Transmission of the blood parasite Hemolivia mariae between its lizard and tick hosts

The haemogregarine Hemolivia mariae is found in the erythrocytes of a natural population of the lizard Tiliqua rugosa. It infects two tick species, Amblyomma limbatum and Aponomma hydrosauri, which parasitise lizards. In laboratory experiments, engorged Amb. limbatum nymphs from infected lizards transmitted the haemogregarine to uninfected lizards significantly more often than engorged Ap. hydrosauri nymphs. Dissections of larvae and nymphs of both species fed on the same infected hosts showed that Amb. limbatum ticks were significantly more likely to become infected than Ap. hydrosauri ticks. In Amb. limbatum, oval cysts containing parasite stages thought to be infective to the lizard host had developed within 15 days of engorged nymphs detaching from an infected host. The chance of Ap. hydrosauri becoming infected and the intensity of infection in Amb. limbatum increased when ticks were fed on infected hosts as larvae and as nymphs compared with those fed on an infected host only as a nymph. This suggests that infections can accumulate over the tick life stages. Since the two tick species have broadly parapatric distributions, the boundary between the tick species may have implications for the distribution of H. mariae.