Pathology of natural isosporosis in nursing piglets.

In piglets suffering from natural coccidiosis, post-mortem examination showed that pathological changes induced by Isospora suis were evident from day 7 to day 14 of life, and particularly, by days 9 and 10. Macroscopically, the changes were manifest as enteritis varying from catarrhal to pseudomembraneous form. Microscopically, they consisted of more or less extensive atrophy of villi whose apical parts were necrotic, of metaplasia and erosion of epithelium. With the exception of duodenum and the adjoining sector of jejunum, the alterations were manifest along the entire small gut though intensity of lesions and incidence of endogenous stages of Isospora suis varied from sector to sector of the intestine. Predilected was a portion limited approximately by 50 and 140 cm cranially from ostium ileocecale, viz. the caudal sector of central jejunum and the cranial sector of the caudal jejunum. Within this area, lesions were more severe and frequent than in sectors situated cranially and caudally of it. The predilection persisted even in case of concurrent adenovirosis. The lesions contained meronts and gamonts at the same time though gamonts predominated. Advanced merogony and gametogony resulted in distinct displacement of cell nuclei and in cell walls bulging into the inner diameter of the gut. We assume that endogenous stages of Isospora penetrate the submucosis via the narrow opening at the orifice of lymph follicle; such was the case with gamonts and oocysts detected in activated lymph tissue of Peyer's patches.