The Role of Bait Manipulation in the Delivery of Oral Rabies Vaccine to Skunks

The majority of rabies cases reported to the Centers for Disease Control each year occur in wildlife including skunks, raccoons, bats, foxes, and coyotes. Currently, oral rabies vaccination campaigns are employed to immunize coyotes, foxes, and raccoons. Though skunks are vectors of 6 rabies strains, there is currently no effective oral vaccine or delivery system for skunks. More information is needed to determine if baits currently used are sufficiently attractive to skunks, or if the baits are difficult for skunks to handle and consume. We observed bait manipulation by skunks in penned/feeding trials to determine the bait type most conducive to ingestion and delivery of a mock vaccine to skunks. Smaller baits were easier for skunks to manipulate and consume, and vaccine containers coated with bait facilitated sachet puncture and increased the potential for vaccine delivery. Our information will be useful in the development of baits and vaccine containers for large-scale rabies vaccination campaigns that target skunks

Oral Rabies Vaccine (ORV) Bait Uptake by Striped Skunks: Preliminary Results

Aerial delivery of rabies vaccine-laden bait is effective and efficient for large-scale vaccination of wildlife. Oral rabies vaccine (ORV) contained in a sachet (or blister pack) inside baits that serve as the mode of delivery currently are used for orally immunizing foxes, raccoons, and coyotes. The technique remains in the vaccine-development stage for oral immunization of skunks. Since skunks are a major vector of the rabies virus, concurrent development of a bait that is sufficiently attractive to skunks would facilitate an immediate mode of delivery once a vaccine is developed. We ran a palatability experiment with different shapes and flavors of baits to assess uptake by captive skunks. The flavors most preferred were fish and chicken. We also evaluated the fate of the sachet (punctured or not) inside baits, which would assist in assessing the delivery of a vaccine dose. On average, cylindrical-shaped baits had a higher percentage of punctured sachets than did rectangular-shaped baits, and baits with their matrix directly coated onto the sachet had a higher percentage of punctured sachets than did those baits in which the sachet was held. We also used sulfadimethoxine, a short-term quantifiable biomarker, as a mock vaccine inside sachets in an attempt to quantify the amount of liquid ingested by skunks after consuming baits of different shape and size. While this information could have been useful for assessing the amount of vaccine delivered via sachet puncture, it could not be determined due to an aversive tasting biomarker. For effective ORV bait uptake by skunks, modifications to current baits should include a smaller size and a meat flavor matrix that is directly coated onto the sachet

Determination of Sulfadimethoxine Residues in Skunk Serum by HPLC

Sulfadimethoxine (SDM) was extracted from skunk serum and isolated by reversed-phase high performance liquid chromatography. SDM was detected by ultra-violet absorbance at 270 nm and quantified by comparison to an external calibration standard. Recovery data were determined by analyzing SDM fortified control serum. The overall mean recovery with relative standard deviations of SDM in fortified skunk serum samples was 99±7%. The recovery for 0.38, 5.2, and 14.2 μg/mL SDM was 96.0±7.5%, 102±6.1%, and 97.3±5.1%, respectively. The method limit of detection for SDM in skunk serum ranged from 0.032 to 0.057 μg/mL SDM with a mean value of 0.040 mg/mL SDM. The method reported is much simpler and equally efficient as previous methods developed for the determination of SDM residues in serum

Data from: The walk is never random: subtle landscape effects shape gene flow in a continuous white-tailed deer population in the Midwestern United States

One of the pervasive challenges in landscape genetics is detecting gene flow patterns within continuous populations of highly mobile wildlife. Understanding population genetic structure within a continuous population can give insights into social structure, movement across the landscape and contact between populations, which influence ecological interactions, reproductive dynamics, or pathogen transmission. We investigated the genetic structure of a large population of deer spanning the area of Wisconsin and Illinois, USA, affected by chronic wasting disease. We combined multi-scale investigation, landscape genetic techniques and spatial statistical modeling to address the complex questions of landscape factors influencing population structure. We sampled over 2,000 deer and used spatial autocorrelation and a spatial principal components analysis to describe the population genetic structure. We evaluated landscape effects on this pattern using a spatial auto-regressive model within a model selection framework to test alternative hypotheses about gene flow. We found high levels of genetic connectivity, with gradients of variation across the large continuous population of white-tailed deer. At the fine scale, spatial clustering of related animals was correlated with the amount and arrangement of forested habitat. At the broader scale, impediments to dispersal were important to shaping genetic connectivity within the population. We found significant barrier effects of individual state and interstate highways and rivers. Our results offer an important understanding of deer biology and movement that will help inform the management of this species in an area where over-abundance and disease spread are primary concerns

DeerXYData

Spatial coordinates for use with adegenet code

DeerLandscapeGeneticData

This tab-delimited text file contains the spatial and genetic data on which our analysis was based. Column DEER gives a unique reference number for each individual white-tailed deer sampled. Columns SampleTownshipX and SampleTownshipY give the spatial coordinates of the sample township from which each animal was collected (note these coordinates locate each deer to its sample population, not its individual capture location). Coordinates are in WTMs – the UTM specific to Wisconsin. Columns BM6506 thru RT9 give microsatellite genotypes for each individual at each locus listed. Genotypes are given in 3-digit Genepop format, 000 designates a missing allele

DeerGeneticData

Genepop file for use with adegenet code

Evaluating spatial overlap and relatedness of white-tailed deer in a chronic wasting disease management zone.

Wildlife disease transmission, at a local scale, can occur from interactions between infected and susceptible conspecifics or from a contaminated environment. Thus, the degree of spatial overlap and rate of contact among deer is likely to impact both direct and indirect transmission of infectious diseases such chronic wasting disease (CWD) or bovine tuberculosis. We identified a strong relationship between degree of spatial overlap (volume of intersection) and genetic relatedness for female white-tailed deer in Wisconsin's area of highest CWD prevalence. We used volume of intersection as a surrogate for contact rates between deer and concluded that related deer are more likely to have contact, which may drive disease transmission dynamics. In addition, we found that age of deer influences overlap, with fawns exhibiting the highest degree of overlap with other deer. Our results further support the finding that female social groups have higher contact among related deer which can result in transmission of infectious diseases. We suggest that control of large social groups comprised of closely related deer may be an effective strategy in slowing the transmission of infectious pathogens, and CWD in particular