Prevalence of Buggy Creek Virus (Togaviridae:Alphavirus) in Insect Vectors Increases Over Time in the Presence of an Invasive Avian Host

Abstract

Invasive species can disrupt natural disease dynamics by altering pathogen transmission among native hosts and vectors. The relatively recent occupancy of cliff swallow (Petrochelidon pyrrhonota) nesting colonies in western Nebraska by introduced European house sparrows (Passer domesticus) has led to yearly increases in the prevalence of an endemic arbovirus, Buggy Creek virus (BCRV), in its native swallow bug (Oeciacus vicarius) vector at sites containing both the invasive sparrow host and the native swallow host. At sites without the invasive host, no long-term changes in prevalence have occurred. The percentage of BCRV isolates exhibiting cytopathicity in Vero-cell culture assays increased significantly with year at sites with sparrows but not at swallow-only sites, suggesting that the virus is becoming more virulent to vertebrates in the presence of the invasive host. Increased BCRV prevalence in bug vectors at mixed-species colonies may reflect high virus replication rates in house sparrow hosts, resulting in frequent virus transmission between sparrows and swallow bugs. This case represents a rare empirical example of a pathogen effectively switching to an invasive host, documented in the early phases of the host's arrival in a specialized ecosystem and illustrating how an invasive species can promote long-term changes in host-parasite transmission dynamics.

The cost of ectoparasitism in Cliff Swallows declines over 35 years

“…Another potential explanation for our results could be that Cliff Swallows are now better tolerating a swallow bug‐borne pathogen, Buggy Creek virus (BCRV) known to infect Cliff Swallows, rather than the bugs themselves. BCRV is an alphavirus confined to the Cliff‐Swallow–swallow‐bug ecosystem (O’Brien et al 2011, Brown et al 2009, 2010 a , 2012). Bugs serve as vectors for the virus, which has been found only in Cliff Swallows, swallow bugs, and House Sparrows that nest in Cliff Swallow colonies.…”

“…As of 2006–2009, BCRV had no detectable effects on Cliff Swallows, and few birds were found with either active virus or antibodies to it (O’Brien et al 2011). BCRV now seems to circulate mostly among bugs and House Sparrows (Brown et al 2012). Unfortunately, we do not have data on BCRV prevalence or its effects on Cliff Swallows from the earlier years of the study.…”

Immune Responses of a Native and an Invasive Bird to Buggy Creek Virus (Togaviridae: Alphavirus) and Its Arthropod Vector, the Swallow Bug (Oeciacus vicarius)

“…In our study area, most house sparrows have been using cliff swallow colonies for only about 30–40 years [16]. The swallow bug is a hematophagous nest ectoparasite of the cliff swallow that is not known to occur outside swallow colonies, and thus it was historically restricted to cliff swallows as hosts.…”

“…This virus is restricted to a unique ecological setting in which it is transmitted solely by its vector, the swallow bug (Hemiptera: Cimicidae: Oeciacus vicarius ), to the cliff swallow, the primary host for the ectoparasitic bug [13], [14]. Following the introduction of European house sparrows ( Passer domesticus ) to North America in the 1800's [15] and their subsequent invasion of cliff swallow colonies where they usurp the swallows' nests [16], swallow bugs have switched to sparrows as alternative hosts in some cases, and in the process the bugs have exposed house sparrows to BCRV, a novel pathogen [17], [18].…”

The role of seabirds of the Iles Eparses as reservoirs and disseminators of parasites and pathogens

“…Serology-based methodologies (Lundstrom et al, 2001) could reveal whether seabirds of the Iles Eparses are involved in epidemiological cycles of alphaviruses. Molecular detection and virus isolation in mosquitoes and other types of ectoparasites will also be essential to detect their possible presence in this region (Brown et al, 2012;Jost et al, 2010).…”