Resistance of birds to challenge with Eimeria tenella

A technique is described whereby one of the cecal pouches of the domestic fowl was isolated from the digestive tract. Entry into the pouch was effected by a fistula. Fifty-two birds, each with one cecal pouch so modified, were divided into two groups. The members of one group (experimentals) were inoculated with Eimeria tenella sporozoites via the fistula. These parasites initiated a primary, or immunizing infection in the isolated pouch. The birds in the other group (controls) were not given a primary infection. Approximately two weeks following the primary infection the chickens in both groups were given sporulated E. tenella oocysts orally. This represented the challenge infection in the remaining, normal cecal pouch. The effects of the challenge infection in the two groups of birds were compared. The challenge infection in the control chickens was characterized by a more pronounced and consistent reduction in body weight and red blood cell volume when compared with their experimental counterparts. Differences in the gross pathologic condition of the exposed ceca from birds in the two groups were sometimes apparent. It is suggested that resistance to E. tenella is, at least in part, established by some generalized host response, and not limited to a local immunity at the site of the initial infection.