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Charles R Brown - One of the best experts on this subject based on the ideXlab platform.
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Variation in neophobia among Cliff Swallows at different colonies.
PloS one, 2019Co-Authors: Stacey L. Hannebaum, Gigi S. Wagnon, Charles R BrownAbstract:Animal groups often represent nonrandom subsets of individuals, and increasing evidence indicates that individuals may sort among groups based on their personalities. The size of a group can predict its personality composition in some species due to differential suitability of a personality for groups of certain sizes, and the group itself may function more effectively if particular personality types are present. We quantified Cliff Swallow (Petrochelidon pyrrhonota) behavioral measures using linear and generalized linear mixed models to identify whether they: (1) varied among individuals within colonies and among colonies, (2) were related to reproductive success, and (3) predicted levels of parental care. Significant among-individual and among-colony site variation in a Cliff Swallow’s latency to enter its nest when presented with a novel stimulus was revealed. We also found significant among-individual variation in the number of attacks directed toward a novel stimulus at the nest and in the response to broadcast of a Cliff Swallow alarm call recording, but among site variation in these measures was not significant. We did not find evidence for behavioral syndromes linking the personalities measured. Differences among individuals in latency to enter the nest and the number of attacks were not significantly related to reproductive success or to the extent to which birds fed their nestlings. However, extent of nestling feeding was significantly predicted by the number of mist net captures. The limited evidence in general of systematic variation in the behavior we measured among Cliff Swallow colonies may reflect the different and sometimes opposing selection pressures on behavior in different social environments. Future work should perhaps examine variation in other behavioral traits, such as foraging, in Cliff Swallow colonies of different sizes.
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Appendix A. A figure illustrating 30 years of Cliff Swallow colony-size frequency distributions.
2016Co-Authors: Charles R Brown, Mary Bomberger Brown, Erin A. RocheAbstract:A figure illustrating 30 years of Cliff Swallow colony-size frequency distributions
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Costs and benefits of late nesting in Cliff Swallows
Oecologia, 2014Co-Authors: Charles R Brown, Erin A. Roche, Valerie A. O'brienAbstract:Many organisms of temperate latitudes exhibit declines in reproductive success as the breeding season advances. Experiments can delay the onset of reproduction for early breeders to investigate the consequences of late nesting, but it is rarely possible to observe a distinct second round of nesting in species that normally nest only once. The colonial Cliff Swallow (Petrochelidon pyrrhonota) is a migratory songbird that has a relatively short breeding season in the western Great Plains, USA, with birds rarely nesting late in the summer. Previous work suggested that ectoparasitism is a primary reason why reproductive success in this species declines over the summer. At colony sites where nests were fumigated to remove ectoparasitic Swallow bugs (Oeciacus vicarius), Cliff Swallows frequently undertook a distinct round of late nesting after previously fledging young that year. Mark-recapture revealed that late-nesting pairs at these colonies produced fewer offspring that survived to the next breeding season, and that survival of late-nesting adults was lower during the next year, relative to pairs nesting earlier in the season. These reproductive costs applied in the absence of ectoparasites and likely reflect other environmental costs of late nesting such as seasonal declines in food availability or a delayed start of fall migration. Despite the costs, the estimated fitness for perennial early-and-late nesters in the absence of ectoparasites was equivalent to that of birds that nested only early in the season. The collective disadvantages of late nesting likely constrain most Cliff Swallows to raising a single brood in the middle latitudes of North America.
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Variation in age composition among colony sizes in Cliff Swallows
Journal of field ornithology, 2014Co-Authors: Charles R Brown, Erin A. Roche, Mary Bomberger BrownAbstract:Variation in group size is characteristic of most social species. The extent to which individuals sort among group sizes based on age may yield insight into why groups vary in size and the age-specific costs and benefits of different social environments. We investigated the age composition of Cliff Swallow (Petrochelidon pyrrhonota) colonies of different sizes over 18 years at a long-term study site in western Nebraska, USA. Using years elapsed since banding as a relative measure of age for over 194,000 birds, we found that the proportion of age-class-1 Swallows (birds banded as nestlings or juveniles or adults in the year of banding) of both sexes increased in larger colonies and at colony sites becoming active later in the summer. Age composition was unrelated to how often a particular colony site was used. The effect of colony size most likely reflected the fact that older birds return to the same colony site in successive years even when the colony size there decreases, and that yearlings and immigrants benefit more from larger colonies than do older, more experienced individuals. The date effect probably resulted in part from later spring arrival by younger and/or immigrant Swallows. At fumigated sites where ectoparasitic Swallow bugs (Oeciacus vicarius) had been removed, age composition did not vary with either colony size or colony initiation date. The patterns reported here appear to be driven partially by the presence of ectoparasites and suggest that the hematophagous bugs influence variation in Cliff Swallow group composition. Our results are consistent with the hypothesis that variation in colony size reflects, in part, age-based sorting of individuals among groups.
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Fluctuating viability selection on morphology of Cliff Swallows is driven by climate
Journal of evolutionary biology, 2013Co-Authors: Charles R Brown, Mary Bomberger Brown, Erin A. RocheAbstract:The extent to which fluctuating selection can maintain evolutionary stasis in most populations remains an unresolved question in evolutionary biology. Climate has been hypothesized to drive reversals in the direction of selection among different time periods and may also be responsible for intense episodic selection caused by rare weather events. We measured viability selection associated with morphological traits in Cliff Swallows (Petrochelidon pyrrhonota) in western Nebraska, USA, over a 14-year period following a rare climatic event. We used mark-recapture to estimate the annual apparent survival of over 26 000 individuals whose wing, tail, tarsus and bill had been measured. The fitness functions associated with tarsus length and bill dimensions fluctuated depending on annual climate conditions on the birds' breeding grounds. The oscillating yearly patterns may have slowed and occasionally reversed directional change in trait trajectories, although there was a trend over time for all traits except tarsus to increase in size. The net positive directional selection on some traits, despite periodic climate-associated fluctuations, suggests that Cliff Swallow morphology in the population is likely to keep changing and supports recent work contending that selection in general does not fluctuate enough to be an effective driver of stasis.
Larry Clark - One of the best experts on this subject based on the ideXlab platform.
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Cliff Swallows, Swallow Bugs, and West Nile Virus:An Unlikely Transmission Mechanism
Vector borne and zoonotic diseases (Larchmont N.Y.), 2010Co-Authors: Paul T. Oesterle, Nicole M. Nemeth, Ginger Young, Nicole L. Mooers, Stacey A. Elmore, Richard A. Bowen, Paul F. Doherty, Jeffrey S. Hall, Robert G. Mclean, Larry ClarkAbstract:The Cliff Swallow (Petrochelidon pyrrhonota) could play an important role in the transmission of West Nile virus (WNV) because of its breeding ecology, reservoir competence status, and potentially high natural exposure rates. Cliff Swallows nest within colonies and their nests are occupied year-round by Swallow bugs (Oeciacus vicarius), hematophagus ectoparasites that feed primarily on Cliff Swallows. These parasites are likely exposed to WNV while feeding on infectious blood of nesting Cliff Swallow adults and nestlings and thus, if competent vectors, could contribute to seasonal elevations in WNV transmission. In addition, Swallow bugs remain within nests year-round and therefore could provide a potential overwintering mechanism for WNV if persistently infected. To test the hypotheses that Swallow bugs are competent vectors and become persistently infected with WNV, we experimentally inoculated Cliff Swallow nestlings, allowed Swallow bugs to feed on these birds during the acute phase of infection, and then exposed naive Cliff Swallow nestlings to the same Swallow bugs. In addition, a subset of Swallow bugs that fed on infectious Swallow nestlings was maintained through a simulated overwintering period. Although Swallow bugs ingested infectious blood (up to 10(6.8) plaque-forming units of WNV/mL serum) and subsequently blood-fed on naive Swallows, no WNV transmission was detected, and all bugs tested WNV negative after the simulated overwintering period. Although many ecologic scenarios exist beyond the present study, our results suggest that Swallow bugs may be unlikely to serve as competent biological vectors for WNV during active transmission periods or to reinitiate seasonal transmission.
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Cliff Swallows, Swallow Bugs, and West Nile Virus:
Vector-borne and Zoonotic Diseases, 2010Co-Authors: Larry ClarkAbstract:The Cliff Swallow (Petrochelidon pyrrhonota) could play an important role in the transmission of West Nile virus (WNV) because of its breeding ecology, reservoir competence status, and potentially high natural exposure rates. Cliff Swallows nest within colonies and their nests are occupied year-round by Swallow bugs (Oeciacus vicarius), hematophagus ectoparasites that feed primarily on Cliff Swallows. These parasites are likely exposed to WNV while feeding on infectious blood of nesting Cliff Swallow adults and nestlings and thus, if competent vectors, could contribute to seasonal elevations in WNV transmission. In addition, Swallow bugs remain within nests year-round and therefore could provide a potential overwintering mechanism for WNV if persistently infected. To test the hypotheses that Swallow bugs are competent vectors and become persistently infected with WNV, we experimentally inoculated Cliff Swallow nestlings, allowed Swallow bugs to feed on these birds during the acute phase of infection, and then exposed naive Cliff Swallow nestlings to the same Swallow bugs. In addition, a subset of Swallow bugs that fed on infectious Swallow nestlings was maintained through a simulated overwintering period. Although Swallow bugs ingested infectious blood (up to 10 plaque-forming units of WNV=mL serum) and subsequently blood-fed on naive Swallows, no WNV transmission was detected, and all bugs tested WNV negative after the simulated overwintering period. Although many ecologic scenarios exist beyond the present study, our results suggest that Swallow bugs may be unlikely to serve as competent biological vectors for WNV during active transmission periods or to reinitiate seasonal transmission.
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Experimental infection of Cliff Swallows (Petrochelidon pyrrhonota) with varying doses of West Nile virus.
The American journal of tropical medicine and hygiene, 2009Co-Authors: Paul T. Oesterle, Nicole M. Nemeth, Ginger Young, Robert G. Mclean, Larry Clark, Kaci K. Vandalen, Heather J. Sullivan, Kevin T. Bentler, Cynthia A. Smeraski, Jeffrey S. HallAbstract:Cliff Swallows ( Petrochelidon pyrrhonota ) were inoculated with differing doses of West Nile virus (WNV) to evaluate their potential role as reservoir hosts in nature. Swallows often nest in large colonies in habitats and months associated with high mosquito abundance and early WNV transmission in North America. Additionally, Cliff Swallow diet consists of insects, including mosquitoes, leading to an additional potential route of WNV infection. The average peak viremia titer among infected Cliff Swallows was 10 6.3 plaque-forming units (PFU)/mL serum and the reservoir competence index was 0.34. There was no correlation between dose and probability of becoming infected or viremia peak and dura- tion. Oral shedding was detected from 2 to 14 days post-inoculation with an average peak titer of 10 4.4 PFU/swab. These results suggest that Cliff Swallows are competent reservoir hosts of WNV and therefore, they may play a role in early sea- sonal amplification and maintenance of WNV.
Brown, Charles R. - One of the best experts on this subject based on the ideXlab platform.
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Fluctuating survival selection explains variation in avian group size
DigitalCommons@University of Nebraska - Lincoln, 2016Co-Authors: Brown, Charles R., Brown, Mary Bomberger, Roche, Erin A., O\u27brien, Valerie A., Page, Catherine E.Abstract:Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark– recapture study of colonially breeding Cliff Swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in Cliff Swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population
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A Hybrid Cliff × Barn Swallow from Western Nebraska
DigitalCommons@University of Nebraska - Lincoln, 2015Co-Authors: Brown, Charles R., Page, Catherine E.Abstract:The Cliff Swallow (Petrochelidon pyrrhonota) and the Barn Swallow (Hirundo rustica) occupy sympatric breeding ranges across much of North America, often nesting at colony sites that contain both species. Mixed-species nesting aggregations typically occur in box-shaped concrete culverts underneath roads or railways. Cliff Swallows’ enclosed mud nests can be as close as 1 m to Barn Swallows’ open mud nests, and at such sites Cliff Swallows regularly usurp both inactive and active Barn Swallow nests. The close proximity of these two ecologically similar species leads to at least occasional social interaction among them, such as during combined alarm responses at predators. Another consequence may be extra-pair copulation between male Cliff Swallows and female Barn Swallows, leading to intergeneric hybridization. On 12 June 2014, we visited a double-tunnel culvert underneath Interstate 80 about 8 km east-southeast of Roscoe, Keith Co, western Nebraska (41°06.438′N, 101°29.634′W). There were no active Cliff Swallow nests at the site on that date, and we estimated about 15 active Barn Swallow nests, all with eggs. Our attention was drawn to a bird’s vocalization that resembled a Cliff Swallow\u27s alarm call. We observed a Swallow with plumage characters clearly intermediate between those of Cliff and Barn Swallows while the bird flew among Barn Swallows during an alarm response at us as we stood in the culvert
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Data from: Ectoparasitism shortens the breeding season in a colonial bird
2015Co-Authors: Brown, Charles R., Brown, Mary BombergerAbstract:When blood-feeding parasites increase seasonally, their deleterious effects may prevent some host species, especially those living in large groups where parasites are numerous, from reproducing later in the summer. Yet the role of parasites in regulating the length of a host's breeding season—and thus the host's opportunity for multiple brooding—has not been systematically investigated. The highly colonial Cliff Swallow (Petrochelidon pyrrhonota), a temperate-latitude migratory songbird in the western Great Plains, USA, typically has a relatively short (eight to nine week) breeding season, with birds rarely nesting late in the summer. Colonies at which ectoparasitic Swallow bugs (Oeciacus vicarius) were experimentally removed by fumigation were over 45 times more likely to have birds undertake a second round of nesting than were colonies exposed to parasites. Late nesting approximately doubled the length of the breeding season, with some birds raising two broods. Over a 27 year period the percentage of birds engaging in late nesting each year increased at a colony site where parasites were removed annually. This trend could not be explained by changes in group size, climate or nesting phenology during the study. The results suggest that ectoparasitism shortens the Cliff Swallow's breeding season and probably prevents many individuals from multiple brooding. When this constraint is removed, selection may rapidly favour late nesting
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Ectoparasitism shortens the breeding season in a colonial bird
DigitalCommons@University of Nebraska - Lincoln, 2015Co-Authors: Brown, Charles R., Brown, Mary BombergerAbstract:When blood-feeding parasites increase seasonally, their deleterious effects may prevent some host species, especially those living in large groups where parasites are numerous, from reproducing later in the summer. Yet the role of parasites in regulating the length of a host’s breeding season—and thus the host’s opportunity for multiple brooding—has not been systematically investigated. The highly colonial Cliff Swallow (Petrochelidon pyrrhonota), a temperate-latitude migratory songbird in the western Great Plains, USA, typically has a relatively short (eight to nine week) breeding season, with birds rarely nesting late in the summer. Colonies at which ectoparasitic Swallow bugs (Oeciacus vicarius) were experimentally removed by fumigation were over 45 times more likely to have birds undertake a second round of nesting than were colonies exposed to parasites. Late nesting approximately doubled the length of the breeding season, with some birds raising two broods. Over a 27 year period the percentage of birds engaging in late nesting each year increased at a colony site where parasites were removed annually. This trend could not be explained by changes in group size, climate or nesting phenology during the study. The results suggest that ectoparasitism shortens the Cliff Swallow’s breeding season and probably prevents many individuals from multiple brooding. When this constraint is removed, selection may rapidly favour late nesting
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Variation in age composition among colony sizes in Cliff Swallows
DigitalCommons@University of Nebraska - Lincoln, 2014Co-Authors: Brown, Charles R., Roche, Erin A., Brown, Mary BombergerAbstract:Variation in group size is characteristic of most social species. The extent to which individuals sort among group sizes based on age may yield insight into why groups vary in size and the age-specific costs and benefits of different social environments. We investigated the age composition of Cliff Swallow (Petrochelidon pyrrhonota) colonies of different sizes over 18 yr at a long-term study site in western Nebraska, USA. Using years elapsed since banding as a relative measure of age for over 194,000 birds, we found that the proportion of age-class-1 Swallows (birds banded as nestlings or juveniles or adults in the year of banding) of both sexes increased in larger colonies and at colony sites becoming active later in the summer. Age composition was unrelated to how often a particular colony site was used. The effect of colony size most likely reflected the fact that older birds return to the same colony site in successive years even when the colony size there decreases, and that yearlings and immigrants benefit more from larger colonies than do older, more experienced individuals. The date effect probably resulted in part from later spring arrival by younger and/or immigrant Swallows. At fumigated sites where ectoparasitic Swallow bugs (Oeciacus vicarius) had been removed, age composition did not vary with either colony size or colony initiation date. The patterns reported here appear to be driven partially by the presence of ectoparasites and suggest that the hematophagous bugs influence variation in Cliff Swallow group composition. Our results are consistent with the hypothesis that variation in colony size reflects, in part, age-based sorting of individuals among groups
Erin A. Roche - One of the best experts on this subject based on the ideXlab platform.
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Appendix A. A figure illustrating 30 years of Cliff Swallow colony-size frequency distributions.
2016Co-Authors: Charles R Brown, Mary Bomberger Brown, Erin A. RocheAbstract:A figure illustrating 30 years of Cliff Swallow colony-size frequency distributions
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Costs and benefits of late nesting in Cliff Swallows
Oecologia, 2014Co-Authors: Charles R Brown, Erin A. Roche, Valerie A. O'brienAbstract:Many organisms of temperate latitudes exhibit declines in reproductive success as the breeding season advances. Experiments can delay the onset of reproduction for early breeders to investigate the consequences of late nesting, but it is rarely possible to observe a distinct second round of nesting in species that normally nest only once. The colonial Cliff Swallow (Petrochelidon pyrrhonota) is a migratory songbird that has a relatively short breeding season in the western Great Plains, USA, with birds rarely nesting late in the summer. Previous work suggested that ectoparasitism is a primary reason why reproductive success in this species declines over the summer. At colony sites where nests were fumigated to remove ectoparasitic Swallow bugs (Oeciacus vicarius), Cliff Swallows frequently undertook a distinct round of late nesting after previously fledging young that year. Mark-recapture revealed that late-nesting pairs at these colonies produced fewer offspring that survived to the next breeding season, and that survival of late-nesting adults was lower during the next year, relative to pairs nesting earlier in the season. These reproductive costs applied in the absence of ectoparasites and likely reflect other environmental costs of late nesting such as seasonal declines in food availability or a delayed start of fall migration. Despite the costs, the estimated fitness for perennial early-and-late nesters in the absence of ectoparasites was equivalent to that of birds that nested only early in the season. The collective disadvantages of late nesting likely constrain most Cliff Swallows to raising a single brood in the middle latitudes of North America.
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Variation in age composition among colony sizes in Cliff Swallows
Journal of field ornithology, 2014Co-Authors: Charles R Brown, Erin A. Roche, Mary Bomberger BrownAbstract:Variation in group size is characteristic of most social species. The extent to which individuals sort among group sizes based on age may yield insight into why groups vary in size and the age-specific costs and benefits of different social environments. We investigated the age composition of Cliff Swallow (Petrochelidon pyrrhonota) colonies of different sizes over 18 years at a long-term study site in western Nebraska, USA. Using years elapsed since banding as a relative measure of age for over 194,000 birds, we found that the proportion of age-class-1 Swallows (birds banded as nestlings or juveniles or adults in the year of banding) of both sexes increased in larger colonies and at colony sites becoming active later in the summer. Age composition was unrelated to how often a particular colony site was used. The effect of colony size most likely reflected the fact that older birds return to the same colony site in successive years even when the colony size there decreases, and that yearlings and immigrants benefit more from larger colonies than do older, more experienced individuals. The date effect probably resulted in part from later spring arrival by younger and/or immigrant Swallows. At fumigated sites where ectoparasitic Swallow bugs (Oeciacus vicarius) had been removed, age composition did not vary with either colony size or colony initiation date. The patterns reported here appear to be driven partially by the presence of ectoparasites and suggest that the hematophagous bugs influence variation in Cliff Swallow group composition. Our results are consistent with the hypothesis that variation in colony size reflects, in part, age-based sorting of individuals among groups.
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Fluctuating viability selection on morphology of Cliff Swallows is driven by climate
Journal of evolutionary biology, 2013Co-Authors: Charles R Brown, Mary Bomberger Brown, Erin A. RocheAbstract:The extent to which fluctuating selection can maintain evolutionary stasis in most populations remains an unresolved question in evolutionary biology. Climate has been hypothesized to drive reversals in the direction of selection among different time periods and may also be responsible for intense episodic selection caused by rare weather events. We measured viability selection associated with morphological traits in Cliff Swallows (Petrochelidon pyrrhonota) in western Nebraska, USA, over a 14-year period following a rare climatic event. We used mark-recapture to estimate the annual apparent survival of over 26 000 individuals whose wing, tail, tarsus and bill had been measured. The fitness functions associated with tarsus length and bill dimensions fluctuated depending on annual climate conditions on the birds' breeding grounds. The oscillating yearly patterns may have slowed and occasionally reversed directional change in trait trajectories, although there was a trend over time for all traits except tarsus to increase in size. The net positive directional selection on some traits, despite periodic climate-associated fluctuations, suggests that Cliff Swallow morphology in the population is likely to keep changing and supports recent work contending that selection in general does not fluctuate enough to be an effective driver of stasis.
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Spatial and temporal unpredictability of colony size in Cliff Swallows across 30 years
Ecological Monographs, 2013Co-Authors: Charles R Brown, Mary Bomberger Brown, Erin A. RocheAbstract:Most colonially breeding animals occupy colonies that range in size from a few pairs to thousands of individuals, but the causes of colony size variation are largely unknown. Three general hypotheses are: (1) that variation in colony size is maintained by fluctuating selection via spatial and temporal changes in fitness associated with different colony sizes; (2) that colony formation reflects heterogeneity in habitat, with some sites having resources to support more individuals than others; and (3) that individuals assess the presence or annual reproductive success of current colony residents at each site and aggregate preferentially at high-quality sites. These hypotheses make predictions about how consistent colony size should be across sites and among years. We examined temporal and spatial variability of colony size for >200 Cliff Swallow (Petrochelidon pyrrhonota) colony sites in western Nebraska across a 30-year period. A colony's substrate type, annual population size in the study area, and whethe...
Ginger Young - One of the best experts on this subject based on the ideXlab platform.
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an enzootic vector borne virus is amplified at epizootic levels by an invasive avian host
Proceedings of The Royal Society B: Biological Sciences, 2011Co-Authors: Valerie A Obrien, Ginger Young, Nicholas Komar, Amy T Moore, William K Reisen, Charles R BrownAbstract:Determining the effect of an invasive species on enzootic pathogen dynamics is critical for understanding both human epidemics and wildlife epizootics. Theoretical models suggest that when a naive species enters an established host–parasite system, the new host may either reduce (‘dilute’) or increase (‘spillback’) pathogen transmission to native hosts. There are few empirical data to evaluate these possibilities, especially for animal pathogens. Buggy Creek virus (BCRV) is an arthropod-borne alphavirus that is enzootically transmitted by the Swallow bug (Oeciacus vicarius) to colonially nesting Cliff Swallows (Petrochelidon pyrrhonota). In western Nebraska, introduced house sparrows (Passer domesticus) invaded Cliff Swallow colonies approximately 40 years ago and were exposed to BCRV. We evaluated how the addition of house sparrows to this host–parasite system affected the prevalence and amplification of a bird-associated BCRV lineage. The infection prevalence in house sparrows was eight times that of Cliff Swallows. Nestling house sparrows in mixed-species colonies were significantly less likely to be infected than sparrows in single-species colonies. Infected house sparrows circulated BCRV at higher viraemia titres than Cliff Swallows. BCRV detected in bug vectors at a site was positively associated with virus prevalence in house sparrows but not with virus prevalence in Cliff Swallows. The addition of a highly susceptible invasive host species has led to perennial BCRV epizootics at Cliff Swallow colony sites. The native Cliff Swallow host confers a dilution advantage to invasive sparrow hosts in mixed colonies, while at the same sites house sparrows may increase the likelihood that Swallows become infected.
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Cliff Swallows, Swallow Bugs, and West Nile Virus:An Unlikely Transmission Mechanism
Vector borne and zoonotic diseases (Larchmont N.Y.), 2010Co-Authors: Paul T. Oesterle, Nicole M. Nemeth, Ginger Young, Nicole L. Mooers, Stacey A. Elmore, Richard A. Bowen, Paul F. Doherty, Jeffrey S. Hall, Robert G. Mclean, Larry ClarkAbstract:The Cliff Swallow (Petrochelidon pyrrhonota) could play an important role in the transmission of West Nile virus (WNV) because of its breeding ecology, reservoir competence status, and potentially high natural exposure rates. Cliff Swallows nest within colonies and their nests are occupied year-round by Swallow bugs (Oeciacus vicarius), hematophagus ectoparasites that feed primarily on Cliff Swallows. These parasites are likely exposed to WNV while feeding on infectious blood of nesting Cliff Swallow adults and nestlings and thus, if competent vectors, could contribute to seasonal elevations in WNV transmission. In addition, Swallow bugs remain within nests year-round and therefore could provide a potential overwintering mechanism for WNV if persistently infected. To test the hypotheses that Swallow bugs are competent vectors and become persistently infected with WNV, we experimentally inoculated Cliff Swallow nestlings, allowed Swallow bugs to feed on these birds during the acute phase of infection, and then exposed naive Cliff Swallow nestlings to the same Swallow bugs. In addition, a subset of Swallow bugs that fed on infectious Swallow nestlings was maintained through a simulated overwintering period. Although Swallow bugs ingested infectious blood (up to 10(6.8) plaque-forming units of WNV/mL serum) and subsequently blood-fed on naive Swallows, no WNV transmission was detected, and all bugs tested WNV negative after the simulated overwintering period. Although many ecologic scenarios exist beyond the present study, our results suggest that Swallow bugs may be unlikely to serve as competent biological vectors for WNV during active transmission periods or to reinitiate seasonal transmission.
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Experimental infection of Cliff Swallows (Petrochelidon pyrrhonota) with varying doses of West Nile virus.
The American journal of tropical medicine and hygiene, 2009Co-Authors: Paul T. Oesterle, Nicole M. Nemeth, Ginger Young, Robert G. Mclean, Larry Clark, Kaci K. Vandalen, Heather J. Sullivan, Kevin T. Bentler, Cynthia A. Smeraski, Jeffrey S. HallAbstract:Cliff Swallows ( Petrochelidon pyrrhonota ) were inoculated with differing doses of West Nile virus (WNV) to evaluate their potential role as reservoir hosts in nature. Swallows often nest in large colonies in habitats and months associated with high mosquito abundance and early WNV transmission in North America. Additionally, Cliff Swallow diet consists of insects, including mosquitoes, leading to an additional potential route of WNV infection. The average peak viremia titer among infected Cliff Swallows was 10 6.3 plaque-forming units (PFU)/mL serum and the reservoir competence index was 0.34. There was no correlation between dose and probability of becoming infected or viremia peak and dura- tion. Oral shedding was detected from 2 to 14 days post-inoculation with an average peak titer of 10 4.4 PFU/swab. These results suggest that Cliff Swallows are competent reservoir hosts of WNV and therefore, they may play a role in early sea- sonal amplification and maintenance of WNV.