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Wildlife Diseases: UpClose and Personal
Dr. Julia WhittingtonJuly 10, 2006
Ecosystems occur at macro and micro levels. Environments may encompass entire land regions or may represent the components of an individual's gastro-intestinal tract. Regardless of the ecosystem's context, there is a precise balance of environmental conditions, species diversity and resources that keeps the system healthy. When individuals from different ecosystems interact, the potential for disease increases as the balance is disrupted. The same is true when the human-animal interface is compromised. Urban wildlife is an important part of our ecosystem, but when our interaction with wild animals goes beyond the natural limitations, disease may occur.
Some diseases of common wild animal species have zoonotic potential, meaning they have the ability to cause disease in humans. Often, the disease in people is more severe than the disease in the host animal. Some of the most common zoonotic diseases of wild animals include rabies, raccoon roundworms and leptospirosis.
- Rabies. This fatal disease is caused by a rhabdovirus and is transmitted when the saliva of an infected animal is injected into the victim, usually during a bite. The virus impacts the central nervous system and, if left untreated, will cause the death of the infected person within days to weeks of showing symptoms. The onset of disease may be prevented if the bitten person seeks immediate medical attention and receives post-rabies exposure vaccinations. All mammals are susceptible to rabies but the wild animal carriers of rabies in Illinois are most often skunks and bats. Rabies in raccoons is prevalent in the eastern United States and foxes are also known carriers of rabies. Domestic pets who routinely receive the rabies vaccine are at low risk from contracting rabies from wildlife, even if a bite occurs. Owners should seek veterinary care for their pets in these cases. If a person is bitten by a wild animal or if a bat is found in the home, the animal should be humanely euthanized whenever possible and the local public health department contacted to facilitate testing of the animal for rabies. Persons having even the slightest possible contact with an animal suspected of having rabies should seek medical attention. Wild animals acting strangely or that appear to be sick should be reported to the local authorities.
- Raccoon Roundworm (Baylisascaris). Virtually every species of animal has its own intestinal parasites which may cause mild to moderate clinical signs in its host. When that parasite infects a species other than its natural host, severe signs and even death are possible. Baylisascaris is a parasite that lives in the gastrointestinal tract of raccoons. The adult worms lay millions of eggs that are passed in the raccoon's feces. These eggs become infective within two to four weeks and can survive in the environment for years. Human infection occurs when the eggs are accidentally ingested in soil, water or on objects contaminated with raccoon feces. Within one to two weeks of being ingested, larvae hatch from the eggs and migrate throughout the new host's body. Clinical signs and severity of the disease depends on what tissues are affected during larval migration and how many eggs were ingested. Anyone working, living or playing in an area inhabited by raccoons is potentially at risk for contracting baylisascaris but children are at higher risk due to their propensity to place items in their mouths. Prompt removal of raccoon fecal material from the environment will help prevent exposure. Do not keep, feed or adopt raccoons as pets and teach children how to stay safe in their environment.
- Leptospirosis. A bacterial infection occurring worldwide, leptospirosis infects humans, wild and domestic animals. Symptoms are often flu-like but the disease can lead to life-threatening conditions such as kidney, liver and heart failure. An infection is spread through contact with the urine of infected animals, either directly or indirectly through exposure to urine-contaminated water or soil. Domestic pets may be exposed when drinking or swimming in contaminated water. Due to the blurring of natural boundaries, many wild animals including deer, raccoons, skunks, squirrels and opossums visit urban waterways and ponds and may serve as a source of infection. Seek veterinary attention for your pet if they are showing signs of illness. Consult with your medical care provider if you or your pet is suspected of having leptospirosis. Pets should also be vaccinated against leptospirosis to help reduce the risk of disease.
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