The risk of rabid raccoons
Using marshmallow treats to fight a deadly disease
BIOLOGISTS are testing a new weapon in the war against rabies. More than 1m marshmallow-flavoured packets of ONRAB, a trial vaccine designed to be eaten by raccoons, skunks and other furry critters, have been dropped from aircraft or placed by hand in five northeastern states in recent weeks.
Field trials of ONRAB by the Department of Agriculture began in 2011 in West Virginia. Last year, the test area expanded to include New Hampshire, New York, Ohio and Vermont. This year it included a larger area in New York.
The tests are part of a long-running campaign to control rabies, a virus transmitted through saliva that attacks the central nervous system. It makes animals go mad and bite things. In humans, it is almost always fatal if untreated. The government started a national rabies management programme in 1997, after the threat shifted from domestic pets to wildlife. Tame dogs are easy to vaccinate; wild raccoons are not. (Unless you hide the vaccine in your trash can, presumably.) Control efforts have focused mostly on raccoons in 15 states from Maine to Alabama, says Richard Chipman, the programme’s coordinator.
America sees about 6,000-7,000 rabies cases annually, the vast majority among wild animals, and two to six human deaths, down from more than 100 a century ago. Globally, rabies kills about 60,000 people a year; most catch it from dog bites.
In America just one oral vaccine, Raboral V-RG, has been approved for use in wildlife. Over the years, field workers have distributed some 135m doses of the fishmeal-scented stuff, scattering it from small planes, helicopters and car windows, and also placing it by hand. Weeks later, they trap hundreds of animals, take blood samples and examine their teeth for stains that indicate that they have eaten one of the packets. “It’s very much a muddy-boot kind of operation,” Mr Chipman says. But while Raboral V-RG has worked well in coyotes and foxes, it has failed to eliminate the virus in raccoons and skunks.
Enter ONRAB. In Canada, where it is already used, it appears to have been effective. In America, too, the results are promising: immunisation rates among raccoons have risen from 30% to 49% in test areas, says Mr Chipman. Next month, workers will begin trapping animals to measure this year’s results.
Left unchecked, rabies could spread far and wide, which would raise the cost of tackling it. At $1.65 a packet, the vaccine will be excellent value for money—if it works. “We want to march [raccoon] rabies all the way back to the ocean and eliminate it,” says Mr Chipman.
From the print edition: United States