Trypanosoma Brucii: attacks horse, ass, mule, cattle, buffalo,
antelope, camel, hyena, dogs, etc. Elephants and zebra, pigeon and hen
immune. Tsétsé fly. Inoculation only certain channel; virulence in
dead body 24 hours; in vitro 3 to 4 days, or when dried or heated
(122° F.) Symptoms: hyperthermia; anæmia; leucocytosis; buffy coat;
œdemas; catarrhs; wasting; debility. Lesions: as in surra; trypanosoma
in blood at intervals, bone marrow, lymph glands, spleen. Immunizing
unsuccessful. Prevention as in surra.
This is an infective disease caused by the _Trypanosoma Brucii_, which
has been supposed to be identical with _Trypanosoma Evansi_ but differs
in its morphology and in its infectiveness toward a greater variety of
animals. It is 25 to 30μ long by 1.5 to 2.5μ broad, less pointed at its
posterior (nonflagellate) end, broader undulating membrane, more deeply
staining protoplasm, and more sluggish movements. It invades the blood
of horses, asses, mules, cattle, buffaloes, antelopes, camels, hyenas,
and dogs, and can be inoculated on cats, rats, mice, rabbits, hedgehog,
boshbok, zebra hybrids, Guinea pigs, goats, sheep, weasel, and monkey
(Macacus rhesus). Elephants are immune though they suffer from T.
Evansi, and the zebra is immune though a soliped.
The _tsetse fly_ (glossina morsitans) is credited with being the main
agent in transmitting the parasite to mammals, (see _Diptera_).
Kauthack, Durham and Blandford found that Guinea pigs were more
resistant than rabbits, surviving the inoculation for a longer time.
Bruce also found the native South African sheep and goats more
refractory than others, yet their hæmatozoön was as deadly to other
animals as that of horse or dog. Pigeons and South African hens proved
refractory. Manifestly in Africa the present races of some animals are
the products of the survival of the fittest.
_Inoculation._ The disease has been produced experimentally by
inoculation only. Feeding experiments on rabbits, cats and Guinea pigs,
the sucking by puppies of an infected dam for 14 days, coitus, and even
the careful dropping of infected blood under the eyelid failed to convey
it. Lousy rats with sores on face, one cat doubtless scratched by a
bone, and one rabbit supposed to be infected by sexual congress (Rouget)
offer exceptions, which in the light of the general results must be
looked on as probable inoculations through wounds.
Successful inoculations were made with blood, lymph gland, spleen, bone
marrow, aqueous humor, serum, œdema fluid, and testicular juice. The
effectiveness of inoculation did not vary materially with the different
fluids used, with the amount, nor with the point selected for its
insertion, subcutaneous, intravenous, intraperitoneal, or on a mere
scratch.
Virulence is lost in the dead body in 24 hours or less; when the
infected blood is kept aseptically _in vitro_, in 3 or 4 days at most;
or when completely dried. Heating to 122° F. for 30 minutes sterilized,
while at 114.8° F. for half an hour the trypanosoma became nonmotile,
but not quite non-virulent.
_Symptoms._ _Hyperthermia_ is marked about the time of the appearance of
the infusoria in the blood. (Horse 106.7°; dog 104°; rabbit 105.8°), and
in the horse there was a paroxysm with each new swarm of the parasite.
In one ass intermissions were not observed. In rabbits there was no
constant ratio between the temperature and hæmatozoa, hyperthermia was
constant or nearly so. The horse had marked hyperthermia up to death,
dogs and cats showed a marked descent even to subnormal, before death.
_Anæmia_ is a marked feature the red globules being greatly reduced, and
they show a tendency to clump in masses instead of forming rouleaux. The
serum added to healthy blood has the same effect on that. _Leucocytosis_
is not constant nor excessive (15,000 to 34,000 per c.m. at the
highest). In clotting the blood may form a buffy coat.
_Œdema_ is common in horse, rabbit, cat and dog especially about the
head, legs, belly and genital organs. Rabbits often show swellings,
excoriations and sores of the labia, prepuce and penis favoring
inoculation by this channel.
_Conjunctivitis_ is common in cats, dogs, rats, rabbits, often in
connection with facial œdema, and corneal opacities and ulcers, and
turbidity of the aqueous humor may follow.
_Nasal catarrh_ often interferes materially with breathing.
_Muscular wasting_ and _debility_ are prominent phenomena, especially in
horse, dog, cat and rabbit, the loss of weight reaching 20 or 30 per
cent.
_Lesions._ These are like those of surra. Enlargement of the lymph
glands, spleen and liver, firmness, friability and dark color of the
spleen; effusions, petechiæ, and even hæmorrhages of the serosæ, lungs
and stomach, and great atrophy of the muscles and adipose tissue are
prominent features. The liver is always fatty in rabbits. In the shafts
of the long bones, the fat is replaced by red marrow. The bone marrow is
sometimes red, at others pale.
The _trypanosomata_ in the blood vary greatly. In infected rats and mice
they appear 3 or 4 days after inoculation, are almost constantly present
thereafter, and as a rule, encrease steadily up to 2,000,000 or
3,000,000 per c.m. In dogs they appear in 4 to 6 days, in cats in 5, in
Guinea pigs in 5 to 7, and in horses in 7 days. In rabbits there were
found 60,000 per c.m., in dogs 100,000 to 300,000, and in Guinea pigs
200,000 to 500,000. In one Guinea pig they did not appear until 6 weeks
after inoculation and then rapidly encreased to a fatal termination.
More commonly a few can be found about a week after inoculation, and
then they disappear for a variable period. They have been found in the
bone marrow when they could not be recognized in the blood. Again, after
subcutaneous flank inoculation in the rat, they were found in the
corresponding inguinal glands 1 to 3 days before they could be detected
in the blood. After death they are found most abundantly in the bone
marrow and spleen, but they have not been found in the intestinal
contents nor urine except in the case of hæmorrhages or local sores.
_No soluble toxin_ appears to be formed, and _no immunization_ is
effected by the serum. Blood serum kept several days until the infusoria
had died and then passed through a Berkefeld filter had no apparent
effect on the animal economy even in large doses. Blood heated to 122°
F. was equally harmless. The same is true of extracts of organs and of
bile from infected animals.
Attempts to secure _immunity_ by injecting the blood serum of affected
animals, after it had been sterilized by heat, filtration, or standing
one week _in vitro_ proved of absolutely no effect. The blood of the
fœtus almost at full term proved valueless, and the young born of
infected mothers proved fully susceptible when inoculated. The serum of
the Guinea-pig, which is naturally somewhat resistant, proved no
protection to other animals. Bile mixed with infecting blood _in vitro_,
kills the trypanosoma, but such blood has no protective effect on
animals. Sewer rats and white rats inoculated and re-inoculated with the
common rat trypanosoma (T. Lewisi) until immune from that organism, show
a full susceptibility to the trypanosoma of nagana.
_Flesh feeding_ and _vegetable feeding_ have made no difference in the
susceptibility in the case of rats. Feeding with the hæmatozoa has
produced no immunity.
It is evident that prevention must follow the same lines as in Surra,
due consideration being had of the greater number of genera susceptible.