THE EPIDEMIOLOGY OF A DISAPPEARING DISEASE: MALARIA*

FRED L

The honor of the invitation to deliver the 24th
Charles Franklin Craig Lecture is greatly en-
hanced for me by the presence of Dr. Lewis W.
Hackett, my first chief, as our presiding officer.
It is significant that the invitation to speak on
Malaria Eradication comes so soon after the
masterly 22nd Charles Franklin Craig Lerture
on "Malaria Eradication-Growth of the Concept
and its Application" by Dr. Louis L. Williams,
Jr., just 2 years ago. This reflects the interest of
the American Society of Tropical Medicine and
Hygiene in what has come to be the greatest
public health effort of all times and the rccog-
nition by your leaders that the development of
the program for the world-wide eradication of
malaria is so rapid that this Society must have
frequent reports, if it is to discharge properly the
responsibilities assumed in 1951 when the
American Society of Tropical Medicine and the
National Malaria Society were fused to brcomc
the American Society of Tropical Medicine and
Hygiene. This Society must be the voictt of the
tropical public health workers of the ITnitrd
States in all matters related to malaria. The
responsibility of this Society is indeed great since
the economic resources for supplies and equip-
ment and for the technical and administrative
training of national staffs essential to eradication
programs simply are not availablr in many of the
most malarious areas of the world. The continued
and increasing support of the United States
Government through multilateral and bilateral
agencies is indispensable. The responsibility of
this Society as a source of informed professional
opinion will increase as the world program con-
tinues to develop and as obvious SUCC~~SCS in
many areas lead to a false sense of optimism with
a natural tmdency to rclas and reduce the all-out
effort before the goal is reached.

The unusual procedure of inviting a Charles

* The essentials of this paper were given under
the title, "Some 1959 Impressions of World-Wide
Malaria Eradication," as the 24th Annual Charles
Franklin Craig Lecture before t.he American
Society of Tropical Medicine and Hygiene, In-
dianapolis, Indiana, October 28, 1959.

t Emeritus Director, Pan American Sanitary
Bureau. Present, address: 4101 Rosemary Street,
Chevy Chase 15, Maryland.

SOPERt

Franklin Craig Lecturer to speak on a specific
suhjcct followed, and may have been suggested
bJ3 the remarks made a few months ago for the
Washington Tropical Diseases Association after
a trip to Asia with Dr. Robert Briggs Watson of
the Rockefeller Foundation. Our trip to Asia was
to observe at first hand eradication programs
which, after early dramatic declines in malaria
incidence, had failed to reach eradication on the
anticipated schedule. We visited Taiwan, the
Philippines, Ceylon and Mysore State, India,
before attending the Third Asian Malaria
Conference (March, 1959) in New Delhi where
personal contact was established with many
malaria workers from Southeast Asia and the
Western Pacific. Later I visited the eradication
program in Thailand alone. These countries were
carefully selected as those which had solved the
hulk of their malaria problem but were facing the
problem of final cstirpation of the infection.

The impressions from this all too rapid visit
may be summarized as follows: 1. In each of the
countries visited the introdurtion of residual
insrcticidcs was followed by a rapid decrease in
malaria, almost to eradication, in large heavily
populated areas during the first 2 years of overall
coverage. 2. No serious technical difficulties were
encountered in any of the areas visited : anopheles
resistance to DDT was not a problem, nor was
estra-domiciliary transmission of malaria proven.
3. The administrative difficulty of getting full
coverage with residual insecticide of all human
habitations in all of the malarious areas, and the
epidemiological difficulty of identifying areas
where transmission continues, both contributed
to the failure to eradicate malaria rapidly.

There has been a failure to develop proper
supervision and cherking of spraying operations
and to adapt the techniques suitable for heavily
populated, easily accessible populations to fringe
populations, to nomadic populations, and to
scattered populations living in hilly and forested
areas. Particularly has there been a failure in
certain instances to recognize the necessity for
spraying temporary shelters used by rural popu-
lations in connection with seasonal crops. There
has been a tendency to be satisfied with the

357


358

FRED L. SOPER

general reduction of malaria, especially during
the early years of the program, rather than to
evaluate information from local communities to
pinpoint places where malaria transmission con-
tinues. This blurring of the immediate objective
of the eradication program, viz., the interruption
of malaria transmission in each local community
for the period required for spontaneous clearing
of the infection in the human population, has led
to costly delays, since partial eradication is always
expensive.

In none of the countries visited had high blood
indices persisted in the heavily populated, easily
accessible areas, following the interruption of
transmission. Nowhere was the charge of falsity
made against the premise on which the eradi-
cation program is based. When properly used
DDT had caused transmission to cease and
malaria had disappeared rapidly.

The visits to the Asiatic eradication programs
were entirely too short to do little more than
gather general impressions from reading available
reports, discussing details with program leaders
and in some instances observing field operations.
Surprisingly, each of the programs with minor
variations seemed to fit the same pattern as
outlined above. The analysis of the pattern
indicates that the difficulties of malaria eradi-
cation are in general those of any eradication
program and may be classed as, (1) adminis-
trative difficulties encountered in executing one
hundred per cent of the necessary program, and
(2) epidemiologic difficulties in identifying the
places where the program has failed in its im-
mediate objective and permitted transmission to
continue. These difficulties seem to plague the
health officer whenever he shifts from the concept
of communicable disease control to eradication.
The Public Health Administrator responsible for
the control of communicable diseases, that is,
reduction to the point where each disease is no
longer a problem of public health importance in
his community, tends to lose interest in the
individual disease at the point where the eradi-
cationist often encounters his greatest difficulty.
This attitude is supported by international
quarantine experience which shows that the
threat of international movement of the in-
fectious agents of communicable diseases is
correlated with the epidemiological visibility of
such diseases.1 Also, the geographical area for

$ Present day international sanitary regulations
provide, in the case of smallpox, relapsing fever,
cholera, typhus, and plague, that local infected

which the Public Health officer is responsible is
generally small and the threat of peripheral re-
infection great, so it matters little that the seeds
of infection remain in his area. For tht eradi-
cationist, continuing unrecognized transmission
below the threshold of visibility constitutts the
greatest threat to victory in the battle for
complctc elimination of the sources of infection.

The communicable disease control officer can
take satisfaction from the absence of reported
cases and of public clamor, but the rradicationist
can be happy only when he has proven that
transmission has ceased.

To emphasize the need for special study of the
manner in which a communicable disease con-
tinues near or below the threshold of visibility and
of the measures for its final suppression, I pro-
posed some years ago the term, "The Epidemi-
ology of a Disappearing Discasc." I was gratified
to receive an immediate rash award from Dr.
L. L. Williams, Jr., who recognized the value of
the term for this concept in malaria eradication.
Dr. Louis I. Dublin has sinrc used the term,
"The Epidemiology of Rrtreating Tuberculosis,"
and Dr. Luis Vargas the term, "Thr Epidemi-
ology of Evanescent Malaria."

The situation of malaria eradication in certain
countries of Asia at the present time bears con-
siderable resemblance to that of yellow fever
eradication in Brazil in 1930. Since this is a
Society of Tropical Medicine and Hygiene, and
since today we are considering impressions and
general principles rather than detailed statistical
information as to the progress of malaria cradi-
cation in specific countries, WC may well digress
on the problems of yellow fever eradication in
Brazil 30 years ago and the measures taken for
their solution. This digression is entirely fitting
sinre here in Indianapolis 59 years ago this
month Walter Reed made the first presentation
of the work of the Army Yellow Fever 13oard
(Walter Reed, James A. Carroll, A. Agramontc,,
and Jesse W. Lazear) before the American Public
Health Association. 5

areas can he declared free of any of these diseases
when a period of only twice the incubation period
of that disease has passed without the recognition
of locally infected cases. This usage is based
empirically on the observation that the chance of
international movement of a given infection is
relatively small when its incidence is so low t'hat
new cases do not come to the att,ention of the
Public Health authorities.

J Proceedings of the Twenty-eighth Annual
NIeet.ing of the American Public Health Associa-
tion, Indianapolis, Indiana, Oct. 22-26, 1900.


EPIDEMIOLOGY OF MBLARlA

359

Ey 1915 it had brcn observed that anti-
mosquito measures in the important endemic
cnenters of yellow fever in the Caribbean, Gulf
and South Amc,rican regions resulted routinely in
the disappearance of yellow fever within a short
period of time, not only in the endemic centers
worked, but also in large tributary areas. General
Gorgas logically concnluded, and succLec>ded in
convincing Wickliffe Rose of the International
Health Commission of the Rockefeller Foun-
dation, that anti-mosquito measures in thr large
cities of the remaining endemic areas of the
Americas and of Africa would lead to the corn-
pletc disappearance of yellow fever in the world.
The initial efforts of the Rockefeller Foundation,
collaborating with the health authorities of
endemic countries of the Americas, were followed
by the apparent disappearance of yellow fever
from the west coast of South America, from
Central America and Mexico, and from Columbia,
and by 1925 the program for the eradication of
yellow fever in Brazil, belicvcd to be its last
stronghold in the Western Hemisphere, was so
far advancsrd that part of the Foundation's yellow
fever staff was deployed to Africa to scout out
the situation on that continent.

Isut yellow fever had not disappeared from
Brazil, but had rather made a temporary tactical
retreat in the face of the concerted onslaught in
the large coastal cities of that country. Looking
back from the vantage point of today this same
pattern can be seen to have been repeated over
and over again dating back to the first national
eradication effort of the Brazilian Government.
In 1916, General William C. Gorgas, as Chief of
the Rockefeller Foundation's Yellow Fever Com-
mission, had visited Brazil and been given evi-
dence of continuing endemicity in the north-
eastern states. The entrance of the United States
into World War I early in 1917 prevented the
return of Gorgas t'o Ilrazil and interrupted the
program of the Rockefeller Foundation. In 1918
the Brazilian Government, without waiting for
Foundation participation, undertook the eradi-
cation of yellow fever as a national project. The
work of the Federal Yellow Fever Commission,
1919 to 1921, throughout the northern states was
an outstanding accomplishment. Yellow fever
retreated on all sides and disappeared from the
statistics of the area worked and in 1920 the
Brazilian authoritirs saw no reason for accepting
Foundation cbollaboration which was then avail-
able. In 1921, with yellow fever no longer a
problem, the Brazilian Yellow Fever Commission

became a rural health service with diversion of
activity to hookworm disease, malaria, and other
endemic conditions. In 1923, yellow fever re-
appeared and the Rockefeller Foundation under-
took the organization of an eradication program
in north Brazil. The rapid decline of yellow fever
on all sides led once more to false optimism; a
rude awakening came in 1926 when the movement
of revolutionary and government troops through
the interior led to widespread yellow fever out-
breaks. Intensification of anti-mosquito measures
over large areas followed and once more yellow
fever receded precipitously from the statistics of
the endemic arra. In 1927-1928, a period of a
year passed in which yellow fever was not
recognized any place in the Americas. The re-
infection of Rio de Janeiro, Ilrazil's beautiful
capital, in 1928 from some unrecognized focus of
infection, was followed by the widespread ap-
pcarance of yellow fever along the coast from Rio
to the Amazon Valley.

Anti-mosquito mcasur(ls in Rio and the rc-
organization and intensification of such measures
elsewhere led once more to the recession of yellow
fever; but at long last it had become apparent
that the premise on which the Rockefeller
Foundation had embarked on the eradication of
yellow fever was no longer tenable. It was
obvious that the virus of yellow fever persisted
unrecognized in spite of repeated anti-acgypti
campaigns in all known endemic renters.

For almost three decades, 1ldcZe.s aegypti had
been accepted as the one and only vector of
yellow fever; apparent confirmation of the
monopoly of transmission by aegypti had come
repeatedly from the regularity of the disappear-
ance of yellow fever from the health statistics of
endemic and epidemic centers after the breeding
index of this mosquito was brought below five per
cent.

The first reaction following the appearance of
yellow fever in Rio in 1928 was to attribute the
persistence of yellow fever to administrative
failures in the northrrn endemic foci. The
maintenance of top efficiency in anti-aegypti
work over long periods is a notoriously difficult
administrative problem and gross imperfections
were known to have occurred. Support for the
suggestion that administrative failure might be
responsible for failure to eradicate yellow fever
(lame early in 1929 with the finding of yellow
fever within 200 meters of the headquarters of the
Yellow Fever Service in Recife, Brazil, when the
reported aegypti-breeding index was only eight-


360

FKIW L. SOPER

tenths of one per cent, far below the accepted safe
threshold of five per cent. A check sample of
100 houses scattered at ten different points
throughout the city gave an overall aegypti-index
of twenty-six per cent; the percentage of houses
with pupal foci, that is with foci actually pro-
ducing adult aegypti-mosquitoes, was eight per
cent. This result clearly indicated that the
administration of the anti-mosquito work in
Recife was inadequate and raised the question as
to whether or not yellow fever had been able to
maintain itself in the endemic centers themselves,
where its vector had been under attack for a
period of 5 or 6 years.

Beginning in 1930 the anti-aegypti services
were completely reorganized and uniform oper-
ating procedures established throughout Brazil
with adequate provision for checking, rechecking,
and double checking the work done; and with
cross checking by determining the results of anti-
larval work on the density of adult aegypti, and
the overall effect on the occurrcnre of yellow
fever itself.

The most useful method of cross-checking the
results of anti-acgypti work was found to br the
starch for adult mosquitoes in the houses of areas
where low breeding indices were reported. The
capture of adult mosquitoes, long a measure used
by malariologists in a study of anopheline mos-
quitoes, had been largely abandoned by yellow
fevrr workers because of the accessibility and
ease of observation of larval breeding places in
artificial water containers in and around human
habitations. The capture of adult mosquitoes can
be very misleading when the breeding indes is
high with an overlapping of distributional
patterns from individual foci, but once the density
of the species is really low the study of the distri-
bution of adult mosquitoes, which can be caught
in human habitations, tends to rcvcal often
within a matter of a few meters where the guilty
pupal focus lies.

The intensification and improvement of atl-
ministrative procedures together with the intro-
duction of the capture of adult mosquitoes for the
discovery of hidden aegypti brerding resulted in
1933 in the romplcte disappearance or eradication
of the :lddes aeg@i mosquito from some of the
principal cities of north Brazil. This, the first
observation of aegypti eradication during more
than 30 years following the initial work of Gorgas
in Havana in 1901, was of the utmost significance :

(I) in the development of a rational long-term
continental program against yellow fever; (2) as
preparation for the eradication of ~l~lopheles
ga&ine from Brazil and Egypt; and (3) in the
acceptance of the concept of eradication in the
prevention of communicahlc diseases.

A more fundamental cross check on the results
of the work of the Yellow Fever Eradication
Service than that provided by the search for
adult aegypti was gotten through the systematic
search for and diagnosis of unrecognized and un-
suspected cases of yellow fever during silent
inter-epidemic periods. Fortunately, the liver
tissue of the victim of fatal yellow fever has
microscopic changes by which the disease (aan be
diagnosed; the search for yellow fever was based
on the routine collection and examination of liver
tissue throughout all possibly endemic areas, to
which the name viscerotomy was given. Viscrr-
otomy was to show that yellow fever had main
tained itself in Brazil, not in one, but in two
unrecognized forms, neither of which was related
in any way to drficicnt administration of acgypti
programs in the larger endemic centers. The first
revelation of viscerotomy was of silent village
and rural acgypti-transmitted cndrmi~ yellow
fever in a large arca of northeast Rrazil in the
hinterland just back from the coast where the
Yellow Fever Service had been heavily engaged in
combatting yellow fever in the port cities. This
area was silent largely because the endemicity
was so intense that the great majority of in-
fections (and of fatal cases) were in children less
than 5 years of age among whom mortalit,y
caused little comment. The discovery of this
unsuspected endemic situation led to anti-aegypti
measures in interior villages and even in strictly
rural areas throughout several states of northeast
Rrazil. The last case of yellow fever diagnosed in
this region occurred in August 1934; it is now 25
years since endemic, argypti-transmitted yellow
fever occurred in Rrazil. Lowering the threshold
of visibility of yellow fever in this area then led
to the eradication of yellow fever just as lowering
the threshold of visibility of aegypti-breeding led
to the eradication of aegypti.

An rven more surprising revrlation of vis-
crrotomy is the widespread distribution of yellow
fever existing in the absrncc of the :l&%es aegypti
mosquito throughout immrnse forested regions
wherr yrllow fevrr had never been recognized, or
had not been reported for a decade or more. This


EPIDIDIIOLOGY OF MALAltIA                   361

jungle yellow fever, which does not depend for its
maintenance on man as the mammalian host, is
associated with monkeys and other forest
primates and has Iwcm shown since 1932 to be
either cnzootio or epizootir in large areas of the
Americas ranging from northern Argentina to
M&co.

With the discovery of jungle yellow fever
which constitutes a permanent source of virus
from which the cities and towns of the Americas
could be rrinfected, it was realized that the
eradication of yellow fever had been from the
beginning an impossibility. It was recognized
early that the discovery that the .Iddes aegypti
mosquito could be eradicated, just at the time of
the first finding of jungle yellow fever, was
indeed fortuitous. The eradication of aegypti in
Rmzil's port cities was followed by its gra,dual
but complete eradication from suburban villages
and rural areas, and today there is a well atl-
vanced program for the complete eradication of
the acgypti mosquito from the Western Hemis-
phere. Although the IJnited States has not yet
formally embarked on the eradication of /lades
aegypti, the final result is inevitable since as rach
country frees itself of aegypti the pressure
becomes greater on those which have yet to join
in the continental program which is of permanent
advantage to all.

No new administrative, technical nor adminis-
trative methods were involved in uncovering
rural endemic and jungle yellow fever and in
eradicating endemic yellow fever and thr L18des
aegypti mosquito. The improvement in adminis-
tration involved the careful mapping of areas to
br worked, the establishing of itineraries for
working units, careful recording of all work at the
time it was done, careful supervision and checking
of work done, the standardization of operating
procedures according to a written Manual of
Operations, and the inculcation of the principle in
all employees that they were responsible not only
for doing their job, but also for getting the results
expected from the doing of the job. The use of
the capture of adult mosquitoes for the determi-
nation of continued breeding was not new, but
had not been used for many years in yellow fever
work. The identification through viscerotomy of
places where yellow fever is present was de-
veloped 18 years after the diagnostic value of the
liver lesion in yellow fever was established. Only
the viscerotome was new; while it was an im-

portant factor in the suc~ss of visccrotomy its
use was not indispensable to the method.
The malaria eradicationist today faces es-
sentially the same problems that the yellow fever
cradicationist did 30 years ago; how improve the
administration to guarantee complete effective
application of the chosen method of attack, and
how identify, on a continuing basis and at a
rcasonablc cost, the places where transmission
occurs in spite of the attack? How determine the
epidemiology of malaria when there has been
such a great reduction in the incidence of the
disease that cases are not being reported? And
especially, how get these results economically?
Given the essential identity of the malaria
problem with that of yellow fever, it may not be
amiss to outline briefly for the malariologist the
way visrerotomy is organized in the Americas.
Viscerotomy was introduced when there was
good reason to believe that there was no yellow
fever in tlir large citirs of Brazil; information was
ncedcd from rural areas, and eventually from the
most isolated parts of thr country. A considrr-
ation of the cost of maintaining full-time rm-
ployees in hundreds, nay thousands of small
communities in the intrrior, led from the begin-
ning to the decision to appoint local rcprr-
sentatives to collect liver tissue from indicated
cases. The law provides that a burial permit,
wherever a viscerotomist is located, must be
approved by the viscerotomist before the body is
interred. If it is ascertained that death has
occurred in less than 11 days after onsrt of a
febrile disease, the representative removes rapidly
with a special instrument designed for the purpose
(viscerotome) a small section of liver before
approving burial. The viscerotomist receives a
small fee for each spccimrn forwarded to the
laboratory for diagnosis and a considerably larger
one for the first one showing yellow fever lesions.
He also receives a small fee for forwarding
monthly the statistics from the local registrar
which would otherwise not be available.
The results of visccrotomy have not been
perfect; on the other hand the cost is not escessive
and most of the information on the movement of
yellow fever virus during the past three decades
has come from this procedure. Viscrrotomy does
not pretend to the discovery of all cases of yellow
fever since by its very nature, viseerotomy is
limited to fatal cases. Rather viscerotomy
identifies the place where yellow fever trans-


362

FILEI) L. SOPElt

mission is present; of almost equal value is the
negative cvidencr for the non-existence of yellow
fever in certain large areas over a period of years.
The information viscerotomy gives regarding
jungle yellow fever often comes from the most
isolated and difficult areas, where the cost of
maintaining service employees would be in-
ordinatcly high. The local representative has the
advantage of being resident in the community
and is there day after day, week aftrr week,
month after month. It is in just such. arcas as
these that malaria eradicationists arc now cm
countrring their greatest difficulties.

Malaria eradication in various countries today
seems to be following the pattern of endemic
yellow fever eradication in Brazil from 1919 to
1934; in the face of an energetic frontal attack
malaria disappears,  recedes,  evanesces, but
remains to flax up and ridicule the cradicationist
so soon as the attack is abandoned and cradi-
cation put to the critical test of the complete
suppression of preventive measures. All too often
the cradicationist is finding that the insecticidal
work in some of his areas has been as poorly
administcrcd as had been the anti-acgypti work
in Pcrnambuco in 1929 and that his epidcmi-
ologiral investigation has not shown him the
sil(,nt malaria transmission that was continuing
in his "jungle" arcas. Without entering into
d&ails of anopheles resistance to insrcticide and
of plasmodial resistance to drugs, it can be said
that the technical problems in malaria eradication
would br much more easily solved were it possible
to rccognizc every new infection at the time it
orcurs so that th(l failure to block transmission
in each small delimited arca, whether due to
technical or administrative failure, could be
denouncrd and corrected. Thr malariologist does
not havcb any c~c~onomiral method of recognizing
cash new infection and may well have to settle,
as did th Yellow Fever Service years ago, for the
id(&fic~at~ion of the placc~s whrrc transmission is
occurring.

I~pitlrmiologic,al evaluat~ion as a chcxk on the
romplrtcnc~ss of the interruption of transmission
by early insertiridal spraying is hardly less
significant than similar information in the tcrmi-
nal stages of the program when surveillance is
taking over. Proper rvaluation during the attack
phase of cxradication is essential to the derision to
aba,ndon spraying and b(lgin surveillance; pre-
cipitate unjustified action can force a highly

cspcnsivc  rclorganization whereas  continued
spraying when no longer required is equally
wasteful. The malariologist must decide on the
method of rvaluation best adapted to his area:
1) routine systematic collrrtion of blood slides
from fever casts by local resident representatives;
2) routinr collection of blood slides from fever
cases by house visits of service employees at
frequent intervals; and 3) mass or sampling
surveys of all or of certain groups of the popu-
lation without regard to history of fever.

Comments on Malaria Eradication in Certain

Countries

Philippine Islan,ds. In the Philippines after
some 4 years of widesprrad coverage with in-
secticidal sprays in arcas with over 8 million
peoplr, firld surveys wcrc made (1957-l 958) and
interpreted to mean that no transmission had
occurred during a 2 year period among some 5
million people living in previously malarious
areas. Spraying was supprrssed in 1958 in these
areas. Surveillanrr was organized on the basis
of house-to-house visits every 3 weeks with the
rsamination of blood slides from all fever cases
found and of persons reporting fever during the
previous 3 weeks. The analysis of the findings
at the end of 10 months led to the reorganization
of spraying operations throughout much of the
area where they had been suppressed. Most of the
recrudescence of transmission found was at-
tributed to the introduction of the infection in
the "eradicated" areas from the sprayed areas
where transmission had never been interrupted.
Under Philippine conditions, it is apparent that
it is not safe to discontinue spraying in one arca
until the areas from which it can be reinfected
havr also been cleared of infrction.

Ceylon,. Ceylon was one of the first countries in
Asia to benefit from the introduction of DDT
which has been widely used since the malaria
rpidrmir of 1946-47. The government decided
early in 1949 to attempt thr complete eradication
of malaria from the island and by 1954 consider-
able areas where transmission could not be found
were removed from the spraying program. In
many areas j 1 nopheles culicijacies could no longer
be found. During 1955 the starch for fever cases
in dispensaries was relied on to show where
transmission was occurring; many of these
dispensaries were themsclvrs outside of the area
of transmission. The search for fever cases in


EPIDEMIOLOGY OF MALARIA                 363

dispensaries and the follow-up of these cases to
identify the areas where transmission was oc-
curring so that treatment and insecticide could
be applied proved ineffective and in 1956-57
there was a considerable reinvasion of the
"eradicated" area by malaria. In 1958 the
spraying program was reorganized and today
there is an intensified search for fever cases
throughout the island and greater insistence on
finding and spraying temporary shelters in the
forest clearings. The success of the present
program will depend on the seeking out and
spraying of all human habitations rather than
on finding every infected person and treating him
and his contacts.

Taiwan (Nationalist China). Taiwan is another
country in which DDT was introduced fairly
early and from which excellent results have
always been obtained. Here, although malaria
disappeared in a large part of the heavily popu-
lated part of the island, the incidence of the
disease did not continue to zero, as had been
hoped for. An investigation of the situation in
1958 showed that transmission had ceased in the
heavily populated agricultural parts of the island,
but that in the hilly, mountainous areas with
populations with scattered habitations of difficult
access, transmission continued. Investigation
showed that some of these areas had been poorly
sprayed and some had been missed entirely in
the general campaign on the island. Reorgani-
zation and intensification of the search for
infective cases and of the spraying of isolated
habitations have led to a month-by-month
reduction in the number of cases found since
September 1958 and it now appears that practi-
cally all of the transmission on Taiwan has been
blocked and it can be anticipated that this
country will become the first of the Asiatic
countries to be able to declare the eradication of
malaria.

Thuilund. In Thailand the application of DDT
has resulted in a rapid reduction of malaria and
in the practical eradication of Anopheles minimus
in much of the area covered by the spraying
operations. Suppression of spraying has been
possible in certain areas without the recurrence
of malaria transmission. Impressive settlement of
previously uninhabited areas has occurred. The
program has, however, developed slowly with
initial plans for protecting only the 13 or 14
million people living in the most malarious areas;

it is, however, believed that another 9 million of
the population live in areas exposed to risk.
There is evidence that difficulties similar to those
encountered in preventing transmission among
peripheral fringe populations in other countries
exist in Thailand and will become apparent with
the expansion of the program to the forested
areas. In summary, the program in Thailand is
not sufficiently advanced to permit an appraisal
of the problems to be encountered in the terminal
stages of eradication.

India. The decision to undertake the eradi-
cation of malaria in India marked the inclusion
of the largest single malarious population in the
world in the eradication program. Although it
was initially anticipated that anti-malaria
measures would be applied in areas populated by
some 225 million persons, it is now admitted that
measures must be taken throughout areas in-
habited by another 170 million people where
malaria is relatively a minor problem. Although
there are some reports of anopheline resistance
to dieldrin, DDT seems to be giving excellent
results. The program now being developed to
complete the spraying of the homes of some 390
million people during 1960 represents a tre-
mendous effort in financing and in administration.
No serious technical difficulties are anticipated;
the very size of the effort and the necessity of
coordinating the programs of State services and
of covering rural, nomadic and itinerant popu-
lations would seem to be the chief obstacles in
India.

My remarks on malaria to this point have been
devoted to the disappearance of malaria from
parts of Asia. The term world-wide malaria
eradication implies nothing less than the dis-
appearance of all forms of human plasmodia.
This disappearance must be not only from the
Americas, from Asia and the Pacific, but also
from the USSR, Communist China, Outer
Mongolia, North Korea, North Vietnam, East
Germany and from Africa. Some workers have
tended to discount the possibility of malaria
eradication in Asia since little was known of
what was being done in those countries not
members of the United Nations. In general, it
would seem that the communist countries, with
a governmental interest in the productivity of
their populations and with relatively tight con-
trols over their peoples, may be expected to
eradicate malaria as fast as or even faster than


364                            FRED L. SOPER

the free world, especially since most of these
countries are not tropical.

In the USSR11 a deliberate attempt to eradicate
malaria dates from 1952 following an observed
reduction in malaria incidence of almost 80% in
2 years. In the USSR, in addition to the spraying
of homes with insecticide, all cases are given free
treatment, are registered and supervised for a
2-year period. Malaria cases reported since 1950
by years are: 1950, 781,000; 1951, 351,000;
1952, 183,000; 1953, 116,000; 1954, 73,000;
1955, 36,000; 1956, 13,015; 1957, 5,095; 1958,
2,504.

To quote IL. . . the malaria rate in the Soviet
Union has been brought to such a low level that
the country is on the threshold of complete
eradication of this infection . . . the presence of
the high rate of malaria in other countries of the
world, especially in the countries adjacent to
ours, is of real concern to us. Introduction of
malaria . . . is at present gaining importance and
increasing significance in the final period of local
eradication of malaria.** . . . The USSR shares

11 Sergiev, P. G., Reshina, M. G., and Lysenko,
A. Ya. Malaria as a world problem and progress
in eradicating malaria in the USSR. M. Parasitol.
& Parasitic Dis. (Ministry Health USSR), 28:
268-280 (1959).

** This statement is highly significant. The
lecturer has had the opportunity of observing the
step by step development of the eradication of
the yellow fever mosquito, Aedes aegypti, first
from a number of the principal ports of Brazil,
then the gradual peripheral spread of eradication
to the suburbs, to the interior villages and even
to the rural areas of northeast Brazil, to the
Amazon Valley and eventually to the City of
S&o Paulo and to the southern reaches of the
country where urban yellow fever had never
occurred but where the presence of the aegypti
mosquito threatened eventual reinfestation of the
eradicated areas. From Brazil's experience with
reinfestations coming from her neighbors came
the 1947 demand for continental eradication and
Brazil's generous contributions in men and ma-
terials in carrying the program, through the
ausnices of the Pan American Sanitarv Bureau.
to bther countries. Each of these in" turn. ai
aegypti disappears from their territories, jbins
in the clamor for eradication in the territories of
their neighbors.

As th6 global malaria eradication program
advances, inevitably a residuum of malaria will
be found'in certain-countries with low economic
resources and inadequate administrative organiza-
tions, to whom the cost and difficulties of eradica-
tion may seem prohibitive. It is inevitable that
more assistance will flow, if for no other reason
as amatter of self-defense, from the more fortunate
nations. As the number of nations without malaria
increases,. the demand to abolish malaria from
all countnes from which re-infection might come,
will increase and there should be continually

this outlook as to the possibility and necessity
for eradicating malaria throughout the world.

"The participation of the USSR in solving the
malaria eradication problem in the world has not
been limited solely to the framework of WHO.
In 1955, The USSR Ministry of Public Health,
at the request of the Government of the Demo-
cratic Republic of Vi&-nam sent a group of
Soviet malaria specialists to North Vietnam,
where they worked for about three years. . . In
1956, a group of malaria specialists was sent to
the Chinese People's Republic for the basic
purpose of assisting in training local personnel.
As a result of five months work . . . a considerable
number of Chinese specialists were trained."

The optimism and firm intent of the USSR
malaria workers are apparent in the declaration
that :

"The absence of new local cases for the absolute
majority of regions in the country must be
attained in the second half semester of 1959, and
for the Azerbaidzhan SSR and Yukutsk of the
ASSR not later than 1960."

Incomplete reports for 1958 showed 107 cases
of malaria imported into the USSR, of which no
less than 101 came from China. With regard to
China I can do no better than quote from Dr.
Williams' paper :

"Nothing specific can be said at this time of
anti-malaria activities in Communist China but
those familiar with her malarious areas perceive
no technical difficulties standing in the way.
Transportation difficulties are obvious in the
various south-west provinces where terrain is
rugged. However, roads are not entirely impossi-
ble and the local mosquito is notoriously sus-
ceptible to DDT."

In Africa, malaria eradication has been planned
and is being attempted in a number of the more
temperate countries, but there has been a certain
reluctance to undertake eradication under present
conditions in Africa south of the Sahara and
north of Southern Rhodesia. The low economic
level, the high rate of transmission, the shortage
of trained personnel and the difficulty of commu-
nications in many parts of this region, when
taken together, make the problem a formidable
one. In spite of reported difficulties and local
failures in the past, recent developments suggest

decreasing difficulty in getting staff and funds for
the ultimate objective of final eradication from
all countries.


EPIDEMIOLOGY OF MALARIA                 365

there are no sound technical factors which will
preclude success of any serious attempt to eradi-
cate malaria when the time comes. A warning
should be sounded against any attempt to
eradicate malaria on a too limited basis in tropical
Africa since reinfection from the periphery may
be expected to be a more serious problem there
than in other parts of the world. The creation of
national independent governments throughout
Africa may well create a demand for international
participation in eradication programs for that
continent much earlier than would have been the
case had previous political conditions been main-
tained.

In the Americas, practically all of the malarious
countries are engaged in the eradication effort.
Serious difficulties with anopheline resistance to
insecticides have been encountered in El Salvador
and in Nicaragua and to lesser extent in other
countries. Extra-domiciliary transmission seems
to be a factor delaying eradication in certain
areas of Venezuela, Costa Rica and possibly other
countries. The great reaches of the Amazon
Valley present a difficult problem in logistics; an
attempt is being made to solve this problem with
medicated table salt.

I have referred to my impression that the
Malaria Eradication Program in many countries
today is in a position similar to that of the
Yellow Fever Eradication Program in South
America 39 years ago. I believe it is not too much
to anticipate that just as improvement in ad-
ministration and in methods for rendering yellow
fever and its vector visible resulted in a definite
change in the situation for the better at that
time, so may we anticipate that the next few
years will see tremendous advances in the
intensification and improvement of efforts for the
eradication of malaria throughout the world. In
India where the greatest reservoir of malaria
infection has existed, one sees the development
of a truly national effort and a national determi-
nation to eradicate malaria forever. One cannot
fail to be impressed.

There are ties when one can take heart from
the perspective gained by attempting to look
forward from a previous point in the calendar.
May I quote for your consideration from a
forward looking address of 15 years ago, the
Presidential Addresstt of 1945 for the National

tt Johnson, Henry A. Malaria in the Post-War
Era. J. Nat. M&ria Sot., 6: l-6 (1946).

Malaria Society, one of the parent bodies of this
Society:

"We are frequently reminded of the possibility
of eradicating malaria in the United States, now
that it is at a low ebb. I feel this is an untenable
concept as we do not yet know in sufficient detail
just where and under what conditions the disease
occurs, or will occur in its last natural habitant,
Possibly malaria will be eliminated but I much
prefer to entertain the hope that we will build
malaria out in our future developments and that
we will attempt to `reduce' rather than `eliminate'
it in its existing natural setting . . . it is unwise

. . . to put malaria control operations into practice
unless the disease is causing a measurable
economic loss and unless the cost is in a measure
commensurate with the economic ability of the
people to pay."

But even as the President of the National
Malaria Society was speaking, the die had been
cast, and the budget item approved for the
extended Malaria Control Program which was to
become in 1947 the National Malaria Eradication
Program. And indeed in 1950 and 1951 the
National Malaria Society took steps for its own
dissolution, as no longer necessary.

The action of the XIII Pan American Sanitary
Conference in 1950 in recommending national
programs for the eradication of malaria through-
out the Americas was apparently ahead of its
time and little stir was created until after the
action of the XIV Pan American Sanitary
Conference in 1954. The decision of Mexico to
undertake a national malaria eradication program
led to support of this program by UNICEF and
the action of the Joint UNICEF/WHO Health
Policy Committee approving malaria eradication
for joint effort of the two organizations. This was
followed almost immediately by the action of
VIII World Health Assembly declaring for a
world-wide malaria eradication program. The
action and reaction of the 1954-59 period have
been explosive in character in comparison with
the slow speed at which international activities
usually develop.

In 1957 the Pan American Health Organization
received generous contributions to its Malaria
Eradication Special Account from the govern-
ments of the Dominican Republic, the United
States and Venezuela. In the same year the WHO
received a sizeable contribution from the United
States and the International Cooperation Ad-


366                           FRED L. SOPER

ministration began to participate officially in
malaria eradication with funds earmarked for the
purpose by the United States Congress. The ICA
is participating in malaria eradication in some
two dozen countries, including India which has
the world's largest population residing in malari-
ous areas.

The governments of nations throughout the
world have been most enthusiastic in girding
themselves for the task of financing the internal
costs of eradication; the difficulties have been
related to trained professional staff and inter-
national funds to cover materials which must be
imported.

The program for the eradication of malaria in
the world has implications far beyond the
economic, social, health, and cultural effects of
this disease. Once the pattern has been set for
international collaboration on a world-wide basis
in the eradication of a single disease, it is obvious
that the road is open for similar action on other
human, animal, and plant diseases, and insect
and plant pests. On October 22, 1959, the Secre-
tary of Agriculture announced the eradication of
vesicular exanthema of swine in the United
States. Vesicular exanthema had been present for
some 20 years in California in a known but local
focus of infection, which suddenly and unex-
pectedly had an opportunity to spread, ap-
parently on dining cars on inter-state railway
trains some 7 or 8 years ago. At its peak, forty-
three states were known to be infected and
embargoes were placed on the importation of
United States pork products by ten countries:
Canada, the United Kingdom, Columbia, Vene-
zuela, Austria, Belgium, Sweden, Barbados,
Jamaica, and British Guiana. California is now
free of the infection at the price of having
infected the other forty-two states and at the
price of a 7 year campaign waged by the De-
partment of Agriculture in collaboration with the
state governments. In making this announcement
Secretary Benson did not announce a program of
co-operation with the ten clean countries which
embargoed pork from the United States to help
rid the rest of the world of vesicular exanthema,

but might well have done so had malaria eradi-
cation been completed.

Recent success in the dramatic eradication of
the "screw worm" from its eastern range of
distribution in Florida and Georgia leads one to
the question: "If Florida has no `screw worm'
can Texas be far behind?" Eradication of the
screw worm in Florida was possible because of
the isolation of the eastern focus from other
countries by the Gulf of Mexico and the Atlantic
Ocean. Texas is not in a similarly favorable
position and eradication there would put the
United States in a defensive position, vfs-84s
the infested areas of Mexico. As Mexico proceeds
in its program for the eradication of the A&ciks
aegypti mosquito, the urban vector of yellow
fever from its territory, it faces a similar problem
along the border with the United States and in
its contacts with gulf ports. Well may the repre-
sentatives of agriculture and of health of the two
countries hold a combined meeting and arrange
broad collaboration in the solution of both
problems.

It may be well to close this Charles Franklin
Craig lecture by quoting the words of the
Secretary of Health, Education, and Welfare,
when on October 20, 1959 he presented at the
annual meeting of the American Public Health
Association, contributions of two and of three
million dollars respectively to the Malaria
Eradication Special Accounts of the Pan Ameri-
can and World Health Organizations:

"The cause to which this money will be applied
is a triumphant one. Never until very recent
times has man dared to talk of `eradication.' In
all war against disease we have moved from
helplessness to treatment and thence to pre-
vention and control. As we move toward the
eradication of a disease from the face of the earth
we stand on the threshold of total victory for
man over one of his oldest and deadliest enemies."

But total victory over malaria can come only
as there is total coverage of infected populations
and as malaria is not permitted to become a
Disappearing Disease before it has been eradi-
cated.