Opossums, a common North American marsupial, often spark questions regarding their susceptibility to rabies. While it is a widespread belief that opossums cannot get rabies, the truth is more nuanced: they possess a remarkable resistance to the disease rather than complete immunity. This article explores the biological reasons behind their low incidence of rabies, contrasts it with other wildlife, and provides guidance for safe interactions.
Possums’ Unique Resistance to Rabies
Opossums exhibit a notable resistance to the rabies virus, making rabies cases in them extremely rare. The primary factor contributing to this resistance is their lower-than-average body temperature. Opossums maintain a core body temperature ranging from approximately 94 to 97 degrees Fahrenheit (34 to 36 degrees Celsius). This cooler internal environment creates an unfavorable condition for the rabies virus, making it difficult for the virus to replicate effectively within their system.
Although highly resistant, opossums are not entirely immune to rabies. Instances of rabid opossums have been reported, but they are exceptionally infrequent when compared to other wildlife populations. The low viral replication due to their body temperature means that even if an opossum is exposed to the virus, it is less likely to develop clinical symptoms or transmit the disease to other animals. This biological characteristic significantly reduces their role as a vector for rabies transmission.
Understanding Rabies in Wildlife
Rabies is a viral disease that causes severe inflammation of the brain and spinal cord in mammals, and it is almost always fatal once clinical symptoms appear. The virus is typically transmitted through the saliva of an infected animal, most commonly via a bite. In the United States, rabies is predominantly found in wild animals, with certain species acting as primary carriers and reservoirs for the disease.
The animals most frequently identified as rabies carriers include bats, raccoons, skunks, and foxes. These species have body temperatures and biological systems that allow the rabies virus to replicate efficiently, leading to the development of the disease. In contrast, small rodents like mice, rats, and squirrels, as well as rabbits and hares, are rarely found to be infected with rabies and are not known to transmit it to humans. The low incidence of rabies in opossums stands out when compared to these more susceptible wildlife populations, reinforcing their unique position in the epidemiology of the disease.
Safe Encounters with Possums
Encountering a wild opossum is a common occurrence in many populated areas, and understanding how to react safely is important. Healthy opossums are generally docile and non-aggressive animals that prefer to avoid confrontation. Their defense mechanisms, such as hissing, drooling, or “playing dead” (thanatosis), are often mistaken for signs of rabies, but these are normal behaviors for the species.
While extremely rare, any mammal can exhibit signs of illness. If an opossum appears disoriented, unusually aggressive, excessively tame, or shows signs like paralysis, labored breathing, or foaming at the mouth, it may be sick. Never approach or handle any wild animal, especially if it appears ill or injured. Instead, contact local animal control or wildlife rehabilitation authorities, who are equipped to handle such situations safely.