Rabies

Up until the raccoon epidemic of rabies in 1992 , this disease was one which you read about, worried a little about in people bitten by animals but rarely were particularly at risk for actually dealing with someone who was truly exposed. This scenario has changed greatly in this area as numerous wild animals have been testing positive for rabies. Those animal of highest risk are raccoons, bats, skunks foxes, woodchucks and coyotes (yes they are here in southeast Massachusetts). Domestic animals can also contract rabies from the wild animals and should be quarantined in the event of a bite. Stray cats and dogs are also a great risk. Smaller wild animals such as chipmunks, squirrels, mice and rabbits are rarely sources of rabies. However caged rodents and rabbits kept outdoors could be a source of rabies. Rabid animals can act aggressively or be calm. A rabid animal can shed the virus in its saliva for several days before actual signs of rabies are apparent.

An RNA virus causes rabies. It is most often transmitted by a bite from an infected animal but can also be spread by a scratch or contact with infected saliva on an open wound. The virus is inoculated into the skin or muscles by a bite and moves passively to the local neurons. It follows these neurons until it reaches the spinal cord and moves rapidly to the brain causing encephalitis. From here the virus can spread to other sites including the salivary glands allowing it to be shed in saliva. Generally the incubation period for rabies is 20-60 days. The shorter incubation time would be common in bites on the hands where there are more nerves and on the face where there is less distance the virus needs to travel before reaching the brain. Early signs of disease can be pain at the area of entry and less specific signs such as loss of appetite, fatigue, fever, headache, depression, agitation, personality change and loss of sleep. The patient will then progress to various neurological symptoms including stiff neck, some degree of paralysis, bizarre behavior such as terror or agitated states, hydrophobia (attempts to drink or swallow cause spasms of the muscles of the larynx and throat) and seizures. The patient may slip into coma and expire.

Exposure to a rabid or suspected rabid animal which is not available for testing is best handled by receiving the rabies vaccine of which there are currently two types (HDCV and RVA). A third vaccine made from chick embryos should to be licensed soon. Contrary to popular beliefs these vaccines are not administered into the abdomen. It is also recommended that the individual receive Human Rabies Immune Globulin (HRIG). For bites by domestic animals which can be quarantined or tested post exposure prophylaxis may wait pending the health or testing of the animal. Bat exposures fall into a high-risk class as the incidence of rabies in bats is high and bites and scratches from bats can be so small that they may go unnoticed. The presence of a bat in a bedroom where someone has been asleep or with an unattended child makes contact difficult to rule out. The best advice with bat exposures would be to err on the side of administering preventive treatment. Bites by smaller animals must be considered on an individual basis although they are infrequent sources of rabies. It would be best to check with the state department of public health who is aware of any incidences in these animals.

Prevention is key in dealing with rabies. Immunization of all cats, dogs and ferrets is essential. Teaching children to avoid playing with wild animals or trying to hand feed them is recommended. People should avoid stray cats and dogs as well as any sick animals or those behaving in a manner not typical of their species (nocturnal animals being about during the daytime). Prompt washing of any bites with soapy water is recommended as well as washing any bites on your pets for at least ten minutes with soapy water (wear rubber gloves when doing this). Any bites should be reported to your doctor.

Reference: McGuill and Matyas, Prevention of Rabies in Humans, 1997. (Obtained from the Web site of the Massachusetts Department of Public Health)

Reference: Avery and First, Pediatric Medicine, Williams and Wilkins, 1989.