Rabies

Details: Published: 03 November 2017

Rabies

You might think being in the middle of a disease outbreak turning our neighbors into slavering zombies intent on biting everything around them would make all the headlines. Well, we are in the middle of such an outbreak, but it isn’t turning our human neighbors into maddened zombies; it’s affecting our raccoon neighbors. The disease is raccoon rabies, and it’s been on the rampage since 1992.

Around the world, the majority of human rabies cases come from dog bites, but in New England, along with the rest of the United States, dog rabies is almost nonexistent. Yet we learn as children to beware of dogs and animals that behave strangely, because rabies hasn’t gone away. It still lurks in wild animal populations.

If we’re in the middle of a raccoon rabies outbreak, you might be wondering why there aren’t stories in the local papers of slavering raccoons menacing people in their driveways or while out hiking. The reason is that we have very nearly tamed the disease that was symbolic of the frenzied and untamable for centries. How have we managed this feat? Through a vaccine.

Rabies was one of the first diseases early immunologists chose for vaccine development. Louis Pasteur succeeded in 1885 using a laboratory-raised strain of the virus that was in some ways more virulent than wild virus, but had been weakened so that the immune system could defeat it. Even today modern vaccine uses real rabies virus that has been killed.

Unlike most of the vaccines we get, the rabies vaccine typically isn’t used preventatively, although high-risk groups like veterinarians might get vaccinated. Instead, the vaccine is given after a suspicious animal bite, usually in several successive doses. The reason this vaccine can prevent the disease even though it is given after exposure to the virus has to do with the unique nature of rabies.

In many ways rabies is a virus worthy of fascination. As a disease, it is unusual to humans in that we aren’t it’s target host, unlike most of the illnesses we’re at risk of getting. As a virus, it’s unusual in that it travels along the axons of the nervous system, instead of using that ever-popular biological superhighway, the bloodstream.

These two facts explain a lot about our relationship to rabies. First, rabies is always caught from an animal, because rabies’ infection strategy relies on biting. It drives animals into an aggressive frenzy where they will bite everything, but this doesn’t work in a species (like humans) that doesn’t instinctively bite from aggression. Even rabid people aren’t prone to biting other people.

Second, it takes weeks or months for the symptoms of rabies to appear. This is the time it takes the virus to travel from the site of infection (usually a bite wound) to the brain. Rabies’ slow progress through the body has become a window of opportunity for modern medicine, giving the vaccine version of the virus time to put the immune system on high alert before the real virus can get very far. This is why the vaccine can be given after someone has been bitten and still protect them from getting sick. The vaccine also works in animals and a lot of the reason rabies can seem like a disease of the past has been the high rates of preventative pet vaccination, especially for dogs.

We know the Northeast is seeing an outbreak of rabies in raccoons, but raccoons are not going to book themselves a vet appointment any time soon, so how can a vaccine help wild animals? Each year since 1997 the US Department of Agriculture’s National Rabies Management Program has been attempting to vaccinate raccoons through bait dropping. The baits, about the size of two quarters, are packets of oral vaccine covered in fishmeal. The Northeast usually has bait drops from mid-August to mid-September, both by plane and by hand. The goal of the program is to create a buffer of vaccinated animals in the wild that will slow the spread of raccoon rabies, which has been moving north and west. Eventually, the USDA hopes to eliminate rabies once and for all through wildlife vaccination.

A version of this article was published in the Northern Woodlands Magazine. Check out their website here: https://northernwoodlands.org/