Abstract
Disease control programs aim to constrain and reduce the spread of infection. Human disease interventions such as wildlife vaccination play a major role in determining the limits of a pathogen’s spatial distribution. Over the past few decades, a raccoon-specific variant of rabies virus (RRV) has invaded large areas of eastern North America. Although expansion into Canada has been largely prevented through vaccination along the US border, several outbreaks have occurred in Canada. Applying phylogeographic approaches to 289 RRV whole-genome sequences derived from isolates collected in Canada and adjacent US states, we examined the processes underlying these outbreaks. RRV incursions were attributable predominantly to systematic virus leakage of local strains across areas along the border where vaccination has been conducted but also to single stochastic events such as long-distance translocations. These results demonstrate the utility of phylogeographic analysis of pathogen genomes for understanding transboundary outbreaks.
Highlights
Disease control programs aim to constrain and reduce the spread of infection
The highdensity sampling in New York and Vermont enabled us to focus sampling on cases within 75 km of the Canada border in these 2 states (54 sequenced samples in New York and 62 in Vermont), with the aim of capturing representatives of most raccoon-specific variant of rabies virus (RRV) lineages circulating near the border
Because our sampling scheme focuses on RRV infections near the Canada border in western and northern New York, only 5 of the samples from New York sequenced here fall into clade I
Summary
Disease control programs aim to constrain and reduce the spread of infection. Human disease interventions such as wildlife vaccination play a major role in determining the limits of a pathogen’s spatial distribution. RRV incursions were attributable predominantly to systematic virus leakage of local strains across areas along the border where vaccination has been conducted and to single stochastic events such as long-distance translocations. These results demonstrate the utility of phylogeographic analysis of pathogen genomes for understanding transboundary outbreaks. Geopolitical boundaries generally do not directly affect spread of infectious diseases, human-imposed control measures are often structured around national or international borders. The first outbreak of RRV in Quebec occurred during 2006–2009, near the Vermont border [10] Another isolated case of raccoon rabies was reported in 2015 at the border with New York in southwestern Quebec [7]
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