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Andersen DK, Fischer GA, Combrink L. The Alligator and the Mosquito: North American Crocodilians as Amplifiers of West Nile Virus in Changing Climates. Microorganisms 2024; 12:1898. [PMID: 39338572 DOI: 10.3390/microorganisms12091898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2024] [Revised: 09/06/2024] [Accepted: 09/09/2024] [Indexed: 09/30/2024] Open
Abstract
In an age of emerging zoonoses, it is important to understand the intricate system of vectors and reservoirs, or hosts, and their relation to humans. West Nile Virus (WNV) has been detected in a myriad of nonhuman hosts. Transmission of the virus to humans is reliant on amplified seroprevalence within the host, which occurs primarily in birds. However, recent studies have found that other animal groups, including crocodilians, can obtain seroprevalence amplification to levels that make them competent hosts able to transmit WNV to mosquitoes, which can then transmit to humans. Climate change could exacerbate this transmission risk by shifting the distributions of mosquito vectors towards novel geographic ranges. Here, we use maximum entropy models to map the current and future distributions of three mosquito vector species and four crocodilian species in North America to determine the emerging risk of WNV outbreaks associated with changing climates and WNV associated with crocodilians in North America. From our models, we determined that one mosquito species in particular, Culex quinquefasciatus, will increase its distribution across the ranges of all crocodilian species in all tested climate change scenarios. This poses a potential risk to public health for people visiting and living near crocodilian farms and high-density natural crocodilian populations.
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Affiliation(s)
| | - Gracie Ann Fischer
- School of Natural Resources and the Environment, University of Arizona, Tucson, AZ 85721, USA
| | - Leigh Combrink
- School of Natural Resources and the Environment, University of Arizona, Tucson, AZ 85721, USA
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Blom R, Krol L, Langezaal M, Schrama M, Trimbos KB, Wassenaar D, Koenraadt CJM. Blood-feeding patterns of Culex pipiens biotype pipiens and pipiens/molestus hybrids in relation to avian community composition in urban habitats. Parasit Vectors 2024; 17:95. [PMID: 38424573 PMCID: PMC10902945 DOI: 10.1186/s13071-024-06186-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 02/07/2024] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND Culex pipiens sensu stricto (s.s.) is considered the primary vector of Usutu virus and West Nile virus, and consists of two morphologically identical but behaviourally distinct biotypes (Cx. pipiens biotype pipiens and Cx. pipiens biotype molestus) and their hybrids. Both biotypes are expected to differ in their feeding behaviour, and pipiens/molestus hybrids are presumed to display intermediate feeding behaviour. However, the evidence for distinct feeding patterns is scarce, and to date no studies have related differences in feeding patterns to differences in host abundance. METHODS Mosquitoes were collected using CO2-baited traps. We collected blood-engorged Cx. pipiens/torrentium specimens from 12 contrasting urban sites, namely six city parks and six residential areas. Blood engorged Cx. pipiens/torrentium mosquitoes were identified to the species and biotype/hybrid level via real-time polymerase chain reaction (PCR). We performed blood meal analysis via PCR and Sanger sequencing. Additionally, avian host communities were surveyed via vocal sounds and/or visual observation. RESULTS We selected 64 blood-engorged Cx. pipiens/torrentium mosquitoes of which we successfully determined the host origin of 55 specimens. Of these, 38 belonged to biotype pipiens, 14 were pipiens/molestus hybrids and the identity of three specimens could not be determined. No blood-engorged biotype molestus or Cx. torrentium specimens were collected. We observed no differences in feeding patterns between biotype pipiens and pipiens/molestus hybrids across different habitats. Avian community composition differed between city parks and residential areas, whereas overall avian abundance did not differ between the two habitat types. CONCLUSIONS Our results show the following: (1) Cx. pipiens s.s. feeding patterns did not differ between city parks and residential areas, regardless of whether individuals were identified as biotype pipiens or pipiens/molestus hybrids. (2) We detected differences in host availability between city parks and residential areas. (3) We show that in both urban habitat types, biotype pipiens and pipiens/molestus hybrids fed on both mammalian and avian hosts. This underscores the potential role in arbovirus transmission of biotype pipiens and pipiens/molestus hybrids.
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Affiliation(s)
- Rody Blom
- Laboratory of Entomology, Plant Sciences Group, Wageningen University & Research, Wageningen, The Netherlands.
| | - Louie Krol
- Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands
- Deltares, Utrecht, The Netherlands
| | - Melissa Langezaal
- Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands
| | - Maarten Schrama
- Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands
| | - Krijn B Trimbos
- Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands
| | - Daan Wassenaar
- Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands
| | - Constantianus J M Koenraadt
- Laboratory of Entomology, Plant Sciences Group, Wageningen University & Research, Wageningen, The Netherlands
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Duggal NK, Langwig KE, Ebel GD, Brault AC. On the Fly: Interactions Between Birds, Mosquitoes, and Environment That Have Molded West Nile Virus Genomic Structure Over Two Decades. JOURNAL OF MEDICAL ENTOMOLOGY 2019; 56:1467-1474. [PMID: 31549720 PMCID: PMC7182917 DOI: 10.1093/jme/tjz112] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Indexed: 05/15/2023]
Abstract
West Nile virus (WNV) was first identified in North America almost 20 yr ago. In that time, WNV has crossed the continent and established enzootic transmission cycles, resulting in intermittent outbreaks of human disease that have largely been linked with climatic variables and waning avian seroprevalence. During the transcontinental dissemination of WNV, the original genotype has been displaced by two principal extant genotypes which contain an envelope mutation that has been associated with enhanced vector competence by Culex pipiens L. (Diptera: Culicidae) and Culex tarsalis Coquillett vectors. Analyses of retrospective avian host competence data generated using the founding NY99 genotype strain have demonstrated a steady reduction in viremias of house sparrows over time. Reciprocally, the current genotype strains WN02 and SW03 have demonstrated an inverse correlation between house sparrow viremia magnitude and the time since isolation. These data collectively indicate that WNV has evolved for increased avian viremia while house sparrows have evolved resistance to the virus such that the relative host competence has remained constant. Intrahost analyses of WNV evolution demonstrate that selection pressures are avian species-specific and purifying selection is greater in individual birds compared with individual mosquitoes, suggesting that the avian adaptive and/or innate immune response may impose a selection pressure on WNV. Phylogenomic, experimental evolutionary systems, and models that link viral evolution with climate, host, and vector competence studies will be needed to identify the relative effect of different selective and stochastic mechanisms on viral phenotypes and the capacity of newly evolved WNV genotypes for transmission in continuously changing landscapes.
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Affiliation(s)
- Nisha K Duggal
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Kate E Langwig
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Gregory D Ebel
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO
| | - Aaron C Brault
- Division of Vector-borne Diseases, Centers for Disease Control and Prevention, Fort Collins, CO
- Corresponding author, e-mail:
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McMillan JR, Marcet PL, Hoover CM, Mead D, Kitron U, Vazquez-Prokopec GM. Feeding Success and Host Selection by Culex quinquefasciatus Say Mosquitoes in Experimental Trials. Vector Borne Zoonotic Dis 2019; 19:540-548. [PMID: 30964426 DOI: 10.1089/vbz.2018.2381] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Arthropod vector feeding preferences are defined as an overutilization of a particular host species given its abundance in relationship to other species in the community. Numerous methods exist to quantify vector feeding preferences; however, controlled host choice experiments are generally an underutilized approach. In this report, we present results from controlled vector host choice experiments using Culex quinquefasciatus Say (Diptera: Culicidae) mosquitoes and wild avian hosts identified as important contributors to West Nile virus (WNv) transmission in Atlanta, Georgia, United States. In each experiment, we allowed lab-reared F1 Cx. quinquefasciatus to feed freely overnight on two avian individuals of a different species (i.e., northern cardinals, American robins, blue jays, brown thrashers, and gray catbirds). We then estimated WNv transmission potential using vectorial capacity and R0. We found that mosquito blood feeding success was extremely variable among experimental replicates and that patterns of host choice only occasionally aggregated to a particular bird species. Vectorial capacity was highest for American robins and blue jays due to these species' higher reservoir competence for WNv and greater probabilities of mosquito selection of these species. Despite species-specific differences in vectorial capacity, total community capacity was similar among species pairs. R0 estimates were qualitatively similar to capacity, and R0 was below and above unity across species pairs. Our results provide empirical evidence that C. quinquefasciatus is an opportunistic blood feeder and highlight how variability in vector-host contact rates as well as host community composition can influence the likelihood of WNv transmission in avian communities.
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Affiliation(s)
- Joseph R McMillan
- 1 Program in Population Biology, Ecology and Evolution, Emory University, Atlanta, Georgia
| | - Paula L Marcet
- 2 Division of Parasitic Diseases and Malaria, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Christopher M Hoover
- 3 Division of Environmental Health Sciences, University of California, Berkeley School of Public Health, Berkeley, California
| | - Daniel Mead
- 4 Southeastern Cooperative Wildlife Disease Study, University of Georgia, Athens, Georgia
| | - Uriel Kitron
- 1 Program in Population Biology, Ecology and Evolution, Emory University, Atlanta, Georgia.,5 Department of Environmental Sciences, Emory University, Atlanta, Georgia
| | - Gonzalo M Vazquez-Prokopec
- 1 Program in Population Biology, Ecology and Evolution, Emory University, Atlanta, Georgia.,5 Department of Environmental Sciences, Emory University, Atlanta, Georgia
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Mackay AJ, Muturi EJ, Ward MP, Allan BF. Cascade of ecological consequences for West Nile virus transmission when aquatic macrophytes invade stormwater habitats. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2016; 26:219-232. [PMID: 27039521 DOI: 10.1890/15-0050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Artificial aquatic habitats are ubiquitous in anthropogenic landscapes and highly susceptible to colonization by invasive plant species. Recent research into the ecology of infectious diseases indicates that the establishment of invasive plant species can trigger ecological cascades which alter the transmission dynamics of vector-borne pathogens that imperil human health. Here, we examined whether the presence or management of two invasive, emergent plants, cattails (Typha spp.) and phragmites (Phragmites australis), in stormwater dry detention basins (DDBs) alter the local distribution of vectors, avian hosts, or West Nile virus (WNV) transmission risk in an urban residential setting. Mosquitoes and birds were surveyed at 14 DDBs and paired adjacent residential sites. During the study period, emergent vegetation was mowed by site managers in three DDBs. In the absence of vegetation management, the overall abundance and species composition of both adult vectors and avian hosts differed between residential and DDB habitats; however, WNV entomological risk indices were equivalent. Communal bird roosts composed primarily of three species, European Starlings (Sturnus vulgaris), Red-winged Blackbirds (Agelaius phoeniceus), and Common Grackles (Quiscalus quiscula), representing a broad range of WNV reservoir competence, were observed at half (three out of six) of the DDBs containing unmanaged stands of phragmites; however, their presence was associated with a lower seasonal increase in vector infection rate. Conversely, mowing of emergent vegetation resulted in a significant and sustained increase in the abundance of WNV-infected vectors in DDBs and the increase in risk extended to adjacent residential sites. These findings indicate that management of invasive plants in DDBs during the growing season can increase, while presence of communal bird roosts can decrease, WNV transmission risk.
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Komar N, Colborn JM, Horiuchi K, Delorey M, Biggerstaff B, Damian D, Smith K, Townsend J. Reduced West Nile Virus Transmission Around Communal Roosts of Great-Tailed Grackle (Quiscalus mexicanus). ECOHEALTH 2015; 12:144-51. [PMID: 25480320 PMCID: PMC4786297 DOI: 10.1007/s10393-014-0993-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 10/14/2014] [Accepted: 10/14/2014] [Indexed: 05/28/2023]
Abstract
West Nile virus has caused several outbreaks among humans in the Phoenix metropolitan area (Arizona, southwest USA) within the last decade. Recent ecologic studies have implicated Culex quinquefasciatus and Culex tarsalis as the mosquito vectors and identified three abundant passerine birds-great-tailed grackle (Quiscalus mexicanus), house sparrow (Passer domesticus), and house finch (Haemorhous mexicanus)-as key amplifiers among vertebrates. Nocturnal congregations of certain species have been suggested as critical for late summer West Nile virus amplification. We evaluated the hypothesis that house sparrow (P. domesticus) and/or great-tailed grackle (Q. mexicanus) communal roost sites (n = 22 and n = 5, respectively) in a primarily suburban environment were spatially associated with West Nile virus transmission indices during the 2010 outbreak of human neurological disease in metropolitan Phoenix. Spatial associations between human case residences and communal roosts were non-significant for house sparrows, and were negative for great-tailed grackle. Several theories that explain these observations are discussed, including the possibility that grackle communal roosts are protective.
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Affiliation(s)
- Nicholas Komar
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, 3156 Rampart Road, Fort Collins, CO, 80521, USA,
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Janousek WM, Marra PP, Kilpatrick AM. Avian roosting behavior influences vector-host interactions for West Nile virus hosts. Parasit Vectors 2014; 7:399. [PMID: 25167979 PMCID: PMC4159503 DOI: 10.1186/1756-3305-7-399] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 08/22/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Extensive 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). METHODS We 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. RESULTS First, 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. CONCLUSIONS These 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.
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Affiliation(s)
- William M Janousek
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California 95064, USA.
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