Host specificity and age-dependent resistance to Cryptosporidium avium infection in chickens, ducks and pheasants

Abstract Host- and age-specificity of Cryptosporidium avium were studied in 1-, 21- and 365-day-old chickens ( Gallus gallus ), domestic ducks ( Anas platyrhynchos ) and ring-necked pheasants ( Phasianus colchicus ) under experimental conditions. Cryptosporidium avium was not infectious for ring-necked pheasants, but it was infectious for ducks and chickens at all age categories. The course of infection in ducks did not differ among age categories, but 365-day-old chickens had less severe infections than 1- and 21-day-old chickens. The patent period in chickens and ducks was >30 DPI, but ducks started to shed oocysts of C. avium earlier (5–6 DPI) and at a lower intensity (accumulated value of infection intensity of 58,000–65,000 OPG) than chickens (9–11 DPI and accumulated value of infection intensity of 100,000–105,000 OPG). Experimentally infected birds showed no clinical signs of cryptosporidiosis.