In Canada eight species of ticks are implicated with ten and possibly seventeen diseases of man and animals. The most important of these, tick paralysis, is caused by Dermacentor andersoni Stiles, and of three hundred human cases in British Columbia since 1910, thirty have been fatal. In livestock, outbreaks have involved up to four hundred cattle in a single herd, with losses of up to fifty head. Other diseases resulting from tick toxins include a paralysis of cattle by Oyobius megnini Dugès, which has caused twelve deaths since 1955; occasional deaths in deer and moose from heavy infestations of Dermacentor albipictus (Packard); and slow-healing sores in man resulting from the bites of Ixodes pacificus Cooley and Kohls.