Rabies kills an estimated 55 thousand people each year, almost all of them in Africa and Asia. About half of the victims are children. The disease is transmitted to humans from infected animals, and even though effective animal vaccines exist, injections must be repeated to maintain immunity. In developing countries, inadequate access to rabies vaccines and treatments - as well as their cost - have hampered efforts to eradicate the disease. A promising new vaccine could help change all that.
Preventing rabies in dogs key to eradication
Rabies is a viral disease that attacks the central nervous system, causing symptoms ranging from hyperactivity and hallucinations to paralysis. It is fatal if left untreated.
Bernhard Dietzschold is a professor at Thomas Jefferson University in Philadelphia who specializes in nervous system viruses like rabies. He says that since 97 percent of all human rabies cases are caused by dog bites, preventing rabies in dogs is the key to eradicating the disease worldwide.
And the only way to do that, he believes, is with a vaccine that is effective for the life of the dog, after only one injection.
"Our working hypothesis is that the best vaccine[s] are actually live vaccines," he says.
Unlike so-called "killed vaccines," which only contain dead or inactivated virus, vaccines made from a live virus provide much longer-lasting protection. But up until now, live rabies vaccines came with a risk: In some cases, they could actually cause rabies instead of preventing it.
"What we have done," says Dietzschold, "is to remove all the pathogenic component[s] from these viruses, so that they become almost absolutely harmless."
Encouraging test results
So far, Dietzschold and his colleagues have only tested their new vaccine in the laboratory in mice, but they have found it to be safe, even for newborn mice and mice with induced immunodeficiencies. The vaccine is also highly immunogenic.
"That means this vaccine induces or creates a strong anti-viral, anti-rabies virus immune response."
By providing developing countries with a cheap, long-lasting way to protect against rabies in dogs, Dietzschold says the new vaccine could substantially reduce rabies transmission to humans.
Vaccine could treat humans, too
Dietzschold also believes the vaccine could also provide a new, more effective way to treat rabies in people who have been infected.
Currently, the only effective treatment is to clean the bite wound with soap and water and administer a month-long series of injections, starting on the day of infection. If treatment is initiated more than 24 hours after infection, Dietzschold says it won't work, and may even accelerate the progression of the disease.
But a person may not realize right away that they have rabies. The first symptoms don't appear until at least 10 days after infection, and in some cases, may take years to develop. Once symptoms do appear, the disease is fatal: The victim will usually go into a coma or die within a week or two.
Based on his research in mice, Dietzschold thinks the new vaccine could be effective even if treatment is not started right away.
"We believe we can […] treat people at least one week after exposure, or even at the onset of clinical symptoms."
The next step will be to test the vaccine on dogs and non-human primates. If all goes well, Dietzschold says the vaccine could be ready to begin the approval process for use in people in just a few years. His study was published online in the Proceedings of the National Academy of Sciences.