Vitamin A Deficiency and Eimeria Acervulina Infection in the Chick

EIMERIA acervulina infections in the chicken are not usually associated with mortality or severe pathological symptoms. Tyzzer et al. (1932) did not consider this species very pathogenic, and Dickinson and Scofield (1939) demonstrated only a decrease in food consumption and a transitory drop in body weight in birds infected with 35–50 million oocysts of E. acervulina. Hein (1968), investigating the pathogenicity of E. acervulina, concluded that mortality was not a feature of the disease and that anorexia and morbidity were seen only after heavy doses of oocysts (5 M and 20 M per bird). However, under field conditions, E. acervulina infections often cause economically disastrous results in a flock and the disease can be associated with high mortality and morbidity. Suboptimal vitamin A levels in the diet may be one factor responsible for the discrepancy between field and experimental observations of the pathogenicity of E. acervulina.