Trypanosomes in cattle in southern Ontario.

Trypanosomes were found in the blood of 155 out of 274 Holstein cows of various ages from southern Ontario. The incidence varied from about 8% in one herd to about 85% in another herd. Two species of trypanosomes were found in cattle in the Guelph area. One was Trypanosoma theileri. The other was a much smaller trypanosome which morphologically resembles T. uniforme of the Salivaria. This is the first report of such a trypanosome in cattle in North America. Epimastigotes from blood agar slants of both trypanosomes, when inoculated into chick embryos, produced blood forms morphologically identical to those found in the blood of the cows. T. theileri survived at least two weeks in blood kept at 4-5 degrees C.