Isolation by distance explains genetic structure of Buggy Creek virus, a bird-associated arbovirus

Center for Infectious Disease Dynamics, Department of Biology, 208 Mueller Laboratory, The Pennsylvania State University, University Park, PA 16802, USA
Evolutionary Ecology (Impact Factor: 2.52). 03/2011; 25(2):403-416. DOI: 10.1007/s10682-010-9419-9


Many of the arthropod-borne viruses (arboviruses) show extensive genetic variability and are widely distributed over large
geographic areas. Understanding how virus genetic structure varies in space may yield insight into how these pathogens are
adapted to and dispersed by different hosts or vectors, the relative importance of mutation, drift, or selection in generating
genetic variability, and where and when epidemics or epizootics are most likely to occur. However, because most arboviruses
tend to be sampled opportunistically and often cannot be isolated in large numbers at a given locale, surprisingly little
is known about their spatial genetic structure on the local scale at which host/vector/virus interactions typically occur.
Here, we examine fine-scale spatial structure of two sympatric lineages of Buggy Creek virus (BCRV, Togaviridae), an alphavirus
transmitted by the ectoparasitic swallow bug (Oeciacus vicarius) to colonially nesting cliff swallows (Petrochelidon pyrrhonota) and invasive house sparrows (Passer domesticus) in North America. Data from 377 BCRV isolates at cliff swallow colony sites in western Nebraska showed that both virus lineages
were geographically structured. Most haplotypes were detected at a single colony or were shared among nearby colonies, and
pair-wise genetic distance increased significantly with geographic distance between colony sites. Genetic structure of both
lineages is consistent with isolation by distance. Sites with the most genetically distinct BCRV isolates were occupied by
large numbers of house sparrows, suggesting that concentrations of invasive sparrows may represent foci for evolutionary change
in BCRV. Our results show that bird-associated arboviruses can show genetic substructure over short geographic distances.

KeywordsArbovirus–Buggy Creek virus–Cliff swallow–House sparrow–Swallow bug–Virus evolution–Virus population genetics

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    • "The swallow bug (Hemiptera: Cimicidae: Oeciacus vicarius) is a vector of Buggy Creek virus (BCRV; Togaviridae, Alphavirus), an arbovirus within the western equine encephalomyelitis virus complex that circulates in colonially nesting cliff swallows (Petrochelidon pyrrhonota) and introduced house sparrows (Passer domesticus) occupying swallow nests (Hopla 1993, O'Brien et al. 2011, Padhi et al. 2011). Swallow bugs increase in larger cliff swallow colonies (Brown and Brown 1986, 1996), and this leads to higher BCRV prevalence at sites with more cliff swallows and/or house sparrows (Brown et al. 2001, Moore et al. 2007, O'Brien and Brown 2011). "
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    ABSTRACT: The swallow bug (Oeciacus vicarius) is the only known vector for Buggy Creek virus (BCRV), an alphavirus that circulates in cliff swallows (Petrochelidon pyrrhonota) and house sparrows (Passer domesticus) in North America. We discovered ants (Crematogaster lineolata and Formica spp.) preying on swallow bugs at cliff swallow colonies in western Nebraska, U.S.A. Ants reduced the numbers of visible bugs on active swallow nests by 74-90%, relative to nests in the same colony without ants. Ant predation on bugs had no effect on the reproductive success of cliff swallows inhabiting the nests where ants foraged. Ants represent an effective and presumably benign way of controlling swallow bugs at nests in some colonies. They may constitute an alternative to insecticide use at sites where ecologists wish to remove the effects of swallow bugs on cliff swallows or house sparrows. By reducing bug numbers, ant presence may also lessen BCRV transmission at the spatial foci (bird colony sites) where epizootics occur. The effect of ants on swallow bugs should be accounted for in studying variation among sites in vector abundance. © 2015 The Society for Vector Ecology.
    Journal of Vector Ecology 06/2015; 40(1):152-157. DOI:10.1111/jvec.12144 · 1.17 Impact Factor