ABSTRACT
In most studies, host specificity of the coccidia has been judged by the completion of the endogenous stages of the parasite’s life cycle culminating in oocyst production after the appropriate patent time. Coccidia of the genus Isospora, which commonly shed oocysts in the feces of cats, dogs, and wild carnivores, have been regarded as host specific and thought to develop only in the intestinal tract of the host. Members of the genus Cryptosporidium are coccidial parasites which parasitize the microvillus border of host epithelial cells in a variety of host species including poultry, domestic animals, and man. The genus Eimeria is one of the most common and best known of the parasitic protozoa with over 900 species found in animals ranging from annelids to insects to reptiles and amphibians to birds to mammals. The use of different species of avian embryos has provided data that show that the coccidia are capable of development in a foreign host.
