Complete Development of Isospora suis of Swine in Chicken Embryos1

Abstract

Development of the swine coccidium, I. suis, in embryonated chicken eggs is described. The allantoic cavities of 8-10 day old white Leghorn embryos were inoculated with either 100,000 or 200,000 sporozoites. Developmental stages morphologically similar to those found in the intestines of piglets were present in the endodermal layer of the chorioallantoic membrane (CAM), beginning three days postinoculation (PI). No stages were found in the mesodermal or ectodermal layers of the CAM and none were observed in heart, lung, liver, or spleen. Type 1 meronts and merozoites were found on days 3 through 10 PI. Type II meronts and merozoites were found days 4 through 10 PI. Mature microgamonts, macrogamonts, and oocysts were found on days 7 through 10 PI. Oocytsts appeared to be retained in the endodermal cells and in ovo sporulation did not occur. Attempts to sporulae CAM-derived oocysts were not successful. I. suis was not pathogenic for embryos under the conditions of this study. This represents the 1st fully documented report of complete development of a mammalian coccidium in chicken embryos.