Anti-larval antibodies in the serum and abomasal mucus of sheep hyperinfected with Haemonchus contortus.

A radioimmunoassay technique was used to follow the anti-larval antibody response in the serum of sheep subjected to repeated dosing with Haemonchus contortus. The response was found to develop slowly and seemed to decline as soon as the sheep stopped receiving larvae. No immunological memory was observed after the sheep were challenged with 4000 larvae nine weeks after daily dosing was stopped. Examination of abomasal mucus collected from the sheep at slaughter revealed the presence of IgA and IgG antibodies. It is suggested that most of this mucus IgG was derived from blood whereas the IgA was locally produced.