Immunity to coccidiosis: maternal transfer inEimeria maximainfections

Chicks hatched from eggs laid in the third and fourth weeks after inoculation of the hens with oocysts ofE. maximaexcreted fewer oocysts in response to a challenge inoculum ofE. maximagiven at 1 week of age than controls hatched from the eggs of uninfected hens. A λ-livetin fraction prepared from the yolks of eggs laid by hens 14–22 days after a single inoculation of oocysts ofE. maximaand injected subcutaneously into 2-week-old chicks caused a similar reduction in oocyst yield from a challenge inoculum. The serum of the donor hens, obtained at the corresponding time intervals was protective. These results confirm that immunity to infection withE. maximais, at least in part, mediated by humoral antibodies.