Roles of host species, geographic separation, and isolation in the seroprevalence of Jamestown Canyon and snowshoe hare viruses in Newfoundland

Abstract

California serogroup viruses, including Jamestown Canyon virus (JCV) and snowshoe hare virus (SSHV), are mosquito-borne members of the Bunyaviridae family and are endemic across North America. These arboviruses are potential pathogens which occasionally cause neuroinvasive disease in humans and livestock. A neutralization assay was used to document JCV and SSHV seroprevalence using blood collected from a variety of domestic and wildlife host species. These species were sampled in an island setting, Newfoundland, which contains diverse ecoregions, ecological landscapes, and habitats. Seroprevalence rates for each virus differed significantly among host species and within certain species across different geographic areas. JCV was significantly associated with large mammals, and SSHV was significantly associated with snowshoe hares. Seroprevalence rates in the 5 species of animals tested for prior exposure to JCV ranged from 0% in snowshoe hares to 64% in horses. Seroprevalence rates for SSHV ranged from less than 1% in bovines to 55% in all snowshoe hares. The seroprevalence of SSHV differed significantly (P < 0.05) among hares occupying the discrete habitats of watersheds separated by 14 to 35 km. Cattle on farms in boreal forest landscapes displayed significantly higher JCV seroprevalence (P < 0.001) than those on farms located in seacoast landscapes. Lifelong geographic isolation of cattle to insular Newfoundland was associated with significantly lower JCV seroprevalence (P < 0.01) than that for cattle which had lived off-island.

Fig 1

Blood sample locations near the Humber River Basin in western Newfoundland in 2008. Samples from horses were collected within this region and on the Avalon Peninsula, over 300 km eastward. Random samples of frozen sheep blood sera collected across the island in 1997 were obtained from an archival serum bank (−70°C) at the Animal Health Division of the Newfoundland and Labrador (NL) Department of Natural Resources in St. John's.

Fig 2

Seroprevalence for prior exposure to CSV (both JCV and SSHV) indicates the proportion of blood sera positive for antibodies to CSV. Different letters indicate significant differences (P < 0.001) in proportion seropositive using a Tukey-type multiple comparison for proportions (41).

Fig 3

Seroprevalence for prior exposure to JCV indicates the proportion of blood sera positive for antibodies to JCV. Different letters indicate significant differences (P < 0.001).

Fig 4

Seroprevalence for prior exposure to SSHV indicates the proportion of blood sera positive for antibodies to SSHV. Different letters indicate significant differences (P < 0.001).