National Wildlife Research Center (NWRC)

PROJECT GOAL: Study the ecology of wildlife and evaluate risk factors that may be involved with the transmission of rabies among wildlife and rabies virus trafficking across landscapes and to develop methods and strategies that reduce or eliminate such transmission.

Project Accomplishments 2008

Rhodamine B as a Biomarker for Raccoons—In late 2006, NWRC researchers began an investigation of rhodamine B as an alternative biomarker to tetracycline in raccoons.  Rhodamine B is a chemical dye that, when ingested, stains the oral cavity and is absorbed systemically in growing tissues (i.e., hair and whiskers), producing fluorescent orange bands under ultraviolet (UV) light.  

In initial studies, rhodamine B marked all raccoons that consumed at least 100 mg of the dye.  An average of 55 percent of whiskers sampled from each individual exhibited fluorescence for up to 13 weeks.  The researchers used two methods to evaluate whiskers: a UV microscope and hand-held UV lights.  Both methods were effective for detecting the fluorescence produced by rhodamine B dye, and thus would be satisfactory for use in the field evaluation of whiskers to provide almost instant information.  The researchers also determined that raccoons did not exhibit a taste aversion to rhodamine B when it comprised less than 3 percent of a food source.    

Use of a Genetic Analysis to Evaluate the Effect of a Natural Barrier to Prevent the Western Spread of Rabies—The primary means of controlling wildlife rabies in the United States is through an oral rabies vaccination (ORV) program using a recombinant vaccinia-rabies vaccine.  This bait is distributed in oral baits targeting specific wildlife host species, principally raccoons and gray foxes.  Understanding the spatial spread of rabies and of the host species is necessary for designing control strategies.  The ORV program uses natural geographic barriers, such as mountains and large bodies of water, to help delineate ORV zones and slow the westward movement of raccoon rabies.

In Alabama, NWRC scientists collaborated with researchers from Auburn University to determine if gene flow occurred between raccoon populations across the Alabama River and thus determine whether this river served as a barrier to movement.  The scientists employed 11 raccoon-specific microsatellite markers to obtain individual genotypes of 70 individual animals.  The scientists examined if population differentiation among microsatellites was due primarily to distances between localities.  They found that gene flow occurred across the river, and therefore, that both the dispersal of animals across the river and possible subsequent rabies transmission can occur.  The spread of rabies across Alabama has been hindered, but this research indicates that the river is not the sole hindrance to the spread of rabies and that other landscape features still need to be investigated.

Project Homepage
Project Goal and Objectives
Accomplishments
Publications