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.