Wednesday, January 16, 2008

A Preventable Epidemic of Rabies

by Olivia Judson
The New York Times
January 15, 2008

Blogger's note: Rabies prevention is just one of countless ways that the US could be spending its trillions to benefit the world instead of on war. Help support a US Department of Peace.

On June 26, 2007, a dog walked into Lupiro, a small village in southern Tanzania. It bit eight people and 11 other dogs before anyone managed to kill it. It had rabies or, as the French call it, la rage.

Neither of the nearby hospitals had any vaccine. The closest place with a supply was a private clinic in Dar es Salaam — a 9-hour drive away. The clinic had enough for a full course — five doses — of vaccine for two people, or a single dose for each person. It would be $40 per dose. In Tanzania, the average income per person is just $340 a year, and Lupiro is in one of the poorest regions.

Exposure to rabies requires immediate treatment: the first dose of vaccine should be taken the day you are bitten; every hour counts. Full treatment requires the four remaining doses to be taken, on a schedule, over the course of the month. In addition, if it’s available, rabies immunoglobulin — antibodies that can attack the virus at once — should be injected at the wound. For although not all bites from a rabid animal lead to infection, you won’t know if you’ve been infected or not. If you have been, and you do not get treatment, you will die: rabies is fatal. And it is a horrible death...

[read more details of the trauma of rabies here]

...Each year, the disease kills about 55,000 people — that’s 150 a day — almost all of them in the poorest parts of Africa and Asia, and more than 7 million people receive post-exposure treatment after being bitten by a rabid animal. Treatment is not just expensive, but time-consuming: a full course of vaccination requires five visits to a hospital or health clinic during one month. Which, if you live in rural Africa, can mean many hours of travel and time not working. Indeed, the global economic cost of rabies is estimated to be more than $583 million. And that doesn’t count the trauma that deaths from rabies inflict on families and communities. For though rabies kills many fewer people than malaria, it causes far, far more fear.

And here’s the most shocking thing about rabies: all the deaths could be prevented. Rabies could be eliminated in as little as five years. We have the knowledge and the tools. All that lacks is the will.

The virus can infect a variety of mammals, including bats, raccoons, skunks, foxes and mongooses. But by far the most important source of human rabies is the domestic dog. (This is why children are so often the victims: being small, they are more likely to be bitten on the head or the neck, and such bites carry the biggest risk of infection.) To eliminate the disease from humans, therefore, it needs to be eliminated from dogs. And the way to do that is through dog vaccination. (At first, it may seem perverse to vaccinate dogs rather than humans, given that it’s humans we want to protect. But because rabies is spread by dogs, not people, we can’t break the chain of transmission unless we vaccinate the animals that spread it.)

The crucial factor in predicting the spread of an infectious disease is a quantity known as the basic reproductive number, or R0. Technically defined as the average number of infections one sick individual will cause if everyone else is susceptible, it’s a measure of how easily a disease spreads. If R0 is smaller than one, the disease can’t get going. The bigger R0, the more difficult the disease is to control.

For rabies in dogs, current estimates put R0 at less than two. This is good news. With such a small R0, the proportion of dogs you need to vaccinate is only 70 percent. We know dog vaccination on this scale is feasible: programs in Kenya, Tanzania and Chad have shown that high levels of cover can reliably be reached. Moreover, it works. After two big vaccination campaigns in the northwest of Tanzania, for instance, dog rabies fell by 97 percent, and 90 percent fewer people were being bitten.

And vaccinating dogs is cheap. The vaccine costs about $1.50 per animal, and that includes the cost of delivering it. A country like Tanzania has around 5 million domestic dogs. To vaccinate 70 percent of them for one year would cost less than $6 million. That is a lot for governments in poor countries, but very little for us in the west. Better yet, since rabies carries such a large economic cost, a dog vaccination program would soon begin to pay for itself: as exposure to rabies falls, so does the demand for treatment, and thus the expense of handing it out. On the other hand, doing nothing will actually make the current problem worse. In countries such as Tanzania, the dog population is growing fast. If the dogs are left unvaccinated, more dogs means more people will be exposed to rabies.

Is it possible to send rabies the way of smallpox, and drive it from the face of the Earth? Probably not. Rabies can lurk in too many different species. However, it is eminently feasible to eradicate it from dogs, and thus drive the number of human cases close to zero.

In principle — if we were super-organized — we could do this with one huge and coordinated dog vaccination campaign. More realistically, however, a concerted effort would take four or five years to do the job. Would vaccination programs need to be maintained indefinitely? Not necessarily. That depends on whether the disease is likely to be reintroduced to dogs from another species. And in most parts of Africa, for example, it isn’t: the disease spreads from dogs to other kinds of wildlife, not the other way around.

So many of the problems we face are huge and hard to solve — climate change, malaria, war in the Middle East, destruction of the rain forests. Rabies is not on that list. To deal with it is just a matter of logistics and money. We should act. Now.

Copyright 2007 The New York Times Company

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