SAFETY AND IMMUNOGENICITY OF ONRAB® IN RACCOONS AND SKUNKS IN WEST VIRGINIA – 2011FIELD TRIAL REPORT

In 2011, a field trial was conducted in southeastern West Virginia to evaluate the safety and immunogenicity of a live recombinant human adenovirus (serotype 5)-rabies glycoprotein vaccine (ONRAB) in wild raccoons and skunks. ONRAB was selected for evaluation based on the success achieved in eliminating raccoon rabies from Ontario and Quebec, Canada, through the integration of this vaccine into rabies management strategies and significantly higher seropositivity in comparison to Raboral V-RG in studies along the U.S.-Canada border. The field trial site was composed of forested and agricultural habitats in an area where raccoon rabies is enzootic and oral rabies vaccine (ORV) has never been used as a management strategy. The ULTRALITE bait is composed of a small blister pack that contains the ONRAB vaccine with a waxy coating matrix of sweet attractants, impregnated with tetracycline biomarker, camouflaged by a khaki green dye. Approximately 80,000 baits were distributed at 75 baits/km mostly by fixed wing aircraft along parallel flight lines spaced at 750 m intervals. There were no phone calls related to human or pet bait contacts reported through the affixed, legible toll free phone number on each bait. Relatively low human population density in the study area and bait attributes that may make them less attractive to dogs could have been contributing factors resulting in no reported bait contacts. Histopathology results from up to 23 tissue types from diverse target and nontarget wildlife species samples pre (n=290) and post-ORV (n=300) with ONRAB will be provided under a separate cover once the analysis is completed. No differences were observed between control and treatment captive animals, including cottontail rabbit (Sylvilagus floridanus), opossum (Didelphis virginiana), fox squirrel (Sciurus niger), and eastern wild turkey (Meleagris gallopavo silvestri) that received a 10x ONRAB dose in a companion histopathology study conducted at the Wildlife Services (WS), National Wildlife Research Center. These species that have not been previously evaluated for potential ONRAB effects are common to the West Virginia field trial site. The proportion of raccoons categorized as seropositive was significantly higher in (P< 0.05) the post-ORV ONRAB baiting period (49.4%, n=296) in comparison to the pre-ORV (9.6%, n=395)) period (naïve to ORV either with ONRAB or Raboral V-RG but where raccoon rabies is enzootic). The 49.4% sero-positivity in raccoons was the highest observed by WS for areas with similar management histories that were baited once at 75 baits/km with Raboral V-RG. Biomarker presence was significantly (P<0.05) higher among sero-positive raccoons post-ORV and similar (P>0.05) among raccoons during the pre-ORV period, an indication of vaccine-induced rabies virus neutralizing antibodies (RVNA) following bait consumption. Skunk sample size was inadequate to assess ONRAB effects, but other studies have not shown a strong RVNA response at 75 baits/km. Overall, the safety and immunogenicity outcomes from this field trial support replicating the West Virginia field trial to determine if raccoon population immunity would increase as a function of a second annual ORV campaign with ONRAB. Expansion of field trials into other strategic areas such as the Ohio contingency action zone, the Niagara Frontier and along the Quebec border with New York, Vermont and New Hampshire is recommended. ONRAB® (Human Adenovirus Serotype-5) Oral Rabies Vaccine Field Trial Report, West Virginia 2011