Elimination of Rabies From Red Foxes in Eastern Ontario

Abstract

The province of Ontario (Canada) reported more laboratory confirmed rabid animals than any other state or province in Canada or the USA from 1958-91, with the exception of 1960-62. More than 95% of those cases occurred in the southern 10% of Ontario (approximately 100,000 km2), the region with the highest human population density and greatest agricultural activity. Rabies posed an expensive threat to human health and significant costs to the agricultural economy. The rabies variant originated in arctic foxes: the main vector in southern Ontario was the red fox (Vulpes vulpes), with lesser involvement of the striped skunk (Mephitis mephitis). The Ontario Ministry of Natural Resources began a 5 yr experiment in 1989 to eliminate terrestrial rabies from a approximately 30,000 km2 study area in the eastern end of southern Ontario. Baits containing oral rabies vaccine were dropped annually in the study area at a density of 20 baits/km2 from 1989-95. That continued 2 yr beyond the original 5 yr plan. The experiment was successful in eliminating the arctic fox variant of rabies from the whole area. In the 1980's, an average of 235 rabid foxes per year were reported in the study area. None have been reported since 1993. Cases of fox rabies in other species also disappeared. In 1995, the last bovine and companion animal cases were reported and in 1996 the last rabid skunk occurred. Only bat variants of rabies were present until 1999, when the raccoon variant entered from New York (USA). The success of this experiment led to an expansion of the program to all of southern Ontario in 1994. Persistence of terrestrial rabies, and ease of elimination, appeared to vary geographically, and probably over time. Ecological factors which enhance or reduce the long term survival of rabies in wild foxes are poorly understood.

AERIAL DISTRIBUTION OF ONRAB® BAITS AS A TACTIC TO CONTROL RABIES IN RACCOONS AND STRIPED SKUNKS IN ONTARIO, CANADA

“…Although ERAH in Ontario Slim baits have proven to be effective in controlling the Arctic variant rabies in red foxes in Ontario (Rosatte et al, 1992(Rosatte et al, , 1993(Rosatte et al, , 2007aMacInnes et al, 2001), OMNR staff have had to rely on labor-intensive tactics such as population reduction and TVR to control the disease in striped skunks and raccoons because ERAH is not effective in these species (Rosatte et al, 2001). This study focussed on determining the feasibility of the aerial distribution of baits containing ONRABH oral rabies vaccine to immunize raccoons and striped skunks against rabies.…”

“…data). Fortunately, the Arctic variant of rabies has nearly been eliminated in Ontario as a result of oral rabies vaccination campaigns targeting red foxes (MacInnes, 1987;Johnston et al, 1988;Rosatte et al, 1992Rosatte et al, , 1993Rosatte et al, , 2007aMacInnes et al, 2001). During 1999, another strain of rabies, the raccoon (Procyon lotor) variant, was reported in Ontario (Wandeler and Salsberg, 1999;Rosatte et al, 2001).…”

“…The majority (66%) of those cases were in red foxes (Vulpes vulpes; 46%) and striped skunks (Mephitis mephitis; 20%) that were most likely infected with an Arctic variant of rabies virus (Johnston and Beauregard, 1969;MacInnes, 1987;Rosatte, 1988;Nadin-Davis et al, 1994;Canadian Food Inspection Agency, unpubl. data).…”

“…During the past two decades, much research has focused on the development of an oral vaccine that would orally immunize these three species in Ontario (Johnston et al, 1988;Rosatte et al, 1992;MacInnes et al, 2001;Rosatte et al, 2007b). One of the most promising vaccines has been a human adenovirus type 5-rabies glycoprotein recombinant vaccine (AdRG1.3); AdRG1.3 was modified from the first construct (AdRG1.0) in the early to mid-1990s at McMaster University, Hamilton, Ontario, Canada (Yarosh et al, 1996).…”

High-Density Baiting with ONRAB® Rabies Vaccine Baits to Control Arctic-Variant Rabies in Striped Skunks in Ontario, Canada

“…Until the late 1980s, red foxes (Vulpes vulpes) and striped skunks (Mephitis mephitis) accounted for the majority (approximately 60-65%) of rabies cases in Ontario . As red foxes were considered the primary wildlife RV reservoir species in Ontario, wildlife disease models predicted that the Arctic variant of RV would not be sustained in Ontario if 60-70% of the red fox population were vaccinated (MacInnes et al, 1988). A system was developed to orally immunize foxes by aerially distributing vaccine baits (ERAH) in the rabies enzootic areas of southern Ontario (Black and Lawson, 1980;MacInnes et al, 2001).…”