Rapid detection and quantification of Cryptosporidium baileyi oocysts in feces and organs of chickens using a microscopic slide flotation method.

A simple semiquantitative microscopic slide flotation (MSF) method using modified Sheather's sugar solution (MSSS) is presented for the rapid detection and quantification of Cryptosporidium baileyi oocysts in the feces and mucosal and/or organ scrapings of chickens. Oocyst shedding was evaluated by examination of the surface of coverslips, and the average quantitative score (0-5) recorded for 10 microscopic fields (magnification x250) is reported. The equivalence between these scores and the actual number of oocysts counted per gram of feces was assessed (rs = 0.89; P < 0.001). The applicability of this method was tested by comparison of the kinetics of oocyst shedding in feces of inoculated chickens with those reported by other authors working under similar conditions. In organs the MSF method was compared to histology. Fewer false-negative results were obtained using MSF versus the histology method. The MSF method was particularly more efficient in tracheae with low levels of infection and in the lungs, regardless of the level of infection. The MSF method was also very efficient in detecting oocysts in air sacs from chickens with aerosacculitis. It provides a specific and sufficiently sensitive, simple, rapid, reliable, and low-cost means of diagnosing C. baileyi in the feces and organs of chickens. This method can be used in the routine diagnosis of cryptosporidia in chickens, and it could be extended to other avian species and used in epidemiology studies to evaluate the prevalence of cryptosporidiosis in fowl.