Rabies on the Brain

I’ve got rabies on the brain. Well, not literally, because that would mean I’d probably be dying in intensive care.

 
Last week (September 28) was World Rabies Day. It is the anniversary of the death of Louis Pasteur (more on him later).
 
Rabies is virus which causes a virtually 100% fatal neurologic disease in all mammals, including humans. According to “Rabies surveillance in the United States during 2011,” last year rabies was diagnosed in animals in 49 states (not Hawaii). Besides the “usual suspects” of bats, skunks, raccoons, foxes, dogs and cats, it was also diagnosed in cattle, horses, sheep, groundhogs, deer, beavers, otters, javelinas (shaggy piggy creatures), bison and alpaca. Bambi and Thumper could be rabid!
 
Rabies is spread by the saliva of a rabid animal. When the rabid animal bites a victim, it inoculates the virus into the tissues. Unlike most viruses and bacteria, which spread through the bloodstream, the rabies virus spreads along nerve cells. Depending on how far the bite wound is from the brain, symptoms might not develop for weeks to months to years. A person in the US died last year of rabies that was acquired from a dog in Brazil eight years previous! For eight years, the virus had been lazily moseying along, inexorably crawling up to the brain.
 
Once the virus hits the brain, bad things happen. Even in the 21st century, over 50,000 people worldwide die of rabies every year. It is a horrible death of alternating periods of lucidity and psychosis, pain, fever, convulsions, hallucinations and hydrophobia (pathologic fear of water).
 
I recently read Rabid: A Cultural History of the World’s Most Diabolical Virus, by writer Bill Wasik and veterinarian Monica Murphy. It’s a fascinating book, although I guess I might not qualify as a totally objective reviewer since I tend to get a little bit obsessed about public health and infectious diseases.
 
Wasik and Murphy weave together a history of rabies and civilization. Although many of the scary epidemic infectious diseases of humans, including Ebola, West Nile, SARS, swine flu, and hanta, are zoonotic (transmitted from animals), only rabies was known to be zoonotic before humanity ever considered the existence of bacteria and viruses. Think of bubonic plague (“The Black Death”): people didn’t realize it was caused by a bacterium spread by the bite of a rat flea. But rabies: slobbering psychotic dog bites human, human turns into slobbering psychotic animal. It was obvious even four millennia ago that rabies was transmitted by animals, particularly canines.
 
The book looks at theories, preventatives and “cures” over the millennia (the most effective preventative prior to vaccination was cauterizing the fresh bite with a red hot poker); history (St. Hubert is the healer of rabies sufferers); mythology (the slaver of Cerberus spreads both rabies and aconite); connections of rabies to werewolf and vampire legends; the handful of documented survivals of rabid humans; weird ideas that people have had to prevent rabies in dogs (one theory suggested rabies spontaneously arose in dogs due to sexual frustration and suggested prevention by creating “doggy bordellos”); rabies in various species (l’enfant du diable = the devil’s child, a skunk); history of canine mass killings in an attempt to stop epidemics; and a recent rabies epidemic on the supposedly rabies-free island of Bali.
 
The most fascinating chapter explains how Louis Pasteur developed the first rabies vaccine in the late 1800’s. In fifteen years of veterinary practice, I have never seen a case of rabies and hope I never do. Pasteur (who is also the father of pasteurization and food safety) was neither a physician nor a veterinarian, but was a really smart dude who was passionate about human and animal health.
 
You can’t grow rabies virus in a Petri dish. The only way Pasteur and his colleagues could grow rabies virus was by maintaining rabid animals in the lab, putting themselves at continual risk of gruesome death. At first they allowed a rabid animal to bite another to perpetuate the virus; then they started collecting saliva from slobbering aggressive dogs to inject into other animals. Eventually they hit on dicing up the central nervous system of a rabid rabbit and depositing it directly onto the dura mater of the recipient’s brain. By repeatedly transferring rabies directly from one rabbit’s brain to another they developed a highly virulent strain. The next step was to inactivate the virulent virus to make the vaccine strain, which they did by leaving the rabbit’s spinal cord out to air-dry for a few days. This air-dried infectious bunny brain was then injected as a vaccine: either a pre-exposure vaccine to prevent infection or a post-exposure vaccine to prevent development of symptoms after a bite.
 
The first human to receive the vaccine was a boy who had been mauled by a rabid dog. Can you imagine the agonizing wait for Pasteur to see if the boy survived or died? (He survived both the bite and the cure.)
 
We all learned in vet school that rabies is absolutely, guaranteed fatal. But some new research is showing it might not be completely 100% fatal. There was a girl in Wisconsin who survived clinical rabies after a medically-induced coma and months of rehab. And a recent paper was published in The American Journal of Tropical Medicine and Hygiene that looked at humans living in remote areas of Peru where vampire bats are a common carrier of rabies. 11% of the people had rabies neutralizing antibodies; they had not been vaccinated so those antibodies developed after infection with the real, live virus. How come they didn’t die? Has evolution favored people with a more exuberant immune system that can fight off endemic rabies?
 
However, despite this research, the odds of dying are still very, very high. Make sure your dogs, cats and ferrets are current on their rabies immunizations, and never approach an ill or strangely-behaving bat, skunk, raccoon or fox.