Rabies, a topic of concern for dogs and humans

by Stuart Nelson, Jr., DVM

I have chosen to address a topic of concern for dogs and humans in this article. Rabies is a disease we are all familiar with, at least on a superficial level, but I think its important to emphasize some key points about this infection that may not be common knowledge. Obviously, people working with sled dogs will be out and about in the great outdoors where potentially infected wildlife would most likely be encountered. Any warm-blooded animal may contract the disease, but the most commonly affected species include the bat, fox, raccoon and skunk. I’ll start with a brief review of the virus and disease mechanism.

The organism that causes rabies is classified as a lyssavirus. It typically enters the body through bite wounds or from saliva contact with a preexisting open wound. There is also documentation that it may in rare circumstances be contracted through aerosol exposure, primarily in caves heavy populated by infected bats. Once the virus enters the body, it travels along nerves in-route to the spinal cord, and ultimately the brain. There is a direct relationship between where the virus enters the body and the amount of time it takes to reach the brain, with the onset of clinical signs. In other words, a non-vaccinated critter bitten in the face by a rabid animal will develop the disease more quickly than one exposed in a hind toe. It can take up to and possibly even a little longer than six months to develop the disease after exposure. However, once the virus enters the brain, death will occur in less than ten days. Typically, the organism enters the salivary glands a few days prior to the onset of clinical signs and persists in the saliva until death occurs. It is during this limited time frame that rabies can be spread from an infected animal to another victim.
In any animal, the first sign of infection is a change in behavior and loss of appetite. Within one to three days, the condition will typically progress to excitement and aggression, then paralysis and death. When the excitement phase is pronounced, it is referred to as the furious form of rabies. However, this stage may be extremely short, in which case the paralytic form (dumb rabies) is predominant, manifested by the inability to swallow and profuse salivation.

The diagnosis of rabies in animals is best accomplished by submitting the intact brain (head) to a laboratory. Brain tissue will decompose rapidly after death, so every effort must be made to keep it chilled (refrigerated), but not frozen, prior to testing.

Fortunately, vaccination is a very effective way to protect animals, including humans, from the disease. Most veterinarians and wildlife personnel are routinely vaccinated. There are a number of vaccines (produced by several different pharmaceutical companies) available for use in domestic animals. In dogs, there are two general types-one approved only for annual revaccination and the other approved for three years following an initial one-year booster. With either type, puppies must be at least three months old to receive their first in the series. The state of Alaska (and ITC) accepts the use of the three-year vaccine, but other states or countries may only require annual rabies boosters, regardless of the vaccine used. To be recognized as an official vaccinate, the inoculations must be administered by a veterinarian or state approved lay vaccinator.

The following recommendations are summarized from the Compendium of Animal Rabies Control (the complete compendium is available on the internet-just type it in and search):

  • Any human or domestic animal potentially exposed to rabies virus by a wild carnivorous mammal or a bat that is not available for testing should be regarded a having been exposed to rabies. (In the event that the animal is disposed of for testing, make sure further exposure to saliva and nerve tissue does not occur during the process.)
  • If you or someone you know is bitten by such a wild animal, cleanse the wound thoroughly and contact your physician for further recommendations.
  • If your vaccinated (current) dog is bitten by such a wild animal, contact your veterinarian for an immediate booster rabies vaccine, and observe it closely for 45 days.
  • If your dog has been previously vaccinated for rabies, but is no longer current, and is bitten by such a wild animal, contact your veterinarian for recommendations. The amount of time the booster vaccination is overdue and prevalence of rabies in the local area will have to be reviewed.
  • If your dog has never been vaccinated for rabies and is bitten by such a wild animal, your dog should be euthanized immediately. If you are unwilling to have this done, the animal should be placed in strict isolation for six months and vaccinated one month before being released, if allowed by local laws.
  • A healthy dog (vaccinated or not) that bites a person should be confined and observed for ten days. Such animals should be evaluated by a veterinarian at the first signs of illness. If signs of rabies develop, the animal should be euthanized and the head submitted to a laboratory for testing.

In conclusion, rabies can easily prevented through proper vaccination protocols, but fortunately, (I couldn’t resist) there’s no cure for the rabid fans and supporters of the Iditarod!