Immunity against female Ixodes ricinus L.: effect on feeding and haemoglobin digestion.

Rabbits have been infested 3 times with 10 females and 10 males Ixodes ricinus. Immunity which is acquired when ticks feed on naive rabbits (first infestation) perturbs tick feeding on reinfested animals (third infestation). Then ticks ingest less blood (p less than 0.001). Blood meal digestion in also altered. It was estimated by measuring haemoglobin concentration in ixodid midgut during 20 days after their drop off. After the first infestation this concentration decreases linearly with time (r2(1) = 46.14%, n1 = 63, p less than 0.001). After 3 infestations it is no longer correlated with time, indicating an impaired digestive process (r2(3) = 7.15%, n3 = 49, p greater than 0.05). This observation was corroborated by an analysis of multiple regression. Haemoglobin concentration of tick midgut only correlates with time after a first infestation (r2(1) = 45.25%). In ticks fed on immune animals this concentration is predicted with the quantity of midgut C3 and the weight of fed ticks and not with time (r2(3) = 60.99%).