NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
368 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
rats, however, the peaks of curves showed a predominance of trypanosomes measur-
ing 30 µ irrespective of the fact of those trypanosomes being derived from a pony,
a dog or a calf. (Fig. IV). It is not clear why the average length should come up
to 30 µ in the white rat alone, while the same strain when injected into a dog, a
pony, a calf or a guinea pig (Fig. III) gives an average length of 25 µ It is sug-
gested that this apparent increase in the variation of the average length of the
trypanosome in the rat may be due to more uniform multiplication of trypanosomes
in such an animal which offers no resistance whatever to rapid increase. The uni-
formity of the curves of the lengths of trypanosomes in white rats, irrespective of
their source being from a pony, a dog or a calf is however significant. The similari-
ties of the biometric curves suggest that those trypanosomes are identical and that,
as the average length and the range of variation in their lengths coincide with T.
evansi they are identical with it.
OBSERVATIONS ON TRYPANOSOMES OF CATTLE IN SOUTH INDIA
369
FIG. III.
Tryps: Equine Relapse Strain
Guineapig No. 508.
25-8-33.
370 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
FIG. IV.
PATHOGENICITY TO EXPERIMENTAL ANIMALS.
(a) White rats. In the year 1929-30, in a long series of passages of the strains
of these trypanosomes from cattle, dogs and ponies, it was found that in each
OBSERVATIONS ON TRYPANOSOMES OF CATTLE IN SOUTH INDIA
371
strain, when passed through a series of rats, the virulence was exalted to that
animal. In each rat injected trypanosomes appeared uniformly on the 2nd or 3rd
day and the rat died by the 4th or 6th day. All these strains appeared as if they
became " fixed " in their virulence to the white rat. Similar results were obtained
with the new strains of trypanosomes obtained during the year 1933-34. Natten
Larier and Noyer [ 1931 ], while working with the trypanosome of the dromodery
and the horse in Morocco, had the same experience with rats. Laveran and Mesnil
[ 1907 ] observed that white rats when injected subcutaneously with T. evansi
showed them in their blood in 3 to 3½ days and died in 5½ to 6½ days and quote
other workers who obtained similar results. All seem to agree that in white rats
no relapses occur.
(b) Guinea pig. In this animal the course of the disease is subacute with
relapses and they usually die in about 8 to 12 weeks after infection. These results
are in conformity with those of other workers.
When a strain of trypanosomes, in passage through guinea pigs, was passed
through a rabbit, it became more virulent to the guinea pig during the first or
second sub-passage. Terry [1910] observed that a strain of Mauritian surra, when
kept exclusively in guinea pigs, became attenuated for mice. The study of passages
of the South Indian strain of T. evansi did not show any such attenuation to white
rats.
Laveran [1908] has shown that the virulence of the Mauritian strain of surra
when passaged through a series of guinea pigs may become very virulent to it.
During the present study, it was remarkable that an equine strain, during its
passage through guinea pigs, suddenly became very virulent to it and subsequently
resumed its original character after three sub-passages. In the course of this period
of exalted virulence, it was possible to infect two hyper-immunised rats, against the
same strain, to which they succumbed. It is not understood how and why the
virulence flared up to this height, though temporarily. The first of these three
guinea pigs died within 24 hours after infection and the other two in 10 days after
infection without showing any relapses. This is unusual in this animal, when
injected with an ordinary strain.
(c) Ponies. These animals were used to study the pathogenicity of the bovine
and canine strains on them. Five ponies were used. Each pony on purchase was
kept under observation and its blood, in massive doses, was injected into two rats
to make sure that it was free from trypanosomiasis. The ponies were kept in
fly-proof stables.
372 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
The results of inoculation are tabulated below :—
PROTOCOL I.
Pony
No.
444
419
519
449
296
Source of strain
Bovine strain after 10th
passage in white rats,
½ cc. of blood subcu-
taneously in neck.
Bovine strain from guinea
pig, 415, ½ c. c. of blood
subcutaneously in neck.
Bovine strain after pas-
sage through dog, 528,
½ c. c. of blood subcuta-
neously in neck.
Canine strain from white
rat, 452, after 10th
passage. ½ c. c of blood
subcutaneously.
Canine strain from dog.
½ c. c. of blood subcuta-
neously.
Incubation
period
6 days.
(16th to 21st
March 1933.)
7 days.
(8th
to 14th
February 1933.)
4 days.
(2nd
to
5th
October 1933.)
6 days.
(3rd to 9th April
1933.)
5 days.
(20th to 25th
August 1930.)
Duration
of disease
30 days.
Died on 15th
April 1933.
36 days.
Died on 13th
March 1933.
28 days.
Died on 30th
October 1933.
9 days.
Died on 11th
April 1933 with
cerebral symp-
toms.
30 days.
Died on 22nd
September 1930.
Remarks
Relapses two —one on
26th March 1933 and
other on 29th March
1933.
Relapses two —one on
28th February 1933 and
other on 1st March 1933.
Relapses two —one on
11th October 1933 and
other on 13th October
1933.
No relapse.
Relapses nil. The pony
developed swelling in
sternal region 4 days
after injection.
It may be seen from the above protocol that the bovine or canine strain of
trypanosomes is virulent to the horse and it seems that the canine strain is more
virulent than the bovine. It also seems that a strain of trypanosomes after passage
through a highly susceptible animal like the white rat becomes exalted in its
virulence to the horse. Fraser and Symmonds [1909] also found that a pony inject-
ed with a canine strain of T. evansi died in about 8 days after showing trypano-
somes in its blood.
(d) Cattle. Three calves were utilised in testing on them the virulence of an
equine and a canine strain. The results are tabulated below :—
PROTOCOL II.
Calf
No.
418
516
284
Source of strain
Canine strain from a
naturally infected dog,
½ c. c. of blood subcuta-
neously.
Equine strain from white
rat, 514, ½ c.c. of blood
subcutaneously.
Canine strain from dog
after passage, ½ c. c. of
blood subcutaneously.
Period of
incubation
14 days.
(3rd
to 15th
February 1933.)
4 days.
(4th
to
7th
September
1933.)
8 days.
(7th
to 15th
August 1930.)
Duration of
disease
Lived
for
2
months and 19
days. Died on
22nd April 1933.
Still alive .
Developed rin-
derpest
and
died on 19th
August 1930.
Remarks
Showed
trypanosomes
only for one day on 15th
February 1933 and never
afterwards.
Trypanosomes seen from
7th to 13th September
1933. Negative
ever
since.
Trypanosomes seen only
on one day, on 16th
August 1930.
OBSERVATIONS ON TRYPANOSOMES OF CATTLE IN SOUTH INDIA
373
In calf No. 418 very few trypanosomes were found on one day only in a wet
preparation, yet its blood was found to be infective to white rats after the dis-
appearance of the trypanosomes from its blood, but only when over 2 c.c. of blood
was injected.
The blood of calf No. 516, though it was found negative under the microscope
from 14th September 1933 onwards, was found infective to white rats for 60 days
after the disappearance of the trypanosomes, but only when over 2 c.c. of blood was
injected.
In the healthy calves used in these experiments, trypanosomes disappeared
from their peripheral blood within a few days and very small doses of blood
from these calves proved non-infective to such susceptible animals as white rats.
This finding has an important bearing on the question of cattle acting as reservoirs
in bridging the gulf between one surra season and the next. This question will be
dealt with separately later.
Calf No. 516 is still alive at the time of writing (about 10 months after infection)
and its blood is non-infective now to white rats even in massive doses. The blood
of this animal is being tested periodically for adhesion phenomenon and it has com-
pletely lost that property, the loss being a gradual one.
(e) Dogs. Seven dogs were injected with equine, bovine, and canine strains,
and the details are shown in the Protocol below. Four others, Nos. 275, 276, 277
and 278 were infected for the study of adhesion phenomenon and two were treated
with ' Bayer 205 ' to see if they could be reinfected with the surra trypanosome.
Of these two, one (275) was reinfected successfully after sixty-two days and the
other (277) died a few days after treatment.
PROTOCOL III.
Dog
No.
527
528
613
Source of strain
Equine strain from calf,
516.
Bovine strain from white
rat.
Bovine
strain
from
bullock.
Period of
incubation
5 days.
(9th
to 13th
September
1933.)
6 days.
(11th to 16th
September
1933.)
4 days.
(14th to 18th
February 1934.)
Duration of
disease before
death
28 days . .
54 days . .
34 days . .
Remarks
Relapses two.
Do.
Do.
I
374 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
Dog
No.
288
289
301
302
Source of strain
Hound strain . .
Ditto. . .
Hound
strain passed
through pony.
Ditto
Period of
incubation
5 days.
(13th to 18th
August 1930.)
Ditto .
6 days.
(28th
August
1930 to 3rd
September
1930.)
3 days.
(28th to 31st
August 1930.)
Duration of
disease before
death
9 days . .
23 days . .
19 days . .
24 days . .
Remarks
No relapse.
Relapse one.
No relapse.
Relapse one.
From the above it is concluded that strains of this trypanosome whether
obtained from canines or equines, behave practically alike in the dog, but strains
from bovines appear to be milder in virulence.
CROSS IMMUNITY TESTS.
These tests were studied in white rats infected with different strains and cured
with ' Bayer 205 '. The dose of the drug per rat was fixed at 1 c.c. of a 0.5 per
cent. solution given intraperitoneally. In all, 25 rats were used of which 19 remain-
ed refractory to reinfection with any of the strains used or their relapses. As many
as 8 attempts were made, at intervals, to reinfect some of them, the last being
seven months after treatment with ' Bayer 205 ' Kasai and Akaza [1927] found
that they could protect mice against surra for five months only by giving a prophy-
lactic dose of ' Bayer 205 ' (0.005 gram). Thus after the lapse of seven months
after treatment with ' Bayer 205 ' the experimental rats could not have had in their
system any residue of the drug to prevent reinfection with the trypanosomes under
investigation. The blood of all the nineteen rats referred to, when tested for
adhesion phenomenon, proved positive. It is considered that these white rats had
developed a true immunity against the trypanosomes under investigation. All the
strains of trypanosomes under investigation failed to infect the immunised white
rats, and it is concluded that these strains whether from dogs, horses or cattle
belong to the same group, viz., T. evansi [Steel, 1885]. The experiments are sum-
marised in Protocol IV.
In this connection some details of the history of the six white rats which
showed a break-down in immunity will be of interest :
(a) White rat No. 525 was infected with a canine strain of trypanosomes
on 16th February 1933, and treated with ' Bayer 205' on 21st Febru¬
OBSERVATIONS ON TRYPANOSOMES OF CATTLE IN SOUTH INDIA
375
ary 1933. Eleven weeks after recovery, it was reinfected with a
canine strain (passage) to which it succumbed.
(b) White rat No. 437 was infected with a bovine strain of trypanosomes on
4th March 1933 and treated with ' Bayer 205 ' on 9th March 1933.
Two months and five days after treatment it was injected with the
same canine strain (passage) as in the previous rat (No. 525). This
rat also died after taking the infection.
(c) White rat No. 485 was infected with a bovine strain of trypanosomes
on 25th May 1933 and treated with ' Bayer 205 ' on 29th May 1933.
Attempts to reinfect this rat, between 10th July 1933 and 18th Sep-
tember 1933 either with bovine or equine strains of trypanosomes,
failed, showing that it was immune to those strains. On 22nd Sep-
tember 1933, four days after the last attempt at infection, it was
again injected with an equine strain of trypanosomes passed through
a dog (No. 527) to which it succumbed.
(d) White rat No. 510 was infected with an equine strain on 18th August
1933 and was treated with 'Bayer 205' on 22nd August 1933
Twenty-three days later it was injected with the same equine strain
passed through a dog (No. 527) and the rat developed surra and died.
(e) White rat No. 559 was infected with a bovine strain and was treated
with ' Bayer 205 ' on 6th October 1933. Between 3rd October 1933
and 15th January 1934 it was injected twice with an equine strain of
trypanosomes to which it resisted. On 16th January 1934 it was
injected with an equine passage strain from guinea pig (No. 608) in
which the trypanosomes had suddenly acquired an exalted virulence
and succumbed.
(f) White rat No. 537 was infected on 16th September 1933 with the
n th relapse strain under passage in a guinea pig. It was treated on
20th September 1933 with ' Bayer 205 '. It was reinfected successfully
with the equine strain from guinea pig (No. 608) mentioned above.
The interval between the time of treatment and reinfection was thus
three months and 18 days and three months and 26 days respectively.
From the above it seems that the first four rats, did not possess any resistance
to a canine strain of trypanosomes, or to a strain passed through a dog and it is
inferred that a strain of T. evansi [Steel 1885], when passed through a dog, may
become exalted in virulence and may produce the disease in white rats even though
they possess a certain degree of immunity. That these white rats had some degree
I 2
376 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
of immunity is assumed from the fact that they resisted previous attempts to
reinfect, while their blood when tested gave a strongly positive adhesion phenomenon
even to the day of last reinfection.
The history of the last two white rats appears to show that a strain of
trypanosomes, which has become exalted in virulence for some unknown reason,
has the power of breaking down experimentally induced immunity and of producing
infection when injected, into a susceptible animal.
The above findings also seem to show that in some animals acquired immunity
may be overcome by certain strains of the same trypanosome depending upon the
degree of virulence of the strain used and that ' Bayer 205' may not protect white
rats beyond three weeks.
ADHESION PHENOMENON.
The methods adopted in studying this phenomenon were as described by
Taliaferro [1930], Davis and Brown [1927] and Duke and Wallace [1930] and a large
number of tests were made with blood from experimental animals. Wet prepara-
tions were examined after 15 to 20 minutes. Three things were noticed in these
preparations, viz., (1) Agglomeration of trypanosomes, (2) adhesion of platelets to
trypanosomes, especially to their flagellae, and (3) adhesion of red blood cells in
addition to platelets completely enveloping the trypanosomes, particularly in dogs'
blood. Agglomeration of trypanosomes was a constant feature even when relapse
strains were tested with their original passage strains in white rats or other animals.
From the uniform success of the very large number of tests in obtaining positive
adhesion and agglomeration, with different strains, it is concluded that these strains
are identical. It appears, therefore, that the strains of trypanosomes found in
Southern India are identical, and further that the trypanosome in question is
identical with T. evansi.
It is of interest that only in a few instances was slight deviation seen in the
degree of the adhesion phenomenon between the original strain and its relapses.
RESERVOIRS OF SURRA.
By a ' reservoir' of surra, in the strictest sense of the term, it is meant that
the disease is latent, so that the causal agent is carried over from one surra season
to another in the system of an animal in apparently good health. Such an animal
may not show trypanosomes in its blood, under the microscope, but it should be
possible to demonstrate their presence by animal inoculation, during the non-surra
season.
OBSERVATIONS ON TRYPANOSOMES OF CATTLE IN SOUTH INDIA
377
It is admitted, on all hands, that the surra season in India is between June
and October, but sporadic cases have been known to occur during the so-called
non-surra season.
In the camel, we have an accredited ' reservoir' of surra, because in that
animal surra runs a chronic course extending over a period of three years;
punctuated with frequent paroxysms, when T. evansi is demonstrable under the
microscope. Hence, wherever camels are found, it is easy to conceive, that
diseased camels act as foci of outbreaks of surra in horses or other animals, provided
the agent believed to mechanically transmit those trypanosomes are present at the
time. From the available literature on trypanosomiasis in India, it is found that
any work done on this disease, including the question of fixing the probable
reservoirs, has been done only in Northern India where the well-known reservoir —
the camel—is present. In the Madras Presidency there are no camels and the
question of cattle and buffaloes being the reservoirs has to be examined.
No work appears to have been done to find out if the wild animals which abound
in India serve to bridge the gulf from one surra season to another and we have no
knowledge of a real vector like the tse-tse fly in South Africa. Hence with a certain
amount of reserve we draw our own conclusions as to the possible reservoir-hosts
of surra.
Workers in Northern India have attempted to show that in addition to the
camel, cattle and buffaloes are likely to be carriers.
Montgomery [1908] said that the virus of surra is found wherever the camel
of Northern India abounds and there is a possibility of its existence wherever
cattle and buffaloes exist, and until the contrary be proved all these maybe
considered as the possible hosts of the trypanosome. He further said that the
conditions under which bovines work render them less dangerous than camels as
originators of the disease, and as a class not so important as store-houses.
It may be pointed out here that in countries where camels — the admitted
reservoirs — exist, the argument that such refractory animals as cattle also act
as reservoirs appears to be of doubtful value, because the latter may have been
infected from the camel and the infection may have caused death, or spontaneous
recovery may have occurred within a few months. It is undoubtedly true that
infected cattle showing trypanosomes in their blood, may, like all other animals,
act as temporary foci of infection, but this does not prove that they really carry
trypanosomes in their tissues from one surra season to another, to be the real
reservoir hosts.
In the months of January and February 1934, it was possible to test, in the
Madras Veterinary College Laboratory, the blood of 16 emaciated cart-bullocks
378 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
brought to the College Hospital for treatment and of one calf experimentally
inoculated with surra in September 1933. Many of these bullocks came from places
over 20 or 30 miles away and some of them came from near Saidapet, where surra
is known to break out periodically. January and February were the months
chosen for these tests, because they are about the middle of the so-called ' non-
surra ' season. The blood of each was examined under the microscope and each
sample of blood was tested for adhesion phenomenon before injection into white rats,
each of which was injected with ½ c.c. of blood intra-peritoneally. The results are
noted in the following table :—
PROTOCOL V.
Serial No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
No. of
case Sheet
1134
1240
1101
1266
1241
1146
1224
1141
1109
...
1153
996
983
1225
765
895
Expl. calf 516
Result of
microscopical
examination
Negative .
„ .
„ .
„
.
„
.
„
.
„
.
„ .
„
.
„
.
„
.
„
.
„
.
„
.
„ .
„
.
„
.
Result of
adhesion
test
Negative ..
Positive ..
Doubtful ..
Positive ..
Doubtful ..
Positive ..
Negative ..
Positive ..
Negative ..
Doubtful ..
„
.
.
Negative . .
„
.
.
„
.
.
„
.
.
„
. .
Positive ..
Result of
animal
inoculation
Negative
„ .
„ .
„
.
„ .
„ .
„
.
„
.
„
.
„ .
„
.
„
.
„
.
„
.
„
.
„
.
„
.
Remarks
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
This calf is still
under observa-
tion and is
negative
to
tests.
OBSERVATIONS ON TRYPANOSOMES OF CATTLE IN SOUTH INDIA
379
It may be seen that none of these harboured trypanosomes though five
showed a positive adhesion phenomenon and the history of experimental calf
No. 516, which had been kept in a fly proof stable, is of interest. This calf was
injected on 4th September 1933 with an equine strain of trypanosomes, which
appeared in its blood in large numbers from 7th September 1933 to 13th September
1933. After this date its blood was negative under the microscope for trypano-
somes but remained infective to white rats from 13th September 1933 to 13th
November 1933 whether given subcutaneously or intraperitoneally. This animal is
still negative at the time of writing (11 months from the date of primary
inoculation). The blood when tested for adhesion phenomenon in the early periods
was strongly positive; but its strength has progressively diminished and is now
absent. The result of these observations, when compared with the positive ad-
hesion tests of the other bullocks, may be interpreted to mean that those animals
had had trypanosomiasis during the so-called surra season, a few months before
the tests and had recovered. The failure to infect white rats indicate that none
of these animals had latent trypanosomiasis and were not reservoirs of surra,
but before drawing conclusions it will be of interest to discuss the observations
of workers who hold that cattle and buffaloes are likely to act as reservoirs of
surra between one and the next surra season.
Lingard [1899 and 1907] observed that when cattle infected with surra
develop the disease, many recover spontaneously and a few die showing paroxysms
just as in the horse, while the blood of those that recover becomes negative for
trypansomes after the lapse of a few months to microscopical examination and to
animal inoculation and remains so.
Pease [1906] injected 3 buffaloes with camel surra. Two died in the course
of one and three months respectively and the 3rd was kept under observation for
786 days, during which period he found its blood to be infective to dogs from time
to time. There is however one defect in this experiment in that the buffalo was
apparently not protected from fresh infection.
Schien [1908] says that an experimentally infected buffalo remained infective
to laboratory animals for 5 months only. Some time later he infected the same
buffalo successfully with surra and it remained infective, to animal inoculation, only
for 4½ months from the time of second injection. This finding of Schien contra-
dicts what Pease had observed in India.
Cross and Patel [1922] injected camel surra into buffaloes and found that they
neither lost condition nor did trypanosomes appear in their blood; their blood was
found infective to animal inoculation only for 163 to 172 days after the primary
infection. The observations of these workers are in agreement with those of Schien
regarding the duration of the infective period in a buffalo.