Metastatic mineralisation in brushtail possums (Trichosurus vulpecula) from Kawau Island

To describe the nature and incidence of metastatic mineralisation in brushtail possums (Trichosurus vulpecula) caught on Kawau Island.

Wild-caught possums were individually housed in captivity over a 24-month period and fed a cereal-based mash diet. Possums that became debilitated were examined post mortem for evidence of metastatic mineralisation of the heart, major blood vessels and kidneys. Serum and aortic segments were collected from affected animals and were analysed for mineral composition. Non-debilitated animals and possums that were experimentally poisoned with cholecalciferol were examined as a comparison.

Fifteen of 42 possums (36%) captured on Kawau Island and housed in captivity were debilitated as a result of metastatic mineralisation of the walls of the aorta and/or of the kidney tubules, with four further possums having evidence of mineralisation when humanely killed. Phosphate and ammonium deposits were found in the aorta, and calcium deposits in the kidney tubules. Serum phosphorus and calcium levels were elevated in the debilitated animals. Similar lesions were found in only one of 288 possums captured from other North Island areas and housed in captivity over the same time period.

Possums from Kawau Island appear to be more predisposed to metastatic mineralisation than possums from other areas of the North Island. The lesions observed in these possums were similar to those caused by cholecalciferol poisoning.