Rapid identification of the raccoon rabies virus variant using a real-time reverse-transcriptase polymerase chain reaction

The raccoon-associated variant of rabies virus (RRV) is enzootic throughout the eastern seaboard of the United States with frequent incursions into Canada. Many wildlife management agencies are actively engaged in control programmes targeting elimination of this disease and rapid identification of raccoon rabies cases is crucial to the success of these operations. This report documents the development of a reverse transcriptase real-time PCR (RT-qPCR) that specifically identifies this rabies virus variant (RRV RT-qPCR) and which can be readily multiplexed with a generic rabies virus RT-qPCR for use as a typing tool. Using a large collection of rabies virus samples representative of the variants circulating around the world, but with a focus on those occurring in the Americas, the RRV RT-qPCR was 100% sensitive and 99.31% specific. To further apply these assays for diagnostic purposes, addition of an RT-qPCR targeting the host β-actin mRNA, which serves as an internal amplification control, in a triplex format was shown to yield highly comparable results using a subset of our viral collection. Use of these assays for early and accurate identification of this viral variant will help to optimize the utilization of resources required for control of this disease.

Raccoon rabies outbreak in Hamilton, Ontario: A progress report

BACKGROUND

Raccoon rabies is caused by a variant of the rabies virus found in raccoons but transmissible to other mammalian species, including humans. The disease of rabies caused by raccoon variant rabies virus is indistinguishable from rabies caused by other rabies virus variants.

OBJECTIVE

This paper describes the raccoon rabies outbreak in Ontario (identified in December 2015) and the control measures undertaken to curb the spread of the epizootic using the One Health approach.

INVESTIGATION AND RESULTS

Representatives from local, provincial and federal agencies collectively activated a raccoon rabies response that involved policy updates, enhanced surveillance, a public education campaign and mass vaccination of wildlife and domestic animals. Between December 2015 and June 2017, 338 animals tested positive for raccoon rabies in Ontario. While the majority of the cases were raccoons, there was significant spillover into striped skunks, as well as other species including two cats, a fox and a llama. Viral genome sequencing determined that this epizootic was likely caused by long-distance translocation from the United States.

CONCLUSION

This outbreak of raccoon rabies is by far the largest to have occurred in Canada and the first raccoon rabies outbreak documented in a densely populated urban area. This is also the first time this rabies virus variant has been identified in a domestic animal in Canada. A collaborative approach involving numerous stakeholders in the public and private sectors has been instrumental in addressing this epizootic. Though case incidence appears to be declining, several years will likely be required to reach elimination. Continued collaboration between these agencies is necessary to achieve this goal.