Avian roosting behavior influences vector-host interactions for West Nile virus hosts

Abstract

BackgroundExtensive work has shown that vectors almost never feed at random. Often, a subset of individual hosts and host species are fed on much more frequently than expected from their abundance and this can amplify pathogen transmission. However, the drivers of variation in contact patterns between vectors and their hosts are not well understood, even in relatively well-studied systems such as West Nile virus (WNV).MethodsWe compared roosting height and roost aggregation size of seven avian host species of WNV with patterns of host-seeking mosquito (Culex pipiens) abundance at communal and non-communal roost sites.ResultsFirst, host-seeking mosquito abundance increased with height and paralleled increased mosquito feeding preferences on species roosting higher in the tree canopy. Second, there were several hundred-fold fewer mosquitoes per bird trapped at American robin (Turdus migratorius) communal roosts compared to non-communal roost sites, which could reduce transmission from and to this key amplifying host species. Third, seasonal changes in communal roost formation may partly explain observed seasonal changes in mosquito feeding patterns, including a decrease in feeding on communal roosting robins.ConclusionsThese results illustrate how variation in habitat use by hosts and vectors and social aggregation by hosts influence vector-host interactions and link the behavioral ecology of birds and the transmission of vector-borne diseases to humans.

Reduced West Nile Virus Transmission Around Communal Roosts of Great-Tailed Grackle (Quiscalus mexicanus)

“…Third, feeding on grackles may be hazardous to mosquito survival, presumably through grackle defensive behaviors such as consumption of host-seeking mosquitoes. Fourth, the high density of birds within a communal grackle roost may reduce the local vector-host ratio and therefore lower virus amplification potential within the roost site (Janousek et al 2014). Lastly, the additional species that often roost together with grackles (such as doves, starlings, and other blackbird species) may dilute the force of transmission within a grackle roost compared to single-species communal roosts like those of the house sparrow.…”

“…Theoretically, this high density of hosts reduces the vector host ratio and ostensibly makes it more difficult for an infectious mosquito to make contact with a susceptible amplifier, or for an uninfected vector mosquito to make contact with an infectious bird (Janousek et al 2014). Mathematical modeling has demonstrated that reducing the vector-host ratio effectively reduces the force of the epidemic wave for WNV, which would result in fewer infected mosquitoes and lower transmission risk to humans (Magori et al 2011).…”

Dispersal in the Urban Matrix: Assessing the Influence of Landscape Permeability on the Settlement Patterns of Breeding Songbirds

“…While we acknowledge that these variables do not represent the totality of habitat variation along the rural-to-urban gradient, these land cover metrics have been shown to be predictive of avian nest success (canopy cover and impervious surface, Ryder et al, 2010), adult survival (impervious surface, Evans et al, 2015), and community composition (impervious surface, Evans, 2015). All spatial analyses were carried out in R using packages raster (Hijmans, 2015) and sp (Pebesma and Bivand, 2005). We calculated the proportional cover of impervious surface and canopy within a 3 × 3 cell neighborhood moving window (for R code used throughout this manuscript, see Supplementary Material).…”

Overlap in the Seasonal Infection Patterns of Avian Malaria Parasites and West Nile Virus in Vectors and Hosts

“…17 Finally, postbreeding dispersal and migration can influence contacts between hosts and vectors that affect disease transmission. 18,19 Co-circulation of pathogens (broadly defined here as the transmission of two or more pathogens in the same population at the same time) can have important implications for patterns of infection. Indeed, co-circulation is a critical factor permitting direct and indirect interactions among pathogens.…”