NAGANA. TSETSE FLY DISEASE.
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.