ANTIBODY-RESPONSES IN CATTLE INFESTED WITH HAEMATOBIA-IRRITANS IRRITANS (DIPTERA, MUSCIDAE)

Antibody response to feeding by the horn fly, Haematobia irritans irri tans (L.), nas measured in naturally infested cattle as well as in con trolled infestations. Humoral antibody level was not correlated with f ly abundance in natural infestations. Correlations between the antibod y response and fly abundance were extremely variable among animals. An tibody response to horn fly salivary antigens peaked within 4 wk after fly abundance reached 150 flies per animal. In controlled infestation s, antibody response was weak during an initial exposure to 200 flies per animal, but increased after flies were removed from the cattle. Ho rn fly salivary antigen may have an immunomodulatory effect on the hos t.