World Rabies Day

September 8th was world rabies day. In the United States, this was celebrated with the news that the canine rabies strain appears to be eliminated from this country. In the U.S., rabies in both humans and domestic animals remains rare, though the virus remains endemic in several species of wildlife (especially raccoons, skunks, and bats). However, worldwide, rabies remains a significant public health problem, causing an estimated 50-60,000 deaths per year worldwide--one death every ten minutes. More after the jump...

First, the news about the U.S. and dog rabies. Like most viruses, rabies has genetically distinct strains--and it's just the "dog strain" of this that the article linked above refers to. This hasn't been seen in the United States since 2004, leading the CDC to officially declare it eliminated from the U.S. Though rabies virus still circulates in many species of wild mammals, this news represents a step forward, because it's the dog strain that's historically caused most disease in humans.

Other good news on the rabies front comes via a recent letter in the New England Journal of Medicine. You may remember the case of a 15-year-old Wisconsin girl who was bitten by a rabid bat, and then survived rabies encephalitis after being put in a coma and treated with antivirals. (Original NEJM article here). They've now followed the girl for over 2 years, and her condition is excellent. She graduated high school and is off to college without any apparent long-term effects on learning or memory. She still has some difficulty with movement, but they note that "she had no difficulties with her instrumental activities of daily living, including driving," and "had no problems with peer relations or mood disorders."

However, while the news is good for her, the results haven't been replicated--at least 4 others have died since despite treatment.

While human rabies is a rarity in the U.S., it's much more prevalent in developing countries, including parts of Africa, Asia, and Latin America. As the WHO notes, even the 50-60,000 cases per year is probably an underestimate:

For example, in Tanzania, incidence of human rabies mortality was estimated to be about 1500 deaths per year (4.9 deaths/100 000 persons) when calculated from active surveillance data on bite incidence, but national statistics reported only 193 deaths per year (0.62/100 000)

And these deaths are despite the approximately 10 million doses of post-exposure prophylaxis administered every year to individuals who've had contact with an infected animal. Most bites come from infected dogs, and most of the victims are children. As noted on the World Rabies Day website:

[Children] are more likely to be bitten by dogs, and are also more likely to be severely exposed through multiple bites in high-risk sites on the body. Severe exposures make it more difficult to prevent rabies unless access to good medical care is immediately available.

As experience in the U.S. and other countries shows, rabies in dogs can be almost completely eliminated via good vaccination campaigns, coupled with good medical care for those exposed to the virus. However, in many other areas of the world, cultural views on dog ownership make it difficult to have high vaccination coverage, and health care resources are lacking in areas where rabies deaths are high.

To draw attention to this public health issue, communities around the world are using World Rabies Day to hold events and educate citizens about the issues surrounding rabies: the virus, the disease, its transmission and control. It's not something that will go away overnight, but human rabies is something that could be much more easily eliminated than some other neglected diseases, since we do have an effective vaccine that works even after exposure to the virus. Unfortunately, what we're lacking now are the widespread knowledge about the virus and what to do in the event of an exposure, and the way to get the vaccine reliably and quickly to those who need it. The reduction of rabies cases in the human population isn't a scientific issue--it's now political and cultural, and raising awareness of the issue is one way to work at combating that.

References

Willoughby et al. 2005. Survival after Treatment of Rabies with Induction of Coma. NEJM. 352:2508-2514.

Hu et al. 2007. Long-Term Follow-up after Treatment of Rabies by Induction of Coma. NEJM. 357:945-946.

Image from http://www.worldrabiesday.org/downloads/logo/WRDEngFinal_Round-4c.png