Experimental infection of chickens with Cryptosporidium.

To study the clinical and pathological manifestations of Cryptosporidium infections, 24 h-old chickens were inoculated via four routes: orally, nasally, cloacally and by contamination, using 10(5) oocysts of Cryptosporidium in each case. The chickens began to shed oocysts of Cryptosporidium on days 7 to 8 after inoculation. There was no difference in the clinical manifestations or histological damage with respect to the inoculation routes. Various developmental stages of Cryptosporidium were also demonstrated microscopically in the smears or sections of bursa of Fabricii, larynx, trachea and cecal tonsils of inoculated chickens. Although the intestinal mucosa and respiratory tract mucosa were scarcely infected with the parasites, the bursa Fabricii was heavily infected in association with hypertrophy and hyperplasia of the lining epithelial cells.