Effect of some stressors on pathogenicity of Eimeria tenella in broiler chicken.
The present investigation was carried out to study the effect of stress on severity of Eimeria tenella infection in chickens. Stressors applied were vaccination and crowdness. One hundred and twenty five one-day old chicks were divided into five groups. The groups were as follow: group (1) control negative, group (2) control positive, group (3) crowded non-vaccinated, group (4) vaccinated, and group (5) vaccinated crowded. The chicks of 2-5 groups were inoculated with 10 x 10(3) sporulated oocysts of E. tenella per chick at 3rd day old, then challenged with 15 x 10(3) sporulated oocysts of E. tenella on day 28. The results revealed that, the highest mortality percent, oocysts production and caecal scores were recorded in the crowded vaccinated group. This group also exhibited the lowest weight of body, spleen, bursa and thymus. At the last four weeks, it was found that overstocking of chickens lead to elevation of corticosterone levels. Total proteins, glucose, calcium and phosphorus levels decreased in crowded vaccinated group.