Raccoon Rabies Project
The Natural Resources DNA Profiling and Forensic Centre (NRDPFC)at Trent Universityis working incollaboration with the Ontario Ministry of Natural Resources (OMNR), Canadian Food Inspection Agency (CFIA), Ontario Fur Managers Federation (OFMF), the Centres for Disease Control (CDC), Sir Sanford Fleming College, Queens University and Cornell University to understand the spread of raccoon rabies in North America. The research objective is to provide data that will be used to refine the control programs that are being implemented by the OMNR. The research is divided into three main areas: raccoon landscape genetics, rabies virus molecular epidemiology, and raccoon landscape ecology.
Photo courtesy: Gerald and Buff Corsi © California Academy of Science
Raccoon Genetic Ecology
The ultimate goal for this area of research is to identify mechanisms of raccoon dispersal and geographic barriers that may impede movement. This is to be accomplished by using raccoon samples collected through our collaborators and including the Fur Harvesters Auction (FHA) and the North American Fur Auctions (NAFA) that cover a broad geographic range of eastern North America. Using these samples genetic markers will be used to create DNA profiles. The profiles will then be analyzed to assess population structuring and gene flow across the landscape. This analysis will indicate what landscape features are acting as barriers to raccoon movement and used to help direct current international rabies control programs. The study will begin with the fine scale analyses of movement across the Ontario/New York border. Raccoon rabies has only recently been detected in the southeastern Ontario region (1999) and it is unclear how effective a barrier the St. Lawrence and Niagara rivers are to raccoon movement that may slow the progression of rabies into the province of Ontario
Rabies Virus Molecular Epidemiology
The prime objective of the viral part of this project is to identify individual raccoon rabies strains in order to monitor the movement of specific virus strains throughout eastern North America. Understanding the migration patterns of virus strains will help future implementation of effective control strategies for the disease when correlated to the movement of the vector, raccoons.
Rabies virus, the prototype of the Lyssavirus genus, is a bullet-shaped, enveloped negative strand RNA virus with an un-segmented genome. Rabies is capable of causing lethal encephalopathies in wide range of mammals, including raccoons. The Lyssavirus genome, that is about 12 kilobases, is organized into five coding regions: N, P, M, G and L. The N and G genes have proved to be the most useful in differentiating between rabies virus strains.
Raccoons that are potentially infected are tested by the Canadian Food Inspection Agency (CFIA) in Canada and by Center for Disease Control (CDC) and rabies lab in New York in the US, using the Fluorescent-antibody test (FAT). FAT positive animals will be further tested at the NRDPFC where sequencing of the N and G genes of the viral isolates will be performed using universal primers. Variations in protein sequence will be used to differentiate between raccoon rabies virus strains.
An additional goal of this project is to identify the early stage incubators for the disease around the infected area. To accomplish this, raccoons that were negative for rabies by the FAT will be re-tested using a highly sensitive PCR reaction that incorporates fluorescence so small amounts of positive product will be detected. This method has a much higher sensitivity for the rabies virus detection than FAT thus, it is potentially better suited for identifying animals that are in the early stage of the disease.
Image of a Rabies virus-infected neuronal cell,the red stain indicates areas of rabies viral antigen, image courtesy of Centre for Disease Control, Atlanta
Photo courtesy: Gerald and Buff Corsi © California Academy of Sciences
Raccoon Rabies Spatial Ecology
The spatial ecology component of the research project has two key elements:
i) investigating the relationships between the spatial and temporal patterns of rabies
a) structuring in the genetic characteristics of virus and raccoon populations and
b) patterns of physiography, climate and land use.
ii) developing the Ontario Raccoon Rabies Model to
a) include genetic information so that the model can be more rigorously validated against raccoon and rabies genetic data collected in the field.
b) improve parameter estimates for the Ontario Raccoon Rabies Model based on results of the raccoon and rabies genetics components of the project.
c)assess the effectiveness of a combinations of rabies control strategies, including trap-vaccinate-release, aerial distribution of oral vaccines, depopulation, more efficient surveillance, more effective vaccines.
Pattern of raccoon rabies spread 1977-1999. Map courtesy of Centre for Disease Control, Atlanta. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4902a3.htm
The map to the left illustrates the variation in the rates of spread of raccoon rabies. Some of this variation is attributable to topography, human transport of raccoons, differences in raccoon behaviour and rabies control efforts. The project is exploring the relative importance these types of determinants of rabies spread and the implications for control measures.
The Ontario Raccoon Rabies Model is the tool which will incorporate the understanding of raccoon rabies ecology gained through the project. It will be the primary means of transferring the results of the research project to managers required to make decisions about how to control rabies. It will also serve as a tool for communicating to the public and political bodies the rationale for particular control decisions.
Model distribution of rabid raccoons after 67 years of simulation. Map courtesy of Queen’s University GIS Laboratory http://www.gis.queensu.ca
– Natural Sciences and Engineering Research Council (NSERC) Strategic grant
1. Ontario Ministry of Natural Resources, Rabies in Ontario
2. Ontario Ministry of Natural Resources Rabies Reporter
3. Canadian Food Inspection Agency
4. Geographic Information Systems Laboratory at Queen’s University, Kingston
5. Centre for Disease Control (USA) rabies home page
6. Cornell St. Lawrence/ Niagara Rabies Control Program
7. Rabies in the Americas
Rees,E.E. Bruce A. Pond, Catherine I. Cullingham, Rowland R. Tinline, David Ball, Christopher J. Kyle, Bradley N. White.(2010) Landscape modeling genetic bottlenecks: implications for raccoon rabies disease spread. Biology Letters, 5(3), 387-390.
Cullingham, C.I., Kyle, C.J., Rees. E.E., Pond, B.A., and White B.N. (2009). Differential permeability of rivers to raccoon gene flow corresponds to rabies incidence in Ontario Canada. Mol. Ecol. 18, 43-53.
Cullingham, C.I., Pond, B.A., Kyle, C.J., Rees, E.E. Rosatte, R.C., White, B.N. (2009).Combining direct and indirect genetic methods to estimate dispersal to inform disease management protocols. Mol. Ecol.17. 4874-4886.
Cullingham, C.I.. Kyle, C.J. Pond, B.A. and White B.N. (2008) Population genetic structure of raccoons in eastern North America based on mtDNA: implications for sub-species designations and rabies disease dynamics. Can J. Zool. 86, 947-958.
Szanto, Annamaria, Susan A. Nadin-Davis, Bradley N. White. (2008) Complete Genome Sequence of a Raccoon Rabies Virus Isolate from Canada. Virus Research, 136, 130-139.
Rees E.E., Pond B.A., Cullingham C.I., Rowland, R.T., Ball, D., Kyle C.J., and White B.N. (2008). Assessing a landscape barrier using genetic simulation modelling: implications for raccoon rabies management. Preventative Veterinary Medicine. 86. 107-123.199
Cullingham, C.I., Kyle, C., White, B.N. (2006) Isolation, characterization and multiplex genotyping of raccoon tetranucleotide microsatellite loci. Mol. Ecol. Notes 7, 160-162.