NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
HAMID
KHAN
379
TABLE V
Amount of carbon dioxide present in the medium before and after the experi-
ment with carp fingerlings in a closed container (Capacity 8.17 litres)
No.
of
fish
1
1
1
1
4
4
4
4
8
8
8
8
8
8
8
8
12
12
12
12
12
12
Tempe-
rature
74° F
74° F
74° F
75° F
74° F
74° F
74° F
75° F
74° F
75° F
74° F
74° F
74° F
74° F
56° F
56° F
55° F
55° F
55° F
55° F
57° F
57° F
Time
Hr.
1
1
1
1
1
1
1
1
1
1
1
1
1
1
10
8
4
4
4
3
2
3
Min.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
31
10
30
12
57
47
16
Carbon dioxide in c.c. per litre
Control
Free
2.022
1.686
0.788
1.264
2.022
1.686
0.788
1.264
2.022
1.264
1.264
0.788
0.788
1.686
Neutral
Neutral
Neutral
Neutral
Neutral
Neutral
Neutral
Neutral
Half
bound
25.533
28.325
26.367
26.291
25.533
28.325
26.367
26.291
25.533
26.291
26.291
26.367
26.367
28.325
13.449
12.337
21.71
18.86
22.373
17.949
18.66
18.25
Fixed
25.533
28.325
26.367
26.291
25.533
28.325
26.367
26.291
25.533
26.291
26.291
26.367
26.367
28.325
21.286
20.1734
23.24
20.28
26.367
21.488
22.45
21.34
At the end of experiment
Free
2.022
1.686
0.96
1.264
2.275
2.528
2.136
1.833
4.93
2.427
2.654
2.579
2.781
3.413
3.665
3.223
4.626
4.247
3.893
3.248
3.792
4.98
Half
bound
24.218
27.176
26.418
26.291
23.522
24.268
26.354
26.291
23.005
26.038
26.038
26.797
26.329
25.821
20.186
21.564
19.97
19.33
19.76
20.42
20.06
19.77
Fixed
24.218
27.176
26.418
26.291
23.522
24.268
26.354
26.291
23.005
26.038
26.038
26.797
26.329
25.821
20.186
21.564
19.97
19.33
19.76
20.42
20.06
19.77
pH
Control
...
...
...
...
...
...
...
...
...
...
...
...
...
...
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
At end of
experi-
ment
...
...
...
...
...
...
...
...
...
...
...
...
...
...
7.4
7.4
7.3
7.3
7.2
7.2
7.2
7.2
380
Oxygen Requirements of Indian Carp
TABLE VI
Oxygen requirements of carp fingerlings in open container (capacity 8.17 litres) and amount of carbon
dioxide present in the medium before and after the experiment
No.
of
fish
8
12
12
12
12
12
Tempe-
rature
56° F
55° F
55° F
55° F
57° F
57° F
Dura-
tion of
experi-
ment
Hrs.
10
4
4
6
3
7
Min.
4
34
16
35
20
0
Dissolved oxygen in c.c. per litre
Control
8.385
6.527
6.637
6.637
5.914
5.914
At end
of
experi-
ment
0.7105
0.6325
0.5401
4.3993
0.602
1.472
At end
of
experi-
ment
avail-
able
per
fish
0.0888
0.0527
0.045
...
0.50
...
Con-
sumed
by all
fish
7.6745
5.8945
6.0969
...
5.312
...
Con-
sumed
per fish
0.9593
0.4912
0.508
...
0.443
...
Carbon dioxide in c.c. per litre
Control
Free
Neutral
Neutral
Neutral
Neutral
Neutral
Neutral
Half
bound
12.3366
19.01
18.454
18.454
16.15
16.15
Fixed
20.2296
20.93
21.7408
21.7408
19.95
19.95
At end of experiment
Free
4.74
3.135
3.223
3.085
3.947
4.601
Half
bound
20.375
19.26
19.53
19.79
19.61
20.53
Fixed
20.375
19.26
19.53
19.79
19.61
20.53
pH
Control
8.2
8.2
8.2
8.2
8.2
8.2
At end
of ex-
periment
7.4
7.3
7.2
7.4
7.2
7.2
Remarks
Condition of fish
at end of ex-
periment
Fishes in good con-
dition.
Restless.
Do.
Water was stirred
at end of 4 hrs.
16 mins. for 2
hours 19 mins.
Restless.
Water was stirred
at end of 3 hours
20 minutes
for
3 hours 40 min.
HAMID
KHAN
381
REFERENCES
American Public Health Association (1933). Standard Methods for Examination of
Water and Sewage. Ed. 7. New York.
Ellis, M.M. (1937). Bull. U. S. Bur. Fish. 48, 22.375.
Kemmerer, G., Bovard, J. F. and Boorman, W. R. (1924). Bull. U.S. Bur. Fish. 39, 51-
140.
Keys, A. B. (1930). Bio. Bull. Woods Hole 59, 187-198.
Kupzis, J. (1901). Zeitscrift für
Untersuchen d.
Nahrungs-und Genussmittel,
sowie der Gebrauchs-gegenstande, 4, 631-668.
Plehn, M. (1924). In Handbuch der Binnen fischerei Mittel-europas 1, 301-470.
Schuett, F. (1933). Ecology 14, 106-122.
Thompson, D. H. (1925). Bull. Nat. Hist. Sur. 15, 423-437.
D
SELECTED ARTICLES
THE TICKS OF EAST AFRICA
I. SPECIES, DISTRIBUTION, INFLUENCE OF CLIMATE, HABITS AND
LIFE-HISTORIES
BY
E. ANEURIN LEWIS
Veterinary Research Laboratory, Kabete, Kenya Colony
(Reprinted from the Empire Journal of Experimental Agriculture, Vol. VII, No. 27,
July, 1939)
T ICKS have been referred to as 'the scourge of East Africa '. The phrase
is rather exaggerated. Yet the abundance and vitality of the pests did not
fail to impress the early travellers in East Africa : big-game hunters have
written of the ' loathsome ' creatures on every species of wild animal; and the
pioneer settler-farmers quickly discovered that ticks provided one of the most
serious problems of stock-raising. Furthermore, the development of native
reserves and native agriculture has been hindered by the ravages of ticks ;
the improvement of indigenous stock has been impeded by difficulties in con-
trolling the pests ; and the free movement of cattle has been restricted because
ticks convey and transmit organisms of fatal diseases.
Seventy-four known species of ticks have been collected and recorded from
three British East African territories. In the report of the Veterinary De-
partment, Uganda, Mettam listed 40 authentic species from Uganda, and the
writer has added four more. Forty-seven species have been recorded from
Tanganyika Territory, whereas 58 species (including sub-species) have been
collected in Kenya Colony—excluding Ornithodoros megnini and Margaropus
winthemi, which have been taken off imported cattle at Mombasa, the chief
port of entry to Kenya and Uganda. At least a few more species have been
collected but not described, and there are many specimens which, on account
of morphological variations, cannot definitely be assigned to any particular
known species. As Warburton wrote in 1912, ' there are what appear to be
a considerable number of species in the making '.
The 74 species are apportioned to 12 genera as follows : 10 belong to the
genus Ixodes, 7 to Haemaphysalis, 2 to Dermacentor, and 20 to Rhipicephalus.
Hyalomma is represented by 7 species or sub-species according to Schulze's
[1930] classification and, in addition, a species in the new genus, Hyalommina.
Boophilus has 1 species, and Aponomma 2, one of which is represented by 2
sub-species ; Amblyomma has 15 species and Ornithodoros and Argas comprise
4 and 3 species, respectively.
At least 18 of these ticks have been incriminated in the transmission of
diseases, but many more are of interest if only from a purely scientific point
of view. The abundance of tick material and the scope for ecological studies
provide numerous problems that await investigation ; and it would be well to
bear in mind the remark of G. H. F. Nuttall [1905] : ' Experience has shown
that new and fruit-bearing knowledge is seldom revealed to those whose sole
purpose is merely utilitarian. '
( 382 )
E.
ANEURIN
LEWIS
383
Of the 74 species (shown in the following list), the life-history of 34 appears
to be known. The larvae and nymphae of 46 have never been fully described ;
and practically nothing beyond a record of the tick and the locality of its host
is known in the case of many.
Species and varieties of ticks in East Africa
Argas
aequalis
persicus
Ornithodoros
megnini
morbillosus
moubata
savignyi
Margaropus
winthemi
Amblyomma
cohaerens
cuneatum
eburneum
gemma
hebraeum
lepidum
marmoreum
nuttalli
paulopunctatum
personatum
petersi
pomposum
splendens
tholloni
variegatum
Aponomma
exornatum
laeve laeve
laeve capensis
Boophilus
annulatus
decoloratus
Dermacentor
circumguttatus
rhinocerotis
Haemaphysalis
aciculifer
bipinosa
calcarata
hoodi
leachi
parmata
spinulosa
Hyalomma*
anatolicum
dromedarii
impressum
transiens
impressum
albiparmatum
planum
savignyi
impeltatum
rufipes
Hyalommina
lewisi
Ixodes
brunneus
cavipalpus
daveyi
nairobiensis
pilosus
rubicundus
sehillingsi
ugandanus
ugandanus
djaromensis
Rhipicephalus
appendiculatus
ayrei
armatus
dursa
capensis
dux
evertsi
falcatus
kochi
longicoxatus
lunulatus
maculatus
neavei
oculatus
pulchellus
sanguineus
simus
sulcatus
supertritus
tricuspis
There is reason to believe that some of the species are invalid and the
specimens described as such are variants of a previously known species.
Several ticks are known only in their male, female, or immature phase of life ;
and comparatively little is known of their adaptation to different hosts and the
immunity of the hosts to infestation by different species of ticks. Larvae and
nymphae of certain species are found naturally only on birds and rodents,
whereas the adults are more often found on larger mammals. Other species
usually infest reptilian hosts but may live equally well on warm-blood animals.
The large wild game are infested with ticks that are rarely met with on farm
animals, and also with species that frequently occur on domestic stock.
DISTRIBUTION OF TICKS
The general geographic distribution of the most common ticks and vectors
of diseases in Kenya Colony has been determined in periodic surveys. The
factors that influence the natural distribution of each species have not been
fully investigated and there is no precise information on the limiting effect
of the separate and combined environmental conditions. Field observations
and laboratory experiments have revealed certain predilections on the part
of different species, but the data do not warrant definite pronouncements.
* The immature ticks of Schuize's species and sub-species for East Africa are being studied
to test the validity of the revised classification.
D 2
E.
ANEURIN
LEWIS
387
appendiculatus infestation within, or adjoining, other larger, free areas. There
are also farms or localities which are clean although surrounded by tick-in-
fested country. These, of course, have been rendered tick-free by efficient
control measures.
CLIMATE AND ITS EFFECT ON TICKS
In many countries outside the equatorial belt it has been shown that
climate and other environmental conditions have a considerable influence on
the distribution and activity of tick-life. In East Africa the weather seasons
are essentially different ; and, apart from a few observations, there has been
no proof of a correlation of fluctuations in tick-activity with climate or its
factors.
The climatic seasons are popularly classified according to the incidence
of rain, which varies in total annual amount and in its monthly distribution
over a vast area.
Rainfall conditions over East Africa are somewhat complex ; but in
general Tanganyika has one season of rainfall, whereas Kenya and Uganda
have two. The Tanganyika rains extend from November to May, whilst
those of Kenya and Uganda have their maxima abut April to May and Octo-
ber to November. There are four areas in Kenya where the rainfall distribu-
tion differs greatly ; the coast, the eastern highlands, the plateau, and the
vicinity of Victoria Nyanza.
Many farmers and others consider that ticks increase at the onset of, or
during, the rains. Collections of different species of ticks off cattle in different
parts of the Colony and at Mpwapwa in Tanganyika have been examined along
with weekly and monthly rainfall records, but so far no correlation of tick
abundance and fall of rain has been observed. Recorded outbreaks of East
Coast fever for the years 1929 to 1938 in Kenya indicate that the disease
exists throughout the year, but also that it is more prevalent from about April
to August. It may tentatively be deduced from this evidence that R. appendi-
culatus, the tick-vector of East Coast fever, is more or less active at all times,
and that it increases in numbers or activity from April to August. Data on
East Coast fever in enzootic areas are lacking, and, as has already been stated
collected batches of the tick do not always support this deduction.
There are pronounced differences in seasons according to temperature and
conditions that affect temperature. Available information on the mean maxi-
mum and mean minimum temperatures does not cover all the areas where
series of tick-collections have been made. It may be stated, however, that the
mean maximum reaches its highest from January to March, drops to its lowest
point in July and August, rises to a secondary peak about October. There is
a short drop in November and a rise again to January. The mean minimum
sometimes coincides with the rise and fall of the mean maximum. Or it may
be lowest from October to January, after which it rises in March to April,
drops slightly in June to rise a little about July and August, and then falls
towards the end of the year. Over a large part of Kenya the mean tempera-
ture and its diurnal range are at a minimum during the cloudy period from
E. ANEURIN LEWIS 391
and drop off in large numbers. This peculiarity cannot always be accounted
for by an acquired immunity on the part of the host. Heavy infestation of
hares by Hyalomma larvae is frequently followed by the death of the host.
It has also been observed that females of R. appendiculatus will engorge on
experimental animals and, for some unaccountable reason, a varying percent-
age fails to oviposit and dies while others of the same batch will reproduce
normally. Such species as R. pulchellus, A. variegatum, and A. gemma collec-
ted in the field will, at times, oviposit, hatch, and feed well; at others, and under
identical conditions, they fail. Another illustration is of the morphological
changes, not only in size, but in superficial characters of ticks of one species
collected from different localities. R. capensis shows a very wide range of
variations whilst R. appendiculatus may often be difficult to recognize.
DIFFERENCES IN INCIDENCE OF ENCEPHALOMYELITIS
IN HORSES*
BY
W. V. LAMBERT
Senior Animal Husbandman, In-charge of Genetics,
S. R. SPEELMAN
Associate Animal Husbandman, Acting In-charge of Horse and Mule Investi-
gations
AND
E. B. OSBORN
Junior Animal Husbandman
U. S. Range Livestock Experiment Station, Bureau of Animal Industry
(Reprinted from The Journal of Heredity, 30, 349, August, 1939)
I NHERENT differences in resistance to certain types of diseases are known to
exist in both animals and plants. Among animals, differences in resistance
to bacterial and virus diseases have been shown by Hagedoorn-LaBrand and
Hagedoorn 2 , Irwin 3 , Schott 6 , Lambert 4 , Webster 7 , Wright and Lewis 8 ,
Gowen and Schott 1 and others. In plants such differences have been ex-
tensively studied and the development of resistant strains has become an
effective means for combating certain plant diseases. Such differences are
relative rather than absolute, the degree of resistance depending upon such
factors as the inborn qualities of the host, the virulence of the pathogenic
agent, the environment, age, and physiological condition of the host, degree
of infection, etc.
In the larger animals, species differences in resistance to certain diseases
are well known but few well-authenticated cases of such intra-species differences
are known. In horses the opportunities for making such observations are
rare and it is believed that the data reported herein, describing a differential
resistance to encephalomyelitis, will be of definite interest to biologists,
horsemen, and veterinarians alike.
MATERIALS USED
These records were obtained from the experimental stud maintained at
the United States Range Livestock Experiment Station at Miles Ciy, Montana.
The 221 horses in this stud represented several types of breeding but the
largest percentage consisted of grade Belgians and grade Thoroughbreds. In
addition, there were a few Morgans, Nonius, and some crosses from Nonius
stallions, on grade Belgian and Thoroughbred mares. Horses of various
ages were represented in most groups, the frequencies for each group and age
being shown in Table I.
*U. S. Department of Agriculture in cooperation with Montana Agricultural
Experiment Station.
( 392 )
W. V. LAMBERT, S. R. SPEELMAN AND E. B. OSBORN 393
TABLE I
The incidence of encephalomyelitis by breeding and age groups resulting from
an outbreak among horses at the United States Range Livestock Experiment
Station in 1938.
Breeding
Nonius . .
Nonius × Belgian
Nonius × Tho-
roughbred.
Morgan . .
Belgian . .
Thoroughbred .
Total .
3 years and over
Total
No.
5
0
0
8
60
54
127
No.
affected
0
0
0
1
1
4
6
2-3 years
Total
No.
0
0
0
0
9
13
22
No.
affected
0
0
0
0
1
0
1
AGE GROUPS
1-2 years
Total
No.
3
1
0
0
9
18
31
No.
affected
1
1
0
0
2
1
5
Foals
Total
No.
4
7
11
0
9
10
41
No.
affected
3
5
8
0
1
1
18
Total
No.
animals
12
8
11
8
87
95
221
No.
affected
4
6
8
1
5
6
30
In July of 1938 a rather severe epizootic of encephalomyelitis occurred
in this stud, 30 of the 221 animals being affected. It is on the basis of these
cases that the conclusions reported herein are based.
It is generally accepted that encephalomyelitis is transmitted by biting
insects such as mosquitoes 5 and not from direct contact with infected horses.
No data are available on the source of or method of spread of the disease in
this epizootic. Since the horses of the different breeding groups were distri-
buted at random in the various pastures of the station, the opportunities
for exposure to the disease were equal between the groups in which the in-
cidence of the disease is compared.
INCIDENCE OF DISEASE BY BREED GROUPS
The incidence of encephalomyelitis for the various types of breeding
and for the different age groups in each type are shown in Table I. Of the
221 horses in the stud 31 were either purebred Nonius or the result of crosses
of Nonius stallions on the grade Belgian or Thoroughbred mares. Of this
group, 18 developed encephalomyelitis this being 58.1 per cent of the animals
of this breeding. Among the 190 animals of all other groups only 12, or
6.3 per cent of the total, were affected. However, a comparison on the
basis of totals is somewhat misleading for, as is apparent from Table I, the
higher incidence of the disease occurred among the younger animals (yearlings
and foals). Since all animals with Nonius breeding were yearlings or foals,
except five mature animals imported from Hungary in 1935, a comparison of
W. V. LAMBERT, S. R. SPEELMAN AND E. B. OSBORN 395
INCIDENCE IN VARIOUS AGE GROUPS
The distribution of animals of the various ages in the stud is shown in
Table I. It is apparent that the younger animals were somewhat more
susceptible to the disease than the older animals. A fair comparison of the
influence of age on susceptibility can be made only for the groups not in-
volving Nonius or crossbred-Nonius breeding since, aside from the five pure-
bred mature Nonius horses, only yearlings and foals of this breeding were
represented.
It would appear that the younger animals of other than Nonius breeding
were somewhat more susceptible than the older ones, although the incidence
of infection was so low in all of these groups that none of the differences are
statistically significant. This is in line, however, with previously reported
observations on age differences in resistance. No sex difference in the inci-
dence of the disease was noted, as 16 of the animals affected were females
and 14 males.
PREVIOUS HISTORY AT THE EXPERIMENT STATION
Only one other outbreak of encephalomyelitis has occurred at the Range
Station. The disease first appeared in the summer of 1937, and five animals
were affected between the dates of August 12 and September 5. One of these
animals was a mature Nonius stallion, two were grade Belgians, one a grade
Thoroughbred, and one was a purebred Belgian. Three of these animals
died, one of them being the Nonius stallion, Longfellow. At that time only
ten animals with Nonius ancestry were on hand. Nine of these were pure-
bred Nonius and one by a Nonius stallion and out of a grade Belgian mare.
Previous to the time of his death, Longfellow had bred a number of mares.
He was the sire of ten horses with Nonius ancestry that were in the stud at
the time of outbreak of the 1938 epizootic, and eight of these were affected.
Sixteen of the other horses of Nonius breeding were sired by the stallion
Shorty, and ten of these were affected. The other Nonius animals, all im-
ported, were sired by several different stallions.
DISCUSSION
From the foregoing facts it would appear that susceptibility to encephalo-
myelitis virus of the western type responsible for this outbreak is dominant
to resistance, for the crossbred progeny from the Nonius stallions appeared
about equally as susceptible as did the purebred Nonius of the same age
groups. The reasons for the greater susceptibility of horses of Nonius an-
cestry are not definitely known. Perhaps there has been some natural selec-
tion for resistance in the horses that have been native to America for some
generations for there is evidence pointing to the existence of virus-induced
encephalomyelitis in this country for decades. The Nonius stock previous
to its importation was not subjected to such selection for American type
encephalomyelitis virus is non-existent in Europe.
If resistance were recessive, natural selection would be favourable to the
development of resistant strains, but the failure of horses in different vici-
nities to be exposed to the disease might explain the failure for the complete
396
Differences in Incidence of Encephalomyelitis in Horses
elimination of susceptibility from a stock. Whether there would be a differen-
tial selection between the eastern and western type viruses is unknown. These
data do not throw any light on this point because most of the horse in this
stud were descendants of horses bred at this station or at other localities in
the western part of the United States. Because of the limited data and the
absence of critical tests designed to answer some of these specific questions,
broad generalizations on the role of previous selection on resistance and sus-
ceptibility, and on the dominance of susceptibility are unjustified. They
do, however, point to the fact that a differential resistance to encephalomyelitis
exists in horses.
The fact that such differences exist should be of considerable interest
and importance to the epizootiologist for such differences might account for
a considerable part of the variation in mortality that is encountered in different
outbreaks of the disease. Differential resistance of the type encountered
here also might influence the response to treatment with vaccines, though no
evidence to this effect now exists.
It is hoped that these observations may stimulate others of a similar
nature, for it is largely from such observations that a knowledge of the role of
inheritance in relation to resistance or susceptibility to disease can be estab-
lished in species such as the horse.
SUMMARY
Statistically significant group differences in resistance to encephalomye-
litis that were observed in an epizootic occurring in 1938 in the stud of horses
at the U. S. Range Livestock Experiment Station are reported. A greater
percentage of horses of Nonius breeding were affected than those of other
breeding. Among all yearlings 50.0 per cent of Nonius breeding were affected,
whereas only 11.1 per cent of the yearlings of other breeding were affected.
In the foals the corresponding percentages were 72.7 and 10.5. The differences
observed were not attributable to the location of the horses on the station,
their distribution being such that all groups had equal opportunity to be ex-
posed to the disease.
The data confirm previously reported observations on age differences in
resistance, the younger animals being the more susceptible. No differences
in resistence were observed between males and females. Possible reasons
for the differences observed are discussed.
LITERATURE CITED
1. Gowen, J. W. and R. G. Schott (1933). Genetic constitution in mice as differentiated
by two diseases: pseudorabies and mouse typhoid. Amer. Jour. Hyg. 18, 674-87
2. Hagedoorn-LaBrand, A. C., and A. L. Hagedoorn (1920). Inherited predisposition
for a bacterial disease. Amer. Nat. 54, 368-75
3. Irwin, M. R. (1929). The inheritance of resistance to the Danysz bacillus in the
rat. Genetics 14, 337-65.
4. Lambart, W. V. (1932). Natural resistance to disease in the chicken. Jour. Immun.
23, 229-60
5. Schoening, H. W. (1938). Recent developments in equine encephalomyelitis. Ad-
dress before 19th Annual Meeting Horse and Mule Association of America, Chicago.
III, Leaflet 234, Horse and Mule Assoc. America, 3-13