W. A. Riley 87 
dogs have not yet been reported for foxes. On the other hand, several fox 
parasites are thought to occur exclusively in these animals. 
In the following list are included such animal parasites as have been 
reported for foxes, together with notes on their occurrence, and probable 
pathogenic significance. 
PROTOZOA. 
There are very few records of the occurrence of parasitic protozoa in foxes. 
While several serious protozoal diseases are known to occur in dogs, they are 
fortunately prevalent chiefly in the tropics and in sub-tropical regions. 
Successful fox fur farming is limited to the cooler zones, a long cold season 
being an important factor in producing suitable fur growth. 
Trypanosoma brucei Plimmer and Bradford, 1879. This trypanosome, the 
well-known causative organism of the tsetse-fly disease “Nagana of cattle 
has been experimentally transmitted to the fox by Yakimoff (1917). Trypano¬ 
soma yambiense has also been inoculated successfully into experimental foxes 
by Laveran (1915). 
In spite of the extensive study devoted to the trypanosomes, there does 
not seem to be any record of their occurrence in the fox in nature. 
Trichomonas sp.—Dr W. L. Chandler informs me that he has found in 
Michigan a species of Trichomonas occasional in foxes. While it is the usual 
tendency to regard the members of this genus as harmless commensals, recent 
studies, notably those of Hadley (1916) and Tyzzer (1920), indicate that under 
some conditions they may be highly pathogenic. 
Isospora bigmenina (Stiles, 1891). (Synonyms: Coccidium bigeminum, 
Stiles, 1891; Diplospora bigemina (Stiles) Wasielewski, 1904.) In foxes from 
three separate ranches we have found a coccidium which agrees fairly closely 
with the species found by Stiles in the dog. The rounded somewhat ovoid cysts 
have a double-contoured wall and measure on the average 30p, by 25/x. Both 
single and two-spored oocysts are found in the fresh faeces. 
Weidman (1915) has discussed the finding of what appears to be this same 
coccidium in the faeces of two swift foxes from the Western United States, 
which were kept in the Philadelphia Zoological Gardens. “ Both foxes when in 
isolation showed diarrhoea, the one more marked than the other. In the 
former the oocysts were in great numbers and in about a week the animal died. 
The second fox, on the other hand, passed very small numbers of cysts, 
spontaneously recovered, and after isolation for several weeks was returned to 
exhibition, the faeces no longer containing oocysts.” Autopsy of the dead fox 
disclosed a most marked haemorrhagic and ulcerative enteritis involving both 
small and large parts of the bowel. Within the ulcers were found mature naked 
protozoa, and upon the mucosal surface double-walled oocysts corresponding 
to those found in the faeces. 
As the oocysts found in the fox averaged considerably larger than those 
reported by Stiles for the dog Weidman considered them sufficient to constitute 
a new variety, canivelocis. The organism should be studied in greater detail. 
