Hosts of two canid genera, the red fox and the dog, as alternate vectors in the transmission of Sarcocystis tenella from sheep.

Microscopic sarcocysts recovered from naturally infected sheep were infective to both the domestic dog (Canis familiaris) and the red fox (Vulpes vulpes). The parasite was passaged through experimental specific-parasite-free (SPF) sheep three times: infection was transmitted twice with sporocysts from foxes and subsequently with sporocysts from dogs. The sarcocysts from sheep muscle were infective to both dogs and foxes on each occasion. A cat was not infected. The prepatent period in individual canids ranged from 7 to 15 days. Sporocyst excretion was still detectable 60 days post infection. This study establishes that canids of two genera may act as vectors for a single isolate of the same Sarcocystis species from sheep.