Tore Buchanan

Aerial distribution of ONRAB® baits as a tactic to control rabies in raccoons and striped skunks in Ontario, Canada.

During August 2006 and 2007, baits containing oral rabies vaccine, live adenovirus vector, known as ONRAB®, were aerially distributed in SW Ontario, Canada. Bait acceptance during 2006 was 62 and 74% in raccoons (Procyon lotor) in areas baited at 150 baits/km2 and 75 and 77% in plots baited at 300 baits/km2. During 2007, bait acceptance for raccoons ranged between 59% and 80%, and 83% and 87%, in areas baited at 75 and 400 baits/km2, respectively. Bait acceptance by skunks varied among plots (5–24%). Rabies virus-specific seroconversion during 2006 averaged 66 and 81% in raccoons in areas baited at 150 and 300 baits/km2, respectively. During 2007, seroconversion by raccoons was 76 and 84% in areas baited at 75 and 400 baits/km2, respectively. Seroconversion by skunks varied among plots (17–51%). Vaccine efficacy, as judged by the percentage of animals that consumed a bait and seroconverted, averaged 79 and 87% during 2006 for raccoons in areas baited at 150 and 300 baits/km2, respectively, and 81 and 90% in areas baited during 2007 at 75 and 400 baits/km2, respectively. Because tetracycline marking was poor in skunks, an estimate of vaccine efficacy was not possible. Aerial distribution of ONRAB® vaccine baits seems to be a feasible tactic for controlling rabies in skunks and raccoons.

The control of raccoon rabies in Ontario Canada: proactive and reactive tactics, 1994-2007.

Proactive and reactive tactics have been utilized in Ontario, Canada, to prevent raccoon rabies from becoming established. A total of 96,621 raccoons (Procyon lotor) and 7,967 striped skunks (Mephitis mephitis) were live captured using 1,221,044 trap nights, vaccinated against rabies by injection, and released, during proactive Trap-Vaccinate-Release (TVR) programs in southern Ontario during 1994–2007. During those years, on average, 43% to 83% of the raccoon populations were vaccinated against rabies. In addition, 20,129 raccoons and 2,735 skunks were vaccinated against rabies, and 8,311 raccoons and 1,449 skunks were euthanized, using 576,359 trap nights, during reactive Point Infection Control (PIC) operations in eastern Ontario during 1999–2005. A significant correlation was detected between trapping effort and the percentage of the raccoon population that was vaccinated. Between 1999 and 2007, 132 cases of raccoon variant rabies (130 raccoons, two striped skunks) were reported in eastern Ontario. The last case occurred on 23 September 2005 with Ontario being free of reported raccoon rabies to 10 November 2008, proving that TVR and PIC are effective tactics for the control of this disease.

THE ELIMINATION OF RACCOON RABIES FROM WOLFE ISLAND, ONTARIO: ANIMAL DENSITY AND MOVEMENTS

During 1996 to 1998, an average of 52% to 55% of the raccoon (Procyon lotor) population on Wolfe Island, Ontario was vaccinated against rabies during proactive trap-vaccinate-release (TVR) operations. However, during 1999, the percent of the population vaccinated declined to 39% and an outbreak (6 cases) of raccoon rabies occurred on the island from December 1999 to January 2000. The raccoon population on Wolfe Island declined dramatically (71% reduction) from 1,067 raccoons (mean density=8.4/km2 [6.4–12.4, 95% CI]) during 1999 to 305 raccoons (mean density=2.4/km2 [0.87–4.1, 95% CI]) in the spring of 2000. Raccoon density immediately following the outbreak was significantly lower in cells with rabies cases, suggesting that rabies had a negative effect on population size. However, raccoon density had doubled by 1 yr following the outbreak. Movement of raccoons on Wolfe Island was as great as 24 km. Male raccoons moved greater distances than females. Movements to surrounding islands were also noted for raccoons ear tagged on Wolfe Island which indicates the island could serve as a focus for greater geographic rabies spread. Point infection control (PIC) during 2000, TVR during 2001–02, and the aerial distribution of Vaccinia-Rabies Glycoprotein (V-RG) baits during 2000 and 2003–05 were used to eliminate rabies from Wolfe Island. No cases have been detected since late January 2000 (to February 2007).

Raccoon Density and Movements After Population Reduction to Control Rabies

Abstract Population reduction (PR) and trap–vaccinate–release (TVR) were used to control an outbreak of the raccoon (Procyon lotor) variant of rabies in Ontario, Canada, during 1999. Raccoon density declined significantly following PR; however, density increased significantly 9–10 months post–PR. Recolonization of PR areas with raccoons marked in TVR areas was very low with only 1.8% (32/1,759) of those raccoons dispersing into PR areas during 1999–2000. In addition, the number of raccoons dispersing from TVR areas into PR areas was not significantly greater than the number of raccoons dispersing into treatment areas where population reduction had not been implemented during 1999–2000. Raccoon movements in this study, determined by mark–recapture, averaged <4.0 km during 1999–2000 and did not differ among treatments (with or without PR). In summary, there was not a mass exodus of raccoons from TVR areas to PR areas during 1999–2000, suggesting there was not an immediate, dramatic, vacuum effect drawing raccoons into areas devoid of raccoons due to PR. However, one year post–PR, raccoon populations were near or above pre–PR densities (due to a high reproductive rate of resident raccoons), suggesting that PR would have to be an annual event if rabies is not eliminated from an area.

PREVALENCE OF TETRACYCLINE AND RABIES VIRUS ANTIBODY IN RACCOONS, SKUNKS, AND FOXES FOLLOWING AERIAL DISTRIBUTION OF V-RG BAITS TO CONTROL RACCOON RABIES IN ONTARIO, CANADA

More than 3.6 million baits containing a recombinant vaccinia virus–rabies glycoprotein (V-RG) oral rabies vaccine were aerially or hand-distributed during 1999–2006 in an approximate 4,000-9,000 km2 area of eastern Ontario, Canada, as part of a multitactic approach to control the raccoon variant of rabies. The efficacy of the program was assessed through the collection and testing of >6,900 animals for bait acceptance and rabies virus-specific antibodies. Raccoon acceptance of rabies vaccine baits was significantly greater (71–83%) in areas baited at a density of 150 baits/km2 compared to areas baited at 75 baits/km2 (26–58%), and more raccoons consumed vaccine baits in areas baited with a flight line spacing of 0.75 km (45.3%[321/708[) than with a spacing of 1.5 km (33.8% [108/320[). In addition, greater numbers of raccoons consumed vaccine baits during a drop in September (52.7%[213/404[) as opposed to a June bait drop (34.6% [216/624[). Seropositivity rates for raccoons ranged between 7% and 28% in areas baited at 75/km2 and 10% to 27% in areas baited at 150/km2 with statistical differences varying among years and treatments. The last case of raccoon-variant rabies reported in Ontario was in September 2005. The control of raccoon rabies in Ontario has resulted in an estimated

Rabies in Vaccinated Raccoons from Ontario, Canada

6M to

FIELD EVALUATION OF AN INACTIVATED VACCINE TO CONTROL RACCOON RABIES IN ONTARIO, CANADA

10M Cdn annual savings in rabies-associated costs.

Frequency of Virus Coinfection in Raccoons (Procyon lotor) and Striped Skunks (Mephitis mephitis) During a Concurrent Rabies and Canine Distemper Outbreak

From 1999 to 2006, 132 cases of raccoon rabies, caused by the raccoon variant of rabies virus, were confirmed in eastern Ontario, Canada. Trap-vaccinate-release (TVR) and point infection control (PIC) programs were implemented to control the disease; 43,014 raccoons (Procyon lotor) were vaccinated against rabies by injection (Imrab®3) during that period. Two vaccinated raccoons were diagnosed with rabies at 6 mo and at 2 wk postvaccination. One may have been due to a vaccination failure. The other was likely due to the animal being in the late stages of incubation for rabies at the time of vaccination. This information will be useful to wildlife rehabilitators and agencies that hold raccoons in captivity in that a vaccinated raccoon is not necessarily immune to rabies.

Quantifying moonlight and wind effects on flighted waterfowl capture success during night-lighting

Since raccoon rabies first appeared in Ontario in 1999, >90,000 raccoons (Procyon lotor) have received IMRAB®3 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 IMRAB®3 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. IMRAB®3 by IM injection was found to be an efficacious vaccine for rabies control in raccoons.

Avian metapneumovirus subtype C in Wild Waterfowl in Ontario, Canada

Abstract:  Rabies and canine distemper virus infections in wildlife share similar presenting signs. Canine distemper virus was detected using real-time PCR of conjunctival swabs in rabies positive raccoons (22/32) and skunks (7/34) during a concurrent rabies and canine distemper outbreak in Ontario, Canada in 2015–16. Coinfections with both viruses should be considered, particularly in distemper endemic areas that are at risk of rabies incursion.