Natural cryptosporidial infection in a commercial raised turkey flock: histologic and ultramicroscopic investigation.

Cryptosporidia are small coccidian parasites that infect epithelial cells, usually in the respiratory and/or digestive tracts of mammals, birds, fish, and reptiles. Cryptosporidiosis has been described in galliforms, anseriforms, psittaciforms, ostriches, canaries, and finches, but little is known about the host specificity of this coccidian parasite in fowls. Current differentiation of Cryptosporidium isolates into valid species is based mainly on oocyst morphology, sequence similarities of small subunit ribosomal RNA, host specificity, and site of infection. At present there appear to be two species, Cryptosporidium bailey and Cryptosporidium meleagridis infecting both chickens and turkeys, and a third, unnamed, species infecting quail. In turkeys Cryptosporidium spp. was first reported by Slavin (1955) during a severe outbreak of enteritis. Support for Cryptosporidium meleagridis as a separate species from Cryptosporidium baileyi has been provided by experimental studies. Also recent data indicate that Cryptosporidium meleagridis is very closely correlated with Cryptosporidium parvum, which infects more than 100 species of mammals. In recent years, in Italy, a natural cryptosporidial infection causing a severe enteritis and mortality in 30 days old commercial turkeys, was reported. Cryptosporidium spp oocysts, round in shape, and 4-6 μm in size, were found both in the intestinal content and in stained smears. Light microscopy of histologic stained tissue section detected the protozoon in the respiratory and intestinal epithelium, in the bursa and kidney. Ultramicroscopic studies on ileum and bursal samples showed the presence of all life cycle stages in the microvillar brush epithelial cells in both the organ examined. Based on the micro-organism morphology and sizes, parasitizing the ileum and the bursa, hypothesis for the Cryptosporidium meleagridis involvement are considered. The increasing reports of natural severe outbreaks not species-associated, and the unclear taxonomy suggest the present paper in order: 1) to summarize the morphometric and ultramicroscopic characteristics of this protozoon interpreted to be Cryptosporidium meleagridis; then highlight the importance of Cryptosporidium meleagridis for the possible zoonotic role in public health.