How common is rabies, and what are the symptoms?
Answer: This time of year usually brings numerous sitings of raccoons, skunks and foxes, both on roadways and around farmsteads. This makes it a good time to review rabies and the potential animal reservoirs.
A recent letter published by the Wisconsin state veterinarian reports that since 2005, 154 cases of rabies have been reported in Wisconsin. So far, 149 cases were in bats, two were in dogs and three were in skunks. Minnesota has reported 24 cases of rabies so far this year: 12 skunks, seven bats, two cows, two cats and one dog.
As you can see, over the years bats have been the main reservoirs of the rabies virus, but animals we deal with are also vulnerable. Because rabies can affect domestic livestock, pets and humans, it is important to be on the watch for any wildlife that exhibits strange behavior.
Rabies is a virus that is transmitted through the saliva of an infected animal. The rabies virus enters into a healthy animal when infected saliva enters through a bite or scratch on the skin. Once in the body, the virus works through the nervous system until it reaches the brain. Incubation periods for the virus can run from a few weeks up to several months.
The speed with which the animal starts to show signs depends on how far the bite is from the brain. Bites in the extremities, such as the hind limbs, take longer to get to the brain then bites on the nose or face. Once the virus reaches the brain, it continues to multiply and travel down the nerves into the salivary glands to complete the cycle. Viral shedding from the salivary gland can happen for several days before the animal starts showing signs of the disease.
Because domestic livestock are naturally curious, they tend to get bitten around the head, which causes a fairly rapid progression to neurological symptoms. Once an animal shows signs of rabies, it is always fatal.
The signs of rabies are varied, but all are related to the nervous system. Rabid animals will show either the furious form or the dumb form of rabies. In the furious form, the animal is aggressive and excitable, often biting at anything. There are often excessive amounts of saliva around the mouth. In the dumb form, the animal appears very docile, making it very easy to approach.
As signs progress, the facial muscles become paralyzed and the animal loses the ability to swallow. Cattle have been known to have a different sound to their vocalization because of the weakened laryngeal muscles. Once these signs start to appear, the animal will die within a few days.
If you see a domestic animal exhibiting some of the above signs, it is best to stay away from it and contact a veterinarian or public health official. These animals can be quarantined and observed for further symptoms to verify rabies, or they can be euthanized and the brains submitted for testing.
If a wild animal is suspected of having rabies, it should be destroyed. Make sure to preserve the head in case diagnostics need to be done on the brain.
If you are bitten by an animal, the first thing to do is aggressively wash the wound with soap and water. Capture the animal if possible so testing can be done, and contact your local physician so treatment can be started right away.
Control of rabies involves keeping farmsteads clean and uncluttered to make it less inviting for wild animals. Domestic pets should be vaccinated for rabies since they have a greater chance of contact with wild animals.
Monty Belmer, DVM, is a veterinarian with the Waupun Vet Service in Waupun. To Ask the Vet, e-mail your questions to: firstname.lastname@example.org, or mail them to: Wisconsin Agriculturist, 102 E. Jefferson St., P.O. Box 236, Brandon, WI 53919.
This article published in the September, 2010 edition of WISCONSIN AGRICULTURIST.
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