The anomalous distribution of the possum parasite Parastrongyloides trichosuri (Nematoda: Strongyloididae) in the southern South Island, New Zealand

Abstract

Introduced Australian brushtail possums (Trichosurus vulpecula) in the North Island, New Zealand, are infected commonly with the possum‐specific nematode, Parastrongyloides trichosuri. In the South Island, however, the parasite was thought to be confined to the Longwood Range, Southland, site of the first successful introduction of possums to New Zealand. Current, more widespread surveys revealed, however, that the parasite was distributed widely but discontinuously across Southland and southern Otago, and restricted to the southern third of the Longwood Range. Repeated sampling of possums on two transects along the north‐west and south‐east of the Range suggested that the parasite may be spreading northwards naturally. We hypothesise, therefore, that P. trichosuri has infected possums in the Longwood Range only relatively recently. A similar recent introduction of the parasite to Otago and Southland could also explain its current limited distribution. The most likely explanation for a recent introduction is the release of “pet” possums taken to the area from the North Island. We suggest P. trichosuri will continue to spread in Southland and Otago, unless prevented by reduced possum densities resulting from control for bovine Tb management. © The Royal Society of New Zealand 2005.