Thursday, September 2, 2010

Dog/Racoon/Bat Bites Man

I live in a city of 1.7 million people and 1.5 million bats. Mexican Free-tailed bats set up camp under the Congress Avenue Bridge where they spend the spring through autumn months before heading south for the winter. Amidst gathering throngs of tourists, the colony emerges from the bridge nightly to stretch their wings and eat some bugs (we have quite a few of those as well). It’s an impressive spectacle. Bats are fascinating little animals. They’re also one of the principle agents implicated in the spread of rabies from animals to humans in the United States. * I’ve heard the word rabies more in my 2 years of living here than in the 2 decades prior.With the advent of post-exposure prophylaxis, rabies fatalities are now relatively rare in the US †, but the disease still kills about 55,000 people worldwide each year, mostly in Asia and Africa. What rabies lacks in numbers it makes up for with its dismal prognosis – it is nearly always fatal once symptoms are observed and the death it delivers is not a humane one, to say the least.

Rabies is a zoonotic virus that causes severe inflammation of the brain. It is transmitted to humans when the saliva of an infected animal enters a wound or a mucous membrane. Usually this happens via an animal bite. The virus travels through the peripheral nerves to the central nervous system. This incubation period can last weeks to months, and during this time the victim exhibits no symptoms. Eventually, the virus breaches the blood-brain-barrier and enters the brain, where it is conveniently out of reach of medication. There it multiplies and also enters the salivary glands. Now the symptoms appear. These start as flu-like complaints of fever, headache and general weakness but rapidly snowball into agitation, delirium, hallucinations, seizures, the characteristic drooling and inability to swallow, and eventually coma and death. After the onset of symptoms, it typically takes between 5 and 7 gruesome days to die from rabies.

As a child growing up in suburban Minneapolis, I was somewhat aware of the existence of the rabies virus. We fed raccoons and approached stray dogs as children everywhere do. Mostly, I knew that the prescribed medical intervention, where one of these adorable animals to bite me, sounded as ghastly as any disease. Back then, the vaccine was administered as a series of intraperitoneal injections (that means a needle jabbed into your stomach, in case you’ve never been threatened with such a thing), ranging from 10 to 20, depending on who was telling you the story. It seemed almost suspiciously sadistic, something cooked up by parents weary of their children playing with dubious wildlife. Modern rabies prophylaxis is less dread-inspiring, consisting of a mere 4-dose regimen of rabies vaccine, given intramuscularly (ie, hurts about as much as a tetanus shot), and a single dose of human rabies immune globulin (HRIG) to provide immediate antibodies while the body gets to work on generating its own.

This is a small price to pay considering the alternative. Having covered the broad strokes of the disease, I now offer the following As to your possible Qs....

Q: I was scratched by a stray cat, what are my chances of getting rabies?

A: Slim to none, leaning heavily toward none. Remember, rabies is transmitted through saliva, so unless the cat stuck around to lick the wound it inflicted, you’re probably in the clear.

Q: Hypothetically speaking, let’s say I was bitten by a rabid animal, and that I didn’t opt for the vaccine, and that I then did develop rabies symptoms, would there be any options still available?
A: Not really. In 2004 a 15-year-old girl survived rabies following the onset of symptoms and having received no post-exposure prophylaxis. Doctors at a Wisconsin hospital employed an experimental treatment in which the girl was placed into an induced coma in order to minimize damage to the brain while giving her own immune system time to fight off the virus. After a long hospitalization and subsequent rehabilitation, the patient emerged with only mild neurological impairment. ‡ This caused quite a stir in the medical world, but subsequent attempts to employ the treatment, referred to as “The Milwaukee protocol”, on similar cases have failed. There is some question as to whether other factors, such as an unusually weak strain of the rabies virus, contributed to the one-time success of the treatment. The only other record of possible survival of rabies without post-exposure prophylaxis is dodgier still. § Just get the shots, ok. It’ll only hurt for a second.

Q: I’m a raging hypochondriac, should I be concerned about anything else in regard to this disease?
A: Absolutely. In 2004 (apparently, it was a big year for rabies) 4 patients developed rabies and died after receiving organs from a single donor who was eventually determined to have been infected with the virus at the time of his death. Previous cases of rabies transmission through corneal transplants have also been documented. In a 2005 New York Times article about the changing standards for acceptable donor organs, CDC rabies expert Charles Rupprecht is quoted as saying, "I doubt very much that this is the only time," (that rabies has killed transplant patients) "And I doubt that it will be the last time." With this in mind, the first step in protecting yourself from rabies is trying to stay off the organ transplant recipient list. So take good care of your internal organs. Avoid saturated fats, excessive consumption of alcohol and all the other usual culprits. Holding on to your original organs will also help to ensure a greater supply (and ideally higher quality) of donor organs for those people requiring transplants due to less avoidable misfortune, such as traumatic injury and genetic ailments.

* Most cases of rabies in the US are reported in wild animals. Bats, accounting for 26.4% of cases, are second only to raccoons (34.9%). And if you need an additional reason to avoid skunks, you might note that they’re in third place (23.2%).

† About 2-3 deaths per year in the past decade. So your chance of dying from rabies in this country is about 0.009% of your chance of dying in a car acciden
t (26,689 deaths in 2008, not including cyclists and pedestrians).

‡ A 2008 Scientific American article notes lingering problems as being slower speech and a list to one side while walking. However, the girl was studying Biology in college by this time, so it’s safe to say she was doing pretty well cognitively.

§ In 2009 a 17-year-old Texas girl recovered from a series of neurological episodes possibly caused by the rabies virus. Though admitted to hospitals on multiple o
ccasions, she never required intensive care. The doubts about whether she was actually infected with rabies arise from an absence of some of the classic symptoms, such as hydrophobia and malfunctioning of the autonomic nervous system (the part that controls heart rate and breathing and such). Additionally, rabies virus-neutralizing antibodies were only detected after she had already received a dose of rabies vaccine and HRIG. However, no other possible cause for her symptoms was found and she did have a run in with bats about 2 months prior to her illness.

Who told you this?

Center for Disease Control website:

World Health Organization website:

Willoughby R.E. et al. 2005. “Survival after Treatment of Rabies with Induction of Coma.” New England Journal of Medicine 352: 2508-2514.

Srinivason, A. et al. 2005. “Transmission of Rabies Virus from an Organ Donor to Four Transplant Recipients.” New England Journal of Medicine 352: 1103-1111.

“Presumptive Abortive Human Rabies.” 2010. Morbidity and Mortality Weekly Report 59: 185-190.

Lite, J. “Medical Mystery: Only One Person Has Survived Rabies without Vaccine--But How?” Scientific American. October 8, 2008.

Reynolds, G. “Will Any Organ Do?” New York Times Magazine. July 10, 2005.

1 comment:

  1. Nice blog, I arrived here from a Google search on Rabies. Thank you for posting references, I am very skeptical of things I read online.