Chacha, a farmer and businessman from northern Tanzania, returned home from market one afternoon to find that his family’s newly adopted puppy had bitten five of his children. The puppy had been playful that morning, but by the evening it was clear that its behaviour was abnormal, snapping at any passing movement and running with an awkward disorientated gait. The puppy was euthanised and tested positive for rabies.
Chacha then faced a terrible dilemma; at more than US$100, one course of life-saving vaccination was more than his annual income, so Chacha had to choose which of his five children would get the vaccine.
Post-exposure vaccines are the only lifeline guaranteed to prevent the onset of rabies, if delivered promptly following the bite of a rabid animal. But they are not provided for free in most developing countries. These vaccines are very expensive and hard to find, and often only accessible from capital cities or major urban centres.
Chacha’s dilemma is not unique. More than 50 people are bitten every minute from a rabid dog. Rabies was eliminated in the UK rabies well over a century ago, and if you live in a developed country it is easy to think of it as a disease of history. But every few years, a shocking news story covers a rabies death on home turf, typically acquired by the victim after being bitten by a dog while on holiday. In contrast, more than 50,000 people die every year of rabies following a bite by a rabid dog in Africa and Asia, and it is children who are most at risk.
About 20% of bite victims develop rabies, but the probability gets higher the worse the bite, for example from deeper and/or multiple wounds, and the closer it is to the brain and central nervous system. A bite leads to distressing and unnerving symptoms: initial pain and stiffness starts at the site of the wound, followed by fever, delirium, aggression, strange and uncontrollable vocalisations and inevitable and rapid progression to death. It is no coincidence that your classic scary movie (think zombies, werewolves, vampires) shares more than a passing resemblance to rabies. It is a disease that strikes terror into communities and, to this day, without treatment it is the disease that has the highest known fatality rate (100%). This makes succumbing to rabies especially traumatic as victims pass in and out of periods of lucidity and understand their condition, but know that there is no hope.
This disease of the nervous system, which causes animals to bite and transmit infection is straightforward to control. Mass vaccination interrupts transmission in the reservoir population, which in developing countries is domestic dogs.
Other species are accidental hosts and short-lived chains of transmission may happen in these species. The slight complication is that different rabies (or rabies-related) variants do circulate in bats and some other terrestrial carnivores (for example raccoons in the US), but these pose much less risk to people since we hardly ever touch them. This seems to pose a real psychological barrier as to why people think rabies is actually much harder to control than it is. In fact, if it was eliminated from dogs then the rabies virus that causes more than 99% of human rabies deaths around the world today would disappear entirely.
To do this, we need to reach at least 70% of dogs vaccinated, during sustained vaccination campaigns. This is how rabies was eliminated from most industrialised countries. However, the same effort has not been put into dog vaccination in developing countries. Instead, health services strive to provide post-exposure vaccination, but often at great cost to bite victims, such as Chacha’s family.
Great strides have been made in the development of human vaccines to prevent rabies. These previously required a series of very painful injections into the stomach, with occasional adverse events that caused serious neurological problems. Human rabies vaccines today are extremely safe (nerve tissue vaccines have been phased out around the world except for a handful of countries), and new regimens are making them less costly, but they still require repeat hospital visits. The problem remains, though, that not every bite victim gets vaccinated and so deaths continue.
Doggy vaccines cheaper
Dog vaccination is a more cost-effective measure to prevent rabies, not least because animal vaccines are much cheaper than human vaccines.
Eliminating rabies from dogs means that no family, however poor, has to suffer from the panic and anxiety of a suspect exposure. Thanks to millions of dog vaccinations delivered every year rabies is close to being eliminated from the entire American continent. It was eliminated from dogs in North America several decades ago, but occasional reintroductions occurred across the Mexico border every few years. Cases in Latin America and the Caribbean have been declining every year. The only places with continued transmission are the poorest (Haiti and Bolivia), which tells you a great deal about what rabies elimination actually requires. But the situation in the Americas serves as an excellent example of just what is possible, given financial and political commitment.
The Global Alliance for Rabies Control is advocating just such a strategy for developing countries where rabies remains endemic in domestic dogs. However, linking the fragmented (underfunded) veterinary sector with the similarly fragmented human health sector in the parts of the world where rabies is most prevalent requires capital investment for rabies vaccination to become a obligatory part of routine veterinary services, as well as community ownership and political momentum. Nonetheless it is possible, we just need to mobilise political will.
One happy ending
Luckily for Chacha’s family, they all managed to get vaccines. Because of the incidence of rabies the local government had recently requested more vaccines stock. These had just arrived when Chacha made it to hospital and were given out free. So, amazingly, Chacha’s family got their first vaccine doses for free and he was later able to sell a cow to raise money for subsequent doses. It was a happy ending for this family, however it is unusual. But being rabies free can become a reality for others with increased dog vaccinations.