An aggressive approach against rabies

THE BALTIMORE SUN

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.

Successes there led to larger efforts in other states. Today, major efforts are under way in Ohio, West Virginia, Tennessee and Alabama to establish a "buffer" of immunized raccoons along the western slope of the Appalachians and prevent the disease from spreading west.

"We're never going to wipe it out. There are too many raccoons," DuVernoy said.

Costly effort

It's also costly in time and money, she said, which is why other Maryland counties that might benefit have not gotten involved. Baltimore, Montgomery and Frederick counties each counted more rabid raccoons in 2000 than Arundel.

Authorities in Arundel targeted the Annapolis and Broadneck peninsulas because they are densely populated, and because the surrounding creeks and highways help to block the return of infected animals.

The rabies vaccine being used there this week is a liquid, contained in a plastic pouch similar to ketchup packets at fast-food stores. The pouch is concealed inside a brown, one-inch cake of fishmeal, fish oil and binders.

Attracted by the smell, raccoons bite into the bait, break open the plastic and swallow the vaccine.

Horman had no cost estimate for the 2002 campaign, but said it would probably exceed the $40,000 spent in previous years.

Each dose costs $1.27 -- a total of more than $21,000 for the 17,000 to be distributed. Labor and equipment add to the cost.

The vaccine cakes will be scattered by hand on the Broadneck peninsula, which is being targeted for the first time.

Teams of workers in fluorescent orange vests will drop them along streams and storm drains, in woods and scrubland.

On the Annapolis peninsula, they'll target only rural areas, dropping the vaccine from helicopters.

Raccoons should consume all the bait quickly, officials said.

Dogs and cats that eat them won't be harmed. People who find them should don gloves and toss them into the woods, or discard them, Horman said.

It's best to avoid contact with the vaccine, Horman said, because it is composed of a live, genetically modified vaccinia virus, the same virus used to create the smallpox vaccines routinely administered to schoolchildren before 1972.

Health authorities said there is a small risk of a skin infection similar to smallpox vaccination sores.

"Millions have been used without serious health effects," he said, "but we still don't want people [with weakened immune systems] or real young children coming into contact with it unnecessarily."

If they do, particularly if the inner vaccine packet has broken open, he said, "they should call their doctor to be on the safe side."

Residents who don't want the vaccine on their land can call the county Health Department at 410-222-7256.

Copyright © 2019, The Baltimore Sun, a Baltimore Sun Media Group publication | Place an Ad
34°