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Rabies, Rabies, Everywhere?

August 23, 2012

Eva Gusnowski

With the recent news regarding outbreaks of the Ebola virus (not to be confused with the Ev(ol)a virus) hitting the internet, it’s no surprise that people are interested in other nasty viruses. One such virus is the one that causes rabies, aptly named the “rabies virus”. Rabies is an interesting disease because when symptoms appear, the disease is nearly 100% fatal and causes nearly 55 000 deaths annually. Even though this is historically true, new evidence has surfaced from villages in Peru that brings this risk of fatality into question.

Rabies is spread by animal bites, or contact of an infected animal’s saliva with an open wound. We usually tend to think of bats as the jags that transmit rabies, but the truth is that common reservoirs also include raccoons, foxes and skunks. From the wound site, the virus travels up to the brain where it causes inflammation and swelling. This leads to convulsions and other clinically significant symptoms that result from loss of proper brain function. Other typical symptoms include the characteristic drooling and foamy mouth, and anxiety, stress, excitability, restlessness and tension, as well as numbness, tingling, loss of muscle function and sensation and fever. Altogether an unpleasant experience to say the least…just ask Old Yeller.

 

http://www.in.gov/boah/images/bite2.gif

http://www.in.gov/boah/images/bite2.gif



The good news is that if you get bit by a suspicious animal, and go to the doctor’s office, you can get a vaccine for the rabies virus after the fact (one of the few vaccines that can work this way). This post-bite vaccination is very effective when its given shortly after the bite occurred and in the correct manner. However, once clinically significant symptoms start, patients usually die of respiratory failure a week after onset. As of February 2012, only 10 patients have been documented to survive rabies once these symptoms have set in. Until now, that is.

In Peru there is a high number of rabies cases caused by bites and attacks from vampire bats. A recent survey of villagers in high-risk areas was performed to assess the interaction of these individuals with vampire bats. In fact, although the authors report that the population they used to assess the situation was slightly biased, 54% of the respondents reported having been bit by bats in the past. The highest risk area was Santa Marta, confirming that I will be unlikely to visit this area on vacation anytime soon, although this is still speculation at this point in the study. And the bloodsuckers don’t stop there, as there were frequent attacks on pet dogs as well as livestock living in the area.

 

science in seconds, vampire bat



Additionally, the investigators took blood samples from a number of these villagers and tested them for antibodies against the rabies virus. In order to generate antibodies, these villagers would either have 1) been vaccinated against the rabies virus (which only one of the villagers reported receiving), or 2) been exposed to the virus. 11% of the tested villagers were seropositive (meaning they had the antibodies), all of them having reported known exposure to bats (bites, scratches, contact with unprotected skin). This means that these individuals (without the vaccine) were exposed to the rabies virus and survived. Other studies have looked at the number of seropositive individuals among fox trappers, and also found a high prevalence of antibodies. This implies that the extremely high level of fatality associated with the virus is not likely to be as high as we once thought. Similar to innate resistance to malaria with sickle cell trait, some individuals may have a genetic resistance to infection by the rabies virus.

Take that rabies. You may have taken Old Yeller down, but you won’t get us all.

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