Eimeria tenella is a protozoa which is a causative agent of avian cecal coccidiosis. The disease results in bleeding, diarrhea, weight losses, high morbidity and mortality in chickens. This study investigated lesion scores, oocysts output, hematological and histopathological changes of the 7 days life cycle of E. tenella. Fifty-six, broilers were randomly divided into 2 groups of which group 1 were uninfected and group 2 were infected with 2x104 E. tenella oocysts. Lesion scores and oocyst output of the infected group were significantly higher than in the uninfected group at 5, 6 and 7 dpi (p < 0.05). PCV was significantly lower than in the uninfected group at 3 to 7 dpi (p < 0.05). WBC count was significantly higher than in the uninfected group at 4 dpi (p < 0.05). Lymphocytes and heterophils were significantly higher than in the uninfected group at 4 dpi (p < 0.05). Monocytes were significantly higher than in the uninfected group from 3 to 5 dpi (p < 0.05). The developmental stages of E. tenella in cecum tissue during the 7 days life cycle included trophozoite at 2 dpi, first generation of schizonts at 3 dpi, secondary generation of merozoites and schizonts at 4 and 5 dpi and gametocytes and oocysts at 6 and 7 dpi. These finding suggest that monocytes were the most effective white blood cell on E. tenella infection and secondary generation schizonts was the most pathogenic developmental stage of E. tenella.

Background and Aim: Eimeria tenella is a causative agent of avian cecal coccidiosis resulting in bleeding, diarrhea, weight loss, high morbidity, and mortality in chickens. Zinc supplementation increases body weight gain, reduces mortality, and improves some immune response parameters of broilers infected with E. tenella. This study aimed to investigate the effects of zinc hydroxychloride (ZnOHCl) supplementation and ZnOHCl combined with an anticoccidial drug on E. tenella infection in broiler chickens. Materials and Methods: Forty one-day-old broilers were randomly divided into five groups, the study was replicated twice and had four chickens per replicate. Group 1 was an uninfected and unmedicated control group, and Group 2 was an infected but unmedicated control group. Group 3 was infected and treated with 120 mg/kg ZnOHCl, Group 4 was infected and medicated with 7 mg/kg toltrazuril (TOL), and Group 5 was infected and treated with 120 mg/kg ZnOHCl and 7 mg/kg TOL. Body weight gain, feed intake, and feed conversion ratio were monitored on days 15, 21, and 28. Oocyst shedding, hematological data, and lesion scores were analyzed on 7 days post-infection. Results: The average weight gain, feed intake, and packed cell volume of chickens treated with ZnOHCl and TOL were significantly higher than those of the infected and unmedicated controls (p = 0.05). Lesion scores, oocyst output, and lymphocytes of the chickens treated with ZnOHCl and TOL were significantly lower than those of the infected and unmedicated controls (p = 0.05). Conclusion: This study demonstrated that zinc supplementation alone reduced only oocyst output. However, growth performance, lesion scores, and oocyst output were affected by the combination of ZnOHCl and TOL supplementation. This suggests that ZnOHCl supplementation combined with an anticoccidial drug can improve growth performance and lessen the severity of E. tenella infection. Keywords: anticoccidial drug, broilers, Eimeria tenella, zinc hydroxychloride.