Opossums are interesting ambassadors of the night that often attract the attention of domestic dogs. While domestic dogs represent a much greater threat to opossums than the reverse, opossums may be able to transmit diseases to your beloved pooch. While opossums can transmit a variety of bacterial and protozoal diseases to your dog, they do not typically carry or transmit the dreaded rabies virus.
Virginia opossums (Didelphis virginiana) are the only marsupials found in North America, and are only distantly related to the other North American mammals. Like most marsupials, opossums carry their young inside a protective pouch until they are old enough to take care of themselves. Nocturnal omnivores, opossums are highly adaptable animals that feed on insects, fruits, berries, plants, garbage and carrion – essentially, they eat whatever is currently available. Though forests, swamps and riparian areas are their ancestral habitat, opossums adapt well to disturbed or suburban environments. Generally, they are shy creatures, unlikely to attack a dog. In fact, opossums exhibit death-feigning behavior when attacked by predators.
Remarkably Rabies Resistant
Although it happens on very rare occasions, opossums do not typically carry the rabies virus. This contrasts starkly with many similarly-sized animals that have carnivorous or omnivorous diets, such as skunks, foxes and raccoons, which are important rabies reservoirs. While no one knows exactly how opossums avoid the virus, some scientists suggest that it may be due to their relatively low body temperature. However, opossums have very different blood chemistry and react differently than many other mammals do when exposed to toxic substances; for example, snake venoms have little to no effect on opossums.
Leptospirosis is one of the most significant, transmittable pathogens that afflicts opossums. Caused by bacteria of the genus Leptospira, the disease can sicken humans and many other animals, in addition to domestic dogs. Your dog can acquire Leptosiprosis by ingesting contaminated food or water. Opossums may host some of the same flea species that infect domestic dogs and cats. Some of these fleas may carry the bacteria responsible for spotted fever and, therefore, may transmit it to your dog. Opossums often carry the spotted fever bacteria themselves, but they do not typically exhibit symptoms. Opossums also can carry and transmit tularemia and tuberculosis.
Parasites and Protozoans
Opossums may carry internal parasites, such as the nematode responsible for causing trichinosis, but your dog would likely have to eat the opossum to ingest infectious cysts. Scientists are beginning to accumulate evidence that suggests that opossums can harbor and transmit equine protozoal myeloenchephalitis (EPM), a protozoal disease of horses. EPM does not typically affect dogs, but a 2007 report by A.J. Cooley et al, published in the journal “Veterinary Pathology,” documented the first case of canine infection. Opossums also may carry toxoplasmosis, Lyme disease, coccidiosis, trichomoniasis and Chagas disease, which they may transmit to your dog through contact or, in some cases, ingestion of contaminated food.
Reducing the Risk
While it can be difficult to stop opossums from traveling through your yard, many strategies can help dissuade them from frequenting your land. Do not feed dogs outside if possible; if you must do so, be sure to remove any uneaten food promptly, and keep stored food locked tight. Opossums avoid traversing open expanses if possible, so try to remove all forms of cover they may use. Understand that the urine, feces and saliva of opossums can carry pathogens, so it is wise to discourage their presence.
- University of Missouri: The Opossum -- Its Amazing Story
- Internet Center for Wildlife Damage Management: Wildlife Diseases
- County of Los Angeles Public Health: Overview of Zoonoses
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- University of California, Integrated Pest Management Program: Opossum
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- Washington Department of Fish and Wildlife: Living With Wildlife: Opossums
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- Centers for Disease Control and Prevention: Mycobacterium Tuberculosis Transmission from Human to Canine
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- PetMD: Toxoplasmosis in Dogs
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- Texas A&M Veterinary Medical Diagnostic Laboratory: Chagas Disease in Dogs: Transmission, Diagnostic Testing and Clinical Signs
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