Some physio-pathological changes associated with experimental Eimeria brunetti infection in the chicken

Abstract Chickens aged 16 weeks were inoculated with either 3·2 × 10 5 or 1·28 × 10 6 oocysts of Eimeria brunetti . During the acute phase of the infection total protein, sodium and chloride concentrations declined, potassium levels increased, while the packed cell volume (PCV) increased initially and then decreased. These changes appeared to be dose dependent. Mortality was 10 per cent. and 45 per cent. in the low and high dosed groups respectively. In the surviving chickens electrolyte values returned to normal by day 10. The PCV continued to fall after clinical recovery and normal plasma protein levels were not regained by day 13 in the higher dose group given 1·28 × 10 6 oocysts. The progressive alteration in plasma proteins, electrolytes and the PCV were attributed to the severe enteritis associated with the development of E. brunetti . In surviving birds the return of plasma electrolytes to normal concentrations corresponded to the time of resolution of intestinal lesions. The weight of organs examined at autopsy indicated that the decline in body weight could not be attributed to any particular tissue or organ. Rapid and severe dehydration appeared to be a significant factor in the loss in body weight, while rapid rehydration probably contributes to the rapid initial recovery in weight. The complete inappetence of the severely affected chickens confirmed that reduced food consumption is another important factor in weight loss in coccidiosis.