Assessment of other native animal diseases in Tasmania


Detailed below is information on a range of other diseases that have the potential to affect native animals in Tasmania.

Toxoplasmosis

Toxoplasmosis is a nervous system and systemic disease that can affect mammals and birds that is caused by a protozoan parasite (Toxoplasma gondii). The parasite reproduces in the cat's gut, and the infective stage of the organism, the oocyst, is passed in the cat's faeces. Cats are therefore the definitive host of the disease. Although the major vector in the spread of Toxoplasmosis is cats, other vectors such as earthworms have also been identified. In Tasmania, this disease can lead to paralysis, incoordination, blindness and death in bandicoots and other wildlife species such as penguins, wombats, pademelons, Bennetts wallabies and bettongs. Agricultural animals such as sheep are also vulnerable to Toxoplasmosis, and the infection in ewes in early pregnancy can cause foetal death and often abortion, and in later pregnancy can cause a live infected lamb to be born which is often weak (Internal linkTFGA 2005).

Toxoplasmosis occurs in places where introduced or naturally occurring cat species (from the family Felidae) are found. The parasite was introduced into Australia (and Tasmania) through the cat and has since become established within urban/domestic, rural and wildlife populations (Internal linkDPIW 2007). DPIW reports also indicate that the disease is known to be a significant cause of mortality in captive marsupials and has been reported in free-living herbivorous, omnivorous and carnivorous marsupials. Introduced animals like sheep, goats, to a lesser degree cattle, pigs and deer species can also be affected.

Toxoplasmosis tends to express itself in vulnerable mammals or birds, such as threatened species, animals with restricted populations, or when environmental conditions cause stress to animals. The impacts of toxoplasmosis on native animals in Tasmania are largely unknown although it is known to be fatal to some species such as the threatened eastern barred bandicoot (Perameles gunnii) (Driessen et al. in Internal linkTSN 2005). There are also concerns that with the decrease in Tasmanian devil numbers from the DFTD, the large population of cats has the potential to result in a greater chance of the (Toxoplasma gondii) parasite and the toxoplasmosis disease spreading in the Tasmanian devil population.

Sarcoptic mange

Sarcoptic mange is a disease that occurs in a range of Australian native and introduced mammals that is caused by an obligate parasitic mite (Sarcoptes scabeii). It is widespread across Australia and occurs in Tasmania and on Flinders Island. The disease is endemic in wombat populations throughout their range and is relatively common in fox populations. The disease can cause sickness and death, and is more widespread in wombats and possibly denning foxes than compared to other native animal populations (Internal linkSkerratt et al. 2004).

Information on the sarcoptic mange disease that affects common wombats, has largely come from opportunistic wildlife observations and one systematic study on the common wombat in Victoria (Internal linkDPIW 2007). The disease is unlikely to have a significant impact on wombat numbers across Tasmania. However, small local populations that are more vulnerable are at risk from the impacts of the disease (Annie Philips pers. comm. and Internal linkMartin et al. 1998). Treatments are available for common wombats if the disease is caught early enough in this species. To date, there has been no systematic monitoring of the disease in Tasmania.

Seal tuberculosis

Seal tuberculosis has been recorded in seals in Tasmania and other parts of Australia. The disease is caused by the pathogenic Mycobacterium pinnipedii sp. nov. bacteria (known as a novel member of the Mycobacterlum tuberculosis complex). When contracted by a seal, this disease can result in the mammal developing pulmonary lesions and sometimes liver lesions, which can result in coughing and/or dyspnoea, lethargy and weakness (Internal linkDPIW 2007). Seals appear to be the natural host for seal isolates of this disease, although it is thought that the organism is also pathogenic in other animals such as guinea pigs, rabbits, humans and possibly cattle (Internal linkCousins et al. 2003).

Although Tasmania was the first State in Australia to eradicate bovine tuberculosis and bovine brucellosis, this disease could impact upon Tasmanian seal populations (see Obendorf and Woods in Internal linkAWHN 2004). Seal tuberculosis was first confirmed in pinnipeds (e.g. seals) at an open-air marine park 60 km north of Perth, Western Australia in 1986 (Internal linkDPIW 2007 and Internal linkForshaw and Phelps 1991). The bacteria have been subsequently isolated from captive and wild populations of Australian sea lions (Neophoca cinerea), New Zealand fur seals (Arctocephalus foresteri), and an Australian fur seal (Arctocephalus pusillus).

The first suspected case of tuberculosis was first recorded in a wild Australian fur seal in Hobart in March 1992 (Internal linkWoods et al. 1995). Currently, there is no systematic monitoring or assessment of the prevalence of the tuberculosis in seals in Tasmania. However, passive observations and opportunistic testing are being conducted. Although the prevalence of tuberculosis in wild, free-ranging seals is largely unknown in Tasmania, the risk of humans or domestic stock becoming infected with tuberculosis is likely to be low because of the usually rare and/or brief duration of their contact with wild seals.

Avian influenza

A disease that potentially poses a significant threat to Tasmanian bird populations and possibly mammals (terrestrial and marine) if it entered the State is the avian influenza virus (equine influenza also recently emerged within Australian horse populations in 2007 although Tasmania remains free from this virus). The avian influenza virus is caused by viruses of the Orthomyxoviridae family (Internal linkDPIW 2007). Wild bird populations such as water fowl (e.g. geese, ducks and swans) and seabirds can carry the disease without developing any signs of illness, while commercially introduced species like chickens and turkeys can be significantly affected (e.g. suffering high mortality rates). Water birds generally do not show clinical signs of the disease unless a very virulent strain is involved (e.g. H5N1). Highly pathogenic strains of influenza viruses that infect birds have been rarely detected in migratory wild birds and the spread of these viruses is poorly understood. More information on the avian influenza virus is available within the disease manual compiled by DPIW (Internal linkDPIW 2007) and the External linkDPIW website.

The occurrence of avian influenza was actively monitored in Tasmania between 2004–07, including checks on Mutton birds (Puffinus tenuirostris) on the Bass Straight islands and in the Sorell area to the east of Hobart. To date, there has been no evidence of avian influenza in mutton birds in Tasmania, nor has there been an outbreak of the virus in Tasmanian poultry (Internal linkDPIW 2008 and Internal linkDPIW 2007).

  External linkTasmanian Planning Commissioninternal SOE link to larger image

  Contact the Commission on:

email: External linksoe@justice.tas.gov.au
Phone: (03) 6233 2795 (within Australia)
Fax: (03) 6233 5400 (within Australia)
Or mail to: Tasmanian Planning Commission, GPO Box 1691, Hobart, TAS, 7001, Australia

 


Last Modified: 1 Mar 2010
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