Susceptibility to Eimeria tenella of chickens and chicken embryos of partly inbred lines possessing homozygous major histocompatibility complex haplotypes.

Susceptibility to Eimeria tenella infection of chicken embryos and chickens of partly inbred lines possessing different major histocompatibility complex haplotypes was investigated. Chicken embryos of line H-B2 possessing B2 homozygous haplotype showed lower mortality and higher oocyst production than embryos of line H-B15 possessing B15 homozygous haplotype. Embryos of line H-B2 chickens were considered more resistant to E. tenella infection than those of line H-B15. Seven days after 10-day-old chickens were infected with E. tenella, the two lines showed no significant differences in percent bodyweight gain, cecal lesion score, and oocyst production; they differed significantly only in cecal shrinkage. Results suggest that the B system affects chicken embryos and chickens differently in susceptibility to E. tenella infection.