Mike the Mad Biologist

Olivia Judson describes what it would take to prevent almost all rabies deaths from Africa (rabies currently kills around 55,000 people annually):

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.

When you read the piece, Judson’s frustration is evident. We could do this: there’s no missing cure that’s needed. This is simply a matter of logistics. It’s the same frustration I’ve expressed when we fail to vaccinate enough people, and the right ones, against the annual influenza epidemic:

….we don’t need a medical or technological breakthrough that might or might not happen. We also don’t need behavioral modification, such as STD awareness or smoking cessation campaigns. And, while behavioral modification is worth pursuing, the number of lives saved is relatively modest compared to vaccination (it’s not like AIDS or lung cancer have gone away).

With annual influenza, all we need is more vaccine stuck into the appropriate people. There’s no new technology to develop (although cell-based culture would be an improvement). Once a person is vaccinated, there’s no behavioral modification needed. We could have an effective vaccination strategy up and running in two to five years (being a pessimist, I’ll say five). A couple of years to increase vaccine production facilities, two years to work out the distribution kinks, and year five, it works.

There are very few problems can be solved solely by throwing buckets of money at them (although buckets of money are either helpful or necessary). Annual influenza is one of those problems than can be solved simply by investing more resources. That’s why this is so frustrating: it is utterly within our power to save roughly 28,000 lives, and yet we fail to do so.

That we do neither of these things is shameful. And murderous.

Comments

  1. #1 Anon
    January 22, 2008

    A small comment, on the last quote.

    Vaccinating (and getting vaccinated) are behaviors as well, and are subject to environmental contingencies. Behavior modification techniques can be (and have been) used to examine the contextual reasons why people do or do not get vaccinated. Knowing what manipulations will increase vaccination rates and which do not allows us to concentrate money and effort where it will do the most good. Unfortunately, the public perception of Behavior Modification is only barely past the Clockwork Orange stereotype, so a very effective tool is dismissed before it gets a chance.

  2. #2 Nancy Reyes
    January 22, 2008

    Actually, the way to get rid of rabies is not merely to vaccinate, but to shoot the unvaccinated stray dogs.

    The sad secret is that after independence, much of the increase of African rabies was due to lack of money for bullets and sharpshooters. SIGH.

  3. #3 şişme bebek
    June 8, 2009

    Vaccinating (and getting vaccinated) are behaviors as well, and are subject to environmental contingencies. Behavior modification techniques can be (and have been) used to examine the contextual reasons why people do or do not get vaccinated. Knowing what manipulations will increase vaccination