SPOROZOITES INTRA- AND EXTRA-ENTERICALLY

Chickens were dosed orally with sporulated oocysts ofEimeria acervulina, E. brunetti, E. maxima, or E. praecox and the subsequent presence, in various tissues, of parasites capable of inducing patent infections was detected by transferring the tissues to coccidia-free recipients. Similar results were obtained with each of the 4 species studied, irrespective of whether initial development occurs in the superficial (E. praecox, E. brunetti) or crypt (E. acervulina, E. maxima) epithelium. Infection was transferable by gut scrapings and liver homogenates at all time intervals (3, 6, 12, 18, 24, and 36 hr postinoculation) studied. Infection was also transferable with blood and with splenic homogenates but not consistently. Transfers made within a short time of the inoculation of donors were more successful in producing patent infections in the recipients. In all transfers the prepatent period was normal for the species. These findings suggest that sporozoites enter the mucosa very shortly after inoculation, and some of them pass to the liver and spleen and then leave these tissues at a somewhat slower rate, possibly to reenter the mucosa. Sporozoites in the lamina propria of the gut were found within host mononuclear cells in all 4 species studied. Most of the cells harbouring E. maxima and some of those with E. praecox were identified as intraepithelial lymphocytes while all others could only be identified as agranular mononuclear cells that were not character- istically macrophages. Seven species of Eimeria parasitize the chick- en and, although their life cycles in the intestines of this host are fundamentally similar, there are some differences, for example, in the location of the early developmental stages. In the case of all 7 species, the sporozoites penetrate enterocytes of the villi (or the surface epithelium of the large intestine), but only E. brunetti and E. praecox begin their growth there. The first-generation schizonts of the other 5 species are formed in the enterocytes of the crypts. The sporozoites of E. tenella (Lawn and Rose, 1982) and E. necatrix