Immunisation of lambs with drug-abbreviated Haemonchus contortus infections: protection against homologous and heterologous challenge

Haemonchus contortus is known as a prolific parasite, producing high number s of eggs. It could therefore be used as a cheap source of larvae for immun isation of lambs. The value of immunisation would be improved if the immuni ty produced gave protection against not only homologous but also heterologo us infections. Because antibody cross-reactivity between Haemonchus and Ost ertagia has been well established, we wanted to know whether drug-abbreviat ed infections of H. contortus would stimulate production of antibodies that would cross-react with Trichostrongylus colubriformis. The results obtaine d from these trials indicated that H. contortus drug-abbreviated infections produced significant immunity against not only Haemonchus but also O. circ umcincta. Immunisation increased the level of immunoglobulin E (IgE) and Ig E-specific antibodies against T. colubriformis, but the differences between experimental and control animals were not statistically significant. Signi ficantly higher levels of IgG-specific antibodies against T. colubriformis were observed.