The effect of the ovine host parasitaemia on the development of Babesia ovis (Babes, 1892) in the tick Rhipicephalus bursa (Canestrini and Fanzago, 1877).

Batches of Rhipicephalus bursa adult ticks were fed on two lambs with 10.0% (batch 1) and 0.3% (batch 2) Babesia ovis parasitaemia, respectively. Haemolymph and eggs were checked for parasites daily after detachment, before and after appearance of B. ovis in the lamb's blood.B. ovis kinetes were found in the haemolymph and eggs earlier in the engorged ticks detached before appearance of the parasite in the host blood. Rates of haemolymph and egg infection with B. ovis as well as the percentage of infected eggs were much higher in batch 1 (10% lamb parasitaemia) than in batch 2 ticks (0.3% lamb parasitaemia). In eggs incubated at 28 degrees C the optimal period to look for kinetes seems to be days 4-9. Heavily infected ticks laid fewer less eggs within a shorter oviposition period. Pre-oviposition, pre-hatching periods and egg hatchability were not affected. Various parasitic forms are described in the haemolymph and the eggs.