Oral rabies vaccination in raccoons: comparison of ONRAB® and RABORAL V-RG® vaccine-bait field performance in Québec, Canada and Vermont, USA.

ABSTRACT

The control of rabies in raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) in North America has been conducted mainly through aerial distribution of oral vaccine-baits. The effectiveness of the vaccine-bait used is therefore of prime importance for disease eradication. In a previous field comparison between the ONRAB(®) bait in the province of New Brunswick, Canada, and RABORAL V-RG(®) bait in the state of Maine, USA, the ONRAB bait produced a higher percentage of antibody-positive raccoons under nearly identical bait distribution for the two vaccines. The main objective of the present study was to conduct a similar cross-border comparison of these two vaccine-baits using raccoon sera collected during post-oral rabies vaccination monitoring in Québec, Canada, and Vermont, USA, where ONRAB and V-RG, respectively, were distributed aerially at a targeted density of 150 baits/km(2). A comparison of the equivalency of two serologic tests used in Canada and the USA was also conducted using sera from raccoons and striped skunks. Rabies virus neutralization assay (USA) yielded similar results to the competitive enzyme-linked immunosorbent assay (Canada), with agreement between the two tests of 92% for raccoon sera and 96% for skunk sera. With both assays, the percentage of antibody-positive raccoons was greater with ONRAB (51%, n=265) than with V-RG (38%, n=66). These new results support the conclusion from the previous study, that ONRAB vaccine-baits may be more effective for the control of rabies in raccoons.