Disease: Rabies

Electron microscope image of rabies virus, Photo by Norden, a Smith-Kline Company, 1985

Electron microscope image of rabies virus. Photo by Norden, a Smith-Kline Company, 1985.

Does Rabies Affect You?

Agent: Virus Vectors: Mammals, especially raccoon, striped skunk, foxes, bats

Route: Animal bite or scratch; wound/eye/nose/mouth; rarely, inhalation

Symptoms: Paralysis, convulsions, coma. Nearly always fatal.

How do you catch it?

Rabies virus is found primarily in saliva and in the tissues of the central nervous system, especially the brain. It’s usually spread through the bite of an infected animal.

It can also be transmitted if the animal’s saliva or nervous tissue gets into your eyes, nose, mouth, or an open wound or scratch. Airborne transmission is possible but rareā€”it’s more of a concern for laboratory workers who handle animals, or in moist caves with little ventilation.

You cannot catch rabies from contact with blood, feces, urine, or scent glands. The rabies virus hitches a ride up the nerves, traveling directly from the bite wound to the brain. Later on, it may travel from the nerves to other organs, but it never enters the blood. That said, if the animal’s head has been damaged, there could be spinal tissue or fluid mixed in with splattered blood. Animals may catch rabies by eating infected animals. Rabies might be passed from mother to offspring in the womb. However, when people encounter very young animals that are rabid, it’s more likely that they were infected after they were born, either from contact with their mother or another rabid animal.

Although deadly, the rabies virus is actually fragile. It can be destroyed by exposure to sunlight (UV light). Symptoms

An animal may be infected with rabies for a long time before it shows symptoms, anywhere from two weeks to many months. (The incubation period is usually two to three weeks.)

Different species show different signs of the disease. Expect variations even within the same species, because few animals show all of the signs of rabies. Some signs are subtle and easily missed.

Unfortunately, you can’t tell whether or not an animal is rabid just by its behavior. Other diseases, such as distemper or toxoplasmosis, can also cause similar symptoms. An animal that’s been poisoned by lead, mercury, or antifreeze may also act “rabid.” The only way to prove that an animal is rabid is to test its brain tissue in a laboratory. That’s why it’s smart to take precautions.

Here are the rabies symptoms you may see in wild animals:

  1. unprovoked aggression (“furious” rabies). Some animals may attack anything that moves, or even inanimate objects.
  2. unusual friendliness (“dumb” rabies).
  3. animal may stumble, fall, appear disoriented or uncoordinated, or wander aimlessly.
  4. paralysis, often beginning in the hind legs or throat. Paralysis of the throat muscles can cause the animal to bark, whine, drool, choke, or froth at the mouth.
  5. vocalizations ranging from chattering to shrill screams.
  6. nocturnal animals may become unusually active during the day (remember, some daytime activity is normal, especially when nocturnal animals are feeding their young).
  7. raccoons walk as if they’re on very hot pavement.

Skunks, raccoons, foxes, and dogs usually display furious rabies. Bats often display dumb rabies, and may be found on the ground, unable to fly. This can be very risky for children, who are more likely to handle wild animals than adults. In domestic animals, rabies should be suspected if you see a sudden change in disposition, failure to eat or drink, or if the animal becomes paralyzed or runs into objects.

You may become aware of another similarity between rabies and distemper. Both are “density dependent” diseases. That means they spread more easily when wildlife populations are higher, because there’s more contact between individual animals. When enough animals die from rabies or distemper, these viruses can’t spread as easily. That’s why the number of cases spikes and then drops off; this rollercoaster pattern repeats over time.

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