Translocation of coyote rabies - Florida, 1994

Morbidity and Mortality Weekly Report, August 11, 1995

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.

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].