Relative importance of larval and adult Mecistocirrus digitatus in inducing resistance to a reinfection in calves.
Calves immunized with adult Mecistocirrus digitatus implanted directly into the abomasum did not develop a substantial degree of immunity to a subsequent large oral (challenge) dose of larvae, which developed to maturity. In contrast animals immunized by oral infection developed strong resistance. The calves implanted with adult worms appeared to show a greater degree of susceptibility to maturation of the challenge infection than controls which received a challenge of the same magnitude without any previous immunization. The implanted female adult worms established in the hosts and continued to produce more eggs for a longer time than those which developed to maturity from the oral immunizing infection with third-stage larvae. Passive haemagglutination studies revealed that the implanted adult worms stimulated little or no antibody response in the hosts. In the calves which did not show a response to the adult worm implant the subsequent challenge with an oral infective dose of third-stage larvae also failed to stimulate a response. Likewise the two calves from the group which showed a weak antibody response to the adult worm implant did not show an increased response when challenged. In contrast, calves immunized with an oral infection of third-stage larvae had an antibody response which showed a vigorous rise on challenge in four of the five calves. Thus a direct relationship between resistance to challenge infection and the antibody response determined by the passive haemagglutination and gel-diffusion tests was observed in the calves immunized orally.
D000018:Abomasum / Q000469:parasitology; D000818:Animals; D000917:Antibody Formation; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology*; D005243:Feces / Q000469:parasitology; D005260:Female; D006386:Hemagglutination Tests; D007114:Immunization / Q000662:veterinary*; D005779:Immunodiffusion; D007814:Larva; D008297:Male; D010270:Parasite Egg Count; D014251:Trichostrongyloidea / Q000276:immunology*; D014252:Trichostrongyloidiasis / Q000276:immunology / Q000662:veterinary*