The Seasonal Timing of Snowshoe Hare Virus Transmission on the Island of Newfoundland, Canada

A Scoping Review on the Epidemiology of Orthobunyaviruses of Canadian Public and Animal Health Relevance in the Context of Vector Species

Background: Mosquito-borne orthobunyaviruses are a growing priority for public and animal health in Canada. It is anticipated that disease incidence will increase due to a warming climate, given that habitats are expanding for reservoir hosts and vectors, particularly in Canada. Little is known about the ecology of primary vectors that perpetuate these orthobunyaviruses, including the viral transmission cycle and the impact of climatic and landscape factors. Methods: A scoping review was conducted to describe the current state of knowledge on the epidemiology of orthobunyaviruses relevant to Canada. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines was used to characterize studies focused on vector species. A literature search was conducted in six databases and gray literature. Eligible studies characterized orthobunyavirus epidemiology related to vector species, including viral competency, geospatial distributions, seasonal trends, and/or risk factors. Results: A total of 1734 unique citations were identified. Screening of these citations revealed 172 relevant studies, from which 87 studies presented primary data related to vectors. The orthobunyaviruses included Cache Valley virus (CVV), Jamestown Canyon virus (JCV), Snowshoe Hare virus (SHV), and La Crosse virus (LACV). Surveillance was the predominant study focus, with most citations representing the United States, specifically, LACV surveillance in Tennessee, followed by CVV and JCV in Connecticut. Orthobunyaviruses were detected in many mosquito species across multiple genera, with high vector specificity only being reported for LACV, which included Aedes triseriatus, Aedes albopictus, and Aedes japonicus. Peridomestic areas were positively associated with infected mosquitoes compared with dense forests. Orthobunyavirus infections, coinfections, and gut microbiota affected mosquito feeding and breeding behavior. Conclusion: Knowledge gaps included Canadian surveillance data, disease modeling, and risk projections. Further research in these areas, especially accounting for climate change, is needed to guide health policy for prevention of orthobunyaviral disease.

A Scoping Review on the Epidemiology of Orthobunyaviruses in Canada, in the Context of Human, Wildlife, and Domestic Animal Host Species

Background: Mosquito-borne orthobunyaviruses in Canada are a growing public health concern. Orthobunyaviral diseases are commonly underdiagnosed and in Canada, likely underreported as surveillance is passive. No vaccines or specific treatments exist for these disease agents. Further, climate change is facilitating habitat expansion for relevant reservoirs and vectors, and it is likely that the majority of the Canadian population is susceptible to these viruses. Methods: A scoping review was conducted to describe the current state of knowledge on orthobunyavirus epidemiology in Canada. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guideline was used. Literature searches were conducted in six databases and in gray literature. The epidemiology of orthobunyaviruses was characterized for studies focusing on host species, including spatiotemporal patterns, risk factors, and climate change impact. Results: A total of 172 relevant studies were identified from 1734 citations from which 95 addressed host species, including humans, wildlife, and domestic animals including livestock. The orthobunyaviruses-Cache Valley virus (CVV), Jamestown Canyon virus (JCV), Snowshoe Hare virus (SHV), and La Crosse virus (LACV)-were identified, and prevalence was widespread across vertebrate species. CVV, JCV, and SHV were detected across Canada and the United States. LACV was reported only in the United States, predominantly the Mid-Atlantic and Appalachian regions. Disease varied by orthobunyavirus and was associated with age, environment, preexisting compromised immune systems, or livestock breeding schedule. Conclusion: Knowledge gaps included seroprevalence data in Canada, risk factor analyses, particularly for livestock, and disease projections in the context of climate change. Additional surveillance and mitigation strategies, especially accounting for climate change, are needed to guide future public health efforts to prevent orthobunyavirus exposure and disease.