E. A. Watson and S. Hadwen 
23 
is not so centrally located as in that of the rabbit trypanosome nor as far 
forward as in T. lewisi, and the posterior end of the parasite is narrower 
than in either of the other two species. 
Non-pathogenetic for mice and rabbits. (Watson.) 
Trypanosoma eguiperdum Doflein, 1901. 
(PI. I. fig. 4.) 
The first discovery of the Dourine trypanosome in North America 
was made at Lethbridge, Alberta, on Feb. 11, 1907, in a naturally infected 
mare. (Watson and Gallivan.) 
Seasonal prevalence : trypanosome periodicity has been noted in 
horses in every month of the year, not infrequently during the coldest 
winter months, but the parasite becomes most active, usually, towards 
the end of a very hot summer season. 
Pathogenicity; different strains of Dourine trypanosomes have been 
found to vary greatly in virulence. The strain isolated in Feb. 1907, 
became exceedingly virulent for horses after eight or nine early passages 
through young mares and foals. 
Dogs, rabbits, mice and gophers were always resistant; white rats 
were less so, for after a great number of failures to infect with strains 
of ordinary virulence, a few of these animals were at last successfully 
infected with the strain which had become so highly virulent for horses, 
and although the parasites were never seen in the rats’ blood, this 
blood, when injected into horses produced a virulent and fatal infection. 
Morphological characteristics: the average length of the parasite 
is 27 y. The anterior extremity has a free flagellum, usually of short 
length ; the posterior is frequently blunted or has a sawn-off appearance. 
The kinetonucleus is very small, smaller than in any of the pathogenic 
trypanosomes with the exception of Trygjanosoma equinum, and is 
frequently associated with, or just posterior to, a vacuole. (Watson.) 
“ Dourine in Canada.” J. G. Rutherford. The Lancet^ May, 1907. 
Special Report on Dourine. Health of xi nimah Branchy Dept, of Agriculture, 
Canada. Nov. 1907^. 
“Note on the life-history of Trypanosoma equiperdum.” E. A. Watson, in 
Health of Animals Report, 1909 h 
“ An Experimental Study of Dourine.” E. A. Watson, in Health of Animals 
Report, 1910 h 
1 Published by the Department of Agriculture, Ottawa, Canada. 
