Resistance to Eimeria tenella and its transference from one caecum to the other in individual fowls.

Infections were produced in patent caeca by administering oocysts of Eimeria tenella per os to fowls in which one caecum was ligated. The caeca were later challenged with sporozoites and it was found that a resistance to infection had been acquired by the previously uninfected ligated caeca. The observations indicate that resistance to caecal coccidiosis develops in areas not previously exposed to parasitism by E. tenella. It is suggested that the immunity acquired by the ligated caeca is mediated through the circulation either by humoral antibodies or by lymphoid cells, or by a combination of both.