Extension of the Raccoon Rabies Epizootic -- United States, 1992

Raccoon rabies, epizootic among raccoons in the southeastern and mid-Atlantic states, has become an increasingly important problem in the northeastern United States. The extension of the epizootic was largely responsible for the 43% increase in the total number of reported cases of animal rabies in the United States from 1990 (4881) to 1991 (6975). In 1991, 3079 cases of rabies in raccoons were reported, the largest number reported in the history of animal surveillance in the United States. This report summarizes the extension of the epizootic into six additional states since 1989.

Connecticut. The raccoon rabies epizootic was first detected in Connecticut in March 1991, when a rabid raccoon was found in Ridgefield, which borders New York state. As of August 31, 1992, the number of confirmed animal rabies cases associated with the epizootic was 508, compared with 193 in 1991. Of the 1085 raccoons tested in 1992, 456 (42%) were positive for rabies. Rabies has occurred in domestic animals (eight cats, two sheep, and one dog) for the first time since the 1940s. Cases have now been confirmed from 64 of Connecticut's 169 cities. In June 1992, a case of raccoon rabies was confirmed in Scotland, less than 20 miles from the Rhode Island border.

New Jersey. Since the raccoon rabies epizootic was first detected in New Jersey in November 1989, more than 1880 cases of animal rabies have been diagnosed, with 460 cases in 1990, 983 in 1991, and 420 as of July 14, 1992. New Jersey had been free of terrestrial rabies since 1956, when the last case of canine rabies occurred. Most rabies cases since 1989 have occurred in raccoons (1565), followed by skunks (192); cats (57); groundhogs (41); foxes (14); deer (five); domestic rabbits (four); cattle (three); sheep (two); opossums (two); beaver (one); black bear (one); and horse (one). The epizootic currently affects 18 of 21 counties, with only the southernmost counties of the state unaffected.

New Hampshire. On April 6, 1992, a raccoon caught in Rumney, New Hampshire, was confirmed infected with the mid-Atlantic strain of the rabies virus by CDC. The raccoon was wearing two flea collars, suggesting it had been a pet. No owner was found, despite door-to-door canvassing in the area. As of August 31, no other rabid raccoons have been identified.

New York. The raccoon rabies epizootic was first detected in New York in the summer of 1990 and now extends on a 350-mile front involving 24 counties of southern New York. Recent cases in the Albany area, 60 miles north of the rabies front, suggest that translocation of raccoons remains a problem. In 1991, 666 raccoons were confirmed rabid with extensive spillover to other wild and domestic species. As of July 31, 1992, 804 (44%) of 1818 raccoons tested for rabies have been confirmed rabid. The number of persons receiving postexposure rabies prophylaxis increased from 84 in 1989 to 197 in 1990 to 965 in 1991. During the first half of 1992, 589 treatments were administered, a 60% increase over the same period in 1991.

North Carolina. In North Carolina, the first rabid raccoon was found on June 18, 1991, in a county bordering Virginia. During 1991 in two northeastern counties, 12 raccoons and one fox were found to be rabid. The epizootic now involves four additional counties. The rabies epizootic entered southern North Carolina in June 1992. Through July 31, five raccoons and four foxes have been confirmed rabid in two neighboring south-central counties adjoining South Carolina, including the Charlotte metropolitan area, representing the first extension of a rabies epizootic into a major population center of North Carolina.

Ohio. On March 4, 1992, the West Virginia State Rabies Laboratory confirmed rabies in a raccoon from Martins Ferry in Belmont County, Ohio. CDC later confirmed the raccoon strain of the rabies virus, the first documented case from Ohio. Martins Ferry borders the Ohio River across from Marshall County, West Virginia, where a dog was found to have the raccoon rabies strain in June 1990. As of June 30, 1992, 15 animals from Belmont County were submitted for rabies testing. Of these, one bat was positive for rabies.

Reported by: ML Cartter, MD, JL Hadler, MD, State Epidemiologist, Connecticut State Dept of Health Svcs. MG Smith, MD, State Epidemiologist, Div of Public Health Svcs, New Hampshire State Dept of Health and Human Svcs. FE Sorhage, VMD, KC Spitalny, MD, State Epidemiologist, New Jersey Dept of Health. JG Debbie, DVM, DL Morse, MD, State Epidemiologist, New York State Dept of Health. JL Hunter, DVM, JN MacCormack, MD, State Epidemiologist, North Carolina Dept of Environment, Health, and Natural Resources. KA Smith, DVM, TJ Halpin, MD, State Epidemiologist, Ohio Dept of Health. SR Jenkins, VMD, Virginia Dept of Health. LE Haddy, MS, State Epidemiologist, West Virginia Dept of Health and Human Resources. Viral and Rickettsial Zoonoses Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Raccoon rabies was probably introduced into the mid-Atlantic region in the mid 1970s when raccoons were transported from raccoon-rabies-enzootic regions of the southeastern United States to the mid-Atlantic area for replenishment of hunting stocks. The first cases occurred in West Virginia (1977), with subsequent spread to Virginia (1978), Maryland (1981), Pennsylvania (1982), Delaware (1987), New Jersey (1989), New York (1990), and Connecticut (1991). Expansion to New England states other than those reported here is expected during the next several years. With the recent identification of raccoon rabies in North Carolina (1991), raccoon rabies is now enzootic from Florida to Connecticut. Isolated reports of cases from Ohio and New Hampshire may indicate further expansion of the geographic limits of the epizootic to the West and North.

Although raccoon rabies has not been responsible for any known human rabies case, the possibility of transmission exists given the presence of large populations of raccoons in areas of high human population density and the ability of raccoons to coexist with humans in urban and suburban areas, as well as in rural areas.

The rabies threat to humans is greatest when epizootics occur in domestic animals, especially dogs. Reduction of the number of human deaths from rabies in the United States has been largely attributed to vaccination of pets and to stray-animal control. These traditional control measures have been effective in breaking the chain of rabies transmission from domestic animals to humans but do not reduce the vast reservoir of rabies infection present in wildlife in the United States.

The use of oral rabies vaccines has shown promise as a tool to curb the spread of wildlife rabies (1,2). In the United States, a newly developed vaccinia-rabies glycoprotein (V-RG) recombinant vaccine for the oral vaccination of raccoons is being tested. Field trial studies of vaccine safety conducted in Virginia (1990) and Pennsylvania (1991) showed no detrimental effects on the environment or in nontarget species (3). As a result, the U.S. Department of Agriculture (USDA) recently gave permission for an efficacy field test with the vaccine to be conducted in a defined area of New Jersey.

Additional field trials of the oral rabies vaccine for raccoons are needed to establish the appropriate distribution method (e.g., airplane, helicopter, or hand placement), minimum effective geographic area, bait density, frequency, and time(s) of year for vaccination in various habitats. Strategies may vary depending on the reason for an oral-vaccination program (i.e., eliminating rabies, preventing its introduction into an area, or reducing the number of rabid animals in an epizootic area). Until these concerns are addressed, the larger question of whether oral vaccination of wildlife is cost effective cannot be adequately answered.

In addition to threatening the health of humans, domestic animals, and other wildlife, the raccoon rabies epizootic has resulted in severe economic consequences for affected states. A recent study conducted in two counties in New Jersey indicated that private and public expenditures associated with the raccoon rabies epizootic increased from $405,565 per 100,000 population during a preepizootic period to $979,027 per 100,000 population during the epizootic period (4). Extrapolated to the entire mid-Atlantic and New England regions, potential costs associated with prevention and control activities during the epizootic period could amount to hundreds of millions of dollars.

A major focus of the public health response to rabies has been education. Education of the public has emphasized ways to reduce the risk of exposure to wild animals in affected areas, the need to keep rabies vaccinations for pet dogs and cats current, and the importance of seeking medical treatment if bitten by or exposed to a potentially rabid animal. Education of veterinarians, animal-control officers, and others in occupations at high-risk for exposure to rabies has emphasized the importance of preexposure prophylaxis against rabies. Education efforts have also targeted physicians and other medical professionals because many physicians in these areas have never given either preexposure or postexposure prophylaxis for rabies.

CDC is working with public health veterinarians and state epidemiologists to develop recommendations concerning alternative strategies for rabies control. A meeting is scheduled for early 1993 with state epidemiologists, public health veterinarians, officials from the USDA, and rabies researchers to discuss approaches for controlling raccoon rabies in the United States. Information about rabies is available from state and local health departments and CDC's Viral and Rickettsial Zoonoses Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, telephone (404) 639-1075.

References

1. Schneider LG, Cox JH, Muller WW, Hohnsbeen KP. Current oral rabies vaccination in Europe: an interim balance. Rev Infect Dis 1988;10:S654-9.

2. Wandeler AI, Capt S, Kappeler A, Hauser R. Oral immunization of wildlife against rabies: concept and first field experiments. Rev Infect Dis 1988;10:S649-53.

3. Rupprecht CE, Hanlon CA, Hamir A, Kiprowski H. Oral wildlife rabies vaccination: development of a recombinant virus vaccine. Transactions of the 57th North American Wildlife and Natural Resources Conference (in press).

4. Uhaa IJ, Data V, Sorhage F, et al. Epizootic raccoon rabies: cost of control and economic benefits of an oral rabies vaccine. J Am Vet Med Assoc (in press).

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