An aggressive approach against rabies

Arundel health workers set to vaccinate raccoons with laced fishmeal cakes

September 09, 2002|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

The fishmeal cakes smell awful, bad enough to nauseate the people who have to ride in helicopters and drop them into the woods.

But raccoons gobble them up, and Anne Arundel County health officials hope the vaccine hidden inside the cakes will immunize the wild animals against rabies and help to reduce the disease's threat to county residents and their pets.

This morning, weather permitting, two dozen public health employees and volunteers in Arundel -- some on foot and some in the air -- will start scattering more than 17,000 baited vaccine packets across the Annapolis and Broadneck peninsulas.

The 4-year-old project is part of a broader campaign to contain and suppress raccoon rabies, the most common form of animal rabies in the Eastern United States.

Assisted by the Centers for Disease Control and Prevention and by the U.S. Department of Agriculture's Wildlife Services, the effort is already credited with nearly eliminating the disease on the Annapolis peninsula, from Crownsville to the Chesapeake Bay.

"Before we started the program, Anne Arundel had the highest number of rabid animals ... in the state of Maryland," said Dr. Joseph Horman, the county's public health veterinarian. And 20 percent of the county's cases came from the Annapolis peninsula.

Since 1999, the year after vaccination began, Horman said, they had found only one rabid raccoon on the peninsula.

Rabies is a viral disease that attacks the nervous system. It is transmitted to pets and people by the bite of infected raccoons, skunks, foxes, bats and other mammals.

Untreated, it is invariably fatal to humans. But such deaths are rare, because of mandatory vaccinations for domestic dogs and cats, and post-bite vaccinations for people.

There were 120 rabies deaths reported nationwide in the decade between 1946 and 1955. Forty years later, from 1986 to 1995, the total dropped to 18, according to the CDC. Four deaths were reported in 2000. But the danger is always close by.

An epidemic of raccoon rabies spread north from Florida in the 1950s, aided by suburban sprawl, ready access to garbage, and human tolerance for the masked critters.

In the 1970s, raccoon rabies leapfrogged to the mid-Atlantic states, and spread explosively from there, according to Charles E. Rupprecht, rabies section chief at the CDC. It is now entrenched from the Appalachians to the Atlantic, and from Ontario to the Gulf of Mexico.

`Always a big problem'

In 1980, Maryland identified 37 rabid animals -- all of them bats. Four years later, the count had surged to 1,101, and 87 percent were raccoons.

Since then, the state has counted between 300 and 600 rabid animals annually, about three-quarters of them raccoons. And these are only the animals caught and tested. The true extent of the infection in the wild is unknown.

"Rabies is always a big problem," said Tracy DuVernoy, acting public health veterinarian for the state Department of Health and Mental Hygiene.

Hundreds of Marylanders receive rabies treatments every year after animal bites, she said. It's a costly, unpleasant experience -- up to four shots of rabies immune globulin into the bite wound, and a monthlong series of three to five vaccine injections in the upper arm. The medicine costs more than $1,000.

Health authorities are especially worried by the number of rabid cats in Maryland and the more immediate threat they pose to people. Twenty-three were found last year, up from 18 the year before, making them more common than rabid bats.

"It's very disconcerting," DuVernoy said. "Most people have the sense to stay away from wild animals, but they may not have that innate sense of avoidance with cats."

All but one of the cats was infected with the raccoon strain of the virus.

Anne Arundel County officials decided in 1997 to join the new vaccination effort, when the county led the state in rabies cases, with 97 animals testing positive for the virus.

Conceived at the CDC in the 1960s, the idea of vaccinating wild animals got its first field trials in Western Europe in the 1970s, targeting a large rabies outbreak among red foxes.

"The strategy is to vaccinate a critical mass of animals," Rupprecht said. Those animals survive, while the infected ones die, creating an immune barrier between infected wildlife and people.

"It's no different than what we are trying to do with all [human] vaccination schemes -- to break the chain and cycle of infection," he said.

Over 30 years, Rupprecht said, the vaccine "actually eliminated reservoirs [of the virus] in Western Europe, to the extent that France, Switzerland, Belgium, Luxembourg and large parts of Germany are now free of red fox rabies."

A similar effort in the United States had to wait until a vaccine effective against the raccoon strain of the virus was developed and approved. Small safety trials began in Virginia and Pennsylvania in 1990.

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