Intracapsular asexual proliferation of Mesocestoides sp. tetrathyridia in the gastrointestinal tract and mesenteries of the prairie rattlesnake (Crotalus viridis viridis).

Nonproliferous and proliferous tetrathyridia (Mesocestoides sp.) have been reported from natural and experimental infections in reptiles and rodents. Multiple tetrathyridia (1+) in individual capsules (host-derived) were observed for both types of tetrathyridia and in both types of animals. To determine whether proliferous tetrathyridia in this genus could replicate in host capsules of the prairie rattlesnake (Crotalus viridis viridis), 11 snakes were inoculated and maintained in 2 environmental chambers (25 C and 30 C). One snake at each temperature was removed at 4-wk intervals and killed. Sections of the gastrointestinal tract and adjacent mesenteries were histologically examined. The increase in the numbers of tetrathyridia per capsule was significant at both 25 C (P = 0.007) and 30 C (P < 0.001). Identification of 7 intracapsular tetrathyridia with binary scoleces served as collaborative evidence. This paper presents the first significant evidence for asexual replication of the proliferous tetrathyridia (Mesocestoides sp.) in a reptilian host.