The effects of parasites on a wild population of the Mountain Brushtail Possum (Trichosurus caninus) in south-eastern Australia

The effects of a reduction of parasite burdens were determined in adult female Mountain Brushtail Possums, Trichosurus caninus, on the birth, mortality and growth rates of pouch-dependent young, as well as the haematological and serum biochemical values of the mothers. The efficacy of the anthelmintic drug ivermectin for reducing parasite burdens in this host was assessed using faecal and necropsy examinations of a small number of animals. Ivermectin began to reduce parasite burdens by 48 h after treatment. In the second stage of the experiment, animals were treated or sham injected (control individuals) with ivermectin and praziquantel at 8-10-week intervals throughout the breeding season to the time of emergence of young from the pouch. Treatment with ivermectin and praziquantel had no significant effect on the proportion of females giving birth, or on the survival of young to emergence. An effect of treatment was recorded for absolute eosinophil counts in adult females, which, in spring, were higher among control animals than those that were treated.