The world’s deadliest human disease is not Ebola but rabies, which still kills at least 70,000 people every year – probably many more, some say, mostly in poor parts of Asia and Africa.
Scientists at Washington State University who specialize in zoonotics – diseases that pass between animals and humans (aka, most diseases) – say we have the tools and the opportunity to rid the world of human rabies through a concerted and targeted vaccination campaign focused on dogs.
“Rabies is the most uniformly fatal disease known to mankind,” said Guy Palmer, director of WSU’s relatively new Paul G. Allen School for Global Animal Health located in Pullman, WA. It’s not a new area of study for Palmer and his colleagues, but the center funded by the former co-founder of Microsoft (who has also recently donated $20 million to the Ebola fight in Africa) promotes a somewhat unique approach to fighting disease.
Given the public fear generated by the outbreak of Ebola in West Africa, where the fatality rate has lately been estimated at about 70 percent with nearly 3,000 deaths, you’d think a more deadly and ubiquitous infectious disease that causes tens of thousands of deaths would merit equal attention.
But new disease threats get the headlines. And Ebola is almost certainly also a zoonotic disease, with some speculating that fruit bats are the most likely source. Nobody really knows.
“It’s estimated that something like 60 percent of human diseases come from animals,” said Palmer, noting that this is still a rough estimate and if human diseases were looked at from an evolutionary perspective the proportion that could be called ‘zoonotic’ represent the vast majority. Yet most of our efforts to combat disease still split into isolated categories – human, livestock and wildlife health.
“We try to look at disease and health, global health, from the perspective of the human-animal interface,” Palmer said. “Zoonotics is about bridging these categories because the tendency to compartmentalize diseases as if they are only human or only animal means some important problems get neglected.”
“Rabies is a perfect example in that it is doesn’t have a major economic impact on livestock so ministries of agriculture ignore it,” he said. “It doesn’t rise to the same level of burden as many other human diseases, so ministries of health ignore it. It tends to be viewed mostly as a wildlife health issue, but this ignores the significant societal burden – not to mention the fear this disease generates in communities where it remains a deadly threat.”
In this week’s Science magazine, Palmer and his WSU colleagues, including researchers in Tanzania and Scotland, make the global health case for vaccinating the planet’s dogs against rabies – as the best strategy for reducing the human health threat down to near zero.
“Rabies is endemic in the United States, in wildlife, yet we have almost no human disease because we vaccinate our domestic dog population,” Palmer said. Britain, he noted, has no rabies at all. The vaccine for dogs is very effective and has been around for more than a hundred years. And the human disease burden of rabies, Palmer and his colleagues wrote, is probably much greater than the official estimates:
“The true incidence of rabies is estimated to be between 20 and 160 times what is officially reported,” they say in Science, because those most afflicted live in poor communities without access to health services (and the epidemiologists who track disease).
“Rabies is a neglected disease that creates an incredible burden on these communities,” Palmer said. “We have the tools to do something about it and I think there’s a strong social justice case to make for doing this.”
In the report, Palmer and his colleagues lay out the strategy for how to rid the world of human rabies. It is not possible to eradicate the virus, he said, because it is found in so many different animals (including bats). But the main source of human disease is domesticated dogs. A worldwide campaign to vaccinate domesticated dogs, the researchers contend, is economically and technically feasible.
Successful, recent rabies vaccination efforts across Latin America, and in some parts of Africa and Asia, show that reaching just 70 percent of the dog population with immunization is usually sufficient to stop the animal-human transmission of the disease in the community. This still means reaching millions of dogs and a coordinated “zoonotic” disease campaign with human and animal health workers acting in concert. The researchers say it would likely cost hundreds of millions of dollars.
But then again, the world could easily end up spending more than a billion dollars to deal with Ebola in West Africa – just to stop this one outbreak.
“We can’t totally wipe out rabies like we did for smallpox,” Palmer said. “But we can eliminate it as a public health burden, as a human disease.”
And help the world’s dogs in the bargain.