Pathogenicity of Isospora suis in gnotobiotic and conventionalised piglets.

Isospora suis is unequivocally a primary pathogen of swine. Inoculation of I suis in conventionalised and germ-free piglets caused a biphasic disease course with marked diarrhoea, villous atrophy and necrosis of the intestinal epithelium at four to six and eight to 10 days after inoculation. The presence of a normal bacterial flora markedly (P less than 0.05) influenced the survival rate of piglets but did not appear to affect the histopathological changes observed. Mild limited focal necrosis and bile stasis were present in the liver at eight to 10 days after inoculation. In this period there was also ectasia of lymph vessels in the intestinal lymph nodes.