Translocation of a rabies variant from one area to another has been identified increasingly in the United States. During November and December 1994, rabies was diagnosed in five dogs from two associated kennels in Florida; in addition, two other dogs being kept at one of the kennels died with suspected, but unconfirmed, rabies. Rabies virus recovered from the five dogs was identified as a variant not previously found in Florida but endemic in coyotes (Canis latrans) in south Texas. The suspected source of infection was translocation of infected coyotes from Texas to Florida. This report summarizes the findings of an investigation of these cases by the Alachua County Public Health Unit, the Florida Department of Health and Rehabilitative Services, and CDC.

On November 21, 1994, a Walker hound used for fox hunting escaped from one of the fenced kennels; on recapture later that day, the dog was unusually aggressive and bit one of the kennel owners. The dog was euthanized and tested positive for rabies. On November 21, the Alachua County Public Health Unit identified 102 dogs and 10 cats potentially exposed to this dog while it was loose and established a 20-square-mile quarantine area. Measures implemented by public health and animal-control authorities included vaccinating against rabies all unvaccinated dogs and cats within the quarantine area and administering booster vaccine to previously vaccinated animals, prohibiting movement of animals in and out of the quarantine area, systematically mailing rabies update advisories to residents of the quarantine area, and -- with the assistance of the news media -- increasing rabies surveillance by requesting reports of persons or animals that had been bitten by an animal. As a result of exposure to this dog or other animals in the quarantine area, 26 persons received rabies postexposure treatment, and three persons received preexposure prophylaxis.

Concurrent investigations by the Alachua County Public Health Unit revealed that two other dogs from the same kennel had died on November 10 and November 18. Neither of these dogs were tested for rabies; however, rabies was suspected and confirmed in four additional dogs (three from the same kennel and one from an associated kennel), who died November 28 (one), November 30 (one), and December 1 (two). Rabies in the five dogs tested was confirmed at CDC, and the isolates were identified as the variant associated with coyotes in south Texas (1). None of the seven dogs with presumed or confirmed rabies had a history of rabies vaccination. All seven dogs had been kept in Florida for greater than or equal to 7 months preceding their deaths.

Several times each week during September and October, the kennel owner, family members, and a business associate hunted coyotes that were kept in a 320-acre fenced foxpen 18 miles from the dog kennels. The foxpen had not been rented for use by other hunters. The foxpen had housed 20-25 coyotes, which were reported to have been captured in Florida during February 1994 and placed in the pen during the same month with gray foxes and raccoons. The coyotes were reported to have been fed regularly, and no ill or dead wildlife had been noted in the enclosure within the previous 6 months. Six of the dogs with presumed or confirmed rabies had accompanied the hunters in the foxpen. The one rabid dog that was never taken to the foxpen had shared a kennel with two of the dogs with rabies. Four of the seven rabid dogs also had been to a field trial with approximately 400 other hunting dogs in late October; none of these other dogs are known to have died from rabies.

Depopulation of the free-ranging carnivores within the enclosed foxpen was instituted with the assistance of the Florida Game and Fresh Water Fish Commission because the affected dogs in the foxpen may have been exposed to other rabid animals. The potentially exposed or infected animals included 32 coyotes, five raccoons, two gray foxes, two bobcats and one cat; diagnostic tests of these animals at CDC were negative for rabies. Continuing surveillance in the quarantine area subsequently identified rabies in a puppy that had been bitten by the escaped rabid dog. Reported by: T Belcuore, MS, Alachua County Public Health Unit; L Conti, DVM, G Hlady, MD, L Crockett, MD, R Hopkins, MD, State Epidemiologist, Florida Dept of Health and Rehabilitative Svcs. M Dunbar, DVM, Florida Game and Fresh Water Fish Commission. Viral and Rickettsial Zoonoses Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The episode described in this report resulted in six confirmed and two presumed cases of dog rabies and the need for rabies postexposure treatment of 26 persons. It highlights the increasing problem of animal rabies in the United States, which reached record levels in 1993.

The incubation period for rabies in the cases in this report and the rabies variant with which they were infected suggest that the source of infection was coyotes in the foxpen during October. Although the incubation period for rabies in dogs usually is 3-8 weeks, it can vary from 10 days to 8 1/2 months (2). The rabies variant identified is not present in animal populations of the southeastern United States but is found exclusively in 17 counties in southern Texas. Because the dogs had not traveled outside Florida, translocation of infected animals from Texas is suspected. A similar case of dog rabies in Alabama was attributed to coyotes transported for hunting purposes from Texas to Alabama (3).

Enzootic dog rabies has been nearly eliminated in the United States as the result of effective mass vaccination programs and programs initiated during the 1950s to control stray animal populations. Dog-to-dog transmission of the magnitude described in this report has not been documented since the early 1970s, except in areas along the U.S.-Mexico border. However, 12 of the 25 human rabies cases diagnosed in the United States since 1980 were associated with exposure to dog rabies viruses outside the United States or near the U.S.-Mexico border. In the cases in this report, rabies transmission to the dogs probably could have been prevented if the dogs had been appropriately vaccinated against rabies.

Since 1988, rabies in coyotes in southern Texas has accounted for most coyote-associated rabies in the United States, including 70 of 75 cases in 1992, and 71 of 74 cases in 1993 (3). The coyote rabies epizootic has been a source for infection for unvaccinated domesticated dogs and further expansion of rabies. Since 1991, at least two human deaths have been associated directly with the southern Texas rabies variant (4,5), probably associated with interactions between coyotes and dogs. In addition to established measures for preventing rabies, including mandatory vaccination of domesticated dogs (6) and prompt postexposure treatment of humans (7), the development of safe and effective oral rabies vaccines for coyotes and other wild carnivores would be a potentially important adjunct control strategy.

The interstate transport of wildlife from geographic areas with enzootic hazards to new areas has resulted in disease outbreaks with substantial public health and economic impact. For example, the current raccoon rabies epizootic in the mid-Atlantic and northeastern United States is the direct consequence of translocation and spread of infected raccoons from the southeastern United States during the late 1970s; raccoons are now the primary rabies reservoir in the United States (3). A recent surge in popularity of coyote hunting in the southeastern United States has resulted in an increase in sales of wild canids for foxpens; although coyotes are indigenous to that region, some of these animals may have been imported illegally. Intensified surveillance for this rabies variant is warranted in those states where residents participate in coyote hunting in enclosures.

In addition to rabies, public health risks associated with wildlife translocation include zoonotic infections such as plague, hantavirus pulmonary syndrome, brucellosis, echinococcosis, Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, and tularemia. However, federal and state regulations have not been applied consistently to the interstate movement of native wildlife. Because of the public health risks and lack of feasible methods to certify animals as free of many of these zoonotic agents, restrictions on the interstate movement of native wildlife may need to be considered.

The Florida Department of Health and Rehabilitative Services and CDC are strain-typing all rabies variants found in wild and domestic canids. No additional isolates of the coyote rabies variant have been identified in Florida.

References

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

2. Tierkel ES. Canine rabies. In: Baer GM, ed. The natural history of rabies. New York: Academic Press, 1975:123-37.

3. Krebs JW, Strine TW, Smith JS, Rupprecht CE, Childs JE. Rabies surveillance in the United States during 1993. J Am Vet Med Assoc 1994;205:1695-709.

4. CDC. Human rabies -- Texas, Arkansas, and Georgia, 1991. MMWR 1991;40:765-9.

5. CDC. Human rabies -- Alabama, Tennessee, and Texas, 1994. MMWR 1995;44:269-72.

6. CDC. Compendium of animal rabies control, 1995: National Association of State Public Health Veterinarians, Inc. MMWR 1995;44(no. RR-2).

7. ACIP. Rabies prevention -- United States, 1991: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1991;40(no. RR-3).

   
   

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