Raccoon Rabies Epizootic -- United States, 1993

Although the incidence of rabies is low among domestic animals in the United States, the recent increase in the occurrence of wildlife rabies has increased the risk for infection of humans. From 1991 to 1992, the number of reported cases of rabies in raccoons increased 40%, from 3079 to 4311. Of the 8644 animals reported rabid during 1992, a total of 3759 (43%) were raccoons in the mid-Atlantic and northeastern states (1). This report describes the continuing spread of the raccoon rabies epizootic in the mid-Atlantic and northeastern states.

Connecticut. Rabies was first confirmed in raccoons in Connecticut in March 1991 and subsequently has been confirmed in raccoons in all towns but one west of the Connecticut River. Overall, the rabies epizootic in raccoons has involved six of eight counties and 129 of 169 towns. From 1992 to 1993, the number of confirmed cases of rabies in animals decreased 8% (from 831 to 762). Of the 1256 raccoons tested in 1993, 662 (53%) were positive for rabies. Since 1991, when the first case was detected in a raccoon, 1786 cases have been identified among animals, including 31 cases among domestic animals (22 cats, three dogs, three sheep, two horses, and one cow).

Massachusetts. Rabies was first confirmed in raccoons in Massachusetts in September 1992 in Ashby, near the New Hampshire border and more than 60 miles north of the nearest cases of raccoon rabies in Connecticut. During 1993, cases were confirmed in animals in 175 (50%) of 351 towns and 10 of 15 counties; cases were not detected in the southeastern counties. Overall, from 1992 to 1993, the number of confirmed cases increased nearly 17-fold, from 42 to 698. Of the 1486 raccoons tested in 1993, 585 (39%) were positive for rabies. Since September 1992, although most (623) cases have occurred in raccoons, cases also have been detected in skunks (81), cats (14), woodchucks (11), foxes (eight), and cattle (three).

New Hampshire. Rabies was first confirmed in raccoons in New Hampshire in April 1992 in Rumney in midstate. Cases subsequently have been detected in 48 towns in four counties in the southern region of the state. During 1993, 148 animals tested positive for rabies (103 {37%} of 278 raccoons, 32 skunks, five bats, three woodchucks, three cats, one pony, and one rabbit). At least one isolate from each species (except bats) was characterized as the strain associated with the raccoon rabies epizootic. One cat had received one dose of rabies vaccine 8 months before onset of illness.

New York. Rabies was first confirmed in raccoons in New York in May 1990; since then, cases have been confirmed in animals in 50 of the 62 counties. In 1991 and 1992, rabies was confirmed in 666 and 1392 raccoons, respectively. In 1993, rabies was diagnosed in 2747 animals, comprising 17 species of mammals. Of the 4463 raccoons tested, 2369 (53%) were positive. From 1992 to 1993, the number of persons who received postexposure rabies prophylaxis increased from 1125 to 2905. In July 1993, a case of human rabies was attributed to a strain that characteristically infects silver-haired bats (2).

North Carolina. Since 1990, three distinct epizootics of rabies have occurred in animals in North Carolina: during 1990, the skunk rabies epizootic from the Midwest entered two counties of northwestern North Carolina from Tennessee and Virginia; during 1991, the raccoon rabies epizootic from the Mid-Atlantic entered northeastern North Carolina from Virginia; and during 1992, the raccoon rabies epizootic from the Southeast entered from South Carolina into two regions of southcentral and southeastern North Carolina. Since 1990, rabies has been detected in terrestrial animals in 22 of 100 counties; rabies was confirmed in terrestrial animals for the first time in eight of these counties in 1993. The number of rabies cases more than doubled each year during 1991- 1993: 24 cases in 1991, 50 cases in 1992, and 106 cases in 1993. During 1993, 71 (18%) of 386 raccoons tested were positive. In addition, the number of rabid domestic animals -- eight cats and two dogs -- was the highest annual total reported in North Carolina since 1959; none of these animals had been vaccinated against rabies.

Reported by: ML Cartter, MD, GH Cooper, JL Hadler, MD, State Epidemiologist, Connecticut State Dept of Public Health and Addiction Svcs. M McGuill, DVM, A DeMaria, MD, State Epidemiologist, Massachusetts Dept of Public Health. MG Smith, MD, State Epidemiologist, New Hampshire State Dept of Health and Human Svcs. 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. Viral and Rickettsial Zoonoses Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Since the introduction of the raccoon rabies epizootic in the mid-Atlantic region in 1977, cases have been identified in 11 states and the District of Columbia (Figure_1). Cases were first detected in West Virginia (1977) and subsequently in Virginia (1978), Maryland (1981), the District of Columbia (1982), Pennsylvania (1982), Delaware (1987), New Jersey (1989), New York (1990), Connecticut (1991), North Carolina (1991), Massachusetts (1992), and New Hampshire (1992). During January- February 1994, the first cases in Rhode Island were detected in two raccoons and a fox. In the Northeast, only Vermont and Maine remain unaffected by the raccoon rabies epizootic.

In 1990, raccoons surpassed skunks as the species in which rabies was detected most often in the United States, and the number of cases in raccoons continued to increase (Figure_2). Although the raccoon strain of rabies virus has been detected in many species, no known cases have occurred in humans. However, vaccination of dogs and cats remains important for the control and prevention of rabies because these domesticated species may serve as a link in rabies transmission between wildlife and humans.

Rabies control in wildlife through oral vaccination is being evaluated in the United States (3); this approach has been successful in controlling fox rabies in parts of Europe (4) and in Canada (5). In April 1992, a program to administer vaccinia-rabies glycoprotein recombinant vaccine orally to raccoons was initiated in Cape May County, New Jersey. Similar programs are being planned that would target raccoons in areas of Massachusetts and New York, coyotes in Texas (6), and foxes in New York and Vermont. Additional field trials of the oral rabies vaccine should establish distribution methods, the minimum effective geographic area, bait density, frequency, and time(s) of year for vaccination. These assessments will help determine the cost-effectiveness and appropriate use of oral wildlife vaccination. Population reduction of wildlife rabies reservoirs is not a recommended or cost-effective method for rabies control (7).

The costs of programs to prevent rabies have increased in parallel with the spread of the epizootic. For example, in New York, which in 1993 recorded the largest number of cases of rabies in wildlife ever reported by one state (1), the number of persons receiving postexposure rabies prophylaxis increased from 84 in 1989 to 2905 in 1993 (J.G. Debbie, D.V.M., New York State Department of Health, personal communication, 1994). In New Jersey, private and public expenditures associated with the raccoon rabies epizootic in two counties more than doubled from the pre-epizootic period ($405,565 per 100,000 population) to the epizootic period ($979,027 per 100,000 population) (8).

Rabies prevention activities at the state and local levels have been aimed at reducing exposure to rabies-infected animals and insuring proper treatment when exposure occurs. For example, in some states, vaccination requirements for both dogs and cats have been statutorily mandated. Health departments, in collaboration with veterinary associations and animal-control and animal-welfare groups, have provided educational materials to the public about wildlife rabies, pet vaccination, and recognition of exposures to potentially rabid animals. Education efforts have targeted veterinarians and physicians because they often are the first to be informed of possible rabies exposures.

State public health departments, state and local governments, CDC, and other federal agencies are collaborating to develop programs to control rabies epizootics (9). Information about rabies is available from state and local health departments and from CDC's Viral and Rickettsial Zoonoses Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases; telephone (404) 639-1075.

References

1. Krebs JW, Strine TW, Childs JE. Rabies surveillance in the United States during 1992. J Am Vet Med Assoc 1993;203:1718-31.

2. CDC. Human rabies -- New York, 1993. MMWR 1993;42:799,805-6.

3. Rupprecht CE, Wiktor TJ, Johnston DH, et al. Oral immunization and protection of raccoons (Procyon lotor) with a vaccinia-rabies glycoprotein recombinant virus vaccine. Proc Natl Acad Sci U S A 1986;83:7947-50.

4. Brochier B, Kieny MP, Costy F, et al. Large-scale eradication of rabies using recombinant vaccinia-rabies vaccine. Nature 1991;354:520-2.

5. Rosatte RC, Power MJ, MacInnes CD, Campbell JB. Trap-vaccinate-release and oral vaccination for rabies control in urban skunks, raccoons and foxes. J Wildl Dis 1992;28:562-71.

6. Clark KA, Neill SU, Smith JS, et al. Epizootic canine rabies transmitted by coyotes in south Texas. J Am Vet Med Assoc 1994;204:536-40.

7. National Association of State Public Health Veterinarians. Compendium of animal rabies control, 1994. J Am Vet Med Assoc 1994;204:173-6.

8. Uhaa IJ, Dato VM, Sorhage FE, et al. Benefits and costs of using an orally absorbed vaccine to control rabies in raccoons. J Am Vet Med Assoc 1992;201:1873-82.

9. Spencer LM. Taking a bite out of rabies. J Am Vet Med Assoc 1994;204:479-84.

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