Epizootiologic Aspects of Raccoon Rabies in Florida

Raccoon rabies in Florida is documented for the 20-year period 1953–1972. Between 1969 and 1972, raccoons accounted for 301 of 440 (68%) reported cases of rabies. Rabid wild animals in the past 10 years bit or scratched 114 persons; 75 (65%) of them identified the animal as a raccoon. Statewide reported cases of rabies in raccoons occur sporadically throughout the year; however, the peak incidence in March appears to correlate with the breeding season. A recent characteristic of rabies epizootiology among these animals is the occurrence in relatively localized outbreaks in areas with dense human populations. Investigation of three outbreaks between 1969 and 1971 revealed each to be associated with raccoon populations that were concentrated by land development. The virus spread rapidly in one dense population while two lower density populations experienced milder outbreaks. High levels of rabies serum neutralization antibodies were found in at least 20 per cent of the raccoons that survived rabies infection. Virus was recovered from salivary glands of several raccoons which showed no signs of clinical illness. Incubation periods of 39 and 79 days in two naturally infected raccoons were recorded. Outbreaks on islands appeared to be controlled within five months by trapping and shooting clinically ill raccoons. A peninsular outbreak, suppressed but not controlled by these techniques, lasted 10 months and eventually involved associated species of wildlife.