Opossums, North America’s only marsupials, often appear in backyards and urban areas. Despite their frequent presence, a common belief persists that these unique animals rarely contract rabies. This intriguing fact prompts questions about why opossums seem to defy the typical risks associated with wildlife and this severe viral disease.
Understanding Rabies
Rabies is a severe viral disease that affects the central nervous system in mammals, including humans. It is caused by the rabies virus. The virus is primarily transmitted through the saliva of an infected animal, usually via a bite. Once symptoms manifest, the disease is almost always fatal for both animals and humans.
Opossum Biology and Rabies Resistance
The low incidence of rabies in opossums is largely attributed to specific biological characteristics. Opossums possess a naturally lower average body temperature, typically ranging from 94 to 97°F (34 to 36°C). This cooler internal environment is less conducive for the rabies virus to replicate effectively.
The rabies virus thrives in warmer temperatures, and the opossum’s lower body heat makes it difficult for the virus to survive and reproduce sufficiently to cause illness. Even if exposed to the virus, its replication is often inhibited, preventing the disease from progressing. This physiological trait provides a natural defense mechanism against the infection.
Beyond their body temperature, opossums also exhibit a robust immune response. Their immune system is highly effective at fighting off various pathogens and toxins. This strong biological defense contributes to their resistance against the rabies virus, allowing them to often overcome exposure.
While opossums are highly resistant, they are not entirely immune to rabies. In rare instances, an opossum can theoretically contract the virus, though reported cases are exceptionally infrequent. Studies have shown that less than 1% of opossums tested are positive for rabies, making them one of the least likely wildlife carriers of the disease.
Dispelling Common Misconceptions
Despite their low rabies risk, it is important to recognize that opossums can carry other diseases. These can include leptospirosis, tuberculosis, spotted fever, coccidiosis, toxoplasmosis, trichomoniasis, Chagas disease, salmonella, and tularemia. They can also host external parasites like fleas and ticks, which may transmit diseases to humans or pets.
When encountering an opossum, observing from a distance is always advisable. It is best to avoid direct contact with any wild animal. If an opossum exhibits unusual behavior, such as disorientation or aggression, it might be ill from something other than rabies or simply under stress.
Secure garbage cans and avoid leaving pet food outdoors to prevent attracting wildlife. If an opossum enters a home or enclosed space, provide an escape route and allow it to leave on its own. Contacting local animal control or wildlife professionals is recommended if the animal appears injured or does not leave.