Immune responses of the argasid tick Ornithodoros moubata moubata induced by infection with the filarial worm Acanthocheilonema viteae

Investigations were undertaken to determine whether the tick Ornithodoros m oubata moubata mounted a detectable immune response to primary and secondar y infections with Acanthocheilonema viteae. Uninfected control tick surviva l rate was 70%, but only 45% in the primary infection group. Post-secondary infection survival rate (82%) was comparable to controls, indicating that these selected ticks had some protective advantage. Mean A. viteae infectiv e larvae recovery from ticks with secondary infections was 31.4% lower than expected, suggesting the development of immunity. SDS-PAGE of haemolymph f or proteins induced post-primary infection yielded a stronger signal at 45 kDa than controls, which was further elevated post-secondary infection. Pro teins at 48, 22 and 16 to 18 kDa were detected in haemolymph from infected ticks but not seen from controls. The direct effect of haemolymph on microf ilarial viability was examined using a novel in vitro assay; in these preli minary trials no differences were observed in parasite viability when expos ed to haemolymph from infected or uninfected groups of ticks.