Evaluation of oral rabies vaccination programs for control of rabies epizootics in coyotes and gray foxes: 1995-2003.

OBJECTIVE

To evaluate the effectiveness of intervention efforts to halt 2 wildlife rabies epizootics from 1995 through 2003, including 9 oral rabies vaccination campaigns for coyotes and 8 oral rabies vaccination campaigns for gray foxes.

DESIGN

Retrospective study.

ANIMALS

98 coyotes during prevaccination surveillance and 963 coyotes and 104 nontarget animals during postvaccination surveillance in south Texas, and 699 gray foxes and 561 nontarget animals during postvaccination surveillance in west-central Texas.

PROCEDURES

A recombinant-virus oral rabies vaccine in edible baits was distributed by aircraft for consumption by coyotes and gray foxes. Bait acceptance was monitored by use of microscopic analysis of tetracycline biomarker in upper canine teeth and associated bone structures in animals collected for surveillance. Serologic responses were monitered by testing sera for rabies virus-neutralizing antibodies by use of the rapid fluorescent focus inhibition test. The incidence of rabies in the distribution area was recorded via active and passive surveillance activities; tracking of rabies virus variants in confirmed rabid animals was used to determine the number and type of rabies cases before and after distributions of the vaccine.

RESULTS

The expansion of both epizootics was halted as a result of the vaccine bait program. The number of laboratory-confirmed rabid animals attributable to the domestic dog-coyote rabies virus variant in south Texas declined to 0, whereas the number of laboratory-confirmed rabid animals attributable to the Texas fox rabies virus variant in west-central Texas decreased.

CONCLUSIONS AND CLINICAL RELEVANCE

Data indicated that oral rabies vaccination resulted in protective immunity in a sufficient percentage of the target wildlife population to preclude propagation of the disease and provided an effective means of controlling rabies in these species.