Prevalence of Powassan virus in Southwestern Ontario, with a focus on vector and host dynamics

Powassan virus (POWV) is a tick-borne flavivirus that was first diagnosed in 1958 from a fatal human case of encephalitis in Powassan, Ontario. POWV has two distinct genetic lineages: Powassan prototype (POWV-p), which is... [ view full abstract ]

Powassan virus (POWV) is a tick-borne flavivirus that was first diagnosed in 1958 from a fatal human case of encephalitis in Powassan, Ontario. POWV has two distinct genetic lineages: Powassan prototype (POWV-p), which is maintained between Ixodes cookei ticks and groundhogs (Marmota monax), striped skunks (Mephitis mephitis) and other mammals, and deer tick virus (DTV), which is maintained between I. scapularis ticks and white-footed mice (Peromyscus leucopus). Currently, the geographic distribution of POWV in Ontario and the involvement of wildlife in virus maintenance and transmission are poorly understood. The objective of the present study is to determine the prevalence of POWV in targeted regions of Ontario and better understand wildlife host-vector ecology. We predict that: (1) striped skunks and groundhogs will have higher POWV seroprevalence than other mammals tested (e.g., raccoons [Procyon lotor], eastern gray squirrels [Sciurus carolinensis] and red squirrels [Tamiasciurus hudsonicus]); and (2) seropositive animals will have heavier infestations of I. cookei than seronegative animals. Live animal trapping will occur in spring and summer of 2016 and will target striped skunks, groundhogs, raccoons, and eastern gray and red squirrels to collect blood and oral and fecal swabs. Over the summer of 2015, tissues and clotted blood (when possible) from 400 wildlife carcasses were collected, and this will continue in 2016 for the same species. Ticks will be collected from live animals and carcasses and by tick dragging (I. scapularis) and burrow sampling (I. cookei). Swabs and homogenized tissues and ticks will be tested for POWV antigen by RT-PCR and sera will be tested for antibodies by virus neutralization. Results of this study will help determine the current POWV activity in wildlife and ticks in southwestern Ontario, identify likely reservoir hosts for more targeted studies, as well as aid in assessing the potential risks of POWV infection to humans.