Persistent cryptosporidiosis in horses with severe combined immunodeficiency

Abstract

Cryptosporidial infections were established in five young foals with severe combined immunodeficiency following oral administration of 108 Cryptosporidium parvum oocysts. All foals shed oocysts (average of 8 x 106 to 2 x 108/g of feces) until death. Inflammation and C. parvum organisms were observed in the common bile duct, duodenum, jejunum, and ileum. Since foals with severe combined immunodeficiency lack functional T and B lymphocytes and are incapable of antigen-specific immune responses, they are well suited for evaluating the pathogenesis and treatment of persistent cryptosporidiosis.