Why Rabies Is Still a Problem : Discovery News
In light of a spate of rabies attacks, take a closer look at the disease, its risks and how you can avoid it.
Rabies, a deadly virus transmitted through the saliva of infected animals' bites, still poses problems for health and wildlife authorities.
The virus is found mostly in raccoons, bats, skunks, coyotes and foxes, and occasionally seen in pets.
As suburban development increases, so might humans' interactions with potentially rabid animals.
Rabid animals on the loose frequent our TVs and newsfeeds. But despite clues from cinematic rabies cases, such as Cujo and Old Yeller, what do we know about this dismal disease and how it spreads?
Although vaccine campaigns have nearly eliminated canine rabies in the country, officials say they're concerned about suburbanization and whether it will increase chances of encountering other variants of the virus from animals thriving in suburban areas.
Rabies, a deadly virus infecting mammals, is spread through bite wounds laden with the saliva of an infected animal. From the infection site, it moves through nerve cells toward the spinal cord and brain.
"We know that the virus moves through nervous tissue -- so from neuron to neuron," Jesse Blanton, CDC epidemiologist and Rabies Surveillance Coordinator, told Discovery News. "It has a very discrete pathway from the site of inoculation from a bite to the nervous tissue, moving into the nervous system with replication in the brain."
This latent period lasts from weeks to months, and the host may seem healthy. Yet once the virus takes hold in the brain, there's no turning back. The host's behavior goes awry as the virus moves from the brain to the salivary glands, where it can be transmitted to a new host.
"The only thing that's usual about rabies is the unusual," Blanton said. "Under certain cases the classic Cujo image (called furious rabies) is pretty spot on. But there's certainly a manifestation of rabies at the paralytic end that's not that classical foaming-at-the-mouth, attacking-everything type of behavior. Animals can appear to be sick and tense, and not seem to have the frothy-mouth onset."
Because rabies spreads from exposure to saliva or nervous tissue, contact with urine, blood or feces does not constitute an exposure, Blanton said. Animal licks, however, can be dangerous if applied to an open wound. And though the virus is most common among raccoons, bat bites are equally concerning because they can go unnoticed.
Infected animals usually die within a week of rabies reaching the brain, and it's suggested humans share a similar fate. For animals, vaccines are usually effective to stave off the virus, while humans can start prophylaxis within a week of exposure. Bites to the face require immediate action, Blanton said.
Dennis Slate, USDA National Rabies Management Coordinator, organizes efforts to monitor rabies and introduce vaccines to wild populations. One zone of interest, stretching from Maine to Alabama, comprises the western border of raccoon rabies, the most common variant of the virus in the United States. The goal is to work on vaccinating the edge of this area and then move eastward toward the coast in efforts to eliminate the virus, he told Discovery News.
"We're surveying animals that are not involved in exposures generally," he said. "So these are animals that would slip through the system but might be rabid."
Slate and his teams use vaccine baits with squishy centers that rupture and release the vaccine when punctured by animals' teeth. Oftentimes, the vaccines will be dropped from airplane to forested areas below.
Then, experts will return four weeks later to trap and draw blood from animals, allowing researchers to sample the portion of a population that has developed antibodies against rabies. With repeated vaccine waves, the team will create enough population resistance to create a barrier from the virus spreading.
But Slate is equally concerned about humans' contribution to the problem. It turns out battling rabies can be as simple as giving suburban raccoon populations less to live on.
"The reality is there's an abundance of these food subsidies in these suburban areas, and that's why there are so many raccoons," Slate said. "It's not hard for them to make a living or get a meal."