Tasmania, Ground Zero for Toxoplasmosis …

Eastern-barred bandicott

Tasmania’s ecology is now unstable – feral cats, disease in wildlife populations, climate change and habitat loss are progressively reducing the island’s biodiversity. In 1996 the Tasmanian Regional Forest Agreement documents cited research describing the Tasmanian devil population as over abundant and estimated its size at between 130,000 and 170,000 animals. This was the year that the transmissible facial cancer was first detected in north east Tasmania. An astonishing number of devils amplified by the tens of thousands of 1080-poisoned marsupial bodies left In the bush and around farm edges.

In 2009 a discussion paper prepared by DPIPWE to support the Cat Management Act stated that there were 92,000 pet cats and about 150,000 feral cats in Tasmania. In 2012, the new Invasive Species Unit is now claiming that ‘the feral cat population had increased at an alarming rate in recent years and was wreaking havoc on the ecosystem’. [Reference: Sunday Examiner 13 May 2012; page 20].So in 2012 devils are in decline and feral cats only just recognised as a problem to Tasmania’s biodiversity.

The disease is now well established in Tasmania; in fact Tasmania has one of the higherToxoplasma exposure levels in mammals precisely because we have so many cats and the environment favours the long-term survival of these microscopic parasites in soil and through the faunal food chain. The impact of Toxoplasmosis on free-ranging wildlife was first identified in Tasmania almost thirty years ago and in the days when the Department of Primary Industries actually took an interest in monitoring this disease in sheep flocks as well as wildlife some useful research has already been done. The reality is whilst ever there are cats (Feliscatis) in urban, rural and natural environments in Tasmania, all warm-blooded fauna (humans, marsupials and birds) are at risk of exposure and we must live with this parasite. Toxoplasmosis is a disease that Australian fauna had no contact with prior to the introduction of cats with human settlement. The sheer number of free-ranging cats in Tasmania and the longevity of Toxoplasma oocysts survival in the environment lead to the disease being a threatening process for the survival of some species of marsupials and responsible for seasonal mortalities of a number of others. The Eastern Barred Bandicoot (Peramelesgunni) is particularly affected by Toxoplasmosis and it continues to kill these bandicoots.

Detecting a wildlife disease always relies on awareness amongst the general public and a willingness of the animal disease infrastructure in Tasmania’s government to respond. Sadly due to cost-cutting much of the veterinary practitioner surveillance for new and emerging was terminated about two years ago; useful capability to test and report diseases in wildlife was curtailed dramatically. This came at the same time that UTAS wildlife researchers were going to scientific conferences speaking about the unprecedented declines in eastern quoll (Dasyurusviverrinus) populations across Tasmania. In March 2012 Mercury journalist, Helen Kempton interviewed UTAS zoologist Chris Johnson. He said: “Eastern quoll numbers also appear to be on the way down and cats – either eating or stressing populations [of eastern quoll] is one of the theories behind their demise. The [eastern] quoll is also being impacted by the hidden threat Toxoplasmosis which istransmitted by cats”. In May 2012 Bronwyn Fancourt, a PhD zoology student has now nominated the eastern quoll for listing as a threatened species under Tasmanian legislation citing feral cat predation and disease as potential factors in the 60% decline over the last decade.

Just recently the decline of the larger spot-tailed or tiger quolls (Dasyurusmaculatus) in Victoria was also linked to Toxoplasmosis also. Speaking of the demise of Victorian tiger quoll’s biologist and nature writer, Leonard Cronin told ABC Radio National, ‘…they put a bounty on their heads so people used to come in and shoot them, poison them and the population declined dramatically and then they got infected with a parasite called toxoplasmosis and that really damaged the population so now they are endangered basically.’ [Confirmed tiger quoll sighting raises hopes of naturalists – ABC The World Today program Monday 12 May 2012]

Several small dasyuridslike Antechinus, Sminthopsis and Planigale spp. are susceptible to this parasite particularly when they are immune-suppressed or become infected in captivity. Further work is needed to determine whether the disease Toxoplasmosis is actually responsible for any quoll declines of eastern Australia. One thing iscertain,ignorance aboutthe impact of Toxoplasmosis is not bliss for Tasmania!

• LAUNCH OF WILDLIFE EDUCATION KIT
Site 1, Waterworks Reserve, South Hobart, 11am