An assessment of ONRAB oral rabies vaccine persistence in free-ranging mammal populations in Ontario, Canada.

ONRAB is a rabies glycoprotein recombinant human adenovirus type 5 oral vaccine developed for application in baits to control rabies in wildlife populations. Prior to widespread use of ONRAB, both the safety and effectiveness of this vaccine required investigation. While previous research has focused on field performance and the persistence and pathogenicity of ONRAB in captive animals, we sought to examine persistence and shedding of ONRAB in populations of free-ranging target and non-target mammals. We collected oral and rectal swab samples from 84 red foxes, 169 striped skunks, and 116 raccoons during 2007 and 2008 in areas where ONRAB vaccine baits were distributed. We also analyzed 930 tissue samples, 135 oral swab and 138 rectal swab samples from 155 non-target small mammals from 10 species captured during 2008 at sites treated with high densities of ONRAB vaccine baits. Samples were screened for the presence and quantity of ONRAB DNA using quantitative real-time PCR. None of the samples that we analyzed from target and non-target species contained quantities of ONRAB greater than 10(3)EU/mL of ONRAB DNA which is a limit that has previously been applied to assess viral shedding. This study builds on similar research and suggests that replication of ONRAB in animals is short-lived and the likelihood of horizontal transmission to other organisms is low.

Field evaluation of an inactivated vaccine to control raccoon rabies in Ontario, Canada.

Since raccoon rabies first appeared in Ontario in 1999, >90,000 raccoons (Procyon lotor) have received IMRAB3 inactivated rabies vaccine via intramuscular (IM) injection and were released at the point of capture as part of a multiyear rabies control program, trap-vaccinate-release (TVR). Of the 132 confirmed cases infected with raccoon-variant rabies virus in Ontario between 1999 and 2005, two were from that vaccinated group, as indicated by the presence of identifying ear tags. During ongoing rabies control programs in 2003, sera were collected from 172 wild raccoons that had received IMRAB3 and tested for rabies-virus antibodies. Raccoons had one of three histories: 1) vaccinated in the current year only (to examine the response to primary vaccination), 2) vaccinated in the previous year only (to determine the duration of the primary antibody response), and 3) vaccinated in the previous year and current year (to examine antibody response to booster vaccination). Seroconversion in primary vaccinates could be detected as early as 1 wk postvaccination when sera were measured with the use of a competitive enzyme-linked immunosorbent assay (C-ELISA) with a cutoff value established to correspond to a neutralizing titer of 0.5 IU/ml. During weeks three and four postvaccination, 94% of sampled raccoons had detectable antibodies to rabies virus and 31% were still antibody positive the following year. Differences in the kinetics of the immune response were found in raccoons sampled from the two different TVR areas of the province. A strong anamnestic response was detected after booster vaccinations. IMRAB3 by IM injection was found to be an efficacious vaccine for rabies control in raccoons.