Opossums, North America’s only native marsupial, are often subjects of curiosity and misunderstanding. A common belief is that these animals are immune to rabies. This widespread notion requires a closer look at the science. This article clarifies the true relationship between opossums and the rabies virus.
Understanding Opossums and Rabies
Opossums are not truly immune to rabies, but they exhibit a remarkably low incidence of the disease compared to other wildlife. While any mammal can contract the rabies virus, reported cases in opossums are exceptionally rare. The Centers for Disease Control and Prevention (CDC) indicates that less than 1% of all reported rabies cases in the United States involve opossums.
This low prevalence contrasts sharply with common rabies carriers such as raccoons, bats, skunks, and foxes, which account for a much higher percentage of cases. Despite this rarity, it is important to understand that a case of rabies in an opossum is not impossible. The perception that they are completely immune often stems from their unusual defense mechanisms, like hissing and drooling, which can be mistaken for symptoms of rabies but are merely bluffs to deter predators.
Biological Reasons for Low Rabies Rates
Several biological factors contribute to the low susceptibility of opossums to the rabies virus. Their average body temperature (94 to 97 degrees Fahrenheit / 34.4 to 36.1 degrees Celsius) is lower than that of most placental mammals. This cooler internal environment is thought to inhibit the rabies virus from replicating efficiently and thriving within their system.
Beyond their body temperature, opossums may possess a robust immune system that effectively combats the virus if exposed. Some research suggests their immune response might be more effective at fighting off rabies, potentially through unique antibodies or cellular responses. This inherent resistance, while not fully understood, further contributes to their ability to resist infection.
Behavioral traits also play a role in reducing their exposure risk. Opossums are generally solitary animals, which minimizes their contact with other wildlife, reducing opportunities for virus transmission through fights or bites. Their non-aggressive and timid nature means they are less likely to engage in confrontations that could lead to being bitten by a rabid animal.
Safe Interaction with Opossums
Given their low but not zero risk of rabies, always maintain a respectful distance from opossums and all wild animals. Observe them from afar and never attempt to approach, handle, or feed them. Direct contact should be avoided, as opossums can carry other diseases or parasites, such as leptospirosis, salmonella, toxoplasmosis, and various external parasites like fleas and ticks.
If an opossum appears disoriented, aggressive, paralyzed, or exhibits other unusual behavior, it may be ill, although not necessarily with rabies. In such instances, contact local animal control or wildlife authorities for assistance. Prompt reporting of sick or injured wildlife helps ensure both human and animal safety.