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http://www.nytimes.com/2002/08/13/science/13RABI.html

Raccoons Taking the Bait in a Push to End Rabies

By SAM SMITH

quarter-century ago, experts theorize, a rabid Florida raccoon either wandered onto a West Virginia-bound flatbed or, more likely, was relocated there by a hunting club. Whatever the vehicle, that introduction caused one of the most intensive rabies outbreaks in history.

Once confined to Florida and Georgia, raccoon rabies is now entrenched across the entire Eastern Seaboard, north to Canada and west to Ohio and Alabama.

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In the nation's most ambitious attempt to eradicate rabies from the wild, federal and state officials are trying to halt the proliferation by dropping millions of vaccine-laced pieces of bait in a virtual moat from Lake Erie to the Gulf of Mexico. After the westward push is halted, the vaccine barrier will be moved eastward until, organizers hope, raccoon rabies is snuffed out against the Atlantic.

Over the past century, efforts to prevent rabies in the United States were largely directed at domestic animals, which represented the bulk of the reported cases before 1960.

With new injection vaccines and a new attitude toward the efficacy of vaccinating animals, the balance shifted. Today, domestic animals contribute just 10 percent of the cases, and rabies-related human deaths have consequently dropped, from more than 100 a year in the early 1900's to about two a year in the past decade.

Yet 40,000 people in the United States are treated for rabies exposure every year, primarily from contact with rabid wildlife, which has proved difficult to vaccinate on a large scale.

An oral vaccine, a capsule wrapped in bait (smelly fish meal for raccoons) and dropped by the hundreds of thousands from aircraft, has shown promise, particularly in Europe.

Switzerland, which has been using oral vaccines for more than 20 years, has been declared rid of rabies two times. France, which is generally thought to have reinfected Switzerland, is now declared rabies-free, too, because of oral vaccines. Across the European Union, 15 million pieces of bait are dispersed annually.

The first large-scale trial for the vaccine in the United States was in Texas, where, by 1995, coyote rabies was spreading from the Mexican border at the rate of 50 miles a year and had reached the suburbs of San Antonio.

"We estimated that only 25 percent of pets in San Antonio were vaccinated," Skip Oertli, director of the state's oral vaccine program, said. "If it got into there, we felt sure we would have human deaths."

That year, 850,000 pieces of bait were dropped in a huge arc from Corpus Christi to San Antonio and down to the Rio Grande. Each year, the barrier, and the rabies, was pushed south. Today, a buffer of oral vaccines is maintained along the Mexico-Texas border, and there have been no documented cases of coyote rabies in the state since 1999.

For the Eastern effort, the first phase started in Ohio, which had its first case of raccoon rabies in 1996. By the next year, the state had a 10-mile-wide oral vaccine barrier along the Pennsylvania border.

That barrier, which is fortified every year with 600,000 pieces of bait, has been extended into West Virginia. This year, it will be stretched to eastern Tennessee, where it will join the Appalachians, a natural barrier.

Alabama is determining the leading edge of its raccoon rabies' westward movement, and next year the vaccine barrier will be extended through the state.

It is to be 30 miles wide and will involve five million pieces of bait at a cost of $1.27 each.

A financial analysis by the Agriculture Department, the lead agency in the effort, says the high cost is outweighed by the cost of additional prevention in uninfected Western states.

"A big concern is trying to get everybody to buy in," Dr. Dennis Slate, rabies coordinator in the department, said. "There is still some debate in some states as to whether this is a valid way to go and if the cost is justified."

Maine, which would be asked to assist as the barrier is pushed east and which has rebuked Canadian pressure to establish an oral vaccine barrier on their shared border, continues to balk.

"We don't see an urgent health concern," Henry Hilton, wildlife manager at the Maine Department of Inland Fisheries and Wildlife said, adding that "people aren't dying" of raccoon rabies.

What people are dying from is bat rabies. Of the 26 rabies deaths since 1990, 24 have been from bat bites, most of which were unnoticed or ignored.

"People look at such a small bite and don't realize they could be infected from it," said Dr. Charles E. Rupprecht, chief of the rabies section at the Centers for Disease Control and Prevention. "Or they don't even know they've been bitten."

The number of infected bats found by the authorities reached a record 1,240 in 2000, the last year with available numbers. No effective oral rabies vaccine has been developed for bats. Public health officials have instead focused on education.

"We're doing what we can with bat rabies," Dr. Slate said. "But if we can remove the raccoon variant, that will just get rid of some of the noise, and we can focus more on other things like bat rabies."

In Ohio, which has spent more than $6.5 million on an oral vaccine barrier, uncertainty is being voiced over the chances of banishing raccoon rabies. The number of cases has dropped there, to one last year from 50 in 1997. But a state wildlife biologist involved in the effort, Chris Dwyer, wondered whether the oral vaccine was the reason.

"It makes you question how effective this is when it's estimated that only 30 percent of raccoons are coming in contact with the vaccine," Mr. Dwyer said. "That's a pretty small percentage of the population."

A greater concern for him and others surrounds the wily nature of the disease. Some evidence suggests that raccoon rabies remains virulent in skunks, and no effective oral vaccine has been developed for them.

If that is the case, the reservoir of raccoon rabies will be maintained, Mr. Dwyer said, regardless of the oral vaccine effort.

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