Prevalence and intensity of the blood parasite Hemolivia mariae in a field population of the skink Tiliqua rugosa.

The impacts of virulent parasites on humans or domestic animals are well documented. Less is known of the impact of parasites in natural host-parasite associations. A population of the Australian sleepy lizard Tiliqua rugosa is infected with the blood microparasite Hemolivia mariae, which is transmitted by the ectoparasitic tick Amblyomma limbatum. In most infected lizards a very small proportion, usually < 1%, of red blood cells are infected. A study of the prevalence of the microparasite in the field population found no difference either over 5 years of study or among times within a lizard activity season. Juvenile and sub-adult lizards and larger adults were less frequently infected with H. mariae than were other adults. In sub-adults this was related to a lower level of tick infestation. In adults, male and female lizards were equally frequently infected with H. mariae, but the presence or absence of ticks was not predictive of infection. The lizards' body condition was measured as the residual of the regression of log snout-vent length against log body mass. In female lizards the body condition was not affected by infection. In males the body condition declined over the sampling period each year, probably as a result of mate attendance. The body condition was poorer in male lizards with H. mariae infection than in uninfected males. Possible explanations for the associations of microparasites and host lizards are discussed.