TRANSMISSION OF LOUPING ILL VIRUS BETWEEN INFECTED AND UNINFECTED TICKS CO-FEEDING ON MOUNTAIN HARES

Most of the data on oral infection of ticks by louping ill virus have been obtained from experiments in which animals were infected by syrin ge inoculation with infectious material. Using infected ticks to mimic the natural situation, we have demonstrated that louping ill (LI) vir us transmission can occur from infected to uninfected Ixodes ricinus f eeding in close proximity on mountain hares (Lepus timidus). Under the se conditions the hares developed either low or undetectable viraemias . Highest pre valence of LI virus infection was observed in recipient nymphs which had fed to repletion between days 3 and 7 post-attachment of virus-infected adults; following engorgement, 56% of nymphs acquir ed virus. These results demonstrate the efficient transmission of LI v irus between co-feeding ticks on naive mountain hares. However, when t icks were allowed to co-feed on virus-immune hares a significant reduc tion in the frequency of infection was observed. Neither red deer (Cer vus elaphus) nor New Zealand White rabbits supported transmission of L I virus. The significance of virus transmission between cofeeding tick s on LI virus epidemiology is discussed.