Light and electron microscopic observations of in vitro excystation and asexual development of two bovine Sarcocystis species (Apicomplexa, Sarcocystidae)

Acute infection with species of Sarcocystis (Phylum Apicomplexa) can cause severe, often fatal disease in bovine intermediate hosts. Decreased growth, production, and reproductive success can also occur with chronic sarcocystosis. Elucidation of the mechanism of excystation (i.e. release of infective sporozoites from sporocysts) and host-parasite interactions involved in Sarcocystis spp. infections are necessary to develop preventive control measures. Asexual developmental stages of Sarcocystis cruzi and S. hirsuta were utilized in in vitro light and electron microscopic studies. Specifically, excystation of sporozoites and their subsequent invasion of and development in host cells were examined. Various excystation protocols were evaluated. The tissue culture and processing technique of Kingsley and Cole (1988) was modified for host cell invasion experiments. Four tissue culture lines were tested (Bovine pulmonary artery endothelium, Rat heart myoblasts, Rat skeletal muscle myoblasts, and African green monkey kidney cells). Schizogony was visualized in all cell types. Suitability of host cell type was assessed by quantification of merozoite production. (Abstract shortened by UMI.).