A Field Evaluation in Mexico of Four Baits for Oral Rabies Vaccination of Dogs

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  • Viral and Rickettsial Zoonoses Branch, National Center for Infectious Diseases, Centers for Disease Control, Productora Nacional de Biologicos Veterinarios, Centro de Salud, Jurisdiccion de Atlixco, Servicios Coordinados de Salud Publica de Puebla, Field Epidemiology Training Program, Ministry of Health, Pan American Health Organization, Denver Wildlife Research Center, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Atlanta, Georgia
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We evaluated four baits for the delivery of oral rabies vaccines to dogs. In a controlled study in a town in rural Mexico, 177 randomly selected dogs were assigned to receive one of four experiential baits (two of which were developed by the Denver Wildlife Research Center [DWRC]): one of two cylindrical polyurethane sponges with a corn meal coating (one fried in corn oil [DWRC-corn], the other in fish oil [DWRC-fish]), a fish-flavored polymer bait, or a wax bait. Each dog was also offered a commercial dog biscuit. We recorded whether or not the bait was completely consumed, and used the following measures to estimate the amount of oropharyngeal contact with each bait: total chewing time, presence of pieces of bait on the ground following administration, the total area of ground surrounding the location of ingestion that was covered with green dye contained in each bait, and condition of ampules that contained the dye. The dog biscuits were completely consumed significantly more often than the baits (155 of 176 [88%] for the biscuits versus 89 of 176 [50.5%] for the four baits; P < 10-6), but were chewed for a significantly shorter time than the baits (mean time 34 sec for the biscuit versus 60–82 sec for the four baits: P < 0.001). The ideal bait would probably combine the attractiveness of the commercial biscuit and the ability of the sponge baits to promote contact with the mucous membranes.