Opossums are extremely poor vectors for the rabies virus, with documented cases being exceedingly rare across North America. While any mammal can theoretically contract the disease, surveillance data from the Centers for Disease Control and Prevention show that opossums consistently have one of the lowest rates of rabies positivity among tested wildlife.
Physiological Resistance to Rabies
The primary reason for the opossum’s low rabies risk lies in its unique physiology: a lower-than-average body temperature. The Virginia opossum’s normal internal temperature ranges between 94 and 97 degrees Fahrenheit (34.4–36.1°C), several degrees cooler than most placental mammals.
This low core temperature creates an inhospitable environment for the neurotropic rabies virus, which requires a warmer host to efficiently replicate and spread. Even if an opossum is bitten by a rabid animal, the infection often fails to take hold or progress to the infectious stage because the cooler body temperature inhibits the virus before it can reach a transmissible viral load. The rabies virus is most commonly found in warmer-bodied mammals like raccoons, skunks, foxes, and bats, whose body heat allows for optimal viral proliferation.
Other Diseases Carried by Opossums
While opossums rarely carry rabies, they are hosts for several other pathogens and parasites that pose health risks to humans and pets.
These marsupials can transmit the bacterial disease Leptospirosis through their urine, which can contaminate water or soil. Infection in humans can cause symptoms ranging from fever and muscle aches to severe conditions like kidney damage or liver failure.
Opossums also shed the bacterium Salmonella in their feces, which can lead to Salmonellosis if humans or pets come into contact with contaminated droppings or surfaces. Another risk is the internal parasitic infection Toxoplasmosis, contracted by ingesting particles from infected feces. This disease is particularly concerning for pregnant women and individuals with compromised immune systems.
The presence of opossums is a concern for horse owners because of Equine Protozoal Myeloencephalitis (EPM). Opossums are the definitive host for the protozoan parasite that causes EPM, passing infective sporocysts in their feces. If horses ingest contaminated feed, they can develop the debilitating neurological condition.
Opossums frequently carry external parasites such as fleas, ticks, and mites, which can act as vectors for other diseases like Lyme disease and Tularemia.
Safe Practices During Opossum Encounters
Wildlife encounters should be approached with caution. The best practice is to reduce attractions on your property, such as securing garbage bins with tight-fitting lids and avoiding leaving pet food outdoors overnight. Opossums are scavengers, and removing easy food sources is the most effective way to encourage them to move along.
If you encounter an opossum, maintain a safe distance and never attempt to handle it, even if it appears docile or injured. If the animal seems sick, injured, or is cornered, contact a local animal control agency or a licensed wildlife rehabilitator for assistance. Never try to capture or transport a wild animal yourself.
Should a bite or scratch occur, the immediate priority is to thoroughly wash the wound with soap and water for several minutes. Following cleaning, contact a medical professional immediately to assess the need for post-exposure treatment for potential bacterial infections. You should also report the incident to local health or animal control authorities, who can advise on necessary testing or monitoring of the animal.