Cryptosporidia-Positive Rates of Avian Necropsy Accessions Determined by Examination of Auramine O-Stained Fecal Smears

Fecal smears from 112 avian necropsy accessions representing 431 birds were stained with auramine O and examined for Cryptosporidium oocysts by fluorescence microscopy. Stained Cryptosporidium oocysts fluoresced bright yellow-green and were easily differentiated from extraneous material by their uniform small size (approx. 5 micron) and morphology. The rates of cryptosporidia-positive accessions were 27.3% (9/33) of broilers, 10% (3/30) of broiler breeders, and 5.9% (1/17) of layers. Further analyses of available data for various risk factors that may have influenced rates of cryptosporidia-positive samples in broilers, broiler breeders, and layers failed to show significant relationships. However, it was apparent that positive samples were clustered within accessions and not scattered throughout the population sampled. This survey also resulted in the first reported identification of Cryptosporidium oocysts from a budgerigar, macaw, and tundra swan.