Attempts to induce a passive immunity to Eimeria tenella in young fowls (Gallus domesticus).

Whole serum or γ globulin derived from fowls, either susceptible or immune to coccidiosis (), was injected into fully susceptible fowls. The serum proteins were given by intravenous or intraperitoneal injection and subsequent attempts were made to infect these fowls by giving either a moderate dose of sporulated oocysts or a suspension of viable merozoites . In the agar-gel double diffusion test, the serum from the donor birds, resistant to , formed only weak lines of precipitate when reacting against an antigen prepared from the second schizont stage of the life cycle. However, the immune serum was considered satisfactory because the donor birds on challenge were immune. Although relatively large amounts of γ globulin were injected into the susceptible fowls (up to 0.88 g. per kg. body weight) and subsequently only mild infections were given, no passively acquired resistance was shown either from the results of the oocyst counts on the faeces or by a macrosopic or microscopic examination of the caeca. These results are discussed in relation to earlier studies; they show that passively acquired serum antibody at these dose levels did not provide protection.