Trypanosoma equiperdum, Doflein, 1901.
Syn.: Trypanosoma rougeti, Laveran and Mesnil.
The malady of horses known as “dourine” or “mal du coït” is due to a trypanosome, T. equiperdum, discovered by Rouget in 1894. “Dourine”—also known as “stallion disease” or “covering disease”—is found among horses and asses in Europe, India, North Africa and North America. The trypanosome is transmitted by coitus, and so far as is known not by insect agency.
Fig. 43.—Trypanosoma equiperdum. × 2000 approximately. (Original. From preparation by Fantham.)
The progress of the disease may be considered under three periods. The period of œdema, when signs of œdema of the genitalia are seen. The œdema is generally painless and non-inflammatory. This period lasts about a month. It is succeeded by the period of eruption, which sets in about two months after infection. Circular œdematous areas (“plaques”), often about the size of a two-shilling piece, appear under the skin of the sides and hind quarters, and also, at times, under the skin of the neck, thighs and shoulders. The eruption is variable, but usually lasts about a week and leaves the animal in an enfeebled condition. Gland enlargement and swelling of the joints and synovia also may occur. The third period of the disease is described as that of anæmia and paralysis. The animal becomes very anæmic, emaciation is marked, superficial non-healing abscesses often form, and conjunctivitis and ulcerative keratitis can occur. Paralysis ensues, and in from two to eighteen months the animal dies. In the acute form of the disease the animal may die after the first period from acute paralysis.
It is difficult to find the trypanosomes in naturally infected animals, and they are best obtained from the plaques of the eruption. Apparently the parasite occurs more in the lymph than in the blood.
Ruminants are said to be refractory to this trypanosome.
T. equiperdum is about 25 µ to 28 µ in length on an average, but varies from 16 µ to 35 µ. Its cytoplasm is relatively clear, and does not show chromatic granules (fig. 43). It is stated to be monomorphic.
It has been shown recently by Blacklock and Yorke (1913)105 that there is another trypanosome giving rise to dourine in horses. This trypanosome is dimorphic (resembling T. pecaudi and T. ugandæ), and is named T. equi. Previously T. equiperdum and T. equi had been confused.
Uhlenhuth, Hübner and Worthe have demonstrated the presence of endotoxins in T. equiperdum. These endotoxins may be set free by trypanolysis.
Trypanosoma theileri, Bruce, 1902.
Fig. 44.—Trypanosoma theileri. × 2,000. (After Laveran and Mesnil.)
This parasite, 60 µ to 70 µ long, and 4 µ to 5 µ broad, is distinguished for its large size, though it is not so large as T. ingens from Uganda oxen, whose length may be 72 µ to 122 µ, and breadth 7 µ to 10 µ. The posterior end of T. theileri is drawn out. Small forms of the flagellate are known, 25 µ to 53 µ in length. Probably other forms of the parasite have the nucleus posterior, and these flagellates were formerly separated as T. transvaaliense (Laveran, 1902). Myoneme fibrils may be seen on its body. The pathogenicity of this organism is doubtful, it was formerly thought to be the causal agent of “gall-sickness” in cattle in South Africa. T. theileri also occurs in Togoland, German East Africa, and Transcaucasia. Allied or identical parasites occur in cattle in India.
Trypanosoma theileri, specific to cattle, is perhaps transmitted by the fly Hippobosca rufipes in South Africa.
Trypanosoma hippicum, Darling, 1910.
Trypanosoma hippicum causes the disease of mules known as “murrina.”106 It was found in mules imported to Panama from the United States. It can live in other equines. The parasite varies from 18 µ to 28 µ in length, and is from 1·5 µ to 3 µ broad. Its undulating membrane is little folded. The trypanosome has a noticeable blepharoplast. It can penetrate mucous membranes, and it is thought that the trypanosome may be transmitted during coitus. It may also be spread mechanically by species of Musca, Sarcophaga and Compsomyia, sucking the wounds of infected animals and carrying over the trypanosomes to wounds on healthy ones.
Endotrypanum schaudinni, Mesnil and Brimont, 1908.
This organism was discovered in the blood of a sloth (Cholœpus didactylus), in South America (French Guiana).107 It possesses special interest, in that the best known form of the organism is endoglobular, inhabiting the erythrocytes of the sloth. A free trypanosome in the same animal was considered to be different from the endoglobular form, which was somewhat like a peg-top, and possessed a short flagellum. Darling108 (November, 1914) has seen the organism in Panama. He describes free crithidial forms in shed blood, but not in the blood-stream of the sloth.
Trypanosoma boylei, Lafont, 1912.
This is a parasite of the Reduviid bug, Conorhinus rubrofasciatus. The insect attacks man in Mauritius, Réunion and other places. Lafont infected rats and mice by intraperitoneal injection with the gut-contents of infected bugs. Trypanosomes appeared in the mice. Other flagellate types were assumed by the parasites in the bug.
Monomorphic Trypanosomes.
A number of trypanosomes, characterized by relative uniformity in size and structure, may be considered under this heading. They occur in cattle, sheep, goats and horses in Africa, especially West Africa. Morphologically, they are characterized by the posterior (aflagellar) part of the body being swollen, while the anterior part narrows. The nucleus is central and situated at the commencement of the narrowing of the body. The blepharoplast is almost terminal, the undulating membrane is narrow and not markedly folded, so that the flagellar border lies close to or along the body. The flagellum may or may not possess a free portion.
Some recent workers have considered that T. brucei (Zululand strain) and T. evansi are also monomorphic, but they do not exhibit the general characteristics outlined above. T. brucei and T. evansi have already been considered separately.
The monomorphic trypanosomes, as defined above, include:—
Trypanosoma vivax, Ziemann, 1905.
Fig. 45.—Trypanosoma vivax. × 2,000. (Original. From preparation by Fantham.)
This trypanosome109 occurs in cattle, sheep and goats, and was first found in the Cameroons. It is fatal to cattle. Equines are also affected. Antelopes are the possible reservoirs of the trypanosome. It is probably transmitted by Glossina palpalis and other tsetse flies. Its movement is very active. It possesses a free flagellum (fig. 45) and it averages 23 µ to 24 µ in length. T. cazalboui (Laveran, 1906)—the causal agent of “souma” in bovines and equines in the French Sudan—is probably synonymous with T. vivax.
Trypanosoma capræ (Kleine, 1910) is allied, but is somewhat broader and more massive. It was found in goats in Tanganyika.
Trypanosoma congolense, Broden, 1904.
Probable synonyms.—Trypanosoma dimorphon, Laveran and Mesnil, 1904; Trypanosoma nanum, Laveran, 1905; Trypanosoma pecorum, Bruce, 1910; Trypanosoma confusum, Montgomery, 1909.
This trypanosome causes disease among horses (e.g., Gambia horse sickness), cattle, sheep, goats, pigs, and dogs. It is widely distributed in Central Africa (e.g., Gambia, Congo, Uganda, Nyasaland), the strain probably being maintained naturally in big game. It is transmitted