Shylo R. Johnson

Safety And Immunogenicity Of Ontario Rabies Vaccine Bait (Onrab) In The First Us Field Trial In Raccoons ( Procyon lotor )

Abstract In 2011, we conducted a field trial in rural West Virginia, USA to evaluate the safety and immunogenicity of a live, recombinant human adenovirus (AdRG1.3) rabies virus glycoprotein vaccine (Ontario Rabies Vaccine Bait; ONRAB) in wild raccoons (Procyon lotor) and striped skunks (Mephitis mephitis). We selected ONRAB for evaluation because of its effectiveness in raccoon rabies management in Ontario and Quebec, Canada, and significantly higher antibody prevalence rates in raccoons compared with a recombinant vaccinia-rabies glycoprotein (V-RG) vaccine, Raboral V-RG®, in US–Canada border studies. Raccoon rabies was enzootic and oral rabies vaccination (ORV) had never been used in the study area. We distributed 79,027 ONRAB baits at 75 baits/km2 mostly by fixed-wing aircraft along parallel flight lines at 750-m intervals. Antibody prevalence was significantly higher at 49.2% (n = 262) in raccoons after ONRAB was distributed than the 9.6% (n = 395) before ORV. This was the highest antibody prevalence observed in raccoons by US Department of Agriculture Wildlife Services for areas with similar management histories evaluated before and after an initial ORV campaign at 75 baits/km2 with Raboral V-RG. Tetracycline biomarker (TTCC) was significantly higher among antibody-positive raccoons after ONRAB baiting and was similar among raccoons before ORV had been conducted, an indication of vaccine-induced rabies virus–neutralizing antibody production following consumption of bait containing TTCC. Skunk sample size was inadequate to assess ONRAB effects. Safety and immunogenicity results supported replication of this field trial and led to a recommendation for expanded field trials in 2012 to evaluate safety and immunogenicity of ground-distributed ONRAB at 150 baits/km2 in residential and commercial habitats in Ohio, USA and aerially distributed ONRAB at 75 baits/km2 in rural habitats along US–Quebec border.

Multidisciplinary approach to epizootiology and pathogenesis of bat rabies viruses in the United States.

Zoonotic disease surveillance is typically initiated after an animal pathogen has caused disease in humans. Early detection of potentially high‐risk pathogens within animal hosts may facilitate medical interventions to cope with an emerging disease. To effectively spillover to a novel host, a pathogen may undergo genetic changes resulting in varying transmission potential in the new host and potentially to humans. Rabies virus (RABV) is one model pathogen to consider for studying the dynamics of emerging infectious diseases under both laboratory and field conditions. The evolutionary history of RABV is characterized by regularly documented spillover infections and a series of notable host shifts. Within this context, enhanced field surveillance to improve detection of spillover infections will require validated techniques to non‐invasively differentiate infected from non‐infected individuals. In this study, we evaluate the use of infrared thermography to detect thermal changes associated with experimental RABV infection in big brown bats (Eptesicus fuscus) in a captive colony. Our results indicated that 62% of rabid bats had detectable facial temperature decreases (−4.6°C, SD ± 2.5) compared with pre‐inoculation baseline values. These data suggest potential utility for discriminating rabid bats in natural field settings. In addition, focusing upon RABV circulating in the United States between 2008 and 2011, we confirmed spillover events of bat RABV among carnivores and identified cross‐species transmission events caused by four lineages of RABV associated with insectivorous bats. Additionally, our analysis of RABV glycoprotein sequences identified substitutions in antigenic sites that may affect neutralizing activity associated with monoclonal antibodies proposed for use in human post‐exposure prophylaxis. This study provides a glimpse into RABV pathobiology and spillover dynamics among and between bats and a variety of mesocarnivores.

Active use of coyotes (Canis latrans) to detect Bovine Tuberculosis in northeastern Michigan, USA.

Bovine tuberculosis (bTB) is endemic in white-tailed deer (Odocoileus virginianus) in northeastern Michigan, USA, and research suggests transmission to cattle. Prevalence of the disease in deer is estimated at 1.8%, but as prevalence decreases the difficulty of detection increases. Research suggests coyotes (Canis latrans) have a higher prevalence of bTB in Michigan than deer and sampling coyotes may be a more efficient surveillance tool to detect presence or spread of the disease. Coyotes possess suitable ecological characteristics to serve as a sentinel species, assuming transmission between coyotes is not significant. The question of whether free-ranging coyotes shed Mycobacterium bovis, the causative agent of bTB, has not been previously addressed. We actively used coyotes as a sentinel to detect bTB in infected and uninfected counties in Michigans Northeastern Lower Peninsula. We determined whether bTB infection was present through bacteriologic culture of lymph nodes and tissues containing lesions and cultured oral/nasal swabs and feces to establish shedding. Seventeen of 171 coyotes were M. bovis culture positive, one of which was from a previously uninfected county. All oral, nasal secretions and feces were culture negative suggesting minimal, if any, shedding of M. bovis. Thus, infection of coyotes is likely to occur through ingestion of infected deer carcasses and not from interaction with conspecifics. These findings support previous research suggesting that coyotes are useful sentinels for bTB. The use of coyotes as a sentinel, may allow wildlife managers to detect the spread of bTB into naïve counties. With earlier detection managers may be able to take proactive surveillance measures to detect the disease in deer and reduce the potential risk to domestic livestock and captive deer herds.

A behaviorally-explicit approach for delivering vaccine baits to mesopredators to control epizootics in fragmented landscapes.

Despite the widespread use of aerial baiting to manage epizootics among free-ranging populations, particularly in rabies management, bait acceptance and seroconversion rates often are lower than required to eliminate spread of disease. Our objectives in this study, therefore, were to evaluate the performance of stratified bait distribution models derived from resource selection functions (RSF) on uptake of placebo rabies baits by raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana), as well as the probability of bait uptake as a function of proximity to bait distribution areas in fragmented agricultural ecosystems. Among 478 raccoons and 108 opossums evaluated for presence of Rhodamine B (RB) across 8 sites, only 26% of raccoons and 20% of opossums exhibited marking consistent with bait consumption 14–24 days post-baiting. The effective area treated, based on 90% kernel density estimators of marked individuals, ranged from 99–240 ha larger than bait distribution zones, with RB marked individuals captured up to 753m beyond the bait zone. Despite incorporation of RSF data into bait distribution models, no differences in uptake rates were observed between treatment and control sites. These data likely reflect the underlying constraints imposed by the loss and fragmentation of habitat on animal movement in heterogeneous landscapes, forcing individuals to optimize movements at coarse (i.e., patch-level) rather than fine spatial scales in highly fragmented environments. Our data also confirm that the probability of bait acceptance decreases with increasing distance from bait zone interiors, even within the zone itself. Thus, although bait acceptance was confirmed beyond bait zone boundaries, the proportion of vaccinated individuals may comprise a small minority of the population at increasing distances from baiting interiors. These data suggest focal baiting creates a buffered area of treated individuals around bait zones or bait stations, but repeated treatments may be needed to achieve sufficient uptake to eradicate disease.

Exposure to Rabies in Small Indian Mongooses (Herpestes auropunctatus) from Two Regions in Puerto Rico

Abstract The small Indian mongoose (Herpestes auropunctatus) was introduced to several Caribbean Islands to control rat (Rattus spp.) damage to sugarcane plantations. Mongooses failed at suppressing rat populations and are now considered pests throughout most of their introduced range. Importantly, mongooses are rabies reservoirs on several Caribbean Islands. In Puerto Rico, mongooses have been implicated in up to 70% of reported animal rabies cases. There is no rabies vaccination program for wildlife in Puerto Rico, and data on rabies in mongooses are limited. We conducted a serosurvey of mongooses in two different ecologic environments in Puerto Rico: El Yunque National Forest and Cabo Rojo National Wildlife Refuge. We collected 119 serum samples from 112 mongooses, 44 (39.3%) of which were positive for rabies virus–neutralizing antibodies. We also collected oral swabs from 147 mongooses, including 88 from which we also collected serum. No oral swabs were positive for rabies virus RNA. Our data support previous research suggesting rabies virus is circulating within the mongoose population on Puerto Rico.

EVALUATION OF ANTHELMINTIC FISHMEAL POLYMER BAITS FOR THE CONTROL OF BAYLISASCARIS PROCYONIS IN FREE-RANGING RACCOONS (PROCYON LOTOR)

Abstract Baylisascaris procyonis is a common gastrointestinal parasite of raccoons (Procyon lotor) and is a zoonotic helminth with the potential to cause severe or fatal infection. Raccoons thrive in human-dominated landscapes, and the fecal-oral transmission pathway and lack of effective treatment make B. procyonis a serious threat to public health. The distribution of medicinal baits has emerged as a socially acceptable and cost-effective method for managing disease in free-ranging wildlife. We assessed the suitability of a mass-producible anthelmintic bait for B. procyonis mitigation by evaluating the willingness of free-ranging raccoons to consume anthelmintic baits and determining whether bait consumption successfully cleared B. procyonis infections from raccoons. Anthelmintic baits were modified from standard fishmeal polymer baits, the food attractant commonly used in oral rabies vaccine baits, with the introduction of 220 mg of pyrantel pamoate into the fishmeal mixture. We captured 16 naturally infected raccoons, presented one anthelmintic bait, and monitored B. procyonis infection over 90 d by screening feces for eggs. Treatment cleared B. procyonis infections for nine of 12 raccoons that consumed >10 g of the 15 g bait. We used remote cameras to monitor in situ patterns of bait consumption for anthelmintic baits relative to standard baits. Both anthelmintic and standard baits were rapidly consumed, with no differences in the rate of consumption between bait types. However, after bait contact, raccoons demonstrated a greater willingness to consume standard baits while ignoring anthelmintic baits more frequently (P = 0.06). Initial trials of anthelmintic baits show promise, although refinement in both dose and palatability is needed. At mass production scales, the addition of pyrantel pamoate to fishmeal polymer baits would be inexpensive, potentially making anthelmintic baits a viable management option when coupled with an oral rabies vaccine or used independently for B. procyonis mitigation.

BAIT DEVELOPMENT FOR ORAL DELIVERY OF PHARMACEUTICALS TO RACCOONS (PROCYON LOTOR) AND STRIPED SKUNKS (MEPHITIS MEPHITIS)

Abstract Oral vaccination is one tool used to control wildlife diseases. A challenge to oral vaccination is identifying baits specific to target species. The US has been conducting oral vaccination against rabies since the 1990s. Improvements in bait development will hasten disease elimination. In Colorado, we examined a novel bait for oral vaccination and offered two different flavors, sweet and fish, to captive raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) to assess consumption and flavor preference and observed bait removal by target and nontarget species in the field. During captive trials, raccoons and skunks consumed 98% and 87% of offered baits, respectively. Baits contained a sachet to simulate a vaccine package. Raccoons and skunks consumed 98% and 94% of the sachets, respectively. All unconsumed sachets were punctured, suggesting that animals had oral exposure to the contents. Raccoons preferred fish-flavored bait, but skunks did not have a preference. In the field, raccoons consumed the most baits, followed by fox squirrels (Sciurus niger). Other rabies host species (striped skunks, red foxes [Vulpes vulpes], coyotes [Canis latrans]) had very low visitation and were never observed consuming baits. High consumption rates by raccoons and skunks in captivity and observance of raccoons consuming baits in the field suggest that these baits may be useful for oral delivery of pharmaceuticals. Further field research is warranted to determine how to best optimize bait delivery.

Bait Matrix Flavor Preference by Mongoose (Herpestes auropunctatus) in Puerto Rico: Implications for Oral Rabies Vaccination

Abstract The small Indian mongoose (Herpestes auropunctatus) is the primary rabies vector in Puerto Rico. Mongooses are implicated in up to 74% of rabies cases on the island, and pose a threat to domestic animals and human health and safety. No rabies management program exists in Puerto Rico and development of an oral rabies vaccination program requires determining which flavors on the vaccines bait coating matrix that are attractive to mongooses. Our objective was to evaluate preference among three flavors (cheese, coconut and fish) in the Ultralite bait matrix that is used for delivery of Rabies Vaccine, Live Adenovirus Vector (ONRAB®). Placebo baits were offered to free-ranging mongooses in two different ecological environments. The study was conducted at El Yunque National Forest and Cabo Rojo National Wildlife Refuge. At each site we established bait stations with three bait flavors offered simultaneously. We placed a remote camera at each station to monitor bait fate. Cheese ranked higher than fish flavor (W = 1473, P = 0.0273) and cheese and fish both ranked significantly higher than coconut (W = 2180.5, P < 0.0001 and W = 2065.0, P = 0.0008, respectively). These results suggest cheese and fish flavors should perform better than coconut flavor in attracting free-ranging mongooses to consume ONRAB® baits in Puerto Rico.

FLAVOR PREFERENCE AND EFFICACY OF VARIABLE DOSE ONTARIO RABIES VACCINE BAIT (ONRAB) DELIVERY IN STRIPED SKUNKS (MEPHITIS MEPHITIS)

ABSTRACT In North America, terrestrial wildlife rabies control is achieved by oral rabies vaccination programs that principally target mesocarnivores. Success at rabies control in striped skunks (Mephitis mephitis) has been more limited and may require additional enhancements to existing bait products or novel bait designs and attractants. We evaluated preference among captive striped skunks for six different flavors of placebo Ontario Rabies Vaccine Bait (ONRAB®) “Ultralite” Baits (Artemis Technologies, Guelph, Ontario, Canada). Different doses and delivery methods of ONRAB vaccine were tested for efficacy in a subsequent experiment with the same skunks. Cheese-, egg-, and chicken-flavored baits were preferred over plain-flavored baits, but a strong preference for a singular flavor was not observed. Vaccine efficacy of 80–100% was observed among skunks challenged at 335 d postvaccination across a log range of doses tested by a direct instillation into the oral cavity route, respectively (109.3−1010.2 median tissue culture infective doses), in contrast to more-limited efficacy by bait delivery. Our results extended the duration of ONRAB vaccine efficacy in skunks and suggested that there may be limited flexibility to alter vaccine titer and volume in novel bait designs for skunks.

Bird Feeders as Locations for Skunk Uptake of Oral Rabies Vaccine Baits

Abstract Significantly more (54%, P=0.003) placebo baits placed under 26 bird feeders in Arizona, US were removed by striped skunks (Mephitis mephitis) than at paired, nonfeeder locations (19%). Baiting at bird feeders could supplement traditional oral rabies vaccine bait placement in urban-suburban areas while engaging the public in rabies control efforts.