Coccidiosis in wild rabbits, Oryctolagus cuniculus (L.), at four sites in different climatic regions in eastern Australia I. Relationship with the age of the rabbit

Abstract

A total of 2881 rabbits were shot during 1962-64 in regular samples from four sites representing different climatic regions in eastern Australia. Samples of the faeces were examined for coccidial oocysts. Seven species of Eimeria (E. stiedae, E. media, E. perforans, E. irresidua, E. magna, E. piriformis, and E. exigua) were recorded. Dried lens weight and paunched (eviscerated) body weight of the rabbits were used as estimates of age. A decrease in oocyst output with increasing age of the rabbit was apparent when progeny of particular breeding seasons were followed and when all data were grouped together at the subalpine site. Linear regression analysis showed that the decrease was greatest at the subalpine site, where the young had high oocyst counts, less in the subtropical and Mediterranean climates, and virtually absent at the arid site. The rate of the decrease varied between species; it was greatest for E. magna and was slight and variable in occurrence for E. piriformis. Adult rabbits transported from the arid site to infected pasture in Canberra were found from 1 to 10 weeks after release to have an oocyst count comparable to that of young rabbits at the subalpine site. Cage-reared progeny of the rabbits from the arid site were more susceptible to accidental infection than cage-reared progeny of rabbits from the temperate southern tablelands of New South Wales.