Beginning to understand some impacts of existing and emerging animal diseases.
When field naturalists, bird observers, ecologists and others are in the bush they may be thinking about 'What wildlife lives here? What species, their sex, age, numbers and population trends?'. Wildlife health and disease are rarely considered. Disease is any impairment of normal function, including response to environmental factors (nutrition, toxicants, climate etc.), infectious and non-infectious disease agents, inherent or congenital defects, or a combination of these (Wobeser 2005). Disease and health affect growth and fitness (the ability to escape predators etc.), reproduction, mortality and morbidity (sickness) but are easily missed in the field. The clinical signs of morbidity include weakness, thinness or poor body condition and abnormal behaviour. However, mortality and morbidity of wildlife are not frequently observed, nor reported, nor investigated. Hence we have limited knowledge of baseline wildlife health patterns in free-ranging populations of endemic mammals, birds, reptiles and amphibians. Knowledge of baseline patterns is essential to detect changed morbidity/mortality patterns such as emerging spill-over, or emergency, usually of exotic or zoonotic diseases. Emerging diseases are new occurrences of a disease, infection or infestation, that results from a change of a known pathogenic agent or its spread to a new geographic area or species; or a previously unrecognised pathogenic agent or disease that is diagnosed for the first time (OIE 2016). Anyone who observes wildlife can contribute to this knowledge gap by informing Wildlife Health Surveillance Victoria (WHSV) at the Faculty of Veterinary and Agricultural Sciences of The University of Melbourne, or via state government agencies (Agriculture, Environment, Parks Victoria, EPA) for investigation.
Many factors affect the distribution and abundance of wildlife. Such factors include environment (vegetation, invertebrate vectors etc.), wildlife host (species assemblage etc.) and disease agents (infections, non-infectious disease agents, interactions between these). Moreover, human actions have affected these three areas by causing habitat loss and fragmentation; introducing invasive species; allowing the spread of infections from introduced domestic and feral animals; and producing environmental contaminants from industry, mining, agriculture and various urban activities. Car accidents and hunting cause mortality and morbidity.
Wildlife health is important because it can affect wildlife in three areas, namely wildlife and the environment (biodiversity conservation), domestic animals (biosecurity and food security) and humans (zoonotic diseases). The Australian Department of Environment has identified some diseases as key threatening processes. These include Psittacine Beak and Feather Disease circovirus, Tasmanian Devil Facial Tumour and the introduced Chytrid fungus in amphibians. Introduced dogs and foxes have brought hydatids Echinococcus granulosus, which infects macropods, and sarcoptic mange or scabies Sarcoptes scabiei, which infects wombats and koalas. Introduced cats are the definitive host for Toxoplasmosis Toxoplasma gondii which contaminates the environment via their faeces, causing disease in marsupials such as bandicoots, wombats and macropods. However, the impact of Toxoplasmosis on marsupial biodiversity is not well understood. Animal infections can be transmitted in both directions between wildlife and domestic animals, creating wildlife reservoirs that are very difficult to manage. In all continents except Antarctica and Australia the zoonotic bacterial infection Bovine Tuberculosis Mycobacterium bovis has spread from domestic cattle to create wildlife reservoirs. Parasitic Liver Fluke Fasciola hepatica from sheep and cattle causes disease in macropods. Non-pathogenic avian influenza viruses can be spread from waterbirds to domestic poultry, where mutations can result in disease. Wildlife can also be the source of zoonotic infections for people. Ross River and Barmah Forest viruses are transmitted by mosquitoes and midges to humans from wildlife reservoirs where they are not known to cause disease, only infection. The zoonotic diseases Australian Bat Lyssavirus and Hendra virus both require close contact with bats, or horses infected from bats, respectively.
WHSV (Fig. 1) investigates unusual wildlife mortality/morbidity events and clusters of disease after being informed of these events by people who observe wildlife, such as field naturalists, bird observers, wildlife carers, veterinary practitioners, Landcare members and staff of state agencies and local government. This general or scanning surveillance is the 'most important component of a national wildlife health program' and 'the only way a country can know what pathogens exist in its wildlife' (OIE 2010: 34). Surveillance 'means the systematic, ongoing collection, collation and analysis of information related to animal health and the timely dissemination of information so that action can be taken' (OIE 2016: ix). Surveillance can also be targeted to a particular pathogenic agent, but this will fail to detect other diseases. WHSV was established in 2008 to improve our knowledge of baseline patterns of disease in free ranging wildlife, to detect changed patterns, and investigate factors or drivers of change in host, agent, environment and interactions. WHSV is modelled on both the Canadian Wildlife Health Cooperative (based at Canada's veterinary colleges) and Wildlife Health Australia (WHA). WHSV relies on people from the Victorian community informing WHSV of wildlife health events. Sick wildlife is examined by local veterinary practitioners for animal welfare reasons. Wildlife found dead or euthanised are transported to the Faculty of Veterinary and Agricultural Sciences at Werribee for pathology. Field investigations are also undertaken, involving pathology, microbiology, parasitology, virology and toxicology to determine the causes of death and make diagnoses. Together with data about the wildlife host (species, age, sex, clinical signs, 'population at risk'--the denominator to calculate disease prevalence, number affected/number at risk) and the environment (other species, vegetation, weather, invertebrate vectors, etc.), epidemiology is used to describe and investigate disease in the population. Many of these investigations are collaborative with colleagues from other institutions and agencies involved with animal and zoonotic diseases or wildlife. Feedback is provided to the people involved, key governmental agencies, and results are reported into WHA's national electronic Wildlife Health Information System (eWHIS). WHA is expanding its national wildlife health surveillance program and has provided funding for data entry. Wildlife Health Australia website provides excellent fact sheets about a wide range of wildlife diseases. People interested in wildlife health can become members and receive a weekly email digest.
Since 2008, WHSV has undertaken approximately 100 investigations annually in Victoria, but if funding were available, this could be increased significantly and could be expanded to include feral animals. Veterinary students are involved with wildlife pathology investigations and undertake wildlife disease research projects. These include investigating Chlamydia and Beak and Feather Disease circovirus infections in psittacines, botulism in waterbirds, reviewing Eastern Grey Kangaroo and Southern Brown Bandicoot investigations and undertaking disease risk assessments. Collaborative investigations into incoordination (ataxia) and death in Eastern Grey Kangaroos caused by chronic Phalaris (introduced pasture plant) toxicity were published (Bacci et al. 2014). Other collaborative investigations and research include: Chlamydia and retrovirus infections in Koalas; Herpes virus infections in marsupials; Sarcoptic mange in Koalas; mortality/morbidity in juvenile Eastern Grey Kangaroos from high density populations due to a macropod blood-sucking nematode Globocephaloides trifidospicularis in their small intestines; diagnosis of zoonotic Bairnsdale ulcer caused by bacterial Mycobacterium ulcerans in possums from the Bellarine and Mornington peninsulas; mortality associated with necrotic enteritis of Rainbow Lorikeets in Melbourne in 2012; mass mortalities of shearwaters; surveillance for avian influenza virus in dead waterbirds; detection of pigeon paramyxovirus in feral pigeons; mortality of frogs due to Chytrid fungus and some undiagnosed events; investigating sick blue-tongued lizards (ongoing). We recognise there are many limitations to these investigations, but we are working systematically to expand this wildlife health knowledge. WHSV also identifies research needs and opportunities. If you are interested in more information or wish to support this project please contact Pam Whiteley. Donations made to WHSV through The University of Melbourne are tax deductible.
The WHSV website provides a flier approximately every three months to increase awareness of seasonal wildlife health issues. This can be printed for notice boards or forwarded to anyone interested in wildlife health. We wish to increase awareness and reporting of wildlife health events. Dead wildlife is useful. I am also keen to talk about this program with regional community groups and governmental agency staff, explaining how they can be involved, and report on and discuss local issues.
There is no need for undue concern about wildlife health and disease. Disease is a natural phenomenon. Native species have evolved with endemic diseases. However, human behaviours of moving animals (and their infections, introducing domestic and feral animals to Australia, smuggling, wildlife meat trade internationally), increasing toxic environmental contaminants, and changing human-wildlife and domestic animal-wildlife interfaces through access to water, intensive animal production waste disposal and expanding domestic animal production into natural areas have increased health risks for us all, (One World One Health 2004, Planetary Health 2016), and these should be identified and managed using Wildlife Disease Risk Assessment Guidelines (IUCN 2016). This is a significant task and requires collaboration, goodwill and wisdom.
Received 12 September 2016; accepted 15 September 2016
Bacci B, Whiteley PL, Barrow M, Phillips PH, Dalziel J and El-Hage CM (2014) Chronic phalaris toxicity in eastern grey kangaroos (Macropus giganteus). Australian veterinary journal 92(12), 504-508.
IUCN (2016) Guidelines for Wildlife Disease Risk Assessment. https://portals.iucn.org/library/sites/library/files/ documents/2014-006.pdf Accessed 12 September 2016.
OIE (2010) Training manual on Wildlife Diseases and Surveillance. OIE Workshop for OIE National Focal Points for Wildlife, 2010. Ed FA Leighton. http://www.oie.int/ fileadmin/Home/eng/International_Standard_Setting/ docs/pdf/WGWildlife/A_Training_Manual_Wildlife.pdf Accessed 12 September 2016.
OIE (2016) Terrestrial Animal Health Code glossary. http:// www.oie.int/international-standard-setting/terrestrialcode/access-online/. Accessed 12 September 2016.
One World One Health (2004) The Manhattan Principles. http://www.oneworldonehealth.org/. Accessed 12 October 2016.
Planetary Health (2016). Safeguarding both human health and the natural systems that unperin it. https://www. rockefellerfoundation.org/our-work/initiatives/planetaryhealth/. Accessed 12 September 2016.
Wobeser Gary A (2005) Essentials of Disease in Wild Animals. (Blackwell: Ames, Iowa)
Wildlife Health Surveillance Victoria, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 250 Princes Highway, Werribee, Victoria 3030. Email: email@example.com
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|Publication:||The Victorian Naturalist|
|Date:||Oct 1, 2016|
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