Changes in Some Haematological Parameters of Two Breeds of Chicken Inoculated with Eimeria Oocyst

Coccidian parasites, especially those in the genus Eimeria, are intestinal parasites common in poultry. They cause coccidiosis in infected birds. The effect of the parasites on the haematology of infected chickens was studied using broilers and white-leghorns. A total of 30 day-old chicks, fifteen each from the two breeds, were procured for the experiment. They were grown to three weeks old, and confirmed to be free from any intestinal parasite, before inoculating 10 birds each, randomly selected from the two breeds, with Eimeria oocyst. The packed cell volume (PCV), thrombocyte number, leukocyte number and proportion of leukocyte types were determined from blood samples obtained from the birds within ten days after inoculation and confirmation of infection. Infected broilers (B) and white-leghorns (WL) both had packed cell volumes that were lower than the control (C) (B. 31.8±2.2, WL. 32.8±1.8, C. 34.3±2.6). However, estimates of the effect sizes suggested that coccidiosis accounted for only about 5% of the observed variance in the PCV of broilers and 2% in white-leghorns. The disease significantly affected the thrombocyte number of infected broilers only (B. 7.0±0.5, WL. 10.4±1.1, C. 10.0±0.8). A remarkable difference was found in the leukocyte numbers of infected birds (B. 13.4±2.2, WL. 21.4±3.2, C. 14.9±2.0). However, the infection increased the proportion of circulating monocytes from 1% in control to 5% in the infected birds regardless of their breed. The observation that broilers are prone to parasite induced thrombocytopaenia, supported by the wide disparity in the leukocyte numbers of the two breeds of chicken during an infection, suggest that white-leghorns are better adapted to withstand the effects of coccidiosis when compared with broilers reared under the same environmental conditions.