Host heterogeneity dominates West Nile virus transmission

Abstract

Heterogeneity in host populations and communities can have large effects on the transmission and control of a pathogen. In extreme cases, a few individuals give rise to the majority of secondary infections, which have been termed super spreading events. Here, we show that transmission of West Nile virus (WNV) is dominated by extreme heterogeneity in the host community, resulting in highly inflated reproductive ratios. A single relatively uncommon avian species, American robin (Turdus migratorius), appeared to be responsible for the majority of WNV-infectious mosquitoes and acted as the species equivalent of a super spreader for this multi-host pathogen. Crows were also highly preferred by mosquitoes at some sites, while house sparrows were significantly avoided. Nonetheless, due to their relative rarity, corvids (crows and jays) were relatively unimportant in WNV amplification. These results challenge current beliefs about the role of certain avian species in WNV amplification and demonstrate the importance of determining contact rates between vectors and host species to understand pathogen transmission dynamics.

Host and parasite diversity jointly control disease risk in complex communities

“…S1), even if their long-term suitability to support infections was lower. Host competence, or the tendency of each host species to become infected and maintain infection, also varies among species (6,15,30). Previous work involving Ribeiroia has shown that total host community competence decreases in more diverse assemblages with the progressive addition of "poor-quality" hosts (15), consistent with results of our field and experimental studies.…”

Host compatibility rather than vector–host-encounter rate determines the host range of avian Plasmodium parasites

“…Thus, bloodfeeding patterns effectively set the encounter rate between vector-borne parasites and hosts. Mosquitoes, which are important vectors for a diversity of pathogens, are known to feed heterogeneously across hosts by using some species disproportionately, relative to their abundance [13][14][15]. This heterogeneity in mosquito-feeding patterns can strongly influence disease transmission dynamics [3,4,13,16].…”

West Nile Virus–related Trends in Avian Mortality in California, Usa, 2003–12

“…For example, American Robin WNV prevalence was highest in the Modoc bioregion (12%), but in the San Joaquin Valley region it was quite low (2%). Although the American Robin is likely important in the spread of WNV (Kilpatrick et al 2006;Hamer et al 2009), fewer dead American Robins are reported or discovered by the California public compared to corvids, House Finches, and House Sparrows. In southern California, the House Finch and House Sparrow serve as reservoir populations for WNV because these two peridomestic species are frequent blood meal hosts for several Culex vectors (Thiemann et al 2012) and have been implicated in WNV amplification in that area (Molaei et al 2010).…”

“…American Robins (Turdus migratorius) develop relatively high viremias when infected (Vandalen et al 2013), but do not suffer the high mortality common to corvids. They are a preferential host of Culex pipiens complex mosquitoes (Hamer et al 2009), and WNV spread in northeast and northcentral US has been attributed to American Robins (Kilpatrick et al 2006;Hamer et al 2009). Peridomestic House Finches (Haemorhous mexicanus) and House Sparrows (Passer domesticus) serve as reservoir and amplifying hosts in California Wheeler et al 2009;Molaei et al 2010) and have been associated with human WNV disease outbreaks (Kwan et al 2012), especially in the western US.…”