. Most of thetransmission is of P. falciparum and chloroquine resistance showing Rl and RII response
occurs.
Malaria is one of the principal public health problems of Vietnam; while a satisfactory

level of control has been achieved in the north, many difiiculties still remain in the southernpart of the country and in the mountainous areas of the centre. DDT spraying is widespreadin the southern part of the country but the control programme faces many problems among
them drug resistant strains of parasites, exophilic species of vectors and human population
migrations.
One hundred and fifty‑six million people of the total population of more than 163 million

of Indonesia, Iive in malarious areas. Regular malaria control activities cover much of Javaand Bali with a population of 94 million people and certain settlement areas at particular lisk;

the national budget for malaria control represents a high percentage of the total budget forcommunicable disease control. Indoor residual spraying is still an important component of

139

the programme and 5 million people live in areas where insecticide spraying is carried out on
Java and Bali; there is also a limited amount of residual spraying on some of the outer islands.

Focal larviciding is carried out against An. sundaicus in some of the lagoons in which it
breeds particularly on Bali and, to a lesser extent, on the south coast of Central Java.
Most of the reported cases of malaria originate from Central Java; An. aconitus is themain vector in this area and is highly resistant to DDT and HCH, creating a serious problem
for its control; DDT resistance has also been recorded from An. sundaicus in the same area.
Large scale field trials with fenitrothion in Central Java showed that this compound would
provide satisfactory contro] of transmission (Sudomo et al.. 1985) . A Iarge reservoir ofmalaria exists in the outer islands where control programmes are still limited in extent
though an effort is being made to improve surveillance and treatment through primary healthcare programmes and health centres. Chloroquine resistant strains of P. falciparum havebeen detected in 22 of the country's 27 provinces.

The malaria situation has not changed in recent years in Papua New Guinea. The
disease remains mesoendemic to hyperendemic in most of the originally malarious areas andis a serious public health problem. This has been compounded by shift from a predominanceof P. vivan to that of P. falciparum. Furthermore chloroquine resistance strains of P.
falciparum have also appeared. The effectiveness of vector control programmes has de‑creased and all of this has made the problems associated with the intense year‑roundtransmission more severe (Cattani et al.. 1986) .

The malaria problem in the Solomon Islands has been brought under control by anintensification of routine antimalaria control measures, including improved treatment ofcases, better supervision of spraying activities and the strengthening of the rural healthinfrastructure. Special attention has been given to training activities and a new centre has

just been opened with the support of the Government of Japan. A number of important
problems persist including the high frequency of chloroquine resistant strains of P. falciparumand problems with control of the vectors.

The Philippines have had an intensive malaria control programme for a long period oftime. While a considerable reduction in the intensity of malaria transmission was achievedin the early years of the programme, the incidence still remains quite in many parts of thecountry especially in those areas of difiicult access and there has been little recent improve‑

ment made in the programme. Limited resources pose a problem for further expansion ofactivities even as part of the health services. The wide distribution of P. falciparum strains

resistant to chloroquine adds to the other problems of control.

EUROPEThe only area of the WHO European region where malaria transmission still persists is
Turkey. Though the malaria eradication campaign was quite successful at the onset, thecessation of much of the control activities and the reduction in surveillance coupled withgreatly increased irrigation programme in the south eastern plains resulted in a major
upsurge in the number of cases of the disease. The problem on the Cukurova plain where An.
sacharovi breeds extensively in irrigation run‑off water and is highly resistant to the organo‑chlorines as well as many of the OP insecticides is particularly serious and with implementa‑tion of further irrigation development projects is, in fact, Iikely to grow worse.

140

THE PRESENT TRENDS IN MALARlA CONTROLNo additional review beyond what has been presented above will be made of malaria
control activities on a country basis. There are, however, general trends in malaria control
which can be illustrated.

The 38th World Health Assembly in 1985 adopted a resolution which recommended thatmalaria control be developed as an integral part of the primary health care system of theendemic countries; it also urged the member states of the WHO to undertake an immediate
review and appraisal of their malaria control situation and their existing control strategies
in terms of their effectiveness, efficiency and the prospects of achieving and maintaining, theobjectives of the programmes. It is clear that in the future malaria control programmes andthe measures which they use will have to be better adapted to the varied epidemiologicalsituations than has been the case in the past and there is a now much more realization thanpreviously of how greatly the epidemiology of malaria may differ from one area to another.
It is also clear that much research remains to be carried out on the local epidemiology ofmalaria as a basis for the development of more effective control programmes.
While a number of countries have undertaken such reviews, some find their resources too
limited to easily depart from the type of control structures that they have long establishedand which are accepted within the country while still other countries encounter difflculties in

the planning of new approaches. Some countries have simply chosen not to change their
existing programmes or attempt to plan any new approaches at all.
From the assessment carried out above, it is evident that while there has been some
progress in countries with resolute programme, overall the control of malaria has not very
greatly improved in the last 4 or 5 years; furthermore, due to financial, political and technicalproblems, a deterioration has occurred in certain programmes and epidemiological situations.
There are many different reasons for the reduction in effectiveness in control and for theincrease in transmission and they may vary greatly from one country to another and from one

geographical area to another. The varied causes have been reviewed by the 18th WHO
Expert Committee on Malaria in 1985 (WHO, 1986a) and the following section will be based
essentially upon that review.

RESPONSES To CHANGING EpIDEMIOLOGICAL PATTERNS
In most areas outside tropical Africa the present malaria situation is characterized by amarked focal distribution that is often quite different from that which existed before thebeginning of control activities (Najera, 1986) . Changes in agricultural practices, the migra‑
tion of rural populations seeking better employment opportunities, increased irrigation as aresult of water development projects, the creation of new settlements, usually unplanned,

around dams, mining or other major construction areas and the greatly increased urbaniza‑tion that characterizes most of the developing countries have all resulted in importantchanges in the epidemiology of malaria. Many programmes have been unable to assess thechanges or adapt to them quickly enough to avert the increase in malaria transmission thathas often been the consequence of such changes. In some areas, urbanization has reduced
malaria transmission in areas of dense urban settlement as there are few larval habitats

141

suitable for Anopheles breeding but often the great increase in peri‑urban human populations
in areas still close to intense vector mosquito breeding has resulted in increased transmission.

TECHNICAL PROBLEMS FAaNG MALARIA CONTROL
A number of major technical problems are faced by many malaria control programmes
and the inability to adequately deal with them has been among the reasons for the failure of

not a few of these programmes. Examples of these technical problems are:

VECTOR RESISTANCE To INSECTICIDES
Vector resistance to insecticides was one of the earliest of the technical problems to haveemerged and remains a major and still growing problem. Vector resistance continues toappear in geographical areas in which it was not previously reported and is emerging in
additional species and to additional chemical groups of insecticides. The number of effective

alternative compounds that can be considered as replacements for those to which resistancehas developed is limited and the prospects for a continued flow of new candidate compounds
for field testing from the chemical industry are not very good. The greatly increased costsof pesticide development and the greatly increased toxicological, environmental and ecologi‑
cal strictures on pesticides are among the factors which are reducing the rate of developmentof new insecticides both for agriculture and for public health use. The generally greater costof the newer compounds which are now available as compared with that of older insecticides

such as DDT, HCH and malathion makes it difficult for programmes already faced withfinancial stringencies to purchase the newer and more expensive insecticides in the quantities
they require.

Multiple resistance to more than one chemical group of insecticides has now developed
in at least five important vectors of malaria including An. albimanus. An. culiclfacies. An.

pseudopunctipennis. An. sacharovi and An. stephensi. These species or species complexes,
show resistance to the organochlorines, OP compounds, carbamates and pyrethroids in one ormore geographical areas (WHO, 1986b) . Cases of multiple resistance are often associatedwith the intensive use of many different insecticides in agriculture particularly when they areapplied by aircraft to control pests of such cash crops as cotton and rice; run‑off irrigationwater from the treated fields reaches the breeding sites of anophelines where it may select for
insecticide resistance even at times to insecticides or insecticide groups that have not yet beenused in public health programmes.
By 1986 a total of 50 different species of anophelines had been recorded as resistant to
one or more pesticides in some part of their range. Of these, at least 11 are important speciesof vectors. Taking into account that some of these are now known to a complex of several
different species, the number is actually as high as 57.

Malaria vectors in many areas exhibit an evasive behaviour towards insecticides either
by entering sprayed dwellings in smaller numbers or exiting such buildings before acquiring
a lethal exposure to the insecticide. In still other areas the exophilic and exophagic habitsof some major vector species virtually precludes their control through the application ofindoor residual sprays.

142

PARASITE RESISTANCE TO ANTIMALARIA DRUGSThe development of P. falciparum resistance to most of the currently available
antimalaria drugs has emerged as the main technical problem in malaria control and has beenreported from more than 50 countries. Resistance to chloroquine has spread throughout large
areas of South America and Southeast Asia and is now spreading rapidly in Africa after its

first appearance in East Africa and more recent appearence in West Africa. In both SouthAmerica and Southeast Asia the intensity of resistance is also increasing.
Resistance to the sulfadoxine/pyrimethamine drug combination is also spreading and a
few instances of resistance to mefloquine have even been noted. The presence of resistantparasites in an area necessitates the procurement of alternative drugs whose cost is greater
ranging as high as 33 times greater for sulfadoxine/pyrimethamine as compared to chloro‑

quine curative treatment. Some of the alternative drugs are more likely to produce side
effects and their treatment regimens are often longer thus reducing patient compliance.
One of the important reasons for the selection and appearance of resistance in malaria
parasites is, in probability, the pressure from the widespread use of antimalarial drugs andtheir use should be reduced, where practical, to a minimum. In reality, however, antimalarial

drugs are almost everywhere commercially available; thus, even if they are not distributed aspart of mass drug administration programmes, they will be bought and used, by populations
in endemic areas. Frequently they will be used at subcurative doses, as a result of inadequate
guidance to their correct use, and this will further increase the selection for resistance.

The wide spread development of drug resistant strains has necessitated the developmentof a drug response monitoring programme in endemic and non‑endemic countries; theprocessing of the data from these programmes is done by the WHO but the monitoring is the
responsibility of countries. The necessity for drug monitoring has considerably increased thecost and complexities of the use of antimalarial drugs in malaria control.

ADMINISTRATIVE AND FINANCIAL PROBLEMS OF MALARIA CONTROLTHE INCREASED COSTS OF MALARIA CONTROL
Increased cost is a frequent consequence of the necessity of replacing insecticides anddrugs to which resistance has developed with alternative compounds to which are still
effective. For most countries, the cost of malaria control programmes has risen greatly due
to increasing costs of transport, fuel and equipment; the higher costs of newer insecticides anddrugs, add to a financial burden whose support is already difflcult for many countries. The
shortage of funds for the purchase and distribution of antimalarial drugs by national healthservices, eventually results in the populations in endemic areas procuring them throughcommercial channels and, as has been noted above, such unsupervised use frequently leads toan increase in selection pressure.

Moreover, malaria control programmes in many countries must share the already inade‑quate funds available to the health services with many other priority programmes in healthand development. The generally poor level of development of health services in many of thethird world countries, which, unfortunately, are those countries most in need of adequate

health service, makes the implementation of new or expanded disease control programmes

143

unduly expensive; in an increasing number of countries, malaria control activities in the field

are being incorporated into the general health services. These health services, however, may
find difiictilties in sustaining the costs of the malaria control activities which they have takenover especially the cost of insecticides, drugs and other logistic support and often will seek

donor funds to procure these items. Where donors choose to support the malaria control
activities of the health services, they will often have to consider providing the costs oftransport, fuel, insecticides and spraying equipment as well as equipment and supplies forlaboratories, clinics and hospitals. Not infrequently, even salaries for additional local
personnel engaged in surveillance activities may be beyond the resources of the national
health services. When support is required to this extent, the question must be asked as towhether the programme is sustainable at all by the disease endemic country. Donor assis‑
tance should, therefore, certainly include help in the planning of the financing of such services

as part of long term control programmes.

NEW AppROACHES To CONTROL STRATEGIESIn 1978, the World Health Assembly endorsed a malaria control strategy based on theprinciples of primary health care (PHO and on the recognition of variations inepidemiological situations in different parts of the world and variations in the state ofdevelopment of health infrastructures in different developing countries. However, even
where countries have attempted to integrate malaria control strategies into their PHC
programmes while still retaining central specialized services available to the periphery, there

have been problems of interpretation, delays in implementation and, in many areas, areluctance to change long‑standing and familiar malaria control practices. Consequently
most countries are experiencing difficulties in modifying their established services. Despite
these problems, the persistence of the malaria and the cost of traditional control measures areforcing countries to consider the redeployment of their limited resources. Najera (1986) has
emphasized that a fully developed health infrastructure is not necessarily a prerequisite toundertaking antimalaria activities. Whatever kind of structural elements exist shouldcollaborate in developing a health infrastructure for primary health care and this infras‑
tructure should view malaria control as an essential component in endemic areas and should
distribute appropriate responsibilities to general and specialized health services.

THE EpIDEMIOLOGICAL AppROACH TO MALARIA CONTROL
There are extensive local variations in the intensity of the malaria problem and in the

response to control interventions. A better epidemiological understanding of the ecologicaland social processes interacting with the basic elements of the transmission chain, i.e.
parasite, vector, and infected and susceptible host, may enable more selective and effective
control measures to be applied at lesser cost.

While measures such as insecticides, and mass drug administration can drasticallymodify, and reduce malaria prevalence and even eliminate transmission, eventual reduction
or cessation of these measures can lead to the restoration of the original level of endemicity.

By contrast, Iess spectacular but more permanent effects on malaria transmission can beobtained by elimination of mosquito breeding places, improvements in house construction,

144

and, as a consequence of social and economic development, by changing the way of life toensure that there is an appropriate demand and use of health services.

THE STRATIFICATION OF THE MALARIA PROBLEM
The stratification of malaria problems may be undertaken in a number of different ways;
different epidemiological zones can be characterized in terms of their biological and ecologi‑
cal features including those of the vector, the incidence of disease and the social and economic

characteristics of the human population. These characterizations can be used to develop a
stratification of the control activities to ensure that each area under control has applied to it

the approach most appropriate for it and that the resources for control measures are placedin areas that have the greatest need for them coupled with the greatest possibility of utilizingthem to achieve effective control.

THE SELECTION OF AppROPRIATE TECHNOLOGIESThe main aim of the epidemiological approach is to identify the appropriate technologies

for malaria control as part of pHC. This concept implies that the method selected isscientifically sound for the solution of the given problem in the given place and is adaptable
to the society in which it will be used in terms of acceptability and social affordability.

It has been emphasized that antimalaria measures differ considerably in the degree of
perfection and coverage required during their application so as to obtain an effect. As an
example, coverage by indoor residual insecticide applications must be extensive if they are

to have any effect on the protection of the community. By contrast individual measures ofprotection including the use of bednets with or without insecticide impregnation, screening ofdwellings and the seeking of prompt treatment of fevers, reduce the risk to the individual andeventually have an additive effect for the protection of the community.

Where malaria is a serious public health problem, the training of community workers in
the diagnosis and treatment of malaria and ensuring their continued support by the healthservice through the provision of supplies and the referral of problem cases and situations,should also lead to the development of primary health care programmes. By contrast verticalprogrammes of spraying and mass chemotherapy do not normally engage in development
processes. However, antimalarial activities, where possible, should be incorporated into thedaily life of the community and the individual to meet a special epidemiological situation. Itshould be realized that unless control activities are seen to be effective by the community,
they may hinder not only their own continuation but the establishment of primary health care.

THE MALARIA CONTROL STRATEGY AND ITS AppLICATION AT THE COUNTRY LEVEL
There are two basically different approaches to malaria control:‑The management of malaria without drastically changing the epidemiological equilib‑
rium including the provision of facilities for diagnosis and treatment and developmentof epidemiological information systems allowing for focal management
or‑active intervention to control or even interrupt malaria transmission in large areas‑

145

this approach is aimed at developing an improved malaria epidemiological situationthat can be sustained.
The choice among the two approaches should be based on the feasibility of maintaining
the desired results. As an example, there may be geographical areas in which it is possible
to eiiminate malaria in a relatively short time. Yet if the same area is likely to be later
subject to a recrudescence or a resurgence of malaria and the local health services are unable

to maintain a malaria‑free state with the resources available to them, Iittle will have been

gained by what will have been only a temporary relief from transmission; in fact it can beconsidered that efforts that achieved only transient results were, in reality, wasteful of
resources if populations who, for a time, were protected from the disease were to be later
subjected to it anyway.
It must be realized that it will be seldom possible for a country as to adopt a single
effective approach to malaria control for all its regions. Where malaria is widespread withina country, planning should be carried out by district level personnel to ensure that it isappropriate to the district level. Generally speaking experience has shown that what isneeded to improve malaria control even more than the development of new and improved
technologies, is a better understanding of where and how to apply the general and specificknowledge that is already available. The 18th Expert Committee report has recommended
in conclusion that:

Countries should review their antimalaria activities in light of their state of development

and specific state of development of their PHC structure, taking into account concur‑
rent activities for health promotion and the control of other diseases.

Malaria control should be based on an epidemiological approach which recognizes local
variability in the distribution and nature of the problems thus encouraging the selectionof suitable control and evaluation measures for different ecological areas.

Planing for antimalaria activities should take into accounta ) ensuring that the best available information and experience is available as a basis

for planning and if necessary, acquire additional knowledge;b ) the relevance of the objectives in terms of their fesability and their appropriate‑
ness with which the basic objective, especially the prevention of mortality is to beattained;c ) whether the existing infrastructure can ensure total coverage of the population
with timely diagnosis, treatment and where necessary, prophylaxis and has facilities
for referral for treatment of sever cases and the necessary epidemiological services for
detection of critical areas;d ) the necessity for developing a core group of expertise if this does not already exist

and the related training which will be required for the personnel of such groups;e ) the use of appropriate evaluation and surveillance systems for the monitoring of
the progress of malaria control;f ) the development of methods of integrated vector control especially where they canbe carried out and sustained by the community.

THE PROSPECT FOR FUTURE MALARlA CONTROL
There is unlikely to be a simple solution or a panacea for malaria control or for the146control of most of the vector‑borne or other communicable diseases for that matter. Even
the development of an effective vaccine for malaria would require a national economy
capable of acquiring it, an infrastructure capable of ensuring its application, epidemiologicalservices capable of monitoring and evaluating its efficacy at a community level and a healthservices structure capable of intervening as required in the most appropriate and effective

maner. If the principals and steps which have been described and outlined above arefollowed, the long‑term prospects for malaria control are good. However, it must beemphasized again that the objectives and planning for control should be realistic andobtainable. While there is a great need for additional research on drugs, vaccines, andinsecticides, and many of the problems of malaria epidemiology and control may eventually
be solved by such research, nevertheless a great deal can be achieved by the effective
application of principles and methods already known and already available.

ACKNOWLEDGMENTS
The author wishes to express his appreciation to Dr. J.A. Najera, Director, Malaria
Action Programme, WHO, Geneva, for the time he has taken to read and comment on thismanuscript and to Professor Y. Wada of the Department of Medical Entomology, Institute ofTropical Medicine, Nagasaki University, Nagasaki for his invitation to make the presenta‑tion to the staff and students of the Institute on which this article is based and for his
suggestion to publish it and to Professor M. Sasa for his invitation to visit Japan and present

lectures on the control of malaria.

REFERENCESl ) AID Report (1987) : Report of the terminal evaluation of the Pakistan malaria control project(391‑0472) April 4‑May 3, 1987, AR‑053, VBC Project, Washington, D.C.
2 ) Carnevale, P. and Vaugelade, J. (1987): Paludismes, morbidite palustre et mortalite infantile

et juvenile en Afrique sub‑saharienne, WHO unpublished document WHO/MAL/87, 1036
3 ) Cattani, J.A., Tulloch. J.L., Vrbova, H.. Jolley, D., Gibson. F.D., Moir, J.S., Heywood, P.F.,

Alpers, M.P., Stevenson, A. and Clancy, R. (1986): The epidemiology of malaria in a popula‑tion surrounding Madang, Papua New Guinea, Am. J. Trop. Med. Hyg., 35(1), 3‑154 ) EMRO (1987): Regional technical consultation on malaria control and primary health care,

EM/MAL/216‑E
5 ) Fontenille, D. and Rakotoarivony, I. (1988): Reappearance of Anopheles funestus as a malaria

vector in the Antananarivo region. Madagascar, Trans. R. Soc. trop. Med. Hyg., 82, 644‑645
6 ) Harinasuta, T.. Dixon, K.E., Warrell, D.A. and Doberstyn, E.B. (1982): Recent advances inmalaria with special reference to Southeast Asia, Southeast Asian J. Trop. Med. Pub. Hlth.,
13, 1‑34

7 ) Hyman. B., Ramesh. A. and Chakrapani, K.P. (1983): Urban malaria control situation andenvironmental issues, Madras City, India, Ecol. Dis., 2(4), 321‑335
8 ) Kondrashin, A.V. (1986) : Malaria in Southeast Asia, Southeast Asian J. Trop. Med. Pub. Hlth.,17(4) , 642‑655

9 ) Meek, S.R. (1988): Epidemiology of malaria in displaced Khmers on the Thai‑Kampucheanborder, Southeast Asian J. Trop. Med. Pub. Hlth., 19(2), 243‑251lO) Najera, J.A. (1986): Global analysis of the malaria situation in relation to the development of

147

primary health care, WHO unpublished document, WHO/MAL/86, 1025ll) Najera, J.A. (1986): Malaria control and primary health care: a global concept, USAID AIBS
Proceedings of a conference on malaria in Africa, pp. 299‑310, Washington, D.C.
12) PAHO (1988): Epidemiological status of malaria, region of the America 1986, Epidemiol.
Bull., 9(1) , 10‑14

13) Samarsinghe, L. (1986): Administrative report, anti‑malaria campaign, Columbo14) Sharma, V.P. and Mehrotra, K.N. (1986): Malaria resurgence in India, Soc. Sci. Med., 22(8),835‑845
15) Sudomo, M., Baroji and Sustriayu, N. (1985): Chemical control on malaria vector Anopheles
aconitus in Central Java, Indonesia, Southeast Asian J. Trop. Med. Pub. Hlth., 16(D, 153‑162
16) Suleman, M. (1988): Malaria in Afghan refugees in Pakistan, Trans. R. Soc. trop. Med. Hyg.,82, 44‑47
17) Vittal, M., Mustafa, S.M., Deobhankar, R.B., Deshpande, L.B. and Deo, R.R. (1982) : Insecticide

susceptibility status Qf malaria vectors in Maharashtra, Ind. J. Malariol., 19, 59‑61

18) WHO (1986a) : Expert Committee on Malaria, Tech. Report Ser., no. 735, Geneva, Switzerland
19) WHO (1986b) : Resistance of vectors and reservoirs of disease to pesticides, 10th Report of the
WHO Expert Committee on Vector Biology and Control, Tech. Report, Ser., no. 737

20) WHO (1987): World malaria situation, 1985, WHO Wld Hlth Statis. Quart, (40), 142‑170,
Geneva, Switzerland
2D Wijesundera, M. de S. (1988): Malaria outbreaks in new foci in Sri Lanka, Parasitol. Today,
4(5), 147‑150

Japan. J. Trop. Med. Hyg., Vol. 17, No. 2, 1989, pp. 149 155

149

OBSERVATIONS ON THE VALIDITY OF THE
OVARIAN ACCESSORY GLANDS OF SEVENECUADORIAN SAND FLY SPECIES (DIPTERA=PSYCHODIDAE) IN DETERMlNlNG THEIRPARITYHIROYUKI TAKAOKAl, EDUARDO A. GOMEZ L2., JOHN B. ALEXANDER3

AND YOSHIHISA HASHIGUCH14
Received December 13 1988/Accepted January 29 1989

Abstract: Females of seven sand fly species caught on man in several leishmaniasis‑

endemic foci in Ecuador were examined to assess the value of the accessory glandsecretions as an indicator of parity. It was found that parous females could be
distinguished from nullipars by the presence of granular secretions in the accessory
glands in Lutzomyla ayacuchensis, probable vector of Leishmania in the Andean highlandsof southern Ecuador. Examination of the female accessory glands was not a reliable
method for determining parity in six other sand fly species caught in lowland areas,
including Lu. trapidoi. Lu. hartmanni, and Lu. gomezi, three proven vectors of Leishmania.

since glanular secretions were found in both parous and nulliparous females.

INTRODUCTION
Condition of the ovarioles has proved to be a useful characteristic for distinguishingparous from nulliparous females in several groups of Nematocera, including Phlebotominae(Detinova, 1962) . This ovarian method has been thought of as impractical for routine work
due to the small size of the ovarioles in sand fiies. Examination of the accessory glands ofthe ovaries, which are large enough to examine quickly, is a useful method for distinguishingparous females in several African sand fly species of the genus Phlebotomus (Adler and
Theodor, 1935; Lewis and Minter, 1960). Usefulness of this method seems to be dependent

upon the sand fly species involved when applied to the New World genus Lutzomyia.
Accessory gland secretions were reported as a reliable sign of parity in three species from
northern California (Chaniotis and Anderson, 1967), and also in eight species from Brazil(Lewis et al., 1970), but had no value for determining parity for many other Lutzomyia
species (Johnson and Hertig, 1961; Johnson et al.. 1963; Lewis, 1965; Lewis et al.. 1970; Ward,1974) .

1

2

Division of Medical Zoology, Medical College of Oita, Hazama, Oita 879‑56, Japan
Departamento de Parasitologia, Instituto Nacional de Higiene y Medicina Tropical, Apartado

3961, Guayaquil, Ecuador
3 Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32611,
U.S.A.
4 Department of Parasitology, Kochi Medical School, Nankoku City, Kochi 781‑51, Japan

150

The present study was undertaken to determine if the accessory glands could be used todetermine parity of several Ecuadorian sand fly species, including some proven vectors ofLeishmania.

MATERIALS AND METHODS
Sand fly collections were made at five localities, i.e., Challuabamba and Paute, Depart‑

ment of Azuay, both situated at altitudes of 2,300‑2,500 m above sea level in the Andean
plateau; Echeandia, Department of Bolivar (altitude ca. 500 m a,s.1.), and Puerto Quito,
Department of Pichincha (altitude 450 m a.s.1.) , both situated in the western foothills of theAndes; and Pajan, Department of Manabi, in the Pacific coastal region (altitude ca. 20 m a.
s.1.) . All of these localities lie in regions where Leishmania is endemic (Hashiguchi, 1987) . At

Challuabamba and Paute, collections were carried out for three and six nights respectively
on rocky hillsides covered in grasses, small shrubs and Agave plants. Tree cover was confinedto sparse groves of young Eucal ptus on the lower slopes.
At the other study sites, sand fiy collections were made for one or two nights in secondary

forest near human habitation except at Pajan, where insects were captured in a coffee
plantation.

Flies that alighted on human volunteers between 18.30 and 21.00 were captured using amouth aspirator (Hashiguchi, 1987) and maintained overnight in small plastic vials provided
with sufiicient moisture. Female sand flies captured were dissected in saline on a glass slide

and the accessory glands checked microscopically for the presence of granular secretions. At

the same time, ovaries were examined to determine their parous state, using the follicular
relic method of Detinova (1962) ; the shapes of the spermatheca and cibarium were observed
for sand fly identification, which was done using keys of Young (1979) in reference of C ceresand Bianchi (1988).
The guts of all dissected sand flies were examined for the presence of blood meals. A
number of sand flies caught at Challuabamba were allowed to take blood from an anesthet‑ized golden hamster, and kept in a plaster‑lined 120 ml plastic vial provided with a piece ofsugar cane at a temperature of 15‑20'C for three, seven or nine days. The accessory glandsof these fed fiies were then examined to determine whether granular material had been
secreted in accordance with the gonotrophic cycle. The methods of collection of adult sandflies were detailed previously by Hashiguchi et al. (1985) , and for ovarian dissection by Lewis(1965) .

RESULTSA total of seven sand fly species taken in human bait collections in the five localities

sampled were examined. The numbers of females of each species with or without accessory
gland secretions, in relation to their parous state as demonstrated by the ovarian method, areshown in Table 1. In Lu. ayacuchensis C ceres and Bianchi from Challuabamba and Paute,
granular secretions in the accessory glands were seen in all 27 parous females but not in mostnulliparous females.
The nine nulliparous fiies with granular secretions had developing follicles of stage 11la,but these were all among those that had fed on varying quantities of blood after being

151

Table 1

Granule secretions of accessory glands in relation to parity inseven anthropophilic sand fiy species examined during July ‑August, 1988 in Ecuador

Lutzomyi:a spp.

Blood No. flies

meall examined

Granule secretions
absentpresent
P2
N2
PN

ayacuchensis

Challuabamba

+

52

o

45

7

o

12

6

2

4

o

41

o

15

26

o

16

3

3

10

o

84

38

16

28

2

6

6

O

o

o

ll

7

3

o

35

13

9

o

5

3

l

O

28

14

8

6

O

4

3

O

1

O

Echeandia
panamensls

2

1

l

o

o

Puerto Quito
gomezi

12

4

5

3

O

49

33

16

o

o

14

10

4

o

o

7

2

5

O

o

1

l

O

O

o

Paute

+
tra pid oi

Echeandia+
Puerto Quito

hartmanni
Echeandia+
Puerto Quito+

13

carrerai thula

Pa j n+shan noni

Paj n

+

Fed to a varying degree when collected on men
2. N: nulliparous; P: parous

Table 2Grou pf ed

Changes in secretions of accessory glands of Lutzomyia ayacuchensis from
Challuabamba, fully fed on blood from hamster and kept on sugar cane at
a temperature of 14‑20'C

Day after blood feeding
1

3

5

7

9

414'

414

5/5

5/5

16/18

(IIla) '(IIlb)

(IV)

(V) =

(V)'

0/1

u n f ed

(‑)

(‑)

(ID

0/3

(‑)

(II)

No. positive for granule secretions/no, examined
2

3

Follicular stage
Eggs were already deposited in I of the 5 females dissected on day 7 and in 17 of
the 18 females dissected on day 9,

152collected. The granules found in these nulliparous females are therefore considered to havebeen secreted after the blood meal taken on the preceding day.
In contrast, Lu. trapidoi (Fairchild and Hertig) , Lu. hartmanni (Fairchild and Hertig) ,Lu. panamensis (Shannon) and Lu. carrerai thula Young collected from Echeandia andPuerto Quito showed discordant relations between granular secretions and parity. Accessory
gland secretions were found in more than half of the nulliparous females, as well as in mostof the parous females. All the unfed nulliparous females with granular secretions had follicles
of stage I or II.

Accessory gland secretions were seen in all females irrespective of parity, in two
Lutzomyia species caught from Paj n. No developing follicles were seen except in blood‑fed
flies, which had stage 11la follicles.

The results of dissections of female Lu. ayacuchensis kept for several days after blood

feeding are shown in Table 2. This sand fly species was gonotrophically concordant. Egg
maturation required approximately seven days, and eggs were laid shortly thereafter. The
granules in the accessory glands began to be secreted soon after the blood meal, and wereaccumulated gradually as follicular development proceeded; the accessory glands enlarged
and were filled with dark granules within five days of blood feeding. The accessory glands
in 16 of 18 flies which had oviposited had remnants of dark granules in varying amounts, while

those in the remaining two females had no residues and resembled those of nullipars. One andthree unfed females, examined five and nine days after collection respectively, had no granulesecretions and exhibited no follicular development beyond stage II.

DISCUSSION
The present study clearly demonstrates that the accessory glands are a reliable organ for

distinguishing parous from nulliparous females of Lu. ayacuchensis from Challuabamba andPaute. Granular secretions in the glands of this sand fiy were apparently produced only after

a blood meal was taken. The changes in the quantity of granular secretions during folliculardevelopment and after oviposition are the same as those observed in three Californian sandfly species by Chaniotis and Anderson (1967). It should be remembered that not all femaleswith granular secretions can be judged as parous, since some of the blood‑fed nulliparous

females might have secreted granules shortly after feeding. In future studies it would
therefore be better to discard blood‑fed females or to also check the ovarian follicles when
examination of these females is required. There is also a possibility that some parous females

are mistaken for nulliparous when granules are entirely expelled from the accessory glands
after oviposition, as demonstrated in two of the 18 wild‑caught females that laid eggs in thelaboratory during the present study.

At present little is known about the biology of Lu. ayacuchensis or its role in thetransmission of Leishmania in the Andes of southern Ecuador. This species was first recorded
from Ecuador during the present study but originally misidentified as its close relative, Lu.

peruensis (Shannon) . Closer examination revealed that the sand fly fauna of the Paute area
consisted of two closely related species, i.e., Lu. ayacuchensis and Lu. osornoi (Ristorcelli and

Van Ty), both of which are anthropophilic and may be involved in transmission of Leish‑
mania in the area. Our findings will facilitate future studies on bionomics and dynamics ofwild populations of Lu. ayacuchensis, and may also applied in the future to Lu. osornoi.

153

By contrast, the accessory gland secretions did not prove to be useful in distinguishing

between parous and nulliparous females for Lu. trapidoi. Lu. hartmanni. Lu. panamensis andLu. carrerai thula collected from Echeandia and Puerto Quito. The first two species havebeen reported as probable vectors of leishmaniasis in Ecuador (Hashiguchi et al., 1985),
while Lu. panamensis is a proven vector of Leishmania in Panama (WHO, 1984) . In each ofthese four species, granular secretions were seen in most parous females, but more than halfof the unfed nulliparous females dissect d also had granular secretions. It may be thataccessory gland secretions are produced a few days after eclosion, irrespective of whether or

not a blood meal is taken, as has been observed in Lu. Iongipalpis (Lutz and Neiva) from
Brazil (Ward, 1974).

Accessory gland secretions were observed in all dissected females of Lu. gomezi(Nitzulescu) , another suspected vector of Leishmania in Ecuador (Hashiguchi, 1987) , and Lu.

shannoni (Dyar) from Pajan. This indicates that the glands are of no value in determining
parity. Lewis et al. (1970) reported that some females of Lu. shannoni in Belize and Lu.

gomezi, and three other species in Brazil were probably autogenous, based on the highproportion of flies with granular secretions showing discordant ovarian development. No
sign of autogeny was seen in females of the two species collected from human bait in Paj n.
None of the ovarian follicles in unfed nulliparous females had developed beyond stage II, andaccessory gland. secretions were found in all these females.

It appears that female accessory gland secretions are not associated with autogeny, andthey are probably produced shortly after adult emergence. Autogenous strains have beenreported in Lu. shannoni from Florida (Perkins, 1982) and in Lu. gomezi from Panama(Johnson, 1961) . It is possible that autogenous strains of these species also exist in Ecuador.

A somewhat high proportion of parous females (five of eight dissected, or 62.5%) , among
those collected suggests that an autogenous population may be present. Further studies
would be required to determine whether this is the case.
At present, there are no reliable methods other than the ovarian relic method in determin‑

ing reproductive parity of vector sand flies in lowland areas endemic for Leishmania. Further

efforts are needed to find out reliable methods of distinguishing parous from nulliparousf emales.

ACKNOWLEDGEMENTS
We thank Drs. R. F. Lazo S. and V. V. de Coronel for their encouragement, and express
our appreciation to our collaborators in the Instituto Nacional de Higiene y Medicina
Tropical, Guayaquil, Ecuador. Thanks are also due to our research team members, Drs. T.
Mimori, M. Furuya and S. Nonaka for their support. This study was supported by theOverseas Research Program of the Ministry of Education, Science and Culture, Japan (No.
63041 096) .

REFERENCESl) Adler, S. and Theodor, O. (1935) : Investigations on Mediterranean kala azar VIII, Proc. Trop.
S. Paulo, 3, 230‑238

2) C ceres, A. and Bianchi, G.E.A. (1988): Descricao de Lutzomyia ayacuchensis sp. n. (Diptera,

154

Psychodidae, Phlebotominae) dos Andes peruanos, Revta Bras. Ent., 32, 55‑61
3 ) Chaniotis, B.N. and Anderson, J.R. (1967): Age structure, population dynamics and vector
potential of Phlebotomus in northern California. Part I, J. Med. Entomol., 4, 251‑254

4 ) Detinova, T.S. (1962): Age‑grouping methods in Diptera of medical importance, Monograph
Ser. W.H.O. no. 47, pp. 216

5 ) Hashiguchi, Y. (1987): Studies on New World leishmaniasis and its transmission, withparticular reference to Ecuador, Kyowa Printing & Co. Ltd., Kochi, pp. 174

6 ) Hashiguchi, Y., Gomez L. E.A., De Coronel, V.V.. Mimori, T. and Kawabata, M. (1985):
Natural infections with promastigotes in man‑biting species of sand fiies in leishmaniasis‑

endemic areas of Ecuador, Am. J. Trop. Med. Hyg., 34, 440‑4467 ) Johnson, P.T. (196D: Autogeny in Panamanian Phlebotomus sandfiies, Ann. Ent. Soc. Am., 54,
116‑1188 ) Johnson, P.T. and Hertig, M. (1961) : The rearing of Phlebotomus sandflies, Ann. Ent. Soc. Am.,54, 764‑776

g ) Johnson, P.T., McConnell, E. and Hertig, M. (1963): Natural infections of leptomonad
fiagellates in Panamanian Phlebotomus sandflies, Exp. Parasitol., 14, 107‑122

10) Lewis, D.J. (1965): Internal structural features of some Central American phlebotomine
sandflies, Ann. Trop. Med. Parasitol., 59, 375‑385
11) Lewis, D.J., Lainson, R. and Shaw, J.J. (1970) : Determination of parous rates in Phlebotomine

sandfiies with special reference to Amazonian s ecies, Bull. Ent. Res., 60, 209‑219

12) Lewis, D.J. and Minter, D.M. (1960): Internal structural changes in some African
Phlebotominae, Ann. Trop. Med. Parasitol., 54, 351‑365
13) Perkins, P.V. (1982): The identification and distribution of phlebotomine sand fiies in the
United States with notes on the biology of two species from Florida (Diptera: Psychodidae) ,Ph.D. theses, University of Florida, Gainesville, Florida, pp. 196

14) Ward, R.D. (1974): Granule formation in the accessory glands of a laboratory strain of Lu.
longipalpis (Diptera: Phlebotominae) from Ceara state, Brazil, Trans. R. Soc, trop. Med. Hyg.,68, 171

15) WHO Expert Committee (1984): The Leishmaniases. Tech. Rep. Ser. 701, WHO, Geneva, pp.
14016) Young, D.G. (1979): A review of the bloodsucking psychodid flies of Colombia (Diptera:
Phlebotominae and Sycoracinae) , University of Florida Agricultural Experimental Station
Technical Bulletin 806, pp. 266

155

エクアドルにおける人吸血性サシチョウバエ7種の卵巣付属腺による穎粒分泌と経産歴との関係
高岡宏行1・Eduardo

John

A．Gomez

L2．・

B．Alexander3・橋口 義久4

旧大陸のサシチョウバエでは卵巣付属腺の分泌する穎粒の有無が経産，未経産雌の区別に用いられているが，新大陸のサシチョウバエではこの方法の応用は難しいとされている。今回，エクアドルにおいて人囮法で採集した7種のサシチョウバエを解剖し，ovarianrelic法による経産歴と付属腺での穎粒の有無との関係を検討した。低地のリーシュマニア症媒介種，L城o吻吻≠廻が」扉，L鉱hαz∫郷伽痂およびL鉱go窺θ2iを含む6種では未経産雌，経産雌いずれにも付属腺の分泌穎粒が見られるなど穎粒の有無だけでは経産歴を判定できないという結果を得た。一方，

アンデス高地の五鉱砂鷹鰐h8郷奮では，分泌穎粒は経産雌のみに見られ，経産個体の判別に用いられ得ることが分かった。

1）大分医科大学医動物学教室
2）エクアドル国立衛生学熱帯医学研究所寄生虫部門
3）フロリダ大学昆虫学線虫学部門
4）高知医科大学寄生虫学教室

Japan. J. Trop. Med. Hyg., Vol. 17, No. 2, 1989, pp. 157‑173

157

ECOLOGICAL STUDIES ON THE MOSQUITO FISH,GAMBUSIA AFFINIS FOR ENCEPHALITISCONTROL WITH SPECIAL REFERENCE TO
SELECTIVE FEEDING ON MOSQUITO LARVAE

AND COMPETITION WITH THE MEDAKA,OR YZIAS LA TIPESHIDEKI SATO
Received November 2 1988/Accepted February 15 1989

Abstract: The mosquito fish (Gambusia affinis) that was transferred to Tokushima
City, Tokushima Prefecture in 1969 was studied in relation to the control of mosquitoes.

A number of the fish were collected at several ponds and ditches where the fish had
increased in number and were repeatedly released into swamps, sewers, fallow rice fields,
etc. They were established in 7 places in 1970, 36 in 1971, 76 in 1972 and 104 in 1973. In
27 of those places, both the medaka ( Oryzias latipes) and mosquito larvae co‑existed, but

after the establishment of Gambusia in these places, no mosquito larvae were found. The

population density of Oryzias became low and that of Gambusia increased. The water
areas with high densities of Gambusia were still or had an infiow of household waste water

causing eutrophy. When Gambusia and Oryzias were found together in a water area, thetotal number of fish was as large as 400‑500 per I m'. The result from laboratory
observations demonstrated that Gambusia prey on more mosquito larvae than Oryzias. If
Gambusia were raised together with Oryzias in the same water tank, Gambusia attacked
and eventually exterminated Oryzias. The feeding habits of Gambusia and Oryzias dependon the availability of food in the environment and are highly variable. It was shown thatboth species are involved in the competition for space and food in connection with theirecological niche. The above results indicated that Gambusia is more suitable for thecontrol of mosquito larvae than Oryzias. In fact, it was observed that Gambusia became
more predominant and more expansive in its habitat in the water areas examined.

INTRODUCTION
The mosquito fish, Gambusia afflnis (Baird and Girard, 1853) is a viviparous poeciliid fish,

the original habitat of which is in the southern part of North America. Since the beginningof this century, it has been exported worldwide, primarily for vector control of malaria.
There have been many reports on the results of these vector control attempts, on which
Gerberich and Laird (1966) published a review. According to Nakamura (1941) , who gave
details of its transfer to Japan, Gambusia in Japan originated from 405 fish sent from Texas

to Hawaii by Mr. Albinseal of Stanford University in 1905, then later transfered to Taiwan
Department of Medical Zoology, St. Marianna University School of Medicine, 2‑16‑1 Sugao,
Miyamae‑Ku, Kawasaki 213, Japan
Present address: Public Health Institute of Kawasaki City, 5‑13‑10 Oshima, Kawasaki‑Ku,
Kawasaki 210, Japan158

for the control of Anopheles. Mr. H. Komatsu, a goldfish seller, imported approximately 200

Cambusia by surface shipment from Taiwan and bred them in Shiga and Wakayama
Prefectures in 1916. The descendants of the fish were found in the late 1960's in a swampy
area around Tokyo. The habitat of this establishment was described by Okada (1957) , Sasa
(1972) and others.
In recent years, with the increase of resistance to insecticides in various species ofmosquitoes and the increasing problem of environmental pollution, including loss of nontarget organisms through the use of insecticides, a method of mosquito control that did not
rely solely on insecticides became highly desirable. Because of this, the use of fresh water fish

such as Gambusia has been examined.
The present research was conducted in Tokushima City to examine the usefulness ofGambusia in controlling the mosquito, principally Culex tritaeniorhynchus, vector of Japanese
encephalitis.

Tokushima City, with a population of approximately 230,000, is situated in the delta of
the Yoshino River in the eastern part of Shikoku Island. In the 1960's, many cases of Japanese

encephalitis occurred in this area. With the aim of controlling vector mosquitoes of thedisease, according to an agreement between Tokushima City Medical Association andTokushima Cit Authority, a research center (Tokushima City Laboratory for Mosquito
ControD was set up in April 1969, and control measures using Gambusia against mosquitoes
were started.

Since November 1968, a total of 1,000 Gambusia were sent to Tokushima City from
Tokyo in three lots. They were released and bred in ponds and ditches within the city, andin October of the following year, approximately 25,000 fish were transferred to water areas
such as swamps, sewers, fallow rice fields, etc., in 57 places within the city. From the next
year onwards, they were continuously collected from breeding places and released elsewhere.
As a result, in a short period of five years, Gambusia which had been transferred to Toku‑shima City had greatly expanded their habitat in the swampy area around Tokushima City,and proved to be effective for controlling mosquito larvae. The results were reported partly
by Sato et al. (1972) and Hirose et al. (1978) .
The present paper deals with the results of ecological observations regarding the settle‑

ment and the expansion of distribution of Gambusia in swampy areas where Culex pipiens
pallens, a vector of filariasis, and Cx. tritaeniorhynchus, a vector of Japanese encephalitis,

were breeding. The potential efflciency of Gambusia for mosquito control will also becompared with that of Oryzias, through the studies on the competitive relationship between
the two species.

MATERIALS AND METHODS
1 . Gambusia affinis transferred to Tokushima City

All of Gambusia transferred to Tokushima City were sent by air freight from Haneda
Airport. The first lot, sent in November 1968, consisted of 200 fish raised by the Departmentof Parasitology, Institute of Medical Science, The University of Tokyo. The second lot,which arrived on April 17, 1969, and the third lot, which arrived on May 7 in the same year,

were collected from the drainage ditch alongside the runway at Haneda Airport (400 eachtime) .

159

Before the transfer.,of Gambusia, a preliminary survey was made in Tokushima City andthe neighboring Naruto City, Komatsujima City, Matsushige Town and Aizumi Town. The
results showed that Oryzias lived in a widespread area, but there was no evidence of thepresence of Gambusia in these places.
2 . Releasing of Gambusia affinis
The 200 Gambusia arriving in the first lot were kept in water. tanks at the Tokushima
City Laboratory for Mosquito Control. Of the. 400 fish introduced ih the second lot, 130 werereleased in a pond of 100 m2 area and 40 cm depth in Tokushima Castle Park, and 30 werereleased at each of 2 different places in the sewer in Hachiman‑Cho, Tokushima City. Of the
400 fish introduced in the third lot, 220 were released in an artificial pond in Tokushima Castle

Park with an area approximately 500 m2 and depth approximately 60 cm, 50 in fallow rice
fields in Hachiman‑Cho and 50 in sewers in Hachiman‑Cho. The remaining specimens were
kept in tanks at the Laboratory for Mosquito Control.
All of the six water areas mentioned above‑three in natural or artificial ponds and three
in sewers and fallow rice fields‑were chosen as the first sites for releasing Gambusia, because

the conditions of the sites were expected to provide easy multiplication and recovery.
Gambusia succeeded in settling in all of these water areas.

Between July and October 1969, some fish were captured and the second release wasmade at 63 sites in sewers and swampy areas, mainly within Tokushima City. Afterwards,
the third release of fish was made in 73 places (1970) , the fourth release in 132 places (1971) ,and the fifth release in 74 places (1972). The number of fish released was from 50 to 100
depending on the size of water area.
3 . Investigations regarding the distribution, population density. body length and feeding
habit of Gambusia affinis and Oryzias latipes1 ) Distribution:

In a large number of water areas in Tokushima City, investigations of the distribution of

Gambusia and Oryzias were conducted. In the present paper only the results of studies inthose areas where the investigations were conducted regularly are mentioned.
For most density determinations, fish collection was by a four‑arm scoop‑net (1 m x 1m) applied five times at each site, and the total number of fish was counted. In small water
areas where this scoop‑net did not fit, a dipnet, 25 cm in diameter, was used for sampling fivetimes.

2 ) Population density:

The population density was investigated in the swamp at Kita‑Okinosu. This area is ina brackish water zone, where eularias (Phragmites communis) grows, and is a typically
productive breeding place for Gambusia in Tokushima City. The following two methods wereused for density determination;a . Mark‑and‑release method. Specimens collected from the water area under investi‑
gation were held in a 1:10,000 water solution of neutral‑red for 10‑20 min for marking, andthen released. When marked and unmarked specimens were completely mixed after about 1
hr, they were captured again by scooping, and the number of individuals was estimated using

the Lincoln index method. The population density was estimated by this method on April 17,
July 27 and September 21, 1972.

b . Scooping method. The I m x I m four‑arm scoop‑net was put into the water for
15 min and fish were scooped up and counted. This was repeated at 5 different places in each160

water area and an average was calculated, on April 18, July 28 and September 22, 1972.
3 ) Body length:

All the specimens obtained by the scooping method in the Kita‑Okinosu swamp wereused for measurements of body length.
4 ) Feeding habit:

Gambusia and Oryzias from Kita‑Okinosu and Showa‑Cho, two representative water
areas in Tokushima City in which Gambusia had settled were examined. The specimens
collected were immediately submerged in a solution of alcohol (70%) and formalin (10%) ,and stomach contents were analyzed.
4 . Comparative examination of the, ability of Gambusia affinis and Oryzias latipes to preyon mosquito larvae and other fish

1 ) The number of mosquito larvae preyed on:
One pair of Gambusia and one pair of Oryzias were observed in a 2,500 ml plastic
container, provided with 100 fourth instar larvae of Culex pipiens pallens every 24 hr, and thenumber of larvae ingested by each pair was counted. Together with mosquito larvae, solidsynthetic food (MF mouse food, Oriental Yeast Co.) was given to Group B and D, but not toGroup A and C. Three days before the experiment, food supplies to both fish species were
stopped. The average body length of the Gambusia was 2.6 cm for females and 2.4 cm formales, while that of the Oryzias was 2.5 cm for females and 2.7 cm for males. The experiment
was repeated 5 times.
2 ) Preference in feeding on mosquito larvae or young guppies (Poecilia reticulata):

Ten young Poecilia were placed in a 2,500 ml container with or without 0.02 g solidsynthetic food and 100 mosquito larvae, and the preference of Gambusia and Oryzias for
Poecilia or mosquito larvae was compared. Ten young Poecilia, only, were released into
container number 6 was observed as a control. Gambusia and Oryzias were not fed for threedays prior to the experiment. The solid synthethic food was provided daily. The mosquito
larvae used were Cx. pipiens pallens (fourth instar) . These were replaced daily. Ten young
Poecilia were introduced only at the beginning, and observed for the number surviving eachday.

The average body length of Gambusia used in the experiment was 2.6 cm for females and2.5 cm for males and that of Oryzias was 2.6 cm and 2.7 cm, respectively. The average bodylength of young Poecilia was 0.7 cm.
3 ) Competition for survival in a small space:
Gambusia and Oryzias in ratios of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1 were released

into 2,500 ml plastic containers. Total number of both species was fixed at 20, and the sex

ratio was l:1. During the experiment they were given 0.2 g solid food daily and the numbersof both fish were observed every day. Three days prior to the experiment, food supplies were

stopped. The average length of Gambusia was 2.6 cm for females and 2.5 cm for males, andthat of 07yzias 2.6 cm for females and 2.8 cm for males.

RESULTS
1 . Establishment of Gambusia affinis
Figure I shows the main habitats of Gambusia affinis in Tokushima City in 1973. It isapparent that Gambusia were found to be distributed in most parts of the city four years after

161

Itano County
1

//

/
l.

:
'

i:7 : T h

:9,.

Yo s h '

L

il]O

.

,.,, ,*:."'i'lL ""L.' '!<"= "= '><'

: 3 $S5 i'. . .'' :...#t

,

8 '1

3･:=.

S' 46. .

'1"I"" S . .;i.7" """;"'...
;/// /////; 5;･ ;'I̲‑'2K*

Tokushima City

2a
Koma t s u j 1 ma

City

Figure I Main habitats of Gambusia affinis in Tokushima City. Place numbers are thesame as shown in Figure 2 and Table 3.
: ¥¥¥¥: River and sea.

:S i; : Breeding places of Gambusia affinis in Oct., 1973.

Pond, Tokushima Castle Park (Settling was confirmed in Aug., 1969) .
2. Fallow rice field. Hachiman‑Cho (Settling was confirmed in Aug., 1969).
3. Swamp, Kita‑Okinosu (Settling was confirmed in Aug., 1970) .

Swamp, Yamashiro‑Cho (Settling was confirmed in Aug., 1971) .
5. Agricultural conduit, Kanazawa‑Shinden (Settling was confirmed in Aug., 1971) .
6. Agricultural conduit, Yamashiro‑Cho (Settling was confirmed in Aug., 1971) .
7
Swamp, Tsuda‑Cho (Settling was confirmed in Oct., 1971) .
8. Maot, Tokushima Castle Park (Settling was confirmed in Oct., 1971) .
9. Agricultural conduit, Kawauchi‑Cho (Settling was confirmed in May, 1973) .

162

Table l Establishment of Gambusia affinis during five years

Year

1969*

1970*

1971*

1972

1973

6

63

73

132

74

Ponds & moats

3

3

3

3

3

Agricultural conduits & sewers

2

2

16

49

67

No. of places where
Gambusia were released

No. of places where Gambusia
were found breeding

Fallow rice fields

8

4

Swamps

o

Total

6

7

13

20

26

36

79

l04

* : Cited from Sato et al. (1972).

Table 2 Influence of the release of Gambusia affin is on mosquito larvae andOryzias latipes in 1969‑1973

No. of places
mosquito larvae

Gambusia

Ponds & moats
Agricultural conduits

Oryzias l arvae

settledexisted*disappeared"

existed'

3

OO

mosquito larvae &disappeared"

Oryzias existed'

3

1

O

67

47

33

67

44

3

Fallow rice fields

8

8

7

8

5

3

Swamps

26

21

21

26

O

21

Total

104

76

61

l04

50

27

& sewers* * : After releasing.
* : Before releasing.,
Data in 1969‑1971 were cited from Sato et al. (1972).

Table 3 Water quality of the main habitats of Gambusia affinis from October 1970 to October 1973

pH

Temp ('O

Place

l . Pond(Tokushima Castle Park)2 . Fallow rice field(Hachiman‑Cho)

Transparency(mg/1)

18.3 22.5 28.8 6.8

6.9

7.2 20.0 25.7 28,0 8,24 8.80 9 . 35

l,210

18 .8 23 . 8

6. 2

6. 7

7.0

7.0

9,8 15 . O 2 . 33 3. 45 5 , 19

10 . 84.0

9.8 15 . 5 2.5

33 . 718 . 9 24 . O 34 . o

7.

7

4 . Swamp (Yamashiro‑Cho)

18 . 3 24 .

28 . 7

5. 6

6. 5

20 . o 26 . 3 30 . o

6. 8

6

18 . 5 22 . l 29 . O

6.8

7. 8

l0.0

5 .2 ll.7

18 . O

7 . Swamp (Tsuda‑Cho)

18 . 3 22 . 3 26 . 8

6.2

6. 7

7.4

8 .5

21.0

8 . Maot(Tokushima Castle Park)

20 . 5 25 . O 29 . 7

5.8

6. 5

6.8 20.9 28 . O 30 <(Kanazawa‑Shinden)
6 . Agricultural conduit(Yamashiro‑Cho)

9 . Agricultural conduit(Kawauchi‑Cho)Cl'

Min. Ave . Max. Min. Ave. Max. Min. Ave. Max. Min. Ave. Max.

3 . Swamp (Kita‑Okinosu)
5 . Agricultural conduit

DO (O, mgll)

18.7 23.8 30. l 6.2 7,0Procambarus

Procambaws

4. 31 7, 14 14 800 ' Mugil

7. 2 26 . O 28 . 6 30 < 3 . 98 5. 91 8. 49 15

8.2 12 . O 20 . 2 28 . O 5 . 64 7. 9

14 . 1Other fishes

200

9.71 14 500 *200

Carassius

78 3. 36 5. 92 1, 430

Cgtussius

3. 14 5. 98 8. 32 14

8. 88 9. 56 10 . 9016

7.6 12.5 21.2 30 < 2 . 18 6 . 08 9.51

700

1 , 410* C:arassius

Measurement or observation was made 7‑lO times, except for no 3‑7 times and Cl' once.
Place numbers are the same as in Fig. 1 ., Cl' data with* marked were cited from Sato et al. ( 1972) .

l 63

the start of the release program. Of the six places where Gambusia were first released in 1969,

they became established in all the places (Table 1) . Young Gambusia were observed alreadyin May 1969, and they developed to maturity between July and October of the same year.
Some full grown fish were collected and released again in 63 places in the following year,
1970. The results of investigations conducted between May and October 1970 showed thatthey settled in 7 places, only one more than in the previous year. In the same year, the third
release of fish was made at 73 places, and by 1971, Gambusia had settled in 36 places. Release
were continued in the same way; the fourth in 1971 and the fifth in 1972. As a result, Gambusia
became established in 79 and 104 places in 1972 and in 1973, respectively. In October 1973 they

were found at many places in the delta zone near the central part of Tokushima City. By thistime, they were so widely distributed that it was difficult to count the number of places inwhich they were living.
After the start of Gambusia breeding, mosquito larvae disappeared in 61 out of 76 places(80.3% ) . In 27 out of 61 places, Oryzias and mosquito larvae co‑existed at first. In all of theseplaces, where Gambusia were established, mosquito larvae disappeared (Table 2). Other
places where mosquito larvae continued to develop after the establishment of Gambusia wereusually agricultural conduits and sewers. In the former water areas, Oryzias, the motsugo(Pseudorasbora parva) , the crucian carp (Carassius carassius buergeri) , etc., were present, sothat Gambusia were unable to densely populate the area; or, in other places, Iuxuriant growthof duckweed, etc. protected the mosquito larvae from predation. In the latter, mosquito
larvae were often found living amongst drifting material such as rubbish.
Table 3 shows the quality of water regularly examined in the main habitats of Gambusia.

These water areas share the characteristics of a weak current, an infiow of household wateror brackish water, and eutrophy.
2 . Changes in distribution of Gambusia affinis and Oryzias latipes

The changes in distribution of Oryzias in 9 main water areas, where Gambusia settled(1969‑1973) , are shown in Figure 2. Places No. 1, and 2, chosen as the first release areas for

multiplication, were water areas originally inhabited by Oryzias, but by August 1969,
Gambusia bred sufficiently to allow collection of the fish for the second release.

Gambusia quickly increased in number in most places, but the increase was delayed when
the density of Oryzias was high (places No. 7 and 9) . In place No. 8, Gambusia lived for only
two seasons, and at the time of concluding this research in October 1973, they could no longer

be found there. The reason for this failure was thought to be the unsuitable quality of thewater for breeding. As a consequence of the establishment of Gambusia. Oryzias werereduced in distribution.

3 . Population density and body length of Gambusia affinis and Oryzias latipes1 ) Population density:
Table 4 shows the population densities of Gambusia affinis and Oryzias latipes at a swamp

in Kita‑Okinosu. The densities differed according to whether the method of measurement

was the mark‑and‑release method or the scooping method. The estimated density of
Gambusia per I m' was 377 by the former method and 76 by the latter in April, 504 and ll3
in July, and 488 and 1,018 in September. Likewise, in the case of Oryzias, the figure was 2 by

the mark‑and‑release method and 23 by the scooping method in April, 5 and 29 in July, while

in September only one fish was counted using the former method. The reason for thisdiscrepancy in densities determined by the two method was not clear, but it is certain that the164b:dlb :s/gfyZl :S%lOO 70 30

O 30 70 100%adlb (sl%100 70 30

No.

N* .

1 . 1969 Aug. Z16

54******** **Oct. Z72 ********* *1970 ay 288 ********* *:: i********* ***********
lg71 Apr. 971 **********
Aug. 174 **********
Sep. 225 *;r********
1972 Apr. 531 **********
Jul. 763 **********
Sep. 191 **********
1973
j ********************
Oct: 152 **********A IZ3

2 . Igcg Oc : 255

l970

yAo ･ 4430fi

29

28

lO1

****** ************ ********** ***************1c***** *1971 Apr. 143 **********

24
28
3

O

18
3

O
2
O
O

6g

45
97
8
32
3

AO :137
173 ********************

O

Jul. 25 **********

O
O

3

1972 Apr. 202 **********

3

Sep. I17 **********
rec laiLed

3 . 1970 MAay 25g

No.
OO
1971 AAPr.

5 . Ig70 Aug.

*********+********** 171135**** ******
O . 82
177
1294 ***** *** *659
1972 Apr. 404**** ******Ju I . 833
84********* *Sep . 858 ********* *
75
Nla
A.
126
1501
lg73
********* *lg840**********
O . 1394 **********
28
6 . 1970 {.
O** *** **+O**********+
O
1971 AA Pr.
********** 35G
ll6****** ****
Oc : 1 64
453
Z21*** *******
373
lg7Z Apr. 14G*** *******
Jul . 395 ********* *35,:1 O 5
Sep. 482******** **34
lg73 a'A. 303 ********* *44
50g ********* *O . 44725*** ** ** *7 . 1970 i;.
O**********+O**********+
O
1971 AAP I .
********** 269
O877**********
O . 108244*** *******
115
1972 A pr. 10g***** *****
Jul .
54
89
****** ****
Sep. 9245******* *************+
lOl******* ***rec lailed
116******** **l971 Apr. 2324 ********* *229 8. 1970 Aug. Oo
Ju I . 2851 **********
O
1971 Apr: O
1･ 85**********
Ol972**********^ug .1G81 **********
41972 Apr. O
Oct. 1844 **********
O
Jul. 172
1973 ay 2g48 **********
Sep. 8Olg73 MAayoA : 1734
182g **********O**********
Oc : BO : 583** F*******

uay O**********+**********
Oct.
O1971 Apr. O********** 488
8***** *****O
z3g
A :247***** *****
1972 Apr. 355
Z62****** ****
34
Jul. 647 **********
g5
Sep. 545 ********* *691973 Ma'Ao : {{1838******** **47******** **g**********%100 70 30

O
9 1970+ . 1971 ;. O

O 30 70 100,f

AAPr. OOc : 8l972 Apr.

Jul. *
Sep. Olg73 Vaj!Aoc : 3 42g

+

ZO
47
* **It*,t**** 13G********** 68* ********* 10g********** 95********** 70********************. 9

4 . Ig70

gfyll :S
O 30, 70 100 .

******** * l91
24** *********** ***+**********+
318******************It* 204********** 411********** 5G5********** 432********** 237********** 471334** ********
177******* ***%100 70 ･ 30

O 30 70 100%

Figure 2 The changes in distribution of Gambusia affinis and Oryzias latipes in the main
water areas where released Gambusia affinis settled, Place number are the sameas in Figure 1.

One * shows 10%.
No.

Number of fish, four‑arm scoop‑net or dipnet was used five times at each site.
Oryziaslatipes were captured but the number was not counted.
+
Pond. Tokushima Castle Park (Releasing was in Apr., 1969).
2. Fallow rice field, Hachiman‑Cho (Releasing was in May, 1969) .
3. Swamp, Kita‑Okinosu (Releasing was in May, 1970) .
5.
6.
7.
8.
9.

Swamp, Yamashiro‑Cho (Releasing was in May, 1970) .
Agricultual conduit, Kanazawa‑Shinden (Releasing was in Aug., 1970).
Agricultual conduit, Yamashiro‑Cho (Releasing was in May, 1970).
Swamp, Tsuda‑Cho (Releasing was in May, 1970).
Moat, Tokushima Castle Park (Releasing was in Aug., 1969) .
Agricultual conduit, Kawauchi‑Cho (Releasing was in May, 1970).

165︵N＋﹄︶国︵H＋﹄︶＼︵γQ︶︵H＋Q︶を目︵乞︶＞蕎＋﹄︶を︵H＋Q︶H乞．扇コの窪8慧3︒b︒g馨︒一喜︑H．︒壽曇馨一の窪與こ一．℃①﹄琶§ヒΦρ§き￡も壽．宿邑8差舅き￡Q︑扇更︒も魯℃Φ養g﹄㊤程ヨ︒ε趣
出田2琴︑㌦＼︵セQごを︵Z︶＞℃需ミ出Q Z盈℃①お盲葱田婁︑︵乞︶＞．8需唱孚殺℃壽︑Z︑おρ目ヲ三﹇εoさεづo曇︒988距も濤﹄詩昌㊤曇g︻︽︽︵︵§宅二︒q︒8の︑︒︒N．冒︑︒︒H．ヒ＜︶℃︒届gb︒三α︒8の︵N卜①一εON．α①の︑卜N．弓h︑ト一．一q＜︶℃o

苗gbo肩図﹄oΣ碁o雪 bo郭のo＞三︸08㊦口︵9寸H調りbO唱￡︑9﹇O．N阻一屈き．9﹁ト．O〜Ooつ．O 蝉qΦ℃﹄＄鯉5︶コのOε函OI而一︸出一〇〇9田3の 目O唱邸OO一の㊤目唱ゆ℃888．oZ罵ぢ一蓄菅
8目悪お＞刑一菅

：O

：O

：O

O．Ooっ

マ．oo一〇︑一

卜．〇一料

頃．O曽刑

O．話O

マ︐旨oっ

㎝㎡誘制

O．oり自劇oo．

〇．爲O︑8制 ㎝．一3制

O．頃制

卜．自制

OOoo．マ制

O．O園．雪制：Oき．oo

馨きO．一

：8一

響＆OO㎡

O．N胡．︒〇一

N．一一一．①

O．NOO︑一﹃めお．︒oN寸．翰〇一刑一．oooo寸の．卜oo︒o︑N制①．OOO．︒oH

ooo

H−o

一HO

︸．コ

N．oりOマ寸．OOqD

N．め〇一制O．卜爲嗣qo．

畔．oロH制
頃．oっO

O．寸お

瞬Qo制
O︐まoっ

制

頃︑︒oむ．N

①扁

Oま

漏

oっマ

oooっゆ

嵩g一﹄呂む窃g＆ゆ．︒うト的．N制神．︒08．自

曾
辱〇
一濡

ま一

鴛奮きのε．o乞冤o↑℃Φ﹄琶邸8﹄．o渚冨﹄ヨα8．oZ℃ω器㊤一〇﹄南℃①老邸∈．oZ

おコ∈28の

oo．

Qo
㎝

頃制

珂コ

卜．辱料

㎝．筥制

O㎡自

寸．霧

一．〇一刑

寸．劇っ一制oo．

Ooっ

マ．NOoo国．♂OO．呂一．︒oN︐oQO寸㎝︐曽の刑O．ウQ寺制O．①トN．一制

マ．NO一制Oマ

O蛉マ制寸．〇一〇っ．一

ト．マ制
①．寸

一曽制

O︐需一

N

暮︸コ

：貸

：N守

：き一

：めOめ

爲

O．ooN制O．qo卜O料

一．N

O．O卜

H．一制

N．萬制

一．N刊

：蒜㎝

：寸雪

自

㎝︐N制
oっ．

N

oo．
oo．

oっ．

O．頃

頃．e 制

O．N

O．貸

O．の〇

O．ooO刑

マ．NO刑

一
〇っ一

頃

H
N一

〇

O．〇一寸．卜㎝︐8一．コゆ．O匙

O．O蕊︑一制

一．一一〇．N制

卜．Qo爲

O．苫N

O．のOの

の．等制

の．H卜刑

頃．トN制

。っ．

五昌o霧三．o乞雪o↑・9

卜．oo一制

頃．8刑

H綿

錺卜

トトO

①︒o①．H需

oっOH

蕊ヨ一﹄呂む窃8∩
刊

昭︑0

。っ

℃霊三88﹄．oZ︑℃o﹄琶8．oZ

NON︑一℃￠詔o︻g剣〇鵠

冨溜詩日．oZ
卦コh

oり．

卜制

φり．

で刑

︒O．的制

り．守oっ

O．QoOoっO．O譜

O．マσo刑

マ．O国制

寸．マ〇一制

N．田

O．自

㎝．qっN

oう，

ON制

㎝．O卜

、∞．

O舘制

o︻鳴琿oho罵Σ婁一〇Qoり言一〇：3O．ooooH．N

蛉制

qo

oo．
qo．

O雪

oo．

旨O．H

oっ，

OO

卜

：O目

ーO

馨oo偶

：ひっ頃oっ

oQm

自

一80↑

膏国

︻90↑

㊤憲Σ

マ︐O制
卜．O
oっ．

〇一制

O．O〜
φり

雲
寸

o罵Σ

︻εo↑

㊤罵日o亀

心§嶋§δ

婁N蟄Q

卜．O料
寸．一

oり， 〇っ．

一制

きφっ

寸．8頃．〇一OマN．寸め︒o︑一制

oo

マ

一〇

oっ国

卜

等制

錺

刑

OHqっ．一刑

五塁島三．o客一80↑㎝oo卜．卜

卜N
一NO

〇〇n．一

嵩目一一8智の8∩

良N

︸．OO

O．oっoo卜︑N

扁一

一〇マ

忠旨琶8田．oZ

專O
OooN

ω罵Σ

罵りo↑

o罵昌Φ国

穏N§Q

団百ロooお

oo．

φっ

oo．

00Q
｝縛

濡

昭﹄召9⇔．oZ
瑠詔Φ一雲南℃o受吋g．o客
一唱α＜
國oの

o罵目o山

超oaの

心讐嶋ミ錯QΦ詔〇一ω﹄−℃口

℃o

湿旨︼≧

一〇Σ

℃o￡①εboqaoo81壽℃o曇①ε88一田−℃爵山おξ盈密駕員奮り尽§§暴O℃壽馨§書§ミδも超り甥8℃8慧︻邑￡寸㊤一慧↑1 66

densities were quite high at peak season.
2 ) Body length:

In spring, body length of Gambusia females were larger than those of males, indicatingthat they were fully matured. As shown in Figure 3, Gambusia males in April w:ere small, but

the majority were considered to have survived the winter, because immature Gambusia were
not found in this season. By July, presumably most of the old fish had died, and a number of
immature fish had emerged, because the average size was small and a similar distribution inbody size was seen in both sexs. In September, the body size became larger than in July, andimmature Gambusia were also observed. The results of observations mentioned above seemto indicate that the generation turnover occurs mostly in one year in the field, though the%40

Cafflb l! s j a (18th Apr. )

A

lJ"t'
JP
.,f
1'F

20

.,d" ¥ ,
lb

o
U

40

,,, .

20 24 28

16

32

e:

:
er

c

"I ‑ ‑J･,,.

20

l

d'

Jb

q,

40

36

44

48

52

Ca 7b l! s j a (28thJul. )

32

48

56,,'1･ .
1'1',,o40

16 20 24 28
,

40

44

52

56

Cah7b a s j a(2lth Sep. )J',,,,, ,, ,,

20

36

t

d,

¥

d

o

,,,,

,

36 40
16 20 24 Body 32
length in
28

%
40

48

52

s6

Oryz j a s (18th Apr. )

,
,

20

44

mm

c,

'!'

c:

o

‑ Jr

? 40 16 20 24 28
:

32

36

40

44

48

Oryl j a s (28th Jul. )

L

20

r

,

o

l ..l

,

. ‑,,

,

l

32 36 40
16 20 24
Body28l ength n mm

44

48

Figure 3 Distribution of body length in Gambusia affinis and Oryzias latipes.
dotted lines indicate females and males, respectively.

Solid and

167

average life span is 2‑3 years in the laboratory.

In the case of Oryzias, immature fish were absent and the body length of males andfemales were similar to each other in April and July. In September, no specimens could becaught. From these observations, the life cycle could not be clearly understood from thefrequency distribution of body length, though it may be similar to that of Gambusia.
4 . Feeding habits
Table 5 shows the results of the stomach contents that were studied from the specimensof Gambusia and Oryzias collected from a swamp in Kita‑Okinosu (on August 24 in 1972) anda fallow rice field in Showa‑Cho (on July 21 in 1973) . The characteristic result showed that

Gambusia fed on Asplanchnidae, Euplotidae, adult Chironomidae and wing of Coleoptera,
whereas Oryzias fed on pollen with anther and vegetable fibers in the swamp. In the fallow
Table 5 Stomach contents of Gambusia affinis and Oryzias la ti pes in the main habitats(1) Kita‑Okinosu

Contents

Cyanophyceae
Diatomeae

Gambusia
Oscil latoriar

Na vicu la++llNitzschiallOthersChlorophyceae

Scened esmus

Protozoa
Trochelminthes

Eud orina

As planchnidae

Asplanchna

Daphniidae

Moina

Centro pagidae

Sinocalcnus

Euplotidae
Culicidae

+

r

r

r

+
+

r
r

r
r

r

r

r

+

+

+

r

r

++

++

r

Stylo n ych iarCulex pipiensr(adult)r+r

Othersr

Chironomidae (larvae)r(adult)rll++Trichocerca

Othersll(2) Showa‑Cho
OryziasGambusiar

Othersl''l+

Oryziasr

FormicidaerOdonata (leg of larva)rColeoptera (wing)r

Le pidoptera (scales)
scale of fishrrr

larvae of shellfishrpollen with anthervegetable fibers(1) : Swamp, collected Aug. 24, 1972.
(2) : Fallow rice field, collected Jul. 21, 1973.

In each place, 5 fish were dissected respectively.

r: I‑3.,+ 4‑lO., ++: Il<.

+

r

168

44

A

40
:, 36
4J

1, 32

B

e¥

¥

> 28

Cagb as ja

¥
'b

e

f ¥

e¥

‑ 24

e¥

/ ¥¥

; /

l

¥‑
e

4J

,* 20

e

,,

'b

e,b

:r

n 16

es

'b

'b

C

1lb

12

z 8

,

aryl ja s

D
O

,,,

4

Itt

l‑ Ol' ..O･‑Ib
‑ ‑･O
Ol"I'
.‑.1'‑ O･‑ l. .. 1'1 '‑O

O

o

5

2

6

Days
Figure 4 Changes in mean number of mosquito larvae eaten by one
pair of Gambusia affinis and Oryzias latipes.
A, C (Solid line): Solid synthetic food was not given.
B, D (Dotted line) : Solid synthetic food was given.

l

J:
'

a

1

h

;5
'

:
:
,e
o,

h e
a,

e

c:

o

o

50
C:a busja i n %lOOFigure 5 Relationship between the time in days until all Oryzias
latipes were killed and the ratio of Gambusia affinis to allfish in %, when the two fish species were kept together in
a 2,500 ml plastic container.

169℃㊤＝ロαコの︸oの﹄㊤ρgコZ一＼g①一〇㊤︸oの﹄㊤ρ§Z

oo

①＼一

O＼︒

O

oo＼O

①＼O

OH

︒o＼マ

O＼O

ミN

O＼O

N＼N

O＼O

︒一＼︒

︒〇一＼OO︒H＼O︒一＼︒

OO一＼N︒う

〇一＼︒

OO一＼コ

〇一＼︒

OH＼一

OO一＼HN

O一＼︒①＼O

OOH＼︒うH

OH＼O

①＼︒

︾＆房

︒一＼O

〇＼O

℃呂αεの

︒H＼H

のoo出コ房o目

題でき曙

〇一＼O

廼恥9曽o氏愚N旭9恥oqO一

︒︒＼︒っ

ミ一
〇＼N

︒H＼寸
︒H＼O

O一＼O
O一＼O

愚︑でミq
心〜遷嚇oqO一

〇一＼︒H

O︒一＼き
︒︒一＼苺
OO一＼︒OH

の8唱呂89

ミト

卜

O
の

寸
ぴり

︒︒H＼N︒o〇一＼︒

︒︒H＼︒︒一

︒一＼︒っ

も叶H

も﹄罵OH

書§心ミδ

§蛍§O

窯心ミδ︸o叶H

Q℃q帽心寒心ミδ﹄ρ㊤に＞﹄邸一〇信コσωog℃目帽層︑●e魎oqbogコo＞︸ooo雪邸℃㊤﹄山

§蛍褻

H＼一
︒一＼O

唱噂・遷軸oqOH

書騒㎞9嚇oqO一愚︑塙9嚇oqOH℃oo︸℃＝oのb心NO．O℃oo︸℃＝oωboNO．O§蚊§Q︸oの﹄oごロφのoo謡5房o鋸

o邸ヒoご一〇嵩コσのo門口OOHo￠ヒ≦ 〇溜コ房oヨOO一〇吋＞旨邸一〇嵩5房o∈OOH℃oo︸℃＝oのbのNO．O

遼㎞9嚇o氏〇一

電︵一〇﹄一goo︶O瞬寸心ミ隈︾︸o当邸αH

N

OQ

ぶ軸

き胡醤

N
一

の濤O

の＝o男州℃唱oQ

調の笛﹄o自一邸一goO

一

魅

心、題ミ

気

愚、遷働

母

心園でミ

曙

唱

自 目
O㊤一ρ而﹄い170

rice field, Gambusia fed on adult Culicidae, Formicidae scales of Lepidoptera and larvae ofshellfish, and Oryzias fed on larvae of shellfish and vegetable fibers. Although both species areapparently euryphagous, Gambusia seemed to prefer more animal content in its diet.
5 . Observations of Gambusia affinis and Oryzias latipes preying on mosquito larvae andother fish

1 ) Preying on mosquito larvae:
As shown in Figure 4, Gambusia ate more mosquito larvae than Oryzias. For Oryzias, thenumber of mosquito larvae eaten was smaller when solid food was provided, but for
Gambusia there was no significant change in diet. Both species of fish ate many mosquito
larvae on the first and second days. This is because food supplies were stopped for three days

before the experiment. It was concluded that Gambusia normally eats many more mosquito
larvae than Oryzias, whether or not other food is supplemented.
2 ) Predation on young Poecilia and mosquito larvae:
As shown in Table 6, Gambusia in container No. I ate 82 mosquito larvae and 9 young
Poecilia on the first day. On the second day, they ate all of the mosquito larvae and one
remaining Poecilia. Gambusia in container No. 2 did not eat Poecilia at all on the first day,but consumed all the mosquito larvae. The fish in container No. 3 ate all of the young Poeciliaon the first day.

On the other hand, Oryzias in container No. 5 ate 60 mosquito larvae on the first day, but

did not consume much after that. However, on the eighth day, 2 days after we stopped giving
them mosquito larvae and solid food, they began to attack young Poecilia, and by the twelfth
day consumed all of them. Fish in container No. 4 ate 4 young Poecilia on the fourth day, 2
on the fifth day, I on the sixth day, and the remaining 3 on the seventh day.

The results show that Gambusia prey on young Poetilia even when solid food andmosquito larvae are present, but Oryzias do not prey on young Poecilia if they have other food.

Thus, Gambusia feed on mosquito larvae and young Poecilia more than Oryzias.
3 ) Competition for survival between two fishes in a small space:
As shown in Figure 5, Oryzias were attacked and eaten by Gambusia, and all of theformer died by the tenth day, even when the ratio of Gambusia to Oryzias was 1:9. The
relation between the time, in days, until all Oryzias were killed ( Y) and the ratio of Gambusia

to all fish in % (X) was linear and expressed by the regression line Y = ‑0.08X+9.4444(correlation coefficient r= ‑ 0.9115) . Thus it was shown that in the situation of this experi‑ment. Gambusia is clearly more aggressive than Oryzias.

DrscussroN
Gambusia affinis transferred to Tokushima City established and bred within a year, andtheir distribution spread naturally over wide areas within 5 years. However, when Gambusia
were released into environments in which other fish such as Oryzias. Carassius and Pseudoras‑bora were abundant, Gambusia sometimes could not easily establish nor breed. This isthought to be due to the small number of Gambusia used for releases. However, Gambusia
finally became most abundant in every kind of water areas.
According to the author's observation, when Gambusia affinis and Poecilia reticulata werereleased together into the water area where Oryzias latipes were already present and house‑
hold waste water fiowed in, Poecilia separately lived in places nearest to household waste

171

water escape, Oryzias lived nearest to swamps and irrigated fields and Gambusia lived in the

middle. Thus, the Gambusia is better able to adapt to still water areas in eutrophy. In
addition, Gambusia is more aggressive than Oryzias. This is the reason why they were able
to settle the delta zone of Tokushima City within a: short period. A water area, No. 8 (moat) ,in which they did not establish, had a rather strong current, and thus was an unsuitableenvironment for Gambusia.
Gambusia raised in the laboratory usually live for 2 or 3 years, but the generation isthought to change yearly in the environment in Tokushima City. In July, Iarge Gambusia
disappeared, and small fish, including immature ones, increased. In September, the numberof young and large Gambusia increased and the body length became variable, but a few
specimens were as big as those observed in April. This seasonal change of population
composition seems to indicate that the life span in the field is about one year.

In the area where Gambusia and Oryzias were mixed, the density of Oryzias was high inthe spring, whereas in summer and autumn the number of Gambusia was large. Thistransition in the population density occurs because of different breeding seasons, Oryzias

breeding earlier. Sato et al. (1972) reported that Gambusia tend to maintain a higher
population density than Oryzias, and that the total population of the two species was about
300‑500 per I m2, whether they are separated or mixed in distribution. In the present study,
the density was similar, about 400‑500. When the density of Oryzias is already at this level,

it is more likely to take a long time for the introduced Gambusia to establish and become
abundant. Therefore, in such a situation, a large numb. er of Gambusia would need to bereleased to obtain successful establishment.

It was not unusual for mosquito larvae and Oryzias to co‑exist. However, mosquito
larvae could not live with Gambusia in the same water area, unless Gambusia access to larvae
was impared by rubbish, waterweeds, etc. (Sato et al., 1972). In the laboratory experiment,

Gambusia consumed a lot of mosquito larvae, but Oryzias did not actively feed on them nor
shbw aggressive activity to other fish such as Poecilia reticulata, if other nourishment, e.g.

solid food, was available. Gambusia, on the other hand, attacked and exterminated not only
Poecilia fry but also mature Oryzias when kept in a small space in the laboratory, whether or

not other food was available. The same phenomenon has often been observed in the field.
This characteristic is significant in terms of the ability to establish in the natural habitat ofOryzias in Tokushima City.
There are many reports on the feeding habits of viviparous poecillid fishes (Hess andTarzwell, 1942; Harrington and Harrington, 1961; Yamagishi, 1966; Yamagishi et al., 1966,
1967; Hubbs, 1971; Sholdt et al., 1972; Sawara, 1974), and generally Gambusia is said to be
euryphagous. The investigations show that Gambusia takes a wide variety of food in its
environment; e.g., aquatic insects including mosquitoes, Diatomeae Chlorophyceae and others
floating on the water surface. Those results were similar to the results reported by Sato etal. (1972).

As a result of this program of releasing Gambusia. Cx. tritaeniorhynchus larvae wereremakably reduced in swamps and fallow rice fields by the early 1970's, and Japanese
encephalitis was eradicated from Tokushima City. Since Gambusia can maintain its popula‑tion even though there are no mosquito larvae, it is clear that Gambusia is a good potential

agent for mosquito control. Gambusia is evidently a superior to Oryzias in competing for
habitat under usual circumstances in the field. If we can keep such situations as in Kita‑

172

Okinosu, where Gambusia spread quickly from their bteeding places to swampy areas,
obtaining high densities (Sato et al., 1972) , the scope for mosquito control that does not rely

on insecticides would be broadened.

ACKNOWLEDGEMEN Ts
I would like to express my most grateful thanks to Professor T. Kanda of St. Marianna
University School of Medicine, who has constantly advised me and made valuable sugges‑

tions towards this research. I am also indebted to Professor H. Yamagishi of Teikyo
University, who assisted me greatly with the ecological methods of investigation, to Professor

Y. Wada of Institute of Tropical Medicine, Nagasaki University, for critical reading of themanuscript and useful suggestions, to professor B. Hammerberg of University of North
Carolina for editorial correction of the manuscript, and to Dr. M. Sasa, Emeritus Professorof The University of Tokyo and Dr. S. Okubo, President of Tokushima City Medical
Association, who provided me the opportunity and facilities of studing the Gambusia in

Tokushima City.

REFERENCESl ) Gerberich, J.B. and Laird, M. (1966): An annotated bibliography of papers relating to thecontrol of mosquitoes by the use of fish (Revised and enlarged to 1965) , WHO/EBL/66, 71(Mimeographed, pp. 107)2 ) Harrington, R.W. Jr. and Harrington, E.S. (1961) : Food selection among fishes invading a highsubtropical salt marsh: from onset of flooding through the progress of a mosquito brood,
Ecology, 42, 646‑666
3 ) Hess, A.D. and Tarzwell, C.M. (1942): The feeding habits of Gambusia affinis affinis, withspecial reference to the malaria mosquito, Anopheles quadrimaculatus, Amer. J. Hyg., 35, 142‑151

4 ) Hirose, Y., Okubo, S. and Yasuno, M. (1978): The effect of mosquito control by the use of themosquito fish, Gambusia affinis, in urban area, Tokushima, Japan, Jap. J. Sanit. Zool., 29 (2),163‑1685 ) Hubbs, C. (1971): Competition and isolation mechanisms in the Gambusia affinis, X G.
heterochir hybrid swarm, Bull. Tex. Mem. Mus., 19, 1‑466 ) Nakamura, M. (1941): Breeding of topminnow, Collecting and Breeding, 16, 186‑187 (InJa panese)7 ) Okada, Y. (1957): Fishes (mosquito eating fishes) of natural enemy for the mosquito larvaeof a vector of malaria, especially on the topminnow, Kankyo Eisei, 4 (10) , 613 (In Japanese)8 ) Sasa, M. (1972): Observations on some American poeciliid fish established in polluted watersin Japan and South Asia, with special reference to their use in the control of filaria vectors.

Research in Filariasis and Schistosomiasis, Univ. Tokyo Press, 2, 67‑86
9 ) Sato. H., Okubo, S., Sasa, M.. Wada. Y., Motoki, M., Tanaka, H., Yamagishi, H., Okino, T. andKurihara, T. (1972) : Observation on Gambusia affinis introduced into Tokushima as a natural
enemy of mosquitoes, Jap. J. Sanit. Zool., 23 (2), 113‑127
10) Sawara, Y. (1974) : Reproduction of the mosquito fish (Gambusia affinis affinis) a freshwater
fish introduced into Japan, Jap. J. Ecol., 24 (2), 140‑146ll) Sholdt, L.L., Ehrhardt, D.A. and Michael, A.G. (1972): A guide to the use of the mosquito fish,

Gambusia affinis, for mosquito control. pp. 18, Navy Environmental and Preventive Medicine
Unit No. 2, Norfolk, Virginia

17312）Yamagishi，H．，Nakamura，Y．，Wada，Y．，Okino，T．and
studiesontheguppy，L6δゑs孟召s雇加観麗s，Peters

springs

in Japan，Jap．」．Sanit．Zool．，17（1），48−58

13）Yamagishi，H．（1966）：
Experiments

on predation

Ecologicalofstudiesmosquitoonlarvae bytheNakamoto，N．（1966）：Ecological

I．Acclimatizedguppy inthe waters ofguppy，Lの∫惚s履ゴo銘観銘s，Peters．

guppies，」．Facultyof

Science，Shinshu

hot

II．
Univ．，

1，79−92

14）Yamagishi，H．，Okino，T．，Nakamoto，N．，Nakamura，Y．andstudies

the

on

water

the

guppy，L召δゑsホ8s名罐o％観πs，Petersof Togura−Kamiyamada

III．Onthe

Wada，Y．（1967）：Ecological
guppy

population

acclimatizedin

Spa，Jap．J．Ecol．，17（5），206−213

カダヤシとメダカにおける脳炎媒介蚊の駆除，および両種の蚊幼虫捕食能と競争に関する生態学的研究
佐藤 英毅

1969年に徳島市に移殖されたカダヤシ（3α励％s毎顔眺の，蚊幼虫防除に果たす役割について調査した。繁殖地の池や溝で採集したカダヤシを，低湿地帯や下水溝に繰り返し放魚したところ，

翌1970年には7カ所，1971年には36カ所，1972年には76カ所，および1973年には104カ所の水域に定着した。これらのうち，かつてメダカと蚊幼虫が共存していた水域が27カ所あった。これにカダヤシが定着し，1973年迄には，それらの全ての水域から蚊幼虫が消失した。一方，これらの水域ではメダカの生息密度が低くなった。カダヤシの生息密度が高かったのは，止水域ないし家庭排水が流入して富栄養化の進行している水域であった。カダヤシとメダカの混生する水域では，両種の生息密度が1㎡当たり400−500尾の範囲にあり，メダカの生息密度が既にこの範囲にある水域にカダヤシを定着させるためには，多量に放す必要のあることが示唆された。室内試験の結果，カダヤシはメダカに比べて，蚊幼虫をよく捕食することが分かった。カダヤシとメダカを同一の容器で飼育した場合，カダヤシはメダカを攻撃し，駆逐してしまった。野生個体の胃内容物は類似し，両種とも広食性であるが，カダヤシの方が，より動物食性の傾向を示した。また，両種は空間および食物連鎖上の，競争種であることが示された。この研究では，蚊幼虫の防除にはメダカに比べてカダヤシの方が適していることが示された。ここで観察した水域では，カダヤシはメダカより生存競争上優位であり，その生息域を拡大している事が分かった。

聖マリアンナ医科大学病害動物学教室
現所属：川崎市衛生研究所

Japan. J. Trop. Med. Hyg., Vol. 17, No. 2, 1989, pp. 175‑183

175

A FIELD TEST OF 2‑[1‑METHYL‑2‑ (4‑PHENOXYPHENOXY) ETHOXY] PYRIDINEAGAINST PRlNCIPAL VECTORS OF MALARIAIN A FOOT‑HILL AREA IN THAILAND
VANIDA KERDPIBULE
Received December 14 1988/Accepted March 15 1989
Abstract: An insect growth regulator, S‑31183, 2‑ [1‑methyl‑2‑ (4‑phenoxyphenoxy)ethoxy] pyridine, was applied into 2 slow running streams to evaluate its efficacy against

malaria vectors from the beginning of February to the end of April 1987. The evaluationof the efiicacy was based on bioassay with the waters sampled from the streams and on
the parity of the mosquitoes collected from the study site. The application of S‑31183
induced almost 100% inhibition of emergence of Anopheles maculatus and An. minimus,
24 hr after application. The emergence was inhibited by averages of 80% in An. minimus
and 56.7% in An. maculatus, in the end of the 4th week. Likewise, the nulliparous rates
also decreased till the end of the 8th week.

INTRODUCTION
A number of efforts have been made to develop new compounds that are effective in themalaria vector control, due to insecticide resistance of the target insects and side effects tonon‑target organisms. Among these, attention is drawn to a new group of insecticide, theinsect growth regulator (IGR). They interfere with the development of immature stages,
resulting in prevention of both pupation and adult emergence. With respect to the develop‑
ment of resistance in insects against such chemicals, there were some reports indicating
resistance development (Cerf and Georghiou, 1972; Dyte, 1972) .
During the past decade, these synthetic IGRS have been studied extensively under labora‑
tory and field conditions against insects of public health importance. A number of IGRS havebeen evaluated against mosquito larvae and proved to be quite effective to inhibit emergence(Jacob and Schoof, 1971, 1972; Schaefer and Wilder, 1972; Mulla et al., 1974). Methoprene
and difiubenzuron have been cleared for use in mosquito control program (Estrada and Mulla,1986) . Laboratory as well as field studies of methoprene demonstrated the promising controlof many species of mosquitoes (Schaefer and Wilder, 1972; Hsieh and Steelman, 1974;
Rathburn and Boike, 1975; Dame et al., 1976; Ikemoto et al., 1986; Ishii et al., 1986; Sjogren

Department of Medical Zoology, St. Marianna University School of Medicine, 2‑16‑1 Sugao,
Miyamae‑ku, Kawasaki 213, Japan.
Present Address: Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol
University, 420/6 Rajvithi Road, Bangkok 10400, Thailand.
* This study was funded in part by Grant‑in‑Aid for the Overseas Scientific Survey (No. 61041079)

and by the Grant‑in‑Aid for Experimental Development Research (No. 61879110) from the
Ministry of Education, Science and Culture, Japan. This study was performed by a fund for the
fellowship for Dissertation Ph.D. from the Japan Society for the Promotion of Sciences (JSPS)

under the guidance by Professor Tozo Kanda, St. Marianna University School of Medicine,
Kawasaki. Japan.

176

et al., 1986 ) . Diflubenzuron also offered a good potential for the control of mosquitoes
breeding in diverse habitats (Mulla et al., 1974, 1975; Mulla and Darwazeh, 1975, 1976; El Safi

and Haridi, 1986) . Recently, other types of juvenoid including S‑31183 were introduced forevaluation against mosquitoes, Aedes aeg)pti. Anopheles quadrimaculatus and Cu,lex quin‑quefasciatus by Estrada and Mulla (1986) and Mulla et al. (1986) , and Cx. tarsalis. Ae.
melanimon and Ae. nigromaculis by Mulla et al. (1986) . Those field studies of S‑31183 were
mostly performed in ponds, pools, marshes or ditches with stagnant water. The evaluationin streams, which are breeding places of some important vectors of malaria in Thailand, has
not been performed. Malaria control by residual insecticide did not accomplish effective
results yet, though in addition to DDT residual spray, the larval control by both larvivorous

fish (Poecilia reticulata) and a larvicide (such as Temephos) have been applied into thesebreeding streams by the Thai Government (1985) .

In order to overcome the above mentioned problems the present study embarked toevaluate the activity in inhibition of emergence of the compound in slow running streams, thebreeding habitat of 2 principal anopheline vector species of malaria, Anopheles minimus andA,e. maculatus in Thailand. The assessment of activity of this compound and the develop‑
ment of application method will provide the useful informations on the control of mosquitoes
breeding in streams.

Ao

MATERIAL AND METHOD

A1

A2

Com pound

S‑31183, 2‑[1‑methyl‑2‑(4‑phenoxy‑
phenoxy)ethoxy]pyridine, 0.5 G formulation
provided by Sumitomo Chemical Co. Ltd. was( )Bo

STREAbd A
1

STREAM B

used in this study. In order to have an informa‑elgranule had been placed in 5 1 of deionized(water in a glass jar of 25 cm in diameter and 30

TEMPLEtion on the release rate of the IGR, 5 mg of the

*

2

A3

B, f

!

cm in height. It was kept at 25d:1'C for 24 hr.

All the granules were removed by a pipette tofilter paper in glass funnel then left at 25:!:1'C

Oovernight for drying. The dried granules werecollected by a small brush and weighed. By thismethod the lost weight of the compound wasproved to be 0.1 mg, which indicated thereleased compound within 24 hr in that con‑tainer.

Q:

Scale

l

I OQ m.

fdBjeFigure I Experimental streams for S‑31183
application (Wat tham pra poth‑isat, Tabkwang, Saraburi)

Preparation and Application of the Compound
A muslin cotton bag (20 X 15 cm) contain‑
ing the required amount of the compound was

O application point

fixed to the bottom of the stream at the applica‑

R check pointtion points, Ao and Bo (Fig. 1). The amount of

A*, A, and A==50, 120 and 530 m from A,
B*, B, and B* =50, 20 and 270 m from Bo

the compound to be applied was estimated asfollows: The widths of water surface (x) andC =station for mosquito collection@ = spring

177

bottom (y), depth (h) and velocity of the running water per second (v) were estimated inboth the streams (A and B) . Therefore, the discharge (a) of water per second was calculatedas,a= (x+y) hv/2
thus the amount (a) of the running water for 24 hr at A3 and B3 Were 213,840 and 446,680 l,

respectively. Because the formulation of the compound was 0.5%, 213.8 g was requiered in
A stream and 446.7 g in B as shown in Table 1, for a concentration of 5 ppb.
Insects

Female An. minimus and An. maculatus were collected from the study site. The
collection and maintenance method was the same as that one described by Kanda (1979).
The mosquito maintenance was carried out till larval stage of the progeny for bioassay study,in the insectarium of the Department of Medical Entomology, Faculty of Tropical Medicine,

Mahidol University.
Study Site
The field tests were conducted at a basin with 2 small streams in Tab‑Kwang District,

Saraburi Province, 130 km northeast of Bangkok, Thailand during February to April, 1987.
The streams were designated as A and B (Fig. 1). The total length of both streams wereapproximately I km in A, and 0.55 km in B. They originated from 2 springs in hills andflowed down near a hamlet of approximately 10 houses. An. minimus and An. maculatus
were found breeding in both the streams. These streams were mostly shaded by various
species of tropical trees and with some bushes along both banks. The water was clear andclean with sandy substrate and very few grass vegetations. The water level was fiuctuatedamong seasons, and the streams became dry up in late dry season at points about 15 m

downstream from A3 and B3.
In February, 1987 the water temperature was 25‑26'C with pH 7.0. The detailedhydrological data was presented in Table 1. Besides this basin we did not find any breedingsite of the vectors around the village C (Fig. 1) .

Assessment of Activity
Water was sampled for bioassay weekly in the first month after application and monthly
thereafter. The evaluation was also performed by the density of female mosquitoes and theirparity.

Parity Determination
Mosquito collections were performed by a cattle bait method in an orchard forest near
the stream, indicated as C in Figure l. Approximately 10 houses were scattered along theTable I Hydrological data and the amount of S‑31183 applied at the study site

Width (cm)Stream Surface Bottom

Depth (h)Velocity of running

Discharge ( a)Amount of(cm)

water (v) (cm/sec)( I /day)

S‑31183 (g) *

(x)

(y)

A (A*)

155

70

8

2. 75

213 840 ooO

213 . 8B (B,)

260

140

11

2. 35

446 680 oOo

446 . 7

A and B3*

Check points, see Fig. 1.
See the text.

178

streams where human bait collections were performed also. The collected An. minimus andAn. maculatus Were dissected to examine their ovariole relics following the method describedby Detinova (1962) .
Bioassa y

Two‑hundred and fifty milliliter of water sampled from the study site was put in an
enamel bowl with 10 cm diameter and 8 cm height. Twenty‑five of late 4th instar larvae wereintroduced to the bowls and fed daily with a small piece of artificial diet (Kanda, 1979). The
mortality was examined everyday for 6 days or till all the adults emerged. The efiicacy ofthe compound was expressed as per cent inhibition of emergence (%ED . Control tests werecairied out in deionized water by the same method. Two replications were at least conducted

for each water sample.

Confirmation of the Activity of the Compound in the Streams
Because the concentration of the chemical applied in the stream was not known, theactivity was tested by serial dilution of water sampled. In the bioassay, 250 ml of water was

sampled at 24 hr, 2 weeks and 4 weeks after application, and diluted with distilled water by

x 5, x lO, x20, x40, x80, and x 200. The larvae of An. maculatus were exposed to thesesolution by the same method described above. The similar tests were conducted with thecontrol solution (5 ppb) of S‑31183 which had been prepared and kept under laboratory
condition. The test was performed at the same intervals.

RESULTS
Bioassay of the Water 24 hr after the Application

The activity of the compound, S‑31183 was tested by bioassay method as follows:
Emergence inhibition rates were tested with the water collected from various check points at
24th hr after the application of the compound. The results indicated any significant difference

Table 2 Inhibition rates by the compound (S‑31183) of adult emergence of An. minimus
and An. maculatus in the 2 running streams 24 hr after application

Check points Distance fromapplication points (m)Inhibition rate of emergenceAn. minimus

An. maculatus

Stream A
Ao *

O

lOO

92 . O

Al

50

98 . 996 . 2

A2
A3
Stream B

120

95 . 996 . 3530

98 . O

100

O

100

Bo *

100

B1

50

98 . 9

lOO

B2

120

97 . O

96 . OB3

270

97 . 996 . 1

11.5

13.0

Control* : Application point. Control Deromzed water

179

Table 3 Inhibition rates by the compound (S‑31183) of adult emergence of An. minimus
in the 2 running streams

Stream B

Stream A

No. of weeks

A2

A3

14.2 (98)13.1 (99)lOO (l08)

97 . O ( 10D

100 (l02)

ControlBl

B2

14.7(lOl)

15.0(lOO)

14.2 (98)13.8(lOl)

lO . 2 (107)98.9 (95)

99 . O ( 103)98.9 (98)

88 . 5 ( 104)

12 . O ( 100)

86 . I (l08)91.1 (90)83.7 (92)87 . I (101)93 . O ( 100)

9 . 7 ( 103)lOO (99)

88 . O ( 100)

84.2 (95)45.9 (98)91.9 (99)70 . O ( 100)ll , I (l08)25 . 5 ( 102)32.0(lOO)

22.2 (99)20.2 (94)35.6 (90)22 . O ( 100)

10.5(l04)

after application

Al

o*

B3

2

3

8

( ) : Number of larvae tested * The water was sampled before the applrcation

Table 4 Inhibition rates by the compound (S‑31183) of adult emergence of An. maculatus
in the two running streams

Stream B

Stream A

No. of weeks
after application

A1o*

15 . 5 ( 103)13.9(lOl)

80.8(104)

80 . O ( 100)282.7 (98)87.2 (94)3

54 . 6 ( 110)

4

8

A3

Control

B3

Bl

B2

15.1 (99)

14 . 7 (lO1)

16 . O ( 100)

14 . O ( 100)lO . 7 ( 103)

96 . O ( 100)

78 . 5 ( 104)87.7 (98)

84 . 6 ( 104)11.2 (98)93.3 (90)97 . 7 ( 110)96.9 (99)82 . 2 ( 101)

19.4 (98)86.4(114)

71.1 (90)76 . 7 ( 107)82.1 (78)76.3 (76)18 . 3 ( 104)

60 . O ( 102)53.5 (99)65.2 (88)37 . 3 ( 102)54.2 (96)69.6 (92)

15 . 8 ( 10D

33 . 3 ( 108)

29 . 4 ( 102)

20 . O ( 105)

20.0(110)

20 . 6 ( 102)

23 . 3 ( 105)

10.3(l04)

A2( ) : Number of tested larvae. * The water was sampled before the applrcation

Table 5 Inhibition rates of adult emergence of An. maculatus exposed to vanously diluted
water sampled from one of check points, A3
Sampling time after application

Dilution

24 hr

xl
x5

96 . O(lOO)

93 . 395 . 2(84)

x 10

94 . 5x 20

93 , l

x 40

2w

4W

(92)

(90)

65 . 292 . 9

(98)

51.8

(81)

(91)

90 . 2(92)

51 . 4(72)(87)

87 . 6(89)

34 . 2(76)

88 . 4(95)

81 . 4(86)

34 . 7(69)

x 80

89 . O(82)

83 . 3(90)

35 . 4

(82)

x 200

84 . 5(96)

69 . 5(82)

Control

10 . 4(96)

12 . 8

(86)

9.5

(95)

Control: Tested in deionized water. ( ) Number of larvae tested

among those points. The rates were proved 92.0% for An. maculatus and 100% f o r An.
minimus at Ao (Table 2). Thus the water collected 24 hr after the application had highinhibitory effect on the adult emergence.

180

Bioassay of the Water Collected Weehly from the Study Site
Water from the applied streams was bioassayed weekly in the first month of application.
Though the inhibition of adult emergence of An. minimus decreased gradually at every checkpoint, more than 70% in,,hibition of emergence was retained in both streams till the end of the

4th week (T.able 3) . The inhibition rates were more than 20.0% for An. minimus and An.
maculatus still in the end of the 8th week as Tables 3 and 4 show.
Confirmation of the Activity of the Compound Diluted to the Stream Warter
In order to confirm the activity of the compound resolved in the water, the water sampled
at the check point A3 at various time periods after application was diluted 5 times ( x 5) , x

10, x 20, x 40, x 80, and X 200, and tested by bioassay method (Table 5) . The inhibition rateof An. maculatus in the water collected was 84.5% at x 200 24 hr after application, and83.3% at x 80, and 69.5% at x 200 in the end of the 2nd week. In the end of 4th weeks thediluted water at x 5 and x 10 demonstrated more than 50.0%, but at over x 20 of dilution therate was lower than 50% (Table 5). In order to reconfirm the activity of the test water, thesolutions of the compound by similar diluting times from the concentration of 5 ppb wereprepared and kept in the laboratory as the control of the applied stream water (Table 6).
Table 6 Mortality of larvae of An, maculatus exposed to variously diluted solution of 5 ppb
S‑31183 prepared in laboratory
Time after preparation

Conc.

Dilution

(ppb)

xl
x5

24 hr

2W

4W

(90)

(96)

lOO

lOO

(99)

100

(86)

94 . o

(98)

(100)

94 . 3

(87)
(81)

5.0

100

l.O

95 . 9

(98)

x lO

0.5

100

100

(91)

x 20

O . 2597 . 9(98)

97 . 8(81)

76 . 5x 40

O . 125

95 . 5(89)

94 . O(84)

56 . o(9D

x 80

O . 0625

91 . 5(82)

87 . 8(90)

53 , o

(83)

x 200

O . 02590 . O(90)

83 . 9(8D

40 . 5(84)

Control

10 . 4(96)

12 . 8

(86)

9.5

(95)

Control

Tested in deionized water.

()

Number of larvae tested.

Table 7 Nulliparous rates of the 2 vector species collected periodically on a cattle baitat the point C after applicationNo, ofweeks afterAn. minimus
Density/b/n

No, examin.

treatment

An. waculatus
Nulli p.

Density/b/n

No. examin. Nulliparous

rate (%)

Pre‑app.

174

54

36 . 3rate (%)
43

43

52 . 9

1

11

25

27.3

2

90

50

15 . 91228

33 . 3

7.9

19

35

14 . 3

3

101

50

4

45

45

9.1

8

22

40

10 . 5lO

25

25 , o12

1230

41 . 726

50

64 . O

Density/b/n: Mosquito density per I cattle per night.

181

The results showed stronger inhibition activity than in Table 5.
Even if the water in the streams increase, the inhibition activity might be retained up
to x 20 dilution.

Assessment by Parity of Females Collected by Bait
The parous rate of the vectors and their density were investigated to confirm the efiicacyof the compound. The results are shown in Table 7. Before the zipplication of the compoundthe nulliparous rate was 36.3% for An. minimus and 52.9% for An. maculatus. In An.
minimus, it gradually decreased after the application from 27.3% in the end of the Ist week

to 7.9% in the end of the 3rd week. The low parous rate combined till approximately the 8th

week. The rate, however, increased up to 41.7%, which was similar to the rate before theapplication, in the end of the 12th week. Also in An. maculatus, the nulliparous rate gradually

decreased and indicated the lowest of 14.3% in the end of the 3rd week, and it recovered tothe pre‑application level by the end of the 12th week.

DISCUSSION
The insect growth regulator was tested for the first time by the present study against
vectors breeding in running water. The compound used in this study was found very effective
even at extremely low concentrations. Iwanaga and Kanda (1988) reported that the LC50 of

this compound against An. balabacensis was 0.04 ppb in the laboratory. Therefore, theconcentration of 5 ppb was supposed to be enough to inhibit the emergence of the two species,

An. minimus and An. maculatus in this field application. The amount of the chemical applied

was expected to produce 5 ppb concentration, which was 100 times higher than the LC50
against An. balabacensis (Iwanaga and Kanda, 1988) . Amalraj et al. (1988) induced 100%
mortality with complete inhibition of emergence at I ppb of the compound on An. stephensi.

The concentration of 5 ppb was much lower than in the field application of Temephos
larvicide against An. minimus in Thailand, which was 0.5 ppm (Phatipongse, 1983) and 1.0
ppm (Malaria Division, 1985).
The compound was applied at the dosage of 213.8 g and 446.7 g into the stream A and B,
respectively. These amounts were derived from the water discharge in 24 hr at A3 and B3 ,and the formulation of the chemical (0.5% granule) . The dissolving velocity of the chemical
in stagnant water was 1/50 per 24 hr as estimated earlier. This suggests that 50 days would
be needed for complete dissolving. Therefore, the effective concentration of the chemical
could be estimated as 0.1 ppb and should last for 50 days. The present results for the
inhibition of adult emergence demonstrated the efficacy of about 70% till the end of 4th week

in the field application. This shortening of the duration in the treated water of the streams

was interpreted to be due to the loss of the compound by running water, and the fasterdissolving rate than in stagnant water. From subsequent observations, the inhibition rate of

the compound gradually decreased to 20‑35.6% in An. minimus and 23.3‑33.3% in An.
maculatus by the 8th week (Tables 3 and 4). If 70% inhibition of emergence was considered
as an effective control level (Ishii et al., 1987) , the effective duration of the compound was

4 weeks against the 2 vectors. The effectiveness of this compound in field tests was reported

by many authors. Mulla et al. (1986) obtained 85‑92% inhibition of emergence of Cx. tarsarisby 7 day after treatment with 0.005‑0.01 Ib/acre of S‑31183. Whereas Amairaj et al. (1988)

182

reported 100% inhibition of emergence of Cx. quinquefasciatus in cesspits for 7 days by thapplication of this compound at the dosage of 0.05 mg/1.

The larval control programme of malaria vectors in Thailand was cdnducted in someareas by releasing of larvivorous fish (Poecilia reticulata) and also by applicat'ion of I ppm ofTemephos. An effective control against An. minimus was obtained from the latter but
without residual effect (Annual Report, Malaria Division, 1985) . Phatipongse (1983) tried

0.5 ppm of Temephos in a stream to control An. minimus but did not study the residual
toxicity. The present study suggested that S‑31183 can be used as a larvicide in runningstreams, since it exhibited a prolong activity and was effective at lower dose. Moreover, the

IGRS are recommended for mosquito control because of little effects on non‑target organisms(Mulla et al., 1975). Additionally, most IGRS are known to have low mammalian toxicity
and relative safety to fish and wild life in the breeding place as reported by Mulla et al.
(1986) .

Referring to the present results, it was of interest to note that in rainy season the streams

were full up with water and continuously fiowing with somewhat higher speed. The applica‑tion of the compound might induce a different pattern in inhibition of emergence in dry
season. Even in the period when nulliparous rate was suppressed, the malaria transmission
could occur to a small extent by parous females. The effective control can probably beachieved if other adult control methods were integrated.

ACKNOWLEDGEMENTS
The present author wishes to thank the Japan Society for the Promotion of Science(JSPS) for the fellowship for dissertation Ph.D. under the project of the Government ofJapan. Gratitude to Professor Dr. Masamichi Fujii, President, St. Marianna University forthe acceptance and assistance for research in the university under the supervision byProfessor Dr. Tozo Kanda, Department of Medical Zoology, and Visiting Professor of theFaculty of Tropical Medicine, Mahidol University, Bangkok, Thailand is expressed. Thanks
are also due to Associate Professor Supat Sucharit, Head of the Department of Medical
Entomology, Faculty of Tropical Medicine, and also to Dr. M. Yasuno, National Institute forEnvironmental Studies, Japan Environmental Agency for criticism of the manuscript.

REFERENCES
1 ) Amalraj, D., Vasuki, V.. Sadanandane, C., Kalyanasundaram, M., Tyaki, B.K. and Das, P.K.
(1988): Evaluation of two juvenile hormone compounds against mosquito vectors, Indian J.
Med. Res., 87, 19‑232 ) Cerf, D.C. and Georghiou. G.P. (1972): Evidence of cross‑resistance to a juvenile hormone
analogue in some insecticide‑resistant houseflies, Nature, 239, 401‑402

3 ) Dame, D.A., Lowe, R.E.. Wichterman, G.J., Cameron. A.L., Baldwin, K.F. and Miller, T.W.
(1976): Laboratory and field assessment of insect growth regulators for mosquito control,
Mosq. News, 36, 462‑472
4 ) Detinova, T.S. (1962): Age‑grouping methods in Diptera of medical importance; with specialreference to some vectors of malaria, WHO Monograph Series No. 47, pp. 216
5 ) Dyte, C.E. (1972): Resistance to synthetic juvenile hormone in a strain of the fiour beetle
Tribolium castaneum, Nature, 288, 48‑49

l 836 ) EI Safi, S.H. and Haridi, A.M. (1986): Field trial of insect growth regulator, dimilin, for thecontrol of Anopheles pharoensis in Gezira, Sudan, J. Am. Mosq. Control Assoc., 2, 374‑375
7 ) Estrada, J.G. and Mulla, M.S. (1986) : Evaluation of two new insect growth requlators against

mosquitoes in the laboratory, J. Am. Mosq. Control Assoc., 2, 57‑60
8 ) Hsieh, M.Y.G. and Steelman, C.D. (1974): Susceptibility of selected mosquito species to fivechemicals which inhibit insect development, Mosq. News, 34, 278‑282
9 ) Ikemoto, T., Sumitro, Panjaitan, W. and Shibuya, T. (1986): Laboratory and small scale fieldtest of larvicides and larvivorous fishes against Anopheles sundaicus larvae at Perupuk Village,

North Sumatra, Indonesia, Jpn. J. Sanit. Zool., 37, 105‑112lO) Ishii, T., Kamei, M., Shimada, S. and Asano, S. (1987): Field trials using Altosid 10f growth

regulator against Culex pipiens pallens (Diptera: Culicidae) of Tokushima, Japan, Jpn. J.
Sanit. Zool., 38, 65‑75

11) Iwanaga, K. and Kanda, T. (1988) : The effects of a juvenile hormone active oxime ether

compound on the metamorphosis and reproduction of an anopheline vector, Anopheles
balabacensis (Diptera: Culicidae), Appl. Ent. Zool., 23, 186‑193

12) Jacob, W.L. and Schoof, H.F. (1971): Studies with juvenile hormone‑type compounds against
mosquito larvae, Mosq. News, 32, 541‑543
13) Jakob, W.L, and Schoof, H.F. (1972): Mosquito larvicide studies with MON 585, a juvenile

hormone mimic, Mosq. News, 31, 6‑1014) Kanda, T. (1979): Improved technique for the preparation of polytene chromosomes for someanopheline mosquitoes, Mosq. News, 39, 568‑574
15) Mulla, M.S. Darwazeh, H.A. and Norland, R.L. (1974): Insect growth requlator evaluation
procedures and activity against mosquito, J. Econ. Entomol., 67, 329‑332
16) Mulla, M.S., Majori, G. and Darwazeh, H.A. (1975): Effects of insect growth regulator‑dimilin
or TH‑6040 on mosquitoes and some nontarget organisms, Mosq. News, 35, 211‑21617) Mulla, M.S. and Darwazeh, H.A. (1975): Activity and longevity of insect growth regulators
against mosquitoes, J. Econ. Entomol., 68, 791‑797

18) Mulla, M.S. and Darwazeh, H.A. (1976): The IGR Dimilin and its formulations against
mosquitoes, J. Econ. Entomol., 69, 309‑312
19) Mulla, M.S., Darwazeh, H.A., Kenedy, B. and Dawson, D.M. (1986): Evaluation of new insect

growth regulators against mosquitoes with notes on nontarget organisms, J. Am. Mosq.
Control Assoc., 2, 314‑320
20) Phatipongse, S. (1983): Preliminary studies on the control of Anopheles minimus (Theobald,1901) Iarvae in natural running streams by drop application of temephos (OMS‑786). M. Sc.

Thesis, Faculty of Tropical Medicine, Mahidol University, Thailand21) Rathburn. C.B. Jr. and Boike, A.H. Jr. (1975): Laboratory and small pilot field test of Altosid

and Dimilin for the control of Aedes iaeniorhynchus and Culex nioripalous larvae, Mosq. News,35, 540‑546
22) Schaefer, C.H. and Wilder, W.H. (1972): Insect development inhibitors: A practical evaluation

as mosquito control agent, J. Econ. Entomol., 65, 1066‑1071
23) Sjogren, R.D., Batzer, D.R. and Juenemann, M.A. (1986): Evaluation of methoprene, temephos
and Bacillus thuringiensls var. israelensis against Coquiliiettidia perturbans larvae in Min‑
nesota, J. Am. Mosq. Control Assoc., 2, 276‑279

Japan. J. Trop. Med. H yg. , Vol. 17, No. 2, 1989, pp. 185‑189

185

WATER DEMAND AND SCHISTOSOMIASISAMONG THE GUMAU PEOPLE OF BAUCHI
STATE, NIGERIAOLADELE B. AKOGUN
Received June 13 1988/Accepted April 17 1989

Abstract: A helminthological study of stool and urine samples collected from 1,037

people from four rural communities in Gumau District of Bauchi State, Nigeria wascarried out using formo‑ether concentration and direct centrifugation methods respective
ly. The study is the first parasitological survey to be carried out in the district. Thirty‑nine per cent of examined persons were infected. Ova of Ascaris lumbricoides. Schis ‑tosoma haematobium, Schistosoma mansoni and Trichuris trichiura were most common.
Hookworm, tapeworm and Strongyloides stercoralis were also encountered, 17.9% and lO.
8% of examined persons had S. haematobium and S. mansoni infections respectively.
Water demand index (number of persons per welD for each community was calculated asa ratio of the total population to the number of safe water sources available in that
community. A significant relationship was found between water demand index and S.
haematobium (r=0.95) on one hand, and S. mansoni (r=0.88) on the other (P<0.01) . Such
relationship was not found in soil borne helminth infections. A similarly significant
association was found between distance from river and prevalence of S. haematobium (r=0.94) on one hand and S. mansoni (r=0.95) on the other (P<0.01) but not found in soil‑
bome helminth infections. These findings seem to suggest that water demand index may
be an important factor in the epidemiology of Schistosome infections in rural commu‑
nities. Water demand index may also be a useful field technique for estimating andcomparing the rates of water associated helminth infections in rural communities withcomparable environmental conditions.

INTRODUCTION
The source of drinking water is regarded as one of the most important epidemiologicalfactors in helminth infections. It has been suggested that the provision of potable water is apossible solution to the problem of helminthiasis (Gilles, 1964; Cowper, 1967; Akoh, 1980).

This suggestion is based on the fact that human activities are associated with helminth
infections and that prevalence of helminthiasis is a measure of the extent to which the sourceof water is contaminated with waste. However, there are indications that the provision ofwater alone is not enough to combat the increasing rate of water‑associated helminthiasis,
especially in rural areas where the demand for potable water needs to match its supply to anever rising population.

Department of Brology, Federal University of Technology, Yola, Nigeria

186

MATERIALS AND METHODS
Description of study area: The Gumau district of Bauchi State lies between 1,000 and 1,300
m above sea level in the northern Guinea Savannah of Nigeria (Figure 1).

The annual rainfall ranges between 1,270 and 1,828 mm while the annual temperature

ranges between 20'C and 30'C (Kowal and Knabe, 1972). The studied communities are
situated at the following locations:(10'15'N 9'06'E)(10'03'N 9'16'E)(10'09'N 9'13'E)

1 . Gumau
2 . Laru
3 . Badiko

4 . Magama (10'02'N 9'17'E)
A great deal of human activity (bathing, Iaundry and fishing) takes place along rivers Delimi,

Badiko and Bindiri at specific sites which retain water throughout the year.

Methods: Procedures for the collection and examination of stool and urine specimens were
those described by King (1972). The population estimate of each community was obtained
from the district ofiice which keeps a record of tax‑paying adults, birth and death and of
school enrolment. The number of safe water sources was obtained by personally counting
them with the assistance of the district Clerk and the Social Welfare Ofiicer. The main
criteria for determining safe wells were

GurnauoL JpoBadikoI Bauchi State
C::1 Area sampled

Rivers/=r Minor roads

Major roads

Laru
[]

ll/ll Siteof intenseactivity

O Locat councit capitat
C] Sampled comm uties

Toro

Magamao

2km

Figure 1

Map of study area: Gumau District, Bauchi State.

̲

187

a ) depth must be at least 7.5 mb ) there must be an extension slab at the mouth end which must be 0.5 m above ground level,

andc ) the well must have a metal or wooden cover. These criteria are the approved standards

by the Local Government Council.
The water demand index (the number of persons per well for each community) was
calculated as a ratio of the total population to the number of safe water sources in that
community. The distance from the village centre to the nearest major alternative water
source was determined.
Data analysis: Simple Chi‑square test and Friedman's two‑way ANOVA by ranks were used
to analyze the results for heterogeneity and significant variations.

RESULTSThe water demand index of each community is shown in Table 1, Table 2 shows theprevalence and distribution of each helminth in each of the four communities. S.
haematobium and S. mansoni were the only species of Schistosomes that were encountered.

The prevalence of S. haematobium was analyzed separately but included in Table 2.
Distribution of prevalence of infection does not seem to be even ( X P<0.01) . The distancesfrom the village centre to the nearest major alternative water source are shown (Table 2) .

The water demand index differed between villages. There seemed to be a significant
association between water demand index and S. haematobium prevalence (r= 0.95, t‑test, P <0.01) on one hand and S. mansoni (r=0.95, t‑test P<0.01) on the other (Figure 2). An
association was also observed between Taenia sp. and water demand index (r=0.70, t‑test,
P < 0.05) but not in any other helminth.
A similarly significant association seems to exist between the distance from river and S.

haematobium (r= ‑0.94, t‑test P<0.01) on one hand and S. mansoni (r= ‑0.88, t‑test, P<0.01) on the other. Such an association was not observed between distance from river and anyother helminth.

DISCUSSION
The type of association between Ascaris infection and water which was suggested by
Bidinger et al. (1981) was not observed in this study. The remarkable association between

Table I Water demand index of each community

Commumty Nearest Population
river estimate

No. ofwells

No. of persons
per well*

Gumau

DelimilO , OOO

26

384 . 6

BadikoLaru

Badiko4 , 900

14

350 . O

Bindiri

2 , OOO

7285 . 7

MagamaBindiri

3 , 800

32

ll8 . 820 , 700

79

262 . oTotal*: Water demand index.

188

Distribution of each helminth in the district *Table 2
Helminth

Gumau Badiko Laru

Magama Total

Water demand River distanceInf. (%) Inf. (%) Inf. (%)

Inf. (%) Inf. (%)

and parasite

125 14181
4(2 . 6) (17 . 5)SS, haematobiumt

38(18.0)(24 . O)
(9 . 5)41'112 51(21 . 5) (23 . 9) (27 . 7)

A, Iumbricoides

S. mansord

23

Hookworm(1 . 9) (lO . 8)(3.3) (8.5) (4.0)

17 18 6(3.2) (4.4)(1 . 2) (O . 9) (1 . 4)

(3 . 2) (1 . 4)

7 3

H. nana

3 112(15 . 4) (lO . 8) (4 . O)

6 2 2

Taenia sp.

29 233(18 . 7) (2 . 5)(0.8) (3.3) (2.0)

5 46
5 15
3 17
(1.9)
(1.6)

3

T. trichrura(O . 8)(1.4)(6 . l)S, strercoralis

4
(0.8)

Prevalence (%)

O
384 . 6350 .285
. 7

Water demand index
Distance fromnearest river (m)

l

ns

S

ns

ns

t

ns

ns

ns

16
(1.5)

ns

ns

4

ns

ns

(O . 4)521
213 148
39 . 9 46 . O 41 . 2

No. Exam.

ns

and parasite

600 5 , OOO
410

155 1 , 037
24 . 5 39 . 9188 . 8 262 . O
6 , OOO*: These figures include mixed infection. t : Urinary Schistosomiasis was analyzed separately.
$: P<0.05 S : P<0.01 Il : negative correlation.

30

o
25

¥oX
'10

o Ascaris lumbricoides

x Schistosoma haematobium

20

o

e e

,J
a,

ffff / o

u 15
Ca,

75

e Schistosoma mansoni
A Taenia species

O)L

CL

/X/ e

10

5

( /

.̲̲A'

e
100

200 300 400

Water demand index

Figure 2

Prevalence of some helminths and water
demand index.

189

water demand index and Schistosome infection in the district is self evident. The results
suggest that the rate of Schistosome infections tend to increase with increase in water
demand index. The explanation for these observations may be due to the contamination ofalternative sources of water. This may lead to an increase in the number of Schistosome

intermediate hosts which become infected as a result of contamination. The number of
cercariae that are released by the intermediate hosts increases thus increasing the chances ofhuman‑parasite contact and so enhancing a subsequent rise in the prevalence of disease
among the human population who in turn further contaminate the alternative water source
through continual contact. Water demand index may be a major factor in the transrnissionof water‑associated helminths. The association between Taenia sp. (which has no direct
association with water) is not well understood and may likely be due to sampling error.
It is literarily possible to have almost the entire community infected as a result of theassociation between water demand, the environment and Schistosomes. This explanation isespecially likely since the distances from the rivers seem to have a negative association with

only S. haematobium and S. mansoni infections in this study. This may be duto humanbehaviour; the easier the access to the alternative source, the more the number of people who

may contaminate it in a community with large water demand index and the greater the
chances of contact with infective stage of Schistosomes. The distance from river does notseem to affect the prevalence of other helminths in this study.
Although the findings of the present study may not be conclusive regarding the relation‑
ship between water demand of a community and its rate of Schistosome infections, the results
do reveal an interesting association between them. This association may be a useful fieldtechnique for estimating and comparing the rate of Schistosome infections in communities
with similar environmental conditions.

ACKNOWLEDGEMENT
This study is part of a research project which was supervised by Dr. V.N. Okwuosa towhom I am very grateful for useful advice. The assistance of the Gumau District Ofiice isgratefully appreciated.

REFERENCES
1 ) Akoh, J.1. (1980) : The incidence of intestinal helminthiasis and schistosomiasis in ruralschoolchildren in Jos Plateau, Nig. J. Parasit., 1(1)2 ) Bidinger. P.D., Crompton, D.W.T. and Arnold, S. (1981): Aspects of intestinal parasitism invillages from rural peninsular India, Parasitology, 83, 373‑3803 ) Cowper, S.G. (1967): A review of helminthiasis in the Western region of Nigeria with specialreference to lbadan area, W. Afr. Med. J., 17 (1), 3‑114 ) Gilles, H.M. (1964): AKUFO: And environmental study of a Nigerian village community,
University Press, Ibadan
5 ) King, M. (1973): A medical laboratory for developing countries, ELBS 1984, Ed. OUP Oxford,

London6 ) Kowal, J.E. and Knabe, D.T. (1972): An agroclimatic atlas of the northern states of Nigeria

with explanatory notes, ABU Press, Sararu‑Zaria

Japan. J. Trop. Med. Hyg., Vol. 17, No. 2, 1989, pp. 191 196

191'DESCRIPTION OF A NEW SPECIES OF THE BLACKFLY SUBGENUS SIMULIUM (ECTEMNASPIS)FROM THE ANDES OF ECUADOR (DIPTERA=SIMULIIDAE)SIXTO CoscAR6N* AND HIROYUKI TAKAOKA'
Received january 13 1989/Accepted April 17 1989

Abstract: Simulium (Ectemnaspis) pautense sp. n. was described based on female,
male, pupal and larval specimens collected in small streams of Andean region in Ecuador.

This new species is close to S. (E.) gabaldoni Ramirez Perez from Venezuela by having
the 6‑filamented pupal gills, but differs in the female from the latter species by lacking
denticles in the cibarium and by the coloration of the legs.

INTRODUCTION
Coscar6n (1984) revised a neotropical simuliid fauna, and assigned 37 black fiy species

into the subgenus Simulium (Ectemnaspis) Enderlein. Of these, eight species have beenreported from Ecuador (S. ignescens Roubaud, S. Iutzianum Pinto, S. Iewisi Ramirez P6rez,
S. pseudoantillarum Ramtrez P6rez and Vulcano, S. dinelii (Joan) , S, shewellianum Coscar6n
and S. bicoloratum Malloch, S. romanai Wygodzinsky (e.g., Coscar6n, 1984; Takaoka andHirai, 1987).

Recently, an additional undescribed species of this subgenus was collected from the highAndes of Ecuador. This bears a combination of the following features: the adult scutum andabdomen colored partially yellowish, subtriangular paraprocts, female claws with a small
subbasal tooth, and short, subcylindrical male style. All these fit the definition of the subgenus

Simulium (Ectemnaspis), given by Coscar6n (1984) .
In this paper, this is below described as a new species.

DESCRIPTION
Simulium (Ectemnaspis) pautense sp. n.
Female. Wing length 2.4‑2.6 mm. Head brown; proboscis, maxillary palps and antennae darkbrown to black. Frons and clypeus with silvery pollinosity. Scutum orange, ornamented asin Figure 1, and greenish yellow laterally. Scutellum greenish yellow. Postscutellum velvet
black with I + I small greyish patches. Pleura mostly pale yellow with a small elongatedbrown stripe over the pleural membrane, and brown basally. Wing hairs brown. Legs darkbrown with concolored hairs. Abdominal tergites 1‑IV yellow, with tergal plates 111 and IV

l Facultad de Ciencias Naturales y Museo, universidad de La Plata, Peseo del Bosque 1900, La
Plata, Argentina
2 Division of Medical Zoology, Medical College of Oita, Hazama, Oita 879‑56, Japan192

pale brown; tergal plates V‑IX blackish brown, waxy bright except plate V velvet bright(Fig. 2). Frons convergent below (Fig. 3); frontal angle 78 degrees. Frontoocular triangle
as wide as high (Fig. 4). Mandible with 29‑33 teeth. Maxilla with 24 or 25 teeth. Sensory
organ of maxillary palp shorter than 1/2 of basal segment. Basal portion of cibarium withreinforced border, and without denticles (Fig. 5) . Basal section of R bare. Sternite VIII withdarker middle area, and with about 27 hairs on each side; gonapophyses reinforced on theinternal border (Fig. 6) ; paraproct about as long as wide at base (Fig. 7) ; cercus with straightborder; genital fork with middle branches heavily sclerotized (Fig. 8) .

Male. Wing length 2.3‑2.5 mm. Coloration very close to female. Scutum pale but yellow
orange on the top, and with a T‑formed black stripe on the anterior third and a pair of black,broad longitudinal stripes sublaterally (Fig. 10). Hind basitarsus about 5 x as long as its
width (Fig. 9). Style about 4/5 x length of coxite (Fig. 11). Median sclerite elongated witha distal concavity. Parameres with several stout hooks (Fig. 13).
Pupa. Gill (Figs. 14 and 15) with 6 slender filaments and 2.7‑3.3 mm long. Frontoclypeus andexposed portion of thorax with rounded and smooth tubercles (Figs. 16 and 17). Trichomes
on frontoclypeus and thorax curved basally and divided into 3‑6 branches (Figs. 15 and 16) .
Cocoon (Fig. 14) simple slipper‑shaped, thickly woven with evident threads; its length 3.0‑
3.3 mm at base and 2.4‑2.8 mm dorsally.
Mature larva. Body shaped as in Figure 18, and 5.5‑5.8 mm long. Head brown with negative

head spots (Fig, 19); cephalic capsule 0.55 mm in maximum width. Hypostomium withmedian tooth as high as corner teeth and with 5 setae on each side (Fig, 20) . Postgenal cleftdeep and narrow (Fig. 20). Antenna (Fig. 21) shorter than base of cephalic fan; relative
length of segments 1‑3, 1.0:1.0‑1.2:1.6‑2.0. Cephalic fan with 42‑48 rays. Mandible with 8‑10internal teeth disposed in 2‑3 rows (Fig. 22) . Thorax and abdomen mostly greenish and the,ir

cuticles bare except setose portion near anal sclerite. Proleg sclerite comb with 23‑25 teeth(Fig, 23) . Anal sclerite shaped as in Figure 24, and with several setae on each side. Posterior

circlet with 73‑76 rows of 14‑15 hooks. Anal gill with 12 secondary lobules on each lobe.

Material examined. Holotype female, reared from pupa, was collected from a small stream
about 20 cm wide (ca. 2,500 m in altitude) in Paute, Azuay, Ecuador, 5 July, 1988, by H.
Takaoka; allotype male, paratypes 2 females and I male, 10 pupae and 2 Iarvae, same data
as holotype. Paratypes 8 females and 5 males, reared from pupae, were collected from asmall shallow stream 10‑30 cm wide (ca. 3,000 m in alt.) in Cuenca, Ecuador, 4 July, 1988, by

H. TakaQka. All the type specimens are deposited in Facultad de Ciencias Naturales y
Museo, Universidad Nacional de La Plata, La Plata, Argentina.

Remarks. Simulium pautense sp. n. is close to S. gabaldoni reported from Veneztiela(Ramirez P6rez, 1971) by having the 6 respiratory filaments in the pupa, but differs in thefemale from the latter species by the absence of tubercles in the cibarium and by the entire
darkness in the legs.

193

も

O

響

羅
︸一
幽
一

＝一

！一
■

ノ
・．欝

！

，響∫鶉

層
一
︐
三

1難ll

／り．』㌧講
、

︑

︑︵

￥

ヅr欝
じヂラロ

ほ

一「『f

騰

8

濃産

欝甥

騨慧
／
ぐぐ1㌧
1

Figs．1−9．

S加御伽彫勿鋸勧召sθsp．n．1−8，female
in dorsal

view；2，abdomen

5，cibarium；6，stemite
cercusinlateralindorsalVIII andview；8，genitalandscutellum

view；3，frons；4，frontoocularand9，male．1，scutum

triangle；

anterior

gonapophyses；7，paraproctfork；9，hind basitarsus、

and

194

、麟難、
翫︐琴

．熱

髪蕪・：娯
o

r、望

・

Oo恥

．よ竃 ・亀・・∫

酸
〜

16
1111﹂
＼
一
7一

、ち・魔。．●●％〜・

L一一＿』豊 姦1豊・・ ムし∴

亙
■

難1灘．翻

∫／

Y

15

Figs．10−17

S枷％」勉解加鷹n5θsp．n．10−13，malescutellum
plate

in

dorsalin frontal

15，thoracic

and14−17，pupa．10，Scutum

andview；11，coxite and style in dorsal view；12，ventral

and ventral view；13，parameres；14，pupa andintegument

andrespiratory

tubercles and trichomes；17，roundclypeus．

and

its cocoon；

filaments；16，frontoclypeus

smoothtubercles

on

with

fronto・195*:: t'.':''18 .{;:

Ys'

: i

is'=: :"

: ̲ t

' t : ,' ･:vt"*:

i. .;';

v : .̲.

11 ' 'l !!' t' E;'i:

l

l

¥.I
; ;'

'i: .=}'1:h 1 :E ':' ;' :'a.
L LL:::
1 o;' i'" F ;I

; F'{ Y : ; L +1 e}'t : :f:!'

: :: :'=

:}i

'

:

' ::

" ;

,,:

'/ '=} ;: ,1

t:

' .,
‑ t ': 's i l iL ' ; 't
# t‑:
1; j:,:: 1"'‑:

23 j; ; :

l

l

l

l

l,
l

::::":

l ' L L : :;.l
l" 1

::":l

IL : ! ? ::: ::lI/" :fIif"i:i: i':'1
rl'
20' :'1 lli

1 t L L l':i
! 19 l

le

I

E

"
'***'

. f :* *=+ ; , =; : ;;=

=

'+

':

'*1'=::. ¥l .A
'o (l
(r/ ¥

! ;:'::!"'
"*;i;

ID

Figs. 18‑24:.;‑i; ' *+=:?'*;* *=; 'j:= ii' :,'

, i

(
.

, . r4*

S!'!: ii}**i;*" 'lr ‑o e

eo
24

h¥
‑ a ̲
e r'
' rrl¥.
¥‑o'!

Simulium pautense sp. n. Iarva. 18, Iateral view of larva; 19, cephalicapotome; 20, ventral view of head capsule showing hypostomium andpostgenal cleft; 21, antenna; 22, apical tip of mandible; 23, sclerite comb
of proleg; 24, anal sclerite.

196

AcKNowLEDGEMENTs
We aregrateful to Dr．KleberLoor，DepartamentodeEntomologia，InstitutoNacionalde
Higiene y Medicina Tropical Leopoldo Izquieta P6rez ，Dr．Eduardo Gomez L．，Depar−
tamento de Parasitologia，Universidad Catolica，Guayaquil，Ecuador，and Dr．Y．Hashiguchi，
Kochi
also

Medicaldue toSchoo1，Kochi，Japan
Dr．N61ida

Caligaris

for

for

their klnd support

her

help

in

makinginthefield survey．Thanks areillustrations．

REFERENCES
1）Coscar6n，S．（1984）：Revisi6ndelsubg6nero

SJ吻π1勉勉（Eo∫召窺％s餌s）Enderlein（Simuliidae，Diptera，Insecta），Rev．Soc．Ento．Argentina，43，283−325
2）Ramirez，P6rez（1971）： Distribuci6n geografica y revisi6n（Diptera：Nematocera）deVenezuela

condescripci6ndetaxon6mica de

diez

los

Sim丘lidos

especies nuevas，Acta

Bio1．

Venezuela，7，271−372
3）Takaoka，H．andHirai，H．（1987）：Famistic36−38，伽：Tada，L ed．， A comparative

Americas，Shimoda

Printing

andsurveys

study

on

of

blackflies（Simuliidae）in

onchocerciasis

between

Ecuador，pp．

south

and

centralCo．，Kumamoto，Japan

エクアドルのアンデス高地で見いだされたE碗卿郷吻s亜属の1新種ブユの記載

Sixto Coscar6nl・高岡 宏行2

エクアドルのアンデス高地のパヴテ町において採集されたブユの成虫，婦および幼虫を分類学的に検討した結果，S伽％伽吻属のE吻㈱碑ゑs亜属に属する新種であることが分かったので新種名を与え，記載を行ったるアルゼンチン国立ラプラタ大学自然科学部・博物館
大分医科大学医動物学教室

Japan. J. Trop. Med. Hyg., Vol. 17, No. 2, 1989, pp. 197 203

197

EFFECT OF GASTROGRAFIN ON DIPHYLLOBOTHRIUM
LA TUM, TAENIA SA GINA TA AND

DIPLOGONOPOLUS GRANDIS INFECTIONTOSHIMASA NISHlYAMA*, JUNKO FURUK11, JUN YAGI*, TERUO WADAl,TSUNEJI ARAK11, HIROYUKI AMAN02 AND TADASU TsUJI13
Received November 7 1988/Accepted May 8 1989
Abstract: The successful treatinent of Diphyllobothrium latum. Taenia saginata and
Diplogonopolus grandis infections with Gastrografin is herein reported. Eleven subjects (8cases of D. Iatum, 2 of T. sagi,eata and one of D. grandis infection) found to havetapeworm infection based on the history of discharge of gravid segments and/or positivity

for tape orm egg were first pretreated with barium enema procedure and were treatedwith 300 to 500 ml Gastrografin by duodenal manipulation. All cases who indicated thepresence of the tapeworm as a radiolucent shadows were completely treated with
Gastrografin. All tapeworms with scolex expelled were actively moving in the saline. The
time of treatment (from 15 to 30 min) was shorter than that of other medical treatments.
No side effects were observed. In the present study, the treatment with Gastrografin was

found to be a satisfactory anthelmintic method against D. Iatum. T. saginata and D.
grandis infection.

INTRODUCTION
The drugs such as bithionol (Yokogawa et al., 1962), paromomycin sulfate (Salem andEl‑Allaf, 1969) , mebendazole (Vandepitte and Thienpont, 1972) , niclosamide (Kihara et al.,1973) and praziquantel (Paz, 1977) have commonly been used as anthelmintics against humanintestinal tapeworm infection. Although these drugs are very effective, the scolexs areusually not found in their feces after the treatment.

Recently, it has been shown that the Gastrografin (Shering) , a water soluble contrast

material of the gastrointestinal tract, has possessed an anthelmintic effect on intestinal
tapeworm (Nakabayashi et al., 1984; Waki et al., 1986).
In this report, Gastrografin was used for treating Diphyllobothrium latum (D. Iatum).
Taenia saginata ( T. saginata) and Diplogonoporus grandis (D. grandis) infections and wasmost effective for removing the tapeworms.

MATERIALS AND METHODSThis study consisted of 11 subjects; 8 cases with D. Iatum. 2 with T. saginata and one with

D. grandis infection. All subjects were confirmed to have intestinal tapeworm infection by
1 Department of Parasitology, Nara Medical University, Kashihara, Nara, 634, Japan
2 Department of Overseas Medical Services, Tenri Hospital, Tenri, Nara, 632, Japan
3 The 3rd Department of Internal Medicine, Nara Medical University, Kashihara, Nara, 634,
Ja pan

198

the following two criteria: history of discharge of gravid segments and/or positivity fortapeworm eggs in their stools and their anus.
The treatment was performed according to the methods of Waki et al. (1986) with somemodifications. The routine treatment was as follows: The day before the treatment, thepatient had restricted food intake, for example, Besbion (Fujisawa Pharmaceutical Co., Ltd.)and Boncolon (Ohtsuka Chemical Co.. Ltd.) , instead of ordinary meal. Thereafter, 250 ml ofmagnesium citrate (Magcorol, Horii Pharmaceutical Indus., Co., Ltd.) and 4 tablets of senna(Adjust‑A, Kowa Co., Ltd.) were given to the patient at 8.00 p.m. and 11.00 p.m.,respectively.

On the day of treatment, the patient was kept fast until the treatment but isotonic drink suchas Pokalisweat (Ohtsuka Pharmaceutical Co., Ltd.) was made enough, for the preventationof dehydration. The patient was kept in the bed for X‑ray fluoroscopy. A duodenal tube wasinserted through the mouth until the tip reached the fiexura duodeno‑jejunalis. Gastrografin(300 ml) was injected through the tube with a plastic disposal syringe (50 ml, Terumo Co.,
Ltd.) for 5 min. Under fiuoroscopic monitoring, the worm was found as a radiolucent shadow

descending in the intestinal lumen treated with Gastrografin. When the peristalsis of theintestine did not occur vigorously, the adequate volume of Gastrografin was added. When theparasite reached the anal side through the descending colon, the patient was forced to
defecate. The moving worm with scolex was discharged with the stool.

RESULTS
Table I summarizes the clinical profiles and treatment regimen of the 11 patients. Of the

11 cases with intestinal tapeworm infection included in this study, 9 (81.8% ) were male and2 (18.2%) were female. Their age was ranged from 13 to 55 (41.5 :l0.9) years old. Using
300 to 500 ml Gastrografin, the entire tapeworm with scolex were discharged within 15 to 30
min. In all cases, the tapeworms were alive, unfragmented and moved actively in the saline.
Case l, 2, 3, 5, 6, 8, 10 and 11 were D. Iatum infection occured by eating raw fish (salmon

and trout) . Case 4 and 9 were T. saginaia infection occured by eating incompletely cooked
beef meat. Case 7 was D. grandis infection, but the cause of this case was unknown.
Two cases (case 10 and 11) was not able to find out the tapeworm in X‑ray monitor in
the first treatment. In these cases, tapeworms were not discharged with their stool. But, 45
days after the treatment, the eggs of D. Iatum were detected from their feces by stool
examinations. Two months after the first treatment, the second treatments were done. In
these times, the tapeworms could be found out in X‑ray monitor from both cases. Thesetapeworms were expelled with their stool and these cases were completely treated by therepeat of this method.
Figure I showed T. saginata (case 4) moving very actively in the ileo‑caecalis portionand each proglottid of T. saginaia was clearly descrived as a radiolucent region in thisphotograph. Figure 2 showed D. latum (case 5) revealing at the same region in Figure 1.
Figure 3 showed the worm ( T. saginata, case 4) recognized as a radiolucent region in therectum before defecation. After this photograph, this worm was discharged through the anus(case 4). Figure 4 showed the entire shape of T. saginata (case 9). The scolex (arrow) of

this worm was shown in this photograph.
In every case, the side effects of Gastrografin were not observed.

199

Table l Summary of the treatment with Gastrografin
Gastrografin

Case

g A e

Sub jective

numberSex

symptoms

y48

2
3
4

y39

y

F
y48

M
2

y55

M
Ai i l 3

8
9

10*

F
iL y42

M

D, Iatum

400 ml30 min506 cm

D. Iatumdiscomf ort

300 ml25 min475 cmD. latumnone

400 ml20 min661 cmT, saginata

400 ml15 min450 cmD. latum

500 ml15 min225 cmD, Iatumtenesmus &abdominal

400 ml15 min273 cm

D. grandis

abdominal

300 ml15 min708 cmD, Iatum

500 ml25 min275 cmT, saginata

abdominal

450 ml15 min600 cmD. latum

abdominal

340 ml23 min890 cm

D. Iatumpain

abdominal

discomf ort

abdominal
discomf ort
discomf ort
discomf ort

abdominal
discomf ort

i2 35

soft stool &Mdiscomf ort

1 4 7

11*

736 cmabdominalyL y4 1

7

400 ml25 min

Tirri

y46

M

6

fof treatment

abdominal

M

5

of

tapeworm

Ly42

i

M

Speciesof wormsoft stool

M

Total
lengthM

1dosagepain

required* The data of these cases (case 10 and 11) were showed from the second treatment.

DISCUSSION
For the last 30 years, the intestinal parasite infection such as ascariasis, hookworm
diseases, trichuriasis and clonorchiasis has been markedly reduced in Japan.

However, intestinal tapeworm infection is widely distributed in Japan, because theJapanese likes to eat raw fish (sashimi) and incompletely cooked beef meat which are thesecond intermediate host of D. latum. D. grandis and T. saginata.
In foreign countries such as USA, the Japanese style eating at sashimi and sushi bar
where such dishes are served, is becoming popular as healthy foods. And these foods hasoften been suggested as a contributing factor to the spread of fish tapeworm infections inforeign countries.

Nakabayashi et al. (1984) and Waki et al. (1986) reported that the Gastrografin was auseful drug against T. saginata and D. latum infection. In their reports, they concluded thatsome physical relation between the parasite and the intestine were important for expelling

the tapeworm.

200

Figure 1 T. saginata
shado

r

case 4) is clearly seen as a radiolucent

in the iieo‑coecai segment.

Figure Z D. latum. (c Se 5) is ebserved in the ileo‑coecal
segment .

201

Figure 3 T, saginata (case 4) recogni ed a8 a long rediolucent
shadow in the rectum beiore dei=ecatian.

Figure 4 T. saginata (ca e 9) a
(arrow). This wor

the whole shapo with scolex

n w s 27r"v cnl in length.

202

In this study, we modified the treatment regimen and inserted dose of Gastrografin.
Pretreatment in this method is based on the pretreatment of barium enema procedure. This
procedure has an advantage that the feces in the intestinal lumen of the patients were less,and the initial dose of Gastrografin could be increased up to 300 ml from 100 ml used by Waki
et al. (1986) . According to this modified method, this drug is more effectively utilized.

Relatively new drugs such as paromomycin sulfate, niclosamide and praziquantel show
a good curative efficacy (80‑100%) in intestinal tapeworm infection (Salem and El‑Allaf,
1969; Kihara et al., 1973; Paz, 1977) . However, in almost all cases, tapeworms were destroyed

with these drugs and scolexes of expelled tapeworms were not found in their discharged feces.

In this method, all cases who have confirmed the tapeworm as a radiolucent shadows in

the intestinal lumen were successfully treated with Gastrografin. Case 10 and 11 haddischarged the long fragment of tapeworm before the first treatment, so that these tapeworms

were too small to be recognised by X‑ray monitor at the first treatment.
As regards the tirne required for this treatment (from 15 to 30 min) it was shorter thanthat of other medical treatment.
It is concluded that the present method is more effective for treating these intestinal

tapeworm infection than other vermifuged methods. Therefore, we recommended that
Gastrografin should be a drug of first choice for the treatment of intestinal tapeworm.

ACKNOWLEDGEMENT
The authors wish to express their thanks to Dr. Isamu Sugawara for reviewing themanuscript and Drs. Akira Sano, Hideoki Noshi and Isamu Emi for their support and interestin this study.

REFERENCES
1 ) Kihara, T., Kobayashi, R., Tsuji, O., Okazaki, S. and Kosaka, K. (1973): Studies on large
tapeworm. Part 3. Treatment of large tapeworm infections in man. ( Taenia saginata andDiphyllobothrium latum), Jpn. J. Gastroenterol., 70, 196‑207
2 ) Nakabayashi. T., Ono, T., Nakai, T., Waki, K., Takahashi, S.. Kitani, T., Oi, H. and Naka‑mura, H. (1984): A new therapy for Taenia saginata and Diphyllobothrium latum infections by
duodenal administration of Gastrografin. Jpn. J. Parasitol., 33, 215‑2203 ) Nishiyama, T., Furuki, J.. Yamada, S., Takahashi. Y. and Araki, T. (1987): A case of
diplogonoporiasis treated with Gastrografin, Jpn. J. Parasitol., 36, 390‑396

4 ) Paz, G. (1977): Treatment of taeniasis saginata with praziquantel (Embay 8440), Boletin
Chileno de Parasitologia, 32 (1 & 2), 14‑16

5 ) Salem. H.H. and El‑Allaf, G. (1969): Treatment of Taenia saginata and Hymenolepis nana
infections with paromomycin, Trans. R. Soc. trop. Med. Hyg., 63, 833‑836
6 ) Vandepitte, J. and Thienpont. D. (1972): Trichuris infestations and difetarsone. British
Medical Journal, 4, 549
7 ) Waki, K., Oi, H., Takahashi, S., Nakabayashi, T. and Kitani. T. (1986): Successful treatment

of Diphyllobothrium latum and Taenia saginata infection by intraduodenal "Gastrografin"
injection, Lancet, 2 (8516), 1124‑ll268 ) Yokogawa, M., Yoshimura, H., Okura, T. and Saito, M. (1962): The treatment of Taenia
saginata with bithionol, Jpn. J. Parasitol., 11, 39‑44

203

ガストログラフィンによる広節裂頭条虫，

無鉤条虫，大複殖門条虫の駆虫効果
西山利正1・古木 純子1・八木純1・和田
荒木 恒治1・天野 博之2・辻井
正3

輝夫1

ガストログラフィンを用いて，広節裂頭条虫症（8例），無鉤条虫症（2例），大複殖門条虫症（1例）の条虫症，計11症例に駆虫を試み良好な駆虫効果が得られた。駆虫前日に前処置として，

消化管注腸造影の前処置を応用し，腸管内の食物残渣や糞便を除去し，駆虫時のガストログラフィ

ンと条虫体とが完全に十分接触できる状態にまで処理しておき，ガストログラフィンを十二指腸ゾンデでトライツ靱帯より300mJから500ml注入し，駆虫を行った。駆虫時，条虫体が透視下にて，透亮像として確認された症例は全例，駆虫後頭節を確認することができ，生きた状態で完全駆虫することができた。駆虫時問はわずか15分から30分で，駆虫を完了することができた。

奈良県立医科大学寄生虫学教室
天理よろづ相談所病院海外医療科
奈良県立医科大学第三内科学教室

Japan. J. Trop. Med. Hyg., Vol. 17, No. 2, 1989, pp. 205‑211

205

ENDEMIC ONCHOCERCIASIS ON THE JARAWA
VALLEY AREA OF PLATEAU STATE, NIGERIABERTRAM E. B. NwoKEl, CELESTlNE O. E. ONWULIR12, KUNINORI SHIWAKU3GAD O. UFOMADU4, ISAO TADA5 AND HIROSHI TAKAHASH16
Received February 2 1989/Accepted May 8 1989

Abstract: Clinical and parasitological survey on onchocerciasis was carried out in the

Jarawa Valley area of Nigeria. A total of 1,821 inhabitants from six villages were
examined and 908 (49.9%) were positive for microfilaria of O,echocerca volvulus. On‑
chocercal infection increased with age, reaching the highest level in adults over 40 years

old. Pruritus was the most frequent lesion, followed by skin depigmentaion, visual
impairment, nodule, hanging groin and elephantiasis. Leopard skin occurred in various
parts of the body including areas not exposed to blackfly‑bites. Lymphatic manifestation,
hanging groin and elephantiasis, occurred mostly in old male subjects. The adult had thehighest prevalence of nodules mainly in the pelvic regions. Skin biopsies taken from theiliac crest gave the highest frequency of positive skin snip.

INTRODUCTION
Recently, Dipeolu and Gemade (1983) reported that about 750,000 Nigerians are sufferingfrom onchocerciasis, with between 30,000 and 40,000 suffering from various ocular complica‑
tions of onchocercal etiology. As a result of the serious socioeconomic liabilities caused to

endemic communities of onchocerciasis in this country, the Federal Ministry of Healthrecently inaugurated National (Nigeria) Onchocerciasis Control Programme (NOCP) . By
this programme, the country was divided into zones for research convenience.
Few investigations were carried out on the Jos Plateau (NOCP Zone ID except byRoberts and lrving‑Bell (1985) , Onwuliri et al. (1987) and Nwoke et al. (1986) who showedthat this disease and its vector species are widespread in this region. Many endemic
communities in this zone are yet unidentified and unstudied. We report here results of clinicaland parasitological surveys on the Jarawa Valley area of Nigeria.

l Medical Entomology & Parasitology Unit, School of Biological Science, Imo State University,

Okigwe, Nigeria
2 Department of Zoology, Faculty of Natural Science, University of Jos, Nigeria
3 Department of Parasitology, Aichi Medical University, Aichi 480‑11, Japan

Present address: Department of Environmental Medicine; Shimane Medical University,
Shimane 693, Japan
4 Nigerian Institute for Trypanosomiasis Research, Vom, Plateau, Nigeria

5 Department of Parasitic Diseases, Kumamoto University Medical School, Kumamoto 860,
Ja pan6 The Japan International Cooperation Agency, University of Jos, Jos, Nigeria
Present address: Hayamiya 1‑40‑11, Nerima‑Ku, Tokyo 176, Japan
This study was supported by JICA, Japan‑Jos University, Nigeria Project (JUJIP No. 15) .

206

MATERIALS AND METHODS
Study area: The study area is the Jarawa Valley area in Central Nigeria, Iocated in thenorthern'part of the Jos Plateau. Six villages covered in this study. The six villages arelocated at different distance from the Jarawa river system, the main source of domestic watersupply especially during the dry season. One of the main physical features of this area is therange of hills (Jarawa Hills) surrounding these villages. These highlands are the sources ofa net‑work of rivers and streams; most of which are breeding foci of Simulium damnosum(Nwoke, 1986). This area is in the northern Guinea savanna with yearly temperature
between 12'C and 32'C.
The study area is inhabited mainly by rural farmers. Fishing, hunting and forest guards
are exclusively performed by men. Because of the fact that this area has a special advantage

of being tsetse‑free together with a higher rainfall than the surrounding plains, animalhusbandry is another major occupation of the nomadic Fulani.

Between January, 1985 and April, 1986, villagers were examined according to theonchocerciasis survey form (WHO, 1966) . Mobile parasitology survey teams made up of theauthors and their assistants collected skin biopsies and interviewed to ascertain name,estimated age, sex, occupation and village distance from breeding sites of vectors. The
volunteers were physically examined for clinical manifestations of onchocerciasis. Visualacuity and blindness were evaluated as the inability to quickly count fingers at 3 m distance.

Using a Holth‑type corneo‑scleral punch (2 mm) , six bloodless skin snips (2 from shoulders,

2 from 5 cm above the lateral iliac crests and 2 from the calves) were collected. The
microfilariae emerged in physiological saline of the wells of microtiter plate were counted insitu under a dissected microscope at 24 hr after the collection.

RESULTS
Microfilariae of Onchocerca volvulus emerged from one or more of the skin snips takenfrom 908 (49.9%) out of 1,821 subjects examined (Table 1). There was a gradual increasein the microfilarial rate with age with the highest infection rate of 72.1% recorded among
subjects 40 years and above of age while the least (7.3%) was observed among 0‑9 years ofage.

Table l Microfiralial rate in villages by age
Microfilarial rate in per cent by age in years

Village

Maijemu

10‑19

0‑9

0.0 (0/56)*

24 . O(24/100)

Dass

30‑39

40 +

Total

65.0 (26/40)

72.2 (52/72)

75.0 (84/ll2)

48 . 9 (186/380)

50.0 (8/16)

66.7 (16124)

60.0 (72/120) 60.0 (96/160)

20‑29

Rando

ll.4 (4132)

63 . 6(28144)68.8 (44164)

84.6 (44152)

66.7 (48172)

Gwodong

16.2(18/lll)

50 . O(45/90)90.0 (54/60)

77.8 (21/27)

91 . 7 (99/108) 59 . 9 (237/396)

Dorong2,1 (3/141)

16 . 3(24/147)

56.3 (27/48)

80.0 (24/30)

86.2 (75187)

Federe0.0 (0/2)

60 . O(6/lO)

16.7 (2/12)

52.2 (12/52)

40.5 (68/168) 52.2 (48/92)

Total

7 . 3 (25/342)

32 . 5 ( 127/391)* (No. positive/No. examined)

63 . 6 ( 168/264)

33 . 8 ( 153/453)

67.1(161/240) 65.8(169/257) 72.1(426/591) 49.9(908/1,821)

207

Table 2 Prevalence of onchocercal lesions by villages

Number with onchocercal lesions:

N umber
examined

NoduleMaijemu

380

10

Dass

160

8

Rando

264

Gwodong

396

DorongFedereVillage

Total(%)

VisualDe ‑im pairment

pigmentation

14

26

38

lO

44

20

48

4

28

16

28

60

O

33

21

63

75

O

453

3

12

21

21

O

168

2

10

22

20

O

Hanging groin &Pruritus

elephantiasis

1 , 821

84

117

180

262

14

( 100 . O)

(4 . 6)(6 . 4)(9.9)(14 . 4)

(0.8)

Table 3 Prevalence of onchocercal lesions by age and sex
Sex

Age group( years)Male

N umber
examined

N oduleDe‑ Pruritus Hanging groin &Visualimpairment pigmentation

0‑9

183

2

O

l0‑19

201

8

1

elephantiasis

O

5

o

11

o

20‑29

131

6

13

18

20

2

30‑39

135

18

24

30

44

8

40+

309

15

33

49

60

4

Total

959

49

71

101

140

14

O

O

2

O

11

Female

0‑9

159

O

l0‑19

190

2

20‑29

l09

11

8

13

28

30‑39

122

9

16

18

35

40+

282

13

21

48

46

Total

862

35

46

79

122

Table 4 Frequency distribution of onchocercal nodule by age

Age group

0‑9

10‑19

20‑29 30‑39

40+

Number examined

342

39 1

240

257

591

Number of nodule

5

16

18

24

31

O

2

4 (4.3)6

5

19 (20.2)

48

14 (14.9)

2

6 (6.4)812

43 (45.7)

52

8 (8.5)

Total (%)
1821
94 (lOO . O)

Anatomical region of nodule

Head
Thoraxol23Upper limbsoLumbar & abdomen

O

O

3

Pelvic region

3

11

9

Lower limbs

O

O

3

208

Table 5 Frequency of positive skin biopsy from different anatomical
regions of the body

Anatomical region

Frequency of positive snip (%)

Scapular region

516 (56.8)

Iliac crest

798 (87 . 9)

Calf region

610 (67 . 2)

Total

908 (100.0)

The results showed that in four (Maijemu, Dass, Rondo and Gwodong) out of the six
villages examined, there was no difference in the infection rate by sex. However males
subjects showed a higher microfilarial rate than their females at Dorong and Federe, 40.7%

in male and 29.3% in female at Dorong; 50.0% in male and 33.3% in female at Federe.
The result showed that the frequency of onchocercal lesions was different by villages.
The least number of lesion was observed at Dorong with the least microfilarial rate (Table2) .

The most frequent lesion was pruritus (14.4%) and this was followed by skin depig‑
mentaion (9.9% ) , especially on the shin. The least occurring lesion was hanging groin andelephantiasis (0.8% ) whilst nodule and visual impairment scored 4.6% and 6.4% , respectively.
Like in the microfilarial rate, the percentage clinical manifestations increased with age.

Visual impairment and depigmentaion were not observed in 0‑9 years age group. Hanging
groin and elephantiasis occurred only in older male subjects (Table 3) .
A total of 94 onchocercal nodules were observed in the 84 nodule‑positive persons (Table4) . Nodules were found most abundantly in the pelvic region followed by the thoracic region.

The prevalence of onchocercal nodules varied with age, with lower rate occurring in the agegroup below 19 years old. Of the 25 persons of positive for microfilariae of O. volvulus in theage group 0‑9 years, only five nodules were observed in two. Nodules occurred in all theregions of the body in the group 40 years old or more, with the highest prevalence in the pelvic
region.

Of the 908 persons positive for microfilariae of O. volvulus the highest frequency of
positivity of 798 (87.9% ) occurred in the iliac crest, the scapular region and calf showed
56.8% and 67.2%, respectively (Table 5) .

DISCUSSION

The present study demonstrates that 49.9% of the inhabitants were positive formicrofilariae of O. volvulus in the Jarawa Valley, Nigeria. Thus, adapting the recommenda‑
tion of WHO (1966) , this area must be regarded as mesoendemic area for onchocerciasis.
However, three (Dass, 60.0%; Rando, 63.6% ; Gwodong, 59.9%) , which were shorter distancefrom breeding sites than the other villages, out of the six villages were almost approaching

hyperendemic situation. The microfilarial rate in the present study is much higher than
11.1% infection around the Assob river area (Onwuliri et al., 1987) of the Zone 11 of the
NOCP area. This comparatively high infection rate in the Jarawa Valley area may sternfrom the fact that these villages in the Jarawa District area are surrounded by the fast fiowing

tributaries of the Jarawa river system so that they have more breeding foci of vectors than

209

the other areas in the state (Nwoke, 1986) .
The present study showed that there was a gradual increase in the microfilarial rate withage, similar to the findings of Enarson (1977) in Sudan and Dipeolu and Gemade (1983) inNigeria. This situation bears witness to the chronic and cryptic nature of onchocerciasis
infection. The microfilarial rate of 7.3% in children (0‑9 years old) in the present study is
attributed to early contact with infective blackfly bites in high endemicity. It is not clear thereason of a difference in prevalence by sex at two out of six villages in the present study.

Only 84 (4.6%) of the inhabitants examined had onchocercal nodles in the present study.

This value is certainly low compared to nodules in other foci. In both sexes and ages, thegreat majority of the nodles occurred in the pelvic region followed by thoracic region and thehead, similar to the results reported by Anderson et al. (1974) and Enarson (1977) in other
African foci.

Visual impairment in the present study was found to be concentrated in the working age
groups causing a lot socioeconomic liabilities unable to maintain the productive activity forlong. The visual impairment rate in the present study was, however, comparatively low;
6.4% of the inhabitants examined (both impaired vision and total blindness) . This is incontrast to 16.2% of the inhabitants (Budden, 1957), l0.3% (Dipeolu and Gemade, 1983) inother Savanna areas. This fact may be attributed to the habitual migration of disabled
people in this part of the country to urban centers to beg for alms, consequently reducing theactual number of blind people in the rural communities. It may also be that the microfilariaeof O. volvulus in the Jos Plateau has less toxicity than that of other Savanna region.

Leopard skin was observed in 9.9% of the villagers especially among the older age
groups. It was frequently observed on the thigh, buttocks and the shin. The occurrence of
leopard skin on sites not readily exposed to blackfly bites in the present study supports thefact that this striking manifestation is not caused only by dermatoxic components of blackfiysaliva as suggested by Craig (1932) and Nwokolo (1950) . The present findings agree with theobservation of Gibson et al. (1980) , Connor and Palmieri (1985). On the contrary, theabsence of leopard skin among younger age groups (0‑19 years) supports the fact that thislesion is invariably associated with long‑standing onchocercal infection.

All the cases of hanging groin and scrotal elephantiasis were observed among men ofolder age group. No such cases as described by Cherry (1959) , Connor and Palmieri (1985)
were observed among women. The association between onchocerciasis and elephantiasis had
been recorded by several other workers including Buck et al. (1971) in Chad and Wonde etal. (1973) in Southwest Ethiopia. Although some investigators (Oomen, 1969; Price, 1972;
Heather and Price, 1972) noted that elephantiasis could not be caused by onchocerciasis, amore recent study by Gibson and Connor (1978) noted that in Africans, antigens released
from the microfilariae of O. volvulus lead to the deposition of immune complex in the tissues,

which in turn causes inflammation and fibrosis and, eventually obstructive lymphadenitis.
This process may cause hanging groin and, possibly, also elephantiasis.
There was a marked difference in the frequency of positive skin snip from different
anatomical parts of the body. Of the three anatomical parts compared, iliac crest revealed
the highest positivity snippings. This finding corresponds to a finding that the greater numberof onchocercal nodules observed around the pelvic region and support the idea of Kershaw
et al. (1954) who found that microfilarial distribution in the skin is closely related not only

to clinical manifestation, but also to the location of onchocercomata.

210

ACKN OWLEDGMEN Ts
We are grateful to all our research assistants and the people of Jarawa District for theircooperation.

REFERENCES
1 ) Anderson, J., Fuglsang, H., Hamilton, P.J.S. and Marshal, T.F. De C. (1974): Studies on

onchocerciasis in the United Cameroon Republic l. Comparison of population with andwithout Onchocerca volvulus. Trans. R. Soc. trop. Med. Hyg., 68, 190‑208
2 ) Buck, A.A., Anderson, R.1., Colston, A.C. Jr., Wallace, C.K., Connor, D.H., Harman, L.E. Jr.
Donner, M.W. and Ganley, J.P. (1971): Microfilaruria in onchocerciasis, Bull. Wld Hlth Org.,
45, 353‑369
3 ) Budden, F.H. (1957): Natural history of onchocerciasis, Br. J. Ophthal., 41, 214‑227

4 ) Cherry, J.K.T. (1959): Adenolymphocoele and elephantiasis in onchocerciasis, East Afr. Med.
J., 36, 224‑230

5 ) Connor. D.H. and Palmieri, J.R. (1985) : Blackfly bites, onchocerciasis and leopard skin, Trans.

R. Soc. trop. Med. Hyg., 79, 415‑417
6 ) Craig, C.F. (1932): The possible chemotactic effect of the salivary secretions of certain insects
upon microfilariae, Science, 75, 561‑562
7 ) Dipeolu, 0.0. and Gemade, E.1.1. (1983) : Onchocerciasis in the Benue State of Nigeria. IV. The

prevalence of the disease among the population in Manor, Int. J. Zoonosis, 10, 85‑95
8 ) Enarson, D.A. (1977): Observations on onchocerciasis in the Sudan Republic. Endemicity,
intensity of infection and clinical features, Ann. Trop. Med. Parasitol., 71, 465‑468

9 ) Gibson, D.W. and Connor, D.H. (1978): Onchocercal lymphadenitis: Clinicopathologic studyof 34 patients, Trans. R. Soc. trop. Med. Hyg., 72, 137‑154

10) Gibson, D.W., Heggrie, C. and Connor, D.H. (1980): Clinical and pathologic aspects ofonchocerciasis, Pathology Annual. Vol. 15, pp. 195‑240, Sommers, S.C. and Rosen. P.P. ed.,Appleton Century Crofts, New York11) Heather, C.J. and Price, E.W. (1972): Non‑filarial elephantiasis in Ethiopia. Analytical studyof inorganic materials in lymph nodes, Trans. R. Soc. trop. Med. Hyg., 66, 450‑458
12) Kershaw, W.E., Duke, B.O.L. and Budden, F.H. (1954): Distribution of microfilariae of O.
volvulus in the skin. Its relation to the skin changes and to eye lesions and blindness, Br. Med.
J., 2, 724‑729

13) Nwoke, B.E.B. (1986) : Studies on the field epidemiology of human onchocerciasis on the Jos
Plateau, Nigeria. Ph. D. Thesis University of Jos, Nigeria
14) Nwoke, B.E.B., Onwuliri. C.O.E. and lwuala, M.O.E. (1986): Studies on the field epidemiologyof human onchocerciasis on the Jos Plateau, Nigeria. II. Seasonal relative abundance andinfective biting density; and the effect of parity on the biting pattern of Simulium damnosum
s. l. (Diptera: Simuliidae), Nigerian J. Parasitol., 4, 25‑32

15) Nwokolo, C. (1950) : Studies on onchocerciasis. A review of 100 cases from Enugu District ofEastern Nigeria, Trans. R. Soc. trop. Med. Hyg., 43, 493‑501
16) Onwuliri, C.O.E., Nwoke, B.E.B., Awal. I.A. and lwuala. M.O.E. (1987): Onchocerciasis in
Plateau State of Nigeria. II. The prevalence among residents around the Assob River Area,
Ann. Trop. Med. Parasitol., 81, 49‑52
17) Oomen, A.P. (1969) : Studies on elephantiasis on the legs in Ethiopia. Trop. Geogr. Med., 21, 236*253

18) Price, E.W. (1972): The pathology of non‑filarial elephantiasis of the lower legs, Trans. R.

211
Soc．trop．Med．Hyg．，66，150−159
19）Roberts，D．M、and

Irving−Bell，R．」．（1985）：Circadian night activity of S伽％1ま％吻s餓（Diptera：

Simuliidae）sampled with a vehicle−mounted

net

in

CentralNigeria，Bull．Ent．Res．，75，23−33

20）WHO（1966）：Epidemiology of onchocerciasis Report of a WHO Expert Committee，2ndreport．WHO Tech．Rep．Ser．，335，Geneva21）Wonde，TりTada，1。and Iwamoto，L（1973）：Onchocerciasis．A possible etiology of ele・
phantiasis

in South−west

Ethiopia，Jap．J．TroP．Med．Hyg．，1，25−29

ナイジェリア，プラトー州ジャラワ渓谷におけるオンコセルカ症の流行状況
BERTRAM

E．B．NwoKE1・CELEsTINE O．E．ONwuLIRI2・塩飽
GAD O．UFoMADu4・多田
功5・高橋
弘6

邦憲3

ナイジェリア，プラトー州ジャラワ渓谷においてオンコセルカ症の臨床的，寄生虫学的調査を1985年1月から1986年4月に実施した。6集落1，821名の住民を検皮し，908名（49．9％）の住民
がOn6ho66名昭〃o伽」鰐ミクロフィラリア陽性であった。オンコセルカ症の感染率は加齢とともに増加し，40歳以上の年齢群で最も高率であった。オンコセルカ症の病変は，掻痒疹が最も高率で，次いで皮膚の脱色素斑，視力障害，皮下腫瘤，鼠径下垂・象皮病の順であった。皮膚の脱色素斑leopardskinは下肢だけでなく，腎部等のブユの吸血に直接さらされない部位にも認められた。鼠径下垂・象皮病のリンパ系の病変は，主に高齢の男性に認められた。また，皮下腫瘤は成人に多く，主に腰部に認められた。皮膚の生検では，腸骨部で最もミクロフィラリアの陽性率が高かった。

1 イモ大学生物学部
2 ジョス大学理学部
3 愛知医科大学寄生虫学教室 現所属：島根医科大学環境保健医学教室
4 ナイジェリア・トリパノソーマ研究所
5 熊本大学医学部寄生虫病学教室
6 国際協力事業団・ジョス大学医学部 現住所：東京都練馬区早宮1−40−11
この研究は日本一ナイジェリア医学協力事業によった（JUJIP−No．15）

JAPANESE JOURNAl
OF
TROPICAl

MEDICINE

AND

HYGIENE
June1989

Vol．17No．2

CONTENTS
ReviewGranz，N．G．

The

Present

StatusandFutureProspectsofMalaria131−147

Control

Originalarticle
Takaoka，H．，Gomez
Observations

L．E．A．，Alexander，」．B，and

Hashiguchi，Y．

theAccessoryon

Validityofof

Seven Ecuadorian Sand FlyinDetermining

Their

the

OvarianGlandsSpecies（Diptera：Psychodidae）

Parity一……一……・…………一……・………一一…・

149−155

Sato，H．

EcologicalStudies

Encephalitis

onon

the単osquito

Control

Mosquitowith

LarvaeFish，（議z卿わz4s凌z顔n商forSpecial Reference

and

to

Selective

Competition・with theFeeding

Medaka，0η勿s観膨s157−173

Kerdpibule，V．
A

Field Test of2一［1−methyl−2一（4−phenoxyphenoxy）ethoxy］pyridine

against Principal

VectorsofMalariainFoot−hill

Area

in

Thailand175−183
Akogun，O．B．
Water Demand
BauchiandSchistosomiasis

State，Nigeria・…………

Coscar6n，S．and
Description of

among

the

Gumau

Peopleof……………・・…肇・………………・・……………・

185−189

Takaoka，H．
a New（E6彰吻耀吻s）from

Species

the

Andes

of the BlackofFly Subgenus S伽祝1加nEquador（Diptera：Simuluidae）………

191−196

Nishiyama，T．，Furuki，J．，Yagi，」．，Wada，T．，Araki，T．，Amano，H．and Tsujii，T．
Effectof

Gastrografinon1）ゆhlyJJo60孟hγ伽彫ムα伽吻，7㌃召％宛sαg初α如and伽」・9・卿吻sg欄4ゑsInfecti・n一一…・一・……………・……一……

197−203

Nwoke，B．E．B．，Onwuliri，C．0．E．，Shiwaku，K．，Ufomadu，GO，，Tada，1．

andTakahashi，H．
Endemic Onchocerciasis on the Jarawa Valley Area of Plateau
State，Nigeria……・…・…・一………………・……………一…・…一………・…・… 205−211

PublishedJAPANESE SOCIETY
c／o

InstituteofOF

Tropicalby

TROPICAL

Medicine，Nagasaki

MEDICINE
University

12−4Sakamoto−machi，Nagasaki852，Japan