Raccoons and rabies, the basics

Recent findings of raccoons carrying the rabies virus in New York County parks have raised questions about both the seriousness of the virus and the animals that can carry this disease. Rabies is a virus that can affect any mammal, including humans. This disease affects the central nervous system and if left untreated is fatal.

Rabies is usually linked with dogs and humans. According to the World Health Organization in 1992 rabid dogs accounted for 90% of all human infections. Currently, in Asia and South America dogs carrying the virus remain the main source of transmission to human beings. Red foxes had been a vector in parts of Europe although the disease has now been mostly eradicated. Infected bats in Latin America primarily pass the disease to cattle but can also transmit the disease to human beings.

A 2007 article in a leading veterinary journal reported that rabies control programs in the United States had virtually eliminated the circulation of major strains of canine rabies by the late 1960’s. Canine rabies did re-emerge in the 1980’s in Texas (where coyotes have historically carried rabies) but was successfully eliminated. No incidents of animals infected with canine rabies have been reported since 2004.

In many developed countries including the US, the vast majority of rabies cases are attributed to wild animals not companion animals. Wildlife that can carry the rabies virus includes raccoons, bats, skunks and foxes.

Rabies in raccoons was first identified in the southeastern US in the 1950’s. The disease was introduced to raccoons in the Mid-Atlantic States in the 1970’s by the translocation of infected raccoons from the southeast by hunters seeking to replenish depleted raccoon populations. The first case of raccoon rabies was reported in 1999 in Ontario, Canada. It is believed that rabid raccoons from New York State transmitted the disease.

New York City first identified a case of raccoon rabies in 1992. NYC Health Department records indicate that rabid raccoons were identified in Manhattan in 1993 and not seen again until 2009. (Six rabid raccoons have been further identified as of 1/14/2010 and the health department is currently planning a rabies vaccination program to address the issue.) New York State last conducted a rabies vaccination program on the Queens/Nassau border in 2005.

The progression of rabies in an infected animal is usually classified in three stages or forms (an animal may have some, all or none of these symptoms): The first is the “prodromal” or early stage with few early symptoms of the disease, the next is the “furious” stage which is characterized by unusual agitation, puzzled and anxious facial expression, aggression, dilated pupils, difficulty swallowing, voice changes in pitch and hoarseness, difficulty in movement, convulsions and paralysis (Infected cats will frequently exhibit this form and to demonstrate more aggressive behavior than dogs).

The last stage or form is the “dumb” stage including sluggishness, tremors, excessive salivation, paralyzed hind quarters and coma. Dogs are more commonly known to have all three stages.

Symptoms of rabies vary greatly depending on the species (although the most common indicator across species is some type of paralysis preceding death). It is essential to point out that the above list does not include all symptoms. It is also important to note that other diseases affecting the central nervous system may have identical or similar symptoms. In fact signs of certain diseases such as canine distemper are virtually identical to those of rabies.

Some animals infected with the virus may exhibit no symptoms of the disease. Once an animal is infected with the disease there is an incubation period where the virus passes from the site of the infection to the brain. Once the virus reaches the brain it will begin to shed in the saliva and can be transmitted. Death soon follows shortly in the infected animal.

Research on raccoons and rabies is continuing but it is not as extensive as the work done with companion animals. Researchers believe that the incubation period for rabies may be longer in wild animals infected with the disease.

There does appear to be a general consensus concerning the absence of aggressive behavior in raccoons affected with the rabies virus. Among the articles supporting this one published in 1970 noted: “the typically unaggressive behavior of rabid raccoons”, another in 1992 indicated: “Few rabid raccoons are aggressive indeed, most lose their natural fear of humans.” Other studies outlining unusual behavior in rabid raccoons note “acting “drunk” or “strange” or appearing during the daytime as the most frequent behaviors not aggression. Where aggressive behavior is mentioned it is usually in concert with an interaction with a dog with no mention being made if the dog menaced the raccoon initially.

It is because of the absence of aggressive behavior in raccoons that any encounter with these animals be conducted at a safe and respectful distance. Similarly any behavior a raccoon may demonstrate may not indicate rabies, for instance, a raccoon appearing during daylight hours may simply be a mother raccoon in search of provisions for her young.

Caution should be exercised in the case of any possible transmission. Although, exposure to rabies can be treated in human beings, the best possible way to avoid contact with the disease and to respect wildlife at the same time is to avoid interaction. Keep companion animal vaccinated, in your home and on a leash when outdoors. And allow urban wildlife to be wild.

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Photo: Harlequeen