Light-microscopic lesions associated with naturally occurring bursal cryptosporidiosis in chickens.

Information concerning histologic significance of naturally occurring bursal Cryptosporidium sp. infection in chickens was obtained by retrospective examination of histopathology reports and clinical data from histology accessions received during 1986. Cryptosporidiosis was diagnosed in 197 bursas. In two-thirds of the accessions, more than 50% of the examined bursas were infected with Cryptosporidium sp. The histologic morphologic lesion diagnosis for Cryptosporidium sp.-infected bursas most often was marked diffuse chronic-active superficial purulent protozoal bursitis with mucosal epithelial hyperplasia. Our study clearly indicates that Cryptosporidium sp. is associated with inflammation and disturbed growth in chicken bursas. Additionally, our data indicate that Cryptosporidium sp. infection is not dependent on bursal damage attributable to other agents, including infectious bursal disease virus.