When you were growing up, your parents may have told you to stay away from stray or wild animals. Along with hand washing before eating, this was one of their smarter warnings, because animals can harbor rabies, a deadly virus with no cure. But that may change soon.
A research study published at the end of September may offer the first glimpse of a future cure for rabies. My colleagues at the Uniformed Services University of Health Sciences tested a human monoclonal antibody, F11, against a rabies virus adapted to infect mice. The researchers infected mice and then gave some a single dose of F11. Of the mice that received the F11 on day five, 67% survived, while 50% of mice that received it on day seven survived. The untreated controls died. That was an incredible finding.
Why Is This Big News?
Rabies (Latin for madness) is essentially 100% fatal, meaning it is deadlier than Ebola and the plague. Coincidentally, given its high fatality rate, the virus appears shaped like a bullet when viewed through an electron microscope. If someone has an exposure to rabies, they should seek immediate preventive therapy. If they’re infected and wait for symptoms, it is too late. There is no treatment at that point. This new study could lead to not just a preventive treatment, but a future cure.
Where Does Rabies Occur?
In the United States, rabies infects the occasional dog or cat, but we mostly see it in wild animals like raccoons, skunks, foxes and bats. Most people don’t have direct contact with those animals, but their pets do. By ensuring pets are vaccinated, we reduce the chance that they’ll bring rabies to their owners. In the United States alone, a study a few years ago estimated an annual average of over 46,000 emergency room visits for rabies postexposure management at a cost of greater than $165 million. Because of animal vaccination and human exposure management, there are only an average of one to three cases of human rabies each year in the United States.
In other parts of the world where vaccination isn’t as widespread, though, rabies does occur in stray animals (usually dogs), so it is important to be extra cautious while traveling. Every year, approximately 59,000 people die from rabies all around the world after being bitten by a rabid animal, according to the U.S. Centers for Disease Control and Prevention. The CDC does an annual assessment of the status of rabies in individual countries, so travelers can search by countries of interest.
How Does Someone Get Rabies?
Rabies causes a fatal infection of the brain. Animals that are infected can shed virus in their saliva and therefore transmit it by a bite or scratch. The virus reproduces locally at the site of the bite and eventually enters a nerve. It then travels up the nerve to the brain. Once inside the central nervous system, preventive measures are no longer effective and there is no treatment.
What Are The Signs Of Rabies?
Animals with rabies may not act normally. A previously friendly pet might become aggressive and attack people without being provoked. A stray animal that usually avoids humans may lose its fear and approach people. Rabid animals can also experience excessive drooling. Humans with rabies may experience weakness, fever or headache early on. As the illness progresses, they may develop agitation, muscle spasms, difficulty swallowing, become delirious and have hallucinations and difficulty sleeping before becoming comatose.
One strange phenomenon seen in infected animals or humans is called “hydrophobia,” fear of water. This is caused by spasms of the muscles used in swallowing, which makes it difficult for victims to swallow their own saliva in addition to water. The mere sight of water can prompt a victim to suffer choking spasms.
How Can I Prevent Rabies?
Those with a risk for rabies due to their work with animals or travel to high-risk areas should receive two doses of vaccine for protection. If someone sustains a risky animal bite or scratch and has not been vaccinated, the first thing to do is thoroughly clean the wound and then receive a rabies vaccine. An additional three booster shots are given over the next two weeks. On the day of the first vaccine, rabies immune globulin (antibodies to rabies) is given with half the dose injected at the site of the bite wound and the rest is given in the arm opposite the one that received the vaccine. This is a highly effective combination to prevent rabies.
Travelers who receive the vaccine in advance of an exposure reduce the urgency of receiving the immune globulin in a foreign land, where it may be unavailable, expensive or potentially given under less-than-optimal conditions. Because the clock is ticking after someone is bitten by a rabid animal, delay in preventive therapy can be deadly.
How Could This New Finding Change Rabies Treatment?
Surprisingly, the F11 antibody did not prevent infection of the brain. However—and here is the best news—even after the mice became ill and developed “robust” infection in the brain, some of the treated mice still survived. Even though the monoclonal antibody was too large to enter nerves or the brain directly, it was clear that it worked hand in glove with a robust immune response to fight the disease.
Having a single-dose treatment could be lifesaving for those 59,000 people infected with rabies worldwide. Of course, this study was only done in mice, so there is much work to be done to determine whether a similar approach could eventually work against rabies in humans, but it shows proof of concept for a potential cure that could someday be a game changer.
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