The University Record, May 6, 1998

Racoon rabies headed toward Michigan

By Sally Pobojewski
News and Information Services

A new rabies epidemic transmitted by wild raccoons is virtually certain to move across northern Ohio into Michigan, according to Mark L. Wilson, associate professor of biology and epidemiology. The only question is when the first Michigan raccoon will be exposed to the virus.

The raccoon strain of the rabies virus is no more deadly than other types of rabies already found in Michigan's skunks and bats. Public health experts are concerned, however, because this viral strain's primary host is the raccoon. Attracted by a ready food supply of pet food and garbage, dense populations of raccoons live in close proximity to humans in many areas throughout the state.

"Much of Michigan is prime raccoon habitat," says Wilson. "Raccoons prefer suburban wooded residential areas over areas of intensive agriculture. So the epidemic, now expanding into northeast Ohio, is likely to spread west and north into Michigan."

Wilson began studying raccoon rabies in the early 1990s while he was at Yale University in New Haven, Conn. Working with other scientists at Yale and officials from the state's public health department, Wilson tracked the raccoon rabies epidemic as it spread across Connecticut from March 1991 to December 1996. Raccoon rabies first appeared in Florida in the 1950s and has been moving north through the mid-Atlantic states and New England ever since.

"Before 1991, no rabid animals had been identified in Connecticut for more than a decade," Wilson says. "Over the next four years, Connecticut officials reported 2,612 rabies-positive animals--most of which were raccoons. More than 80 percent of these animals were found in property owner's yards. During this same period, 939 people were exposed to the virus usually by handling a pet that had just fought with a rabies-positive animal."

The first documented case of raccoon rabies in northeast Ohio occurred in April 1997, according to the Ohio Department of Health. Since then, 75 additional cases have been recorded. To try to prevent the epidemic from spreading, the Ohio Department of Health began distributing bait containing an oral rabies vaccine around the perimeter of three northeast Ohio counties.

"Ohio is attempting to create a firewall of immune raccoons to stop the spread of the epidemic," Wilson says. "Unfortunately, baiting programs are expensive and they must be continued indefinitely, since new animals are continually being born or moving into the area. Baiting may slow the spread of the epidemic, but it is unlikely to stop it forever."

One of the biggest dangers to the success of any baiting program is people's tendency to trap nuisance raccoons and release them many miles away in another area. "All it will take is one infected raccoon transported past the baited perimeter to blow everything," Wilson says. "We saw this happen in Connecticut when the leading edge of the epidemic suddenly jumped 60 miles from the last known point of infection. The most likely explanation was that infected raccoons were unintentional stowaways on garbage trucks making deliveries to a large landfill in the area."

The best way to prepare for the spread of raccoon rabies into Michigan, according to Wilson, is to use common sense: make sure your pets have current rabies vaccinations. Don't leave pet food or open garbage cans outside. Avoid any contact with wild raccoons. Above all, don't adopt raccoons as pets and don't trap-and-release animals to another area.

Wilson is a member of a panel of experts appointed by Gov. John Engler to determine what measures the state can take to prepare for and respond to the raccoon rabies epidemic if it reaches the state.