Quantitative description of the development of Babesia ovis in Rhipicephalus bursa (hemolymph, ovary, eggs)

Abstract

The development and infection dynamics of Babesia ovis in the hemolymph, ovaries, and eggs of Rhipicephalus bursa are described quantitatively, based mainly on examination of Giemsastained smears. After alimentary infection of female ticks, their hemolymph became infected 5 days after repletion (p.repl.). The prevalence and mean intensity of infection increased during the course of infection studied, up to 17 days p.repl. After vertical infection of female ticks, their hemolymph was infected only during the first 3 days after the onset of infestation (p.infest.) and again after the onset of alimentary infection 5 days p.repl. There was a positive correlation between prevalence and mean intensity of infection in the hemolymph. The prevalence of infection decreased with aging of the unfed adult ticks. After alimentary infection, the ovaries became infected 6 days p.repl., and after vertical infection, 3 days p.infest; they remained infected until the death of the tick. Ticks selected for susceptibility during 18 and 19 vertically infected generations were more susceptible than ticks in their first to third vertically infected generations or alimentarily infected ticks. Eggs deposited on day 1 of oviposition were noninfected after alimentary infection of the female tick. After vertical infection of the tick, even such eggs became infected; the infection, then, was detectable in eggs produced throughout the oviposition period regardless of the infection mode. Intense hemolymph infections induced an increase of egg degeneration and a decrease of total as well as infected egg production. There was a positive correlation between the number of deposited and infected eggs as well as between prevalence and mean intensity of infection in eggs. Alimentary infection contracted from a refractory host was rare (3%). Vertical infection passed to the next generation in 83%–95% of the female ticks. Hemolymph infection of a female tick during the oviposition period indicated alimentary infection. Ovarian infection of a female tick before the onset of alimentary infection or infection of eggs deposited before the onset of alimentary infection indicated vertical infection.