This section provides brief information about the parasites of species currently covered by the Healthy Wildlife project, as well as other threats to wildlife health. Every living organism has parasites and wildlife, pets and humans are no exception. Parasites are small organisms that live in or on another organism, known as the host, which provides the parasite with food and shelter. Some parasites, are zoonotic, which means they can be transmitted from animals to humans and vice versa.
What is hydatid tapeworm (Echinococcus granulosus)?
Echinococcus granulosus is a tapeworm parasite, the larval form of which causes hydatid disease in people, but also infects a very wide range of other mammals. Hydatid disease causes large parasite cysts to develop in internal organs, mainly in the liver and lungs, and occasionally the brain. As the cysts grow they may cause pain, exercise intolerance, weakness and sudden death if ruptured.
Hydatid tapeworm profile
The adult hydatid tapeworm is small, ranging from 3mm – 6mm in length, and lives in the intestines of carnivorous animals, such as dogs or dingoes. The tapeworm develops into larval cysts in hosts such as sheep, cattle, goats, pigs, horses, kangaroos, wallabies or occasionally humans.
How is the hydatid tapeworm spread?
The hydatid tapeworm was brought to Australia when sheep were introduced by European settlers. Animals digest the tapeworm eggs when eating pasture, or in the case of people, by contact with infected dogs.
Dogs become infected when they eat the organs of infected livestock or wild animals, particularly the liver and lung, which contain the larval, hydatid cysts. The cysts then develop into adult tapeworms.
In the Perth Hills it is likely that the parasite was introduced with dogs used for pig and kangaroo hunting, as the adult tapeworm has been found in hunters’ dogs. Domestic dogs can become infected by scavenging the carcasses of dead kangaroos and pigs. People can be infected by the accidental consumption of soil, water, or food that has been contaminated by the faeces of an infected dog or infected eggs on the dog’s coat.
Is this a problem for wildlife?
Although hydatid disease is rare in people in Western Australia, one study in state forest bordering Perth found a high frequency of the disease in kangaroos, with 29% (n=21) of animals infected, and feral pigs (n=24), with 46% of animals infected. Cysts may seriously impair the ability of marsupials, particularly small species of wallabies, to breathe, exposing them to the risk of predation. This is a serious conservation issue, particularly for species that live in isolated populations.
Did you know:
- Echinococcus eggs can stay viable in the soil for up to a year.
- Infected dogs will have some Echinococcus eggs sticking to their fur.
- Echinococcus is found almost worldwide.
Download the ‘Hyatid Tapeworm and Wildlife’ information sheet.
What is Giardia?
Giardia is a common zoonotic parasite of mammals, including people, as well as birds and other vertebrates. It lives and multiplies in the intestine and causes acute diarrhoea (think gastro or ‘Bali Belly’) or chronic nutritional disorders resulting in weight loss and tiredness. Giardia exists as a variety of different strains. Some strains are only found in certain species of hosts like dogs, cats and quendas. Strains that affect humans have a wider host range including pets and wildlife.
Giardia is a single-celled organism that lives in the small intestine and is found worldwide. The parasite produces resistant cysts that are responsible for disease transmission. The cysts release trophozoites, which are the active feeding stage of the parasite. These multiply and can be free in the bowel or attached by a sucking disc. The cysts are then passed out by infected animals, like dogs and cats, in the faeces.
How is Giardia spread?
Giardia cysts and are found on surfaces, or in soil, food, or water that has been contaminated with faeces. Cysts can survive in water for several months. Infection occurs when the cysts are accidentally swallowed.
Is this a problem for wildlife?
Giardia can be spread from humans, pets and livestock to unique native animals, making them sick. In Australia, studies have found that urban wildlife such as bandicoots (quenda) are commonly infected with Giardia and sometimes with the human strain. The human strain of Giardia has also been found in native freshwater and estuarine fishes.
Did you know:
- Many people infected with Giardia parasites will not have any symptoms, but can still pass on the parasite.
- Giardia is more common in quenda in urban areas than quenda in non-urban areas.
- Giardia is the most common parasite in the gut of domestic dogs.
Download the factsheet ‘Giardia and Wildlife’.
What is anchor worm?
Anchor worm is a parasite of the skin and gills of fish. The parasite was first found in the Canning River in 2008 and has since been found in the Serpentine and Murray Rivers, south of Perth. Although originally a parasite of goldfish and carp, anchor worm has a very wide host range. It has been found on more than 45 species of freshwater fishes throughout the world. Infections in native fishes cause large wounds, bleeding, castration and high death rates.
Anchor worm profile
Anchor worms mate during the last stage of their development. After mating, the female burrows into the flesh of the fish host and attaches with an anchor-like process on the head. This leaves the unsegmented, wormlike body protruding from the skin or gills of the fish.
How is anchor worm spread?
Anchor worm was probably introduced through the accidental or deliberate release of freshwater fishes, such as goldfish and carp. There are currently 13 – 15 species of introduced freshwater fishes in rivers in the south-west of Western Australia.
Is this a problem for native freshwater fishes?
Anchor worm causes Lernaeosis, a parasitic disease of freshwater fishes. Anchor worm is much more capable of causing disease in native freshwater fishes than in its natural hosts, goldfish and carp. This is because native freshwater fishes have limited defence behaviour and a weak immune response.
In general, introduced freshwater fishes are predators of native fishes, compete with native fishes for food, decrease water quality and introduce diseases. Anchor worm poses a significant additional threat to native freshwater fishes in the south-west of Western Australia, where 82% are unique local species and 55% of species are endangered.
What can we do about alien parasites of native freshwater fishes?
In an open, natural river system it is not feasible to eliminate anchor worms. The only way to stop the spread of this parasitic disease is to:
- Stop releasing ornamental fishes, such as goldfish or carp into rivers, lakes or waterways.
- Report fishes with parasites to WA PestWatch at www.fish.wa.gov.au.
Did you know:
- Anchor worms are not actually worms, they are a freshwater copepod. A copepod is small crustacean found in nearly every freshwater habitat.
- Only the female anchor worm attaches itself to the fish. The male attaches itself to the female.
- The parasite is named after its anchor shaped head, which burrows into the muscles of the host.
Download the ‘Anchor Worm and Native Freshwater Fishes’ information sheet.
Infected pygmy perch.
Photo: Fish Health Unit, Murdoch University.
What is Toxoplasma gondii?
Toxoplasma gondii is a common zoonotic parasite of mammals, including people, and birds. The parasite is genetically highly variable with many different strains that vary in how much damage they cause to the host. Wildlife in urban areas may be exposed to more virulent ‘domestic’ strains of Toxoplasma gondii. Healthy wildlife infected with Toxoplasma gondii may remain healthy because their immune system produces antibodies that keep the infection under control. If an animal’s immune system is suppressed due to disease or stress infection with Toxoplasma gondii may cause toxoplasmosis, which is rapidly fatal.
Toxoplasma gondii profile
Toxoplasma gondii is a single-celled parasite with a complex life cycle. In cats, the parasite reproduces sexually and environmentally resistant oocysts are passed in the faeces. These oocysts can then infect other hosts when they are accidently eaten. Within these hosts, the parasite reproduces asexually and may spread throughout the body.
How is Toxoplasma gondii spread?
Sources of Toxoplasma gondii include environmental contamination by domestic cats, exposure to cat faeces, and food or water that has been contaminated by cat faeces.
Eating oocysts is not the only way in which the parasite can be spread. People and animals can also become infected by eating the meat from an animal that has the parasite. Food, particularly meat scraps left in gardens to encourage wildlife, is a common source of Toxoplasma gondii in wildlife. In Perth, quenda taken to wildlife carers with neurological disease due to infection with Toxoplasma gondii are most likely to be infected as a result of eating household scraps, especially if these scraps contain raw or partly cooked meat.
Is this a problem for wildlife?
Toxoplasma gondii is common in wildlife, however large-scale die offs have not been reported. Most cases of clinical disease in wildlife are in captive animals. There have been increasing reports of infection with Toxoplasma gondii in quenda and other marsupials in rehabilitation. The illness and added stress of being captive can cause deadly toxoplasmosis. Reports of outbreaks of severe toxoplasmosis in captive animals have led to a perception that this infectious disease is contributing to population decline in free-ranging wildlife.
Did you know:
- The most common source of infection with Toxoplasma gondii in people and cats is raw or partly cooked meat.
- Cats rarely have symptoms when infected, so you don’t know if your cat has been infected.
- Cats only spread Toxoplasma gondii in their faeces for a few weeks following infection with the parasite. This stops by itself therefore it does not help to have your cat’s faeces tested for Toxoplasma gondii.
Download the ‘Toxoplasma and Wildlife’ information sheet.
Rodentcides and Wildlife
What are anticoagulant rodenticides?
Anticoagulant rodenticides are mouse and rat poisons which work as blood thinners. A lethal dose can cause an animal to die by excessive bleeding from small cuts or internal bleeding and bruising. They are especially effective at killing rodents because they don’t make the rodent feel sick until several days after it has eaten a lethal dose.
Unfortunately, this can create a serious problem for native animals which may eat the dead and dying rodents. Poisoned mice and rats have slower reaction times, spend more time in open areas and are more active during the day (Cox & Smith, 1992). All of these behaviours make rodents easier prey and increase the chance that a predator will catch them. Some of the newer “second generation” anticoagulant rodenticides take a long time to break down. They can remain in the liver for long periods of time – sometimes well over a year. This allows them to move up the food chain and accumulate in the bodies of predatory birds, such as Southern Boobook owls and mammals which eat poisoned rodents.
What wildlife species are at risk?
Some species like native rodents and quenda (bandicoots) can be poisoned if they directly eat baits set for mice and rats but other species which do not directly eat the baits are at risk too. Worldwide, owls, eagles, hawks, foxes and even bobcats and mountain lions have been killed by rodenticides that have accumulated in their prey (Riley et al., 2007). Pets like cats and dogs are also at risk of being poisoned (Robertson, Leggoe, Dorling, Shaw, & Clark, 1992).
There are a number of ways you can reduce the need to use rodenticides. One of the most effective methods is simply cleaning up a bit. Removing rubbish from your yard, keeping pet food indoors, picking up fallen fruits beneath your fruit trees and using chicken feeders which prevent spillage removes potential rat and mouse food from the environment around your house. It is one of the most effective first steps and can make a huge difference to the number of introduced rodents around your property. Cleaning up brush piles and sealing holes in your walls and roof reduces the amount of rodent habitat and helps keep them out of your home. Replacing palms with native trees can be a big help too. It not only removes one of the favourite hideouts for black rats (Rattus rattus), but also provides better habitat for the native predators like owls and hawks which help control rodents. If rodents are still a problem, then old fashioned snap traps baited with peanut butter are also very effective if placed along edges of walls and corners where rodents usually travel.
Read the label to save lives
If you do decide to use rodenticides, then it’s important to know which ones you are using. Warfarin and coumatetralyl are “first generation” anticoagulant rodenticides which break down much faster than other rodenticides and are less likely to cause poisoning in native wildlife like hawks and owls which eat poisoned rodents. Most rat and mouse poison packaging doesn’t make it obvious which rodenticides are used in the product. The actual rodenticide contained in the baits will be after the words “Active Constituent.” If you do choose to use these products, be sure to follow the directions on the label to help reduce the risk of unintentionally poisoning wildlife.
Download Case Study – Southern Boobook Owls and Rodenticides information sheet. Please note this information sheet contains graphic images which may be disturbing to some readers.
Cox, P., & Smith, R. H. (1992). Rodenticide ecotoxicology: pre-lethal effects of anticoagulants on rat behaviour. In Vertebrate Pest Conference Proceedings collection (pp. 165–170). Lincoln, Nebraska.
Riley, S. P. D., Bromley, C., Poppenga, R. H., Uzal, F. a., Whited, L., & Sauvajot, R. M. (2007). Anticoagulant Exposure and Notoedric Mange in Bobcats and Mountain Lions in Urban Southern California.Journal of Wildlife Management(6), 1874–1884. http://doi.org/10.2193/2005-615
Robertson, I., Leggoe, M., Dorling, P., Shaw, S., & Clark, W. (1992). A retrospective study of poisoning cases in dogs and cats: comparison between a rural and an urban practice.Australian Veterinary Journal(8), 194–195.