Pathophysiology of Coccidiosis in Piglets

After the sporulated oocysts are ingested by the piglets, sporozoites are released by excystation process in the small intestine. These sporozoites enter the intestinal cells and multiply  asexually ( described in section devoted to taxonomy and life cycle )  releasing large number of merozoites.

During the process of multiplication and release of merozoites the infected cells are destroyed. In the this process severe lesions in the small intestine ( jejunum and ilium ) may occur, such as epithelial desquamation and villous atrophy( villi become shorter and merging). As a result of coccidia infection big section of the intestinal mucosa  is  destroyed, the absorption and the digestive functions are seriously affected. This may involve an insufficient formation of digestive enzymes, or a shift in balance of the gut flora. All this leads to diarrhoea, poor weight gain and lower growth rates in pigs.

The microscopic lesions produce a picture of a necrotic, inflammatory gut disease. Some of the main alterations are:

• villous atrophy and fusion,
• necrotic enteritis,
• enterocyte metaplasia,
• crypt hyperplasia, and
• presence of I. suis in different developmental stages in the cells of the intestinal epithelium

The lesions encourage the invasion of secondary pathogens since the protective function of the mucous is severely impaired.

The intestinal mucous regenerates relative quickly, but the digestive function will be impaired for considerably longer than the clinical disease due to the fact that it will take time for the villi to grow back´to their original size.

For these reasons, coccidiosis is considered to be a classic erosive disease that seriously affects swine production parameters and hence, the economic results of producers.