The rabies virus, courtesy of Frederick A. Murphy
The rabies virus, courtesy of Frederick A. Murphy
ScienceOnly Human

How To Rid the World of Rabies

Most dog owners have no doubt heard about the horrors of rabies, an infection that’s usually transmitted through dog bites. The bullet-shaped virus begins replicating, quietly, in a dog’s muscle. Then it travels to motor neurons in the central nervous system, and eventually reaches the brain. It wreaks inflammatory havoc there, leading the dog to become confused and extremely aggressive. Then the virus travels through the dog’s peripheral nervous system to the salivary glands. There it makes its host foam at the mouth, leaving the virus fully exposed, in perfect position to infect the next piece of muscle the crazed animal bites into.

The scariest thing about rabies is its potency: If your dog gets rabies, your dog will almost certainly die. And if a rabid dog bites you, you will almost certainly die, too, unless you get a vaccine within 10 days.

And yet, rabies isn’t a problem in developed countries. Last year exactly one person was diagnosed with rabies in the United States (after being bitten in Guatemala), and nobody got it in Western Europe. There’s a very simple explanation for our lack of rabies: We vaccinate our dogs.

That’s not wholly true, of course; some dog owners don’t get their pups the vaccine and some dogs don’t have owners. But in the state of New York, where I live, the law dictates that “every dog, cat and domesticated ferret” be vaccinated. The same goes for most other states.

In developing countries the situation is sadly quite different, as I learned in a commentary published in today’s issue of Science. There, rabies kills at least 69,000 people every year (and because of underreporting, the real number may be many times higher than that). Some 40 percent of victims are children. Rabies in people is a lot like rabies in dogs: It causes confusion, hyperactivity, excessive drooling, and delusions. The new commentary opens with a gut-wrenching photograph of a 16-year-old boy suffering through rabies; he is lying on a pillow with his eyes closed, biting down hard on a wooden stick, with three people holding him down.

If I were to get infected with rabies today, I would go to the hospital and receive a ‘post-exposure prophylaxis‘, or PEP, which is essentially a vaccine that works after the fact. In 1885, Louis Pasteur gave a version of this treatment to a 9-year-old boy bitten by a rabid dog, saving his life. These treatments are available in developing countries, but usually only for affluent people. But it’s poor people who are more frequently exposed to rabid dogs, and who don’t have access to medical facilities or money, the Science authors point out. “It is the poor who die.”

Here’s the rub: Poor people shouldn’t even need access to PEP, which is relatively expensive. The whole problem could be dealt with, just as it is here, by vaccinating dogs. So why isn’t this done?

A big part of the problem, according to the Science piece, is that in many countries the budgets and administration of veterinary medicine and human medicine are kept entirely separate. And the powers that be in veterinary medicine are primarily concerned with preventing economic losses from livestock illnesses. But rabid dogs — which tend to be domestic dogs, not strays — don’t have much effect on livestock. “As rabies does not cause a high burden of disease in livestock,” the authors write, “dog vaccination has not been prioritized by veterinary services in low-income countries.”

There are many countries where these problems have been addressed without much monetary expense, mostly in Latin and South America. They could be used as models for Asia and Africa, the authors say. Some small-scale change has been made in certain regions already. The government of Kenya, for example, has created a Zoonotic Disease Unit that includes leaders from the country’s health and agriculture departments. The unit has a coordinated, long-term strategy for combating rabies that hinges on “sustained mass dog vaccinations.”

Because the virus doesn’t move all that quickly between dogs, full vaccination coverage isn’t necessary for this strategy to work. Vaccinating just 70 percent of the dog population, in fact — which doesn’t cost much more than vaccinating 20 percent — “reduces outbreak probability close to zero,” the authors write. That means the disease can be contained even without vaccinating stray dogs. (Unfortunately, despite all this data, the first strategy against rabies tends to be mass killing of strays.)

The authors have demonstrated the effectiveness of this strategy over the past decade in Tanzania. As part of the Serengeti Health Initiative, the researchers have vaccinated thousands of dogs in 180 villages, ultimately reaching a 70 percent vaccination rate. Since the launch of the project, the number of people dying of rabies dropped from 50 a year to nearly zero.

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The researchers pose with dogs in Tanzania. From left: Machunde Bigambo, Guy Palmer, Imam Mzimbiri, Paulo Tembo, and Felix Lankester. Credit: The Allen School, WSU

I generally avoid writing stories about public health in developing countries because the problems always seem so big and so dire. Ebola, Malaria, Tuberculosis, HIV — these are crazy-difficult problems with no easy solutions. Rabies is different. It can be contained quickly and cheaply, ultimately saving money in medical costs, not to mention many human lives. All that’s needed is the political will.