The effects of infectious dosages on endogenous phage and the excretion of Eimeria tenella oocysts of infected chicken

This study was conducted to evaluate the effects of four dosages of oocyst inoculation (1×102, 1×103, 1×104, and 1×105 oocysts/chick) on oocyst patterns in feces, lesion score, and the endogenous phase of Eimeria tenella in the tissue of infected chickens. Oocysts in feces were collected daily from 4 to 10 day-post-infection (dpi). Chickens were killed at 0, 3, 5, and 10 dpi to evaluate the lesion score and the endogenous phage in the tissue by hematoxylin and eosin staining. The results showed that chickens in the highest dosage group discharged oocysts the earliest (5 dpi), while oocysts were detected in the other 3 groups 1 day later (6 dpi). The results of the histopathological examination showed that the time to detect the development stages of E. tenella in the tissue was similar among the experimental groups. Specifically, the asexual stages (1st and 2nd schizonts) were detected at 3 dpi, and immature oocysts were found in the cecum tissue at 5 dpi in all experimental groups. Overall, the results indicated that the oocyst dosages do not affect the replication of E. tenella in intestinal epithelial cells but may influence the excretion of oocysts from the intestinal tissue.