Prevalence of infection by the protozoan Hemolivia mariae in ticks

Abstract

This paper considers the prevalence of natural infections of the protozoan Hemolivia mariae, in its hosts the Australian sleepy lizard, Tiliqua rugosa, and the ixodid tick species, Amblyomma limbatum. We investigate whether the protozoan may be influencing the tick population in the field, by comparing the observed prevalence of infection in ticks with the prevalence expected from known transmission dynamics. The prevalence of infection in nymphs was similar to the expected prevalence, but the observed prevalence in adults was higher than expected. These results provide no evidence for infection-induced mortality in ticks. We also found that tick loads on infected and uninfected lizards were not significantly different and, overall, infected lizards were as likely to be tick-infested as uninfected lizards. However, infected lizards were less likely to be found carrying female ticks. On balance, the evidence did not strongly support the hypothesis that ticks avoid feeding on infected lizards. We use known parameters of H. mariae transmission to estimate the rate of tick ingestion that may be required to sustain the observed prevalences in the field.