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Danforth ME, Snyder RE, Feiszli T, Bullick T, Messenger S, Hanson C, Padgett K, Coffey LL, Barker CM, Reisen WK, Kramer VL. Epidemiologic and environmental characterization of the Re-emergence of St. Louis Encephalitis Virus in California, 2015-2020. PLoS Negl Trop Dis 2022; 16:e0010664. [PMID: 35939506 PMCID: PMC9387929 DOI: 10.1371/journal.pntd.0010664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 08/18/2022] [Accepted: 07/15/2022] [Indexed: 11/18/2022] Open
Abstract
St. Louis encephalitis virus (SLEV) is an endemic flavivirus in the western and southeastern United States, including California. From 1938 to 2003, the virus was detected annually in California, but after West Nile virus (WNV) arrived in 2003, SLEV was not detected again until it re-emerged in Riverside County in 2015. The re-emerging virus in California and other areas of the western US is SLEV genotype III, which previously had been detected only in Argentina, suggesting a South American origin. This study describes SLEV activity in California since its re-emergence in 2015 and compares it to WNV activity during the same period. From 2015 to 2020, SLEV was detected in 1,650 mosquito pools and 26 sentinel chickens, whereas WNV was detected concurrently in 18,108 mosquito pools and 1,542 sentinel chickens from the same samples. There were 24 reported human infections of SLEV in 10 California counties, including two fatalities (case fatality rate: 8%), compared to 2,469 reported human infections of WNV from 43 California counties, with 143 fatalities (case fatality rate: 6%). From 2015 through 2020, SLEV was detected in 17 (29%) of California's 58 counties, while WNV was detected in 54 (93%). Although mosquitoes and sentinel chickens have been tested routinely for arboviruses in California for over fifty years, surveillance has not been uniform throughout the state. Of note, since 2005 there has been a steady decline in the use of sentinel chickens among vector control agencies, potentially contributing to gaps in SLEV surveillance. The incidence of SLEV disease in California may have been underestimated because human surveillance for SLEV relied on an environmental detection to trigger SLEV patient screening and mosquito surveillance effort is spatially variable. In addition, human diagnostic testing usually relies on changes in host antibodies and SLEV infection can be indistinguishable from infection with other flaviviruses such as WNV, which is more prevalent.
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Affiliation(s)
- Mary E. Danforth
- California Department of Public Health, Vector-Borne Disease Section, Richmond and Sacramento, California
| | - Robert E. Snyder
- California Department of Public Health, Vector-Borne Disease Section, Richmond and Sacramento, California
| | - Tina Feiszli
- California Department of Public Health, Vector-Borne Disease Section, Richmond and Sacramento, California
| | - Teal Bullick
- California Department of Public Health, Viral and Rickettsial Disease Laboratory, Richmond, California
| | - Sharon Messenger
- California Department of Public Health, Viral and Rickettsial Disease Laboratory, Richmond, California
| | - Carl Hanson
- California Department of Public Health, Viral and Rickettsial Disease Laboratory, Richmond, California
| | - Kerry Padgett
- California Department of Public Health, Vector-Borne Disease Section, Richmond and Sacramento, California
| | - Lark L. Coffey
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California, United States of America
| | - Christopher M. Barker
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California, United States of America
| | - William K. Reisen
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California, United States of America
| | - Vicki L. Kramer
- California Department of Public Health, Vector-Borne Disease Section, Richmond and Sacramento, California
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Swetnam DM, Stuart JB, Young K, Maharaj PD, Fang Y, Garcia S, Barker CM, Smith K, Godsey MS, Savage HM, Barton V, Bolling BG, Duggal N, Brault AC, Coffey LL. Movement of St. Louis encephalitis virus in the Western United States, 2014- 2018. PLoS Negl Trop Dis 2020; 14:e0008343. [PMID: 32520944 PMCID: PMC7307790 DOI: 10.1371/journal.pntd.0008343] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 06/22/2020] [Accepted: 05/02/2020] [Indexed: 11/22/2022] Open
Abstract
St. Louis encephalitis virus (SLEV) is a flavivirus that circulates in an enzootic cycle between birds and mosquitoes and can also infect humans to cause febrile disease and sometimes encephalitis. Although SLEV is endemic to the United States, no activity was detected in California during the years 2004 through 2014, despite continuous surveillance in mosquitoes and sentinel chickens. In 2015, SLEV-positive mosquito pools were detected in Maricopa County, Arizona, concurrent with an outbreak of human SLEV disease. SLEV-positive mosquito pools were also detected in southeastern California and Nevada in summer 2015. From 2016 to 2018, SLEV was detected in mosquito pools throughout southern and central California, Oregon, Idaho, and Texas. To understand genetic relatedness and geographic dispersal of SLEV in the western United States since 2015, we sequenced four historical genomes (3 from California and 1 from Louisiana) and 26 contemporary SLEV genomes from mosquito pools from locations across the western US. Bayesian phylogeographic approaches were then applied to map the recent spread of SLEV. Three routes of SLEV dispersal in the western United States were identified: Arizona to southern California, Arizona to Central California, and Arizona to all locations east of the Sierra Nevada mountains. Given the topography of the Western United States, these routes may have been limited by mountain ranges that influence the movement of avian reservoirs and mosquito vectors, which probably represents the primary mechanism of SLEV dispersal. Our analysis detected repeated SLEV introductions from Arizona into southern California and limited evidence of year-to-year persistence of genomes of the same ancestry. By contrast, genetic tracing suggests that all SLEV activity since 2015 in central California is the result of a single persistent SLEV introduction. The identification of natural barriers that influence SLEV dispersal enhances our understanding of arbovirus ecology in the western United States and may also support regional public health agencies in implementing more targeted vector mitigation efforts to protect their communities more effectively. Following the detection of West Nile virus in the United States, evidence of the historically endemic and closely related virus, St. Louis encephalitis virus (SLEV), dropped nationwide. However, in 2015, a novel genotype of SLEV, previously restricted to Argentina, was identified as the etiological agent of an outbreak of neurological disease in Arizona, United States. Since that time, the genotype has expanded throughout the Western United States, including into California, Nevada, Texas, Idaho, and Oregon. In this study, samples containing SLEV, provided by public health and mosquito abatement agencies, were sequenced and used in phylogenetic analyses to infer patterns of SLEV movement. Three independent routes of SLEV dispersal were identified: Arizona to Southern California, Arizona to Central California, and Arizona to all locations east of the Sierra Nevada mountains. The Sierra Nevada mountains and the Transverse Ranges appear to separate the three routes of SLEV movement, suggesting that geographic features may act as barriers to virus dispersal. Identification of patterns of SLEV dispersal can support regional public health agencies in improving vector mitigation efforts to protect their communities more effectively.
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Affiliation(s)
- Daniele M. Swetnam
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America
| | - Jackson B. Stuart
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America
| | - Katherine Young
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America
| | - Payal D. Maharaj
- Division of Vector-borne Diseases, Centers for Disease Control, Fort Collins, Colorado, United States of America
| | - Ying Fang
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America
| | - Sandra Garcia
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America
| | - Christopher M. Barker
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America
| | - Kirk Smith
- Maricopa County Environmental Services Department, Phoenix, Arizona, United States of America
| | - Marvin S. Godsey
- Division of Vector-borne Diseases, Centers for Disease Control, Fort Collins, Colorado, United States of America
| | - Harry M. Savage
- Division of Vector-borne Diseases, Centers for Disease Control, Fort Collins, Colorado, United States of America
| | - Vonnita Barton
- Idaho Bureau of Laboratories, Boise, Idaho, United States of America
| | - Bethany G. Bolling
- Laboratory Services Section, Texas Department of State Health Services, Austin, Texas, United States of America
| | - Nisha Duggal
- Department of Molecular Biology, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States of America
| | - Aaron C. Brault
- Division of Vector-borne Diseases, Centers for Disease Control, Fort Collins, Colorado, United States of America
| | - Lark L. Coffey
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America
- * E-mail:
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Abstract
Pokémon Go is a new game that encourages players to venture outdoors and interact with others in the pursuit of virtual Pokémon characters. With more time spent outdoors overall and in sometimes large congregations, Pokémon Go players could inadvertently elevate their risk of exposure to mosquito-borne diseases when playing in certain areas at certain times of year. Here, we make an initial assessment of the possible scope of this concern in the continental United States, which experiences its highest seasonal transmission of West Nile, Zika, and other viruses during summer and early fall. In particular, we propose that the times of day when many disease-relevant mosquito species are most likely to engage in blood feeding coincide with times of day when Pokémon Go activity is likely to be high, and we note that locations serving as hubs of Pokémon Go activity may in some cases overlap with areas where these mosquitoes are actively engaged in blood feeding. Although the risk of mosquito-borne diseases in the continental U.S. is low overall and is unlikely to be impacted significantly by Pokémon Go, it is nonetheless important for Pokémon Go players and others who spend time outdoors engaging in activities such as barbecues and gardening to be aware of these ongoing risks and to take appropriate preventative measures in light of the potential for outdoor activity to modify individual-level risk of exposure. As Pokémon Go and other augmented reality games become available in other parts of the world, similar risks should be assessed in a manner that is consistent with the local epidemiology of mosquito-borne diseases in those areas.
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Rivarola ME, Tauro LB, Llinás GA, Contigiani MS. Virulence variation among epidemic and non-epidemic strains of Saint Louis encephalitis virus circulating in Argentina. Mem Inst Oswaldo Cruz 2016; 109:197-201. [PMID: 24810175 PMCID: PMC4015247 DOI: 10.1590/0074-0276130475] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 02/19/2014] [Indexed: 11/22/2022] Open
Abstract
Saint Louis encephalitis virus caused an outbreak of febrile illness and encephalitis
cases in Córdoba, Argentina, in 2005. During this outbreak, the strain CbaAr-4005 was
isolated from Culex quinquefasciatus mosquitoes. We hypothesised
that this epidemic variant would be more virulent in a mouse model than two other
non-epidemic strains (78V-6507 and CorAn-9275) isolated under different
epidemiological conditions. To test this hypothesis, we performed a biological
characterisation in a murine model, including mortality, morbidity and infection
percentages and lethal infection indices using the three strains. Mice were separated
into age groups (7, 10 and 21-day-old mice) and analysed after infection. The strain
CbaAr-4005 was the most infective and lethal of the three variants, whereas the other
two strains exhibited a decreasing mortality percentage with increasing animal age.
The strain CbaAr-4005 produced the highest morbidity percentages and no significant
differences among age groups were observed. The epidemic strain caused signs of
illness in all inoculated animals and showed narrower ranges from the onset of
symptoms than the other strains. CbaAr-4005 was the most virulent for Swiss albino
mice. Our results highlight the importance of performing biological characterisations
of arbovirus strains likely to be responsible for emerging or reemerging human
diseases.
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Affiliation(s)
- María Elisa Rivarola
- Laboratorio de Arbovirus, Instituto de Virología Dr JM Vanella, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Laura Beatriz Tauro
- Laboratorio de Arbovirus, Instituto de Virología Dr JM Vanella, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Guillermo Albrieu Llinás
- Laboratorio de Arbovirus, Instituto de Virología Dr JM Vanella, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Marta Silvia Contigiani
- Laboratorio de Arbovirus, Instituto de Virología Dr JM Vanella, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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5
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Reisen WK, Wheeler SS. Surveys for Antibodies Against Mosquitoborne Encephalitis Viruses in California Birds, 1996-2013. Vector Borne Zoonotic Dis 2016; 16:264-82. [PMID: 26974395 PMCID: PMC4800269 DOI: 10.1089/vbz.2015.1888] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
From 1996 through 2013, 54,546 individual birds comprising 152 species and 7 orders were banded, bled, and released at four study areas within California, from which 28,388 additional serum samples were collected at one or more recapture encounters. Of these, 142, 99, and 1929 birds from 41 species were positive for neutralizing antibodies against western equine encephalomyelitis virus (WEEV), St. Louis encephalitis virus (SLEV), or West Nile virus (WNV) at initial capture or recapture, respectively. Overall, 83% of the positive serum samples were collected from five species: House Finch, House Sparrow, Mourning Dove, California Quail, and Western Scrub-Jay. Temporal data supported concurrent arbovirus surveillance and documented the disappearance of birds positive for WEEV in 2008 and SLEV in 2003 and the appearance of birds positive for WNV after its invasion in 2003. Results of these serosurveys agreed well with the host selection patterns of the Culex vectors as described from bloodmeal sequencing data and indicated that transmission of WNV seemed most effective within urban areas where avian and mosquito host diversity was limited to relatively few competent species.
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Affiliation(s)
- William K Reisen
- Department of Pathology, Microbiology and Immunology, Center for Vectorborne Diseases, School of Veterinary Medicine, University of California , Davis, California
| | - Sarah S Wheeler
- Department of Pathology, Microbiology and Immunology, Center for Vectorborne Diseases, School of Veterinary Medicine, University of California , Davis, California
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6
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Parasite prevalence corresponds to host life history in a diverse assemblage of afrotropical birds and haemosporidian parasites. PLoS One 2015; 10:e0121254. [PMID: 25853491 PMCID: PMC4390322 DOI: 10.1371/journal.pone.0121254] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2014] [Accepted: 01/29/2015] [Indexed: 11/19/2022] Open
Abstract
Avian host life history traits have been hypothesized to predict rates of infection by haemosporidian parasites. Using molecular techniques, we tested this hypothesis for parasites from three haemosporidian genera (Plasmodium, Haemoproteus, and Leucocytozoon) collected from a diverse sampling of birds in northern Malawi. We found that host life history traits were significantly associated with parasitism rates by all three parasite genera. Nest type and nest location predicted infection probability for all three parasite genera, whereas flocking behavior is an important predictor of Plasmodium and Haemoproteus infection and habitat is an important predictor of Leucocytozoon infection. Parasite prevalence was 79.1% across all individuals sampled, higher than that reported for comparable studies from any other region of the world. Parasite diversity was also exceptionally high, with 248 parasite cytochrome b lineages identified from 152 host species. A large proportion of Plasmodium, Haemoproteus, and Leucocytozoon parasite DNA sequences identified in this study represent new, previously undocumented lineages (n = 201; 81% of total identified) based on BLAST queries against the avian malaria database, MalAvi.
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7
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Kading RC, Biggerstaff BJ, Young G, Komar N. Mosquitoes used to draw blood for arbovirus viremia determinations in small vertebrates. PLoS One 2014; 9:e99342. [PMID: 24901448 PMCID: PMC4047049 DOI: 10.1371/journal.pone.0099342] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 05/14/2014] [Indexed: 11/19/2022] Open
Abstract
Serial samples from the same individuals may be required for certain virological studies, however, some small animals cannot easily be blood-sampled. Therefore, we evaluated the use of Culex quinquefasciatus Say and Aedes albopictus Skuse mosquitoes as “biological syringes” to draw blood for virus titer determinations in small vertebrates. Groups of chicks (Gallus gallus), hamsters (Mesocricetus auratus), and house sparrows (Passer domesticus) were experimentally infected with West Nile virus (WNV) or Highlands J virus (HJV). In general, good correlation was seen between mosquito- and syringe-derived blood samples at titers ≥5.0 log10 pfu/mL serum as compared with titers <5.0 log10 pfu/mL serum for chicks, hamsters, and sparrows. Ninety-two percent (24/26) of sparrows with virus titers >105 pfu/mL serum had mosquito- and syringe-derived titers within one log of each other. Sparrow viremia profiles generated from single mosquito blood meals and syringe were not significantly different (p>0.05). This technique is valuable for assessing the roles of small vertebrates in the ecologies of arboviruses, and could be used in applications beyond virology and infectious diseases, when <10 µL of whole blood is required.
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Affiliation(s)
- Rebekah C. Kading
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
- * E-mail:
| | - Brad J. Biggerstaff
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
| | - Ginger Young
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
| | - Nicholas Komar
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
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8
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Experimental infections of wild birds with West Nile virus. Viruses 2014; 6:752-81. [PMID: 24531334 PMCID: PMC3939481 DOI: 10.3390/v6020752] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 02/04/2014] [Accepted: 02/04/2014] [Indexed: 01/16/2023] Open
Abstract
Avian models of West Nile virus (WNV) disease have become pivotal in the study of infection pathogenesis and transmission, despite the intrinsic constraints that represents this type of experimental research that needs to be conducted in biosecurity level 3 (BSL3) facilities. This review summarizes the main achievements of WNV experimental research carried out in wild birds, highlighting advantages and limitations of this model. Viral and host factors that determine the infection outcome are analyzed in detail, as well as recent discoveries about avian immunity, viral transmission, and persistence achieved through experimental research. Studies of laboratory infections in the natural host will help to understand variations in susceptibility and reservoir competence among bird species, as well as in the epidemiological patterns found in different affected areas.
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Reisen WK, Lothrop HD, Thiemann T. Host selection patterns of Culex tarsalis (Diptera: Culicidae) at wetlands near the Salton Sea, Coachella Valley, California, 1998-2002. JOURNAL OF MEDICAL ENTOMOLOGY 2013; 50:1071-6. [PMID: 24180112 PMCID: PMC3918163 DOI: 10.1603/me13078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The bloodmeal hosts used by Culex tarsalis Coquillett collected along the Salton Sea in Coachella Valley, CA, during 1998-2002 were identified using sequences of the cytochrome c oxidase I gene identified from Barcode of Life database. Overall, 265 (83.3%) of 318 bloodmeals were identified, of which 76.6% fed on birds, 18.1% on mammals, and 5.3% on reptiles. Forty-seven different hosts were identified, none of which comprised > 12.5% of the total. Although Cx. tarsalis exhibits specific host-seeking flight patterns, bloodmeals seemed to be acquired opportunistically, thereby limiting potential arbovirus transmission efficiency in species-rich environments.
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Affiliation(s)
- William K Reisen
- Center for Vectorborne Diseases, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
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10
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THIEMANN TC, LEMENAGER DA, KLUH S, CARROLL BD, LOTHROP HD, REISEN WK. Spatial variation in host feeding patterns of Culex tarsalis and the Culex pipiens complex (Diptera: Culicidae) in California. JOURNAL OF MEDICAL ENTOMOLOGY 2012; 49:903-16. [PMID: 22897051 PMCID: PMC3542768 DOI: 10.1603/me11272] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
West Nile virus (family Flaviviridae, genus Flavivirus, WNV) is now endemic in California across a variety of ecological regions that support a wide diversity of potential avian and mammalian host species. Because different avian hosts have varying competence for WNV, determining the blood-feeding patterns of Culex (Diptera: Culicidae) vectors is a key component in understanding the maintenance and amplification of the virus as well as tangential transmission to humans and horses. We investigated the blood-feeding patterns of Culex tarsalis Coquillett and members of the Culex pipiens L. complex from southern to northern California. Nearly 100 different host species were identified from 1,487 bloodmeals, by using the mitochondrial gene cytochrome c oxidase I (COI). Cx. tarsalis fed on a higher diversity of hosts and more frequently on nonhuman mammals than did the Cx. pipiens complex. Several WNV-competent host species, including house finch and house sparrow, were common bloodmeal sources for both vector species across several biomes and could account for WNV maintenance and amplification in these areas. Highly competent American crow, western scrub-jay and yellow-billed magpie also were fed upon often when available and are likely important as amplifying hosts for WNV in some areas. Neither species fed frequently on humans (Cx. pipiens complex [0.4%], Cx. tarsalis [0.2%]), but with high abundance, both species could serve as both enzootic and bridge vectors for WNV.
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Affiliation(s)
- T. C. THIEMANN
- Center for Vectorborne Diseases, School of Veterinary Medicine, University of California–Davis, Davis, CA 95616
| | - D. A. LEMENAGER
- Sutter-Yuba Mosquito and Vector Control District, P.O. Box 726, Yuba City, CA 95992
| | - S. KLUH
- Greater Los Angeles County Vector Control District, 12545 Florence Ave., Santa Fe Springs, CA 90670
| | - B. D. CARROLL
- Center for Vectorborne Diseases, School of Veterinary Medicine, University of California–Davis, Davis, CA 95616
| | - H. D. LOTHROP
- Center for Vectorborne Diseases, School of Veterinary Medicine, University of California–Davis, Davis, CA 95616
| | - W. K. REISEN
- Center for Vectorborne Diseases, School of Veterinary Medicine, University of California–Davis, Davis, CA 95616
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11
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Maharaj PD, Anishchenko M, Langevin SA, Fang Y, Reisen WK, Brault AC. Structural gene (prME) chimeras of St Louis encephalitis virus and West Nile virus exhibit altered in vitro cytopathic and growth phenotypes. J Gen Virol 2011; 93:39-49. [PMID: 21940408 DOI: 10.1099/vir.0.033159-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Despite utilizing the same avian hosts and mosquito vectors, St Louis encephalitis virus (SLEV) and West Nile virus (WNV) display dissimilar vector-infectivity and vertebrate-pathogenic phenotypes. SLEV exhibits a low oral infection threshold for Culex mosquito vectors and is avirulent in avian hosts, producing low-magnitude viraemias. In contrast, WNV is less orally infective to mosquitoes and elicits high-magnitude viraemias in a wide range of avian species. In order to identify the genetic determinants of these different phenotypes and to assess the utility of mosquito and vertebrate cell lines for recapitulating in vivo differences observed between these viruses, reciprocal WNV and SLEV pre-membrane and envelope protein (prME) chimeric viruses were generated and growth of these mutant viruses was characterized in mammalian (Vero), avian (duck) and mosquito [Aedes (C6/36) and Culex (CT)] cells. In both vertebrate lines, WNV grew to 100-fold higher titres than SLEV, and growth and cytopathogenicity phenotypes, determined by chimeric phenotypes, were modulated by genetic elements outside the prME gene region. Both chimeras exhibited distinctive growth patterns from those of SLEV in C6/36 cells, indicating the role of both structural and non-structural gene regions for growth in this cell line. In contrast, growth of chimeric viruses was indistinguishable from that of virus containing homologous prME genes in CT cells, indicating that structural genetic elements could specifically dictate growth differences of these viruses in relevant vectors. These data provide genetic insight into divergent enzootic maintenance strategies that could also be useful for the assessment of emergence mechanisms of closely related flaviviruses.
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Affiliation(s)
- Payal D Maharaj
- Center for Vector-borne Disease Research and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.,Division of Vector-Borne Diseases, Centers for Disease Control and Prevention (CDC), Fort Collins, CO 80521, USA
| | - Michael Anishchenko
- Center for Vector-borne Disease Research and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.,Division of Vector-Borne Diseases, Centers for Disease Control and Prevention (CDC), Fort Collins, CO 80521, USA
| | - Stanley A Langevin
- Center for Vector-borne Disease Research and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
| | - Ying Fang
- Center for Vector-borne Disease Research and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
| | - William K Reisen
- Center for Vector-borne Disease Research and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
| | - Aaron C Brault
- Center for Vector-borne Disease Research and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.,Division of Vector-Borne Diseases, Centers for Disease Control and Prevention (CDC), Fort Collins, CO 80521, USA
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12
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Brown CR, O'Brien VA. Are Wild Birds Important in the Transport of Arthropod-borne Viruses? ACTA ACUST UNITED AC 2011. [DOI: 10.1525/om.2011.71.1.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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13
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Brault AC, Kinney RM, Maharaj PD, Green EN, Reisen WK, Huang CYH. Replication of the Primary Dog Kidney-53 Dengue 2 Virus Vaccine Candidate inAedes aegyptiIs Modulated by a Mutation in the 5′ Untranslated Region and Amino Acid Substitutions in Nonstructural Proteins 1 and 3. Vector Borne Zoonotic Dis 2011; 11:683-9. [DOI: 10.1089/vbz.2010.0150] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Aaron C. Brault
- Department of Pathology, Microbiology, and Immunology, Center for Vector Borne Diseases, School of Veterinary Medicine, University of California, Davis
- Division of Vector-Borne Infectious Diseases, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, Fort Collins, Colorado
| | - Richard M. Kinney
- Division of Vector-Borne Infectious Diseases, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, Fort Collins, Colorado
| | - Payal D. Maharaj
- Department of Pathology, Microbiology, and Immunology, Center for Vector Borne Diseases, School of Veterinary Medicine, University of California, Davis
- Division of Vector-Borne Infectious Diseases, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, Fort Collins, Colorado
| | - Emily N.G. Green
- Department of Pathology, Microbiology, and Immunology, Center for Vector Borne Diseases, School of Veterinary Medicine, University of California, Davis
| | - William K. Reisen
- Department of Pathology, Microbiology, and Immunology, Center for Vector Borne Diseases, School of Veterinary Medicine, University of California, Davis
| | - Claire Y.-H. Huang
- Division of Vector-Borne Infectious Diseases, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, Fort Collins, Colorado
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Diaz LA, Nemeth NM, Bowen RA, Almiron WR, Contigiani MS. Comparison of argentinean saint louis encephalitis virus non-epidemic and epidemic strain infections in an avian model. PLoS Negl Trop Dis 2011; 5:e1177. [PMID: 21629729 PMCID: PMC3101189 DOI: 10.1371/journal.pntd.0001177] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 03/30/2011] [Indexed: 11/19/2022] Open
Abstract
St. Louis encephalitis virus (SLEV, Flavivirus, Flaviviridae) is an emerging mosquito-borne pathogen in South America, with human SLEV encephalitis cases reported in Argentina and Brazil. Genotype III strains of SLEV were isolated from Culex quinquefasciatus mosquitoes in Cordoba, Argentina in 2005, during the largest SLEV outbreak ever reported in South America. The present study tested the hypothesis that the recent, epidemic SLEV strain exhibits greater virulence in birds as compared with a non-epidemic genotype III strain isolated from mosquitoes in Santa Fe Province 27 years earlier. The observed differences in infection parameters between adult House sparrows (Passer domesticus) that were needle-inoculated with either the epidemic or historic SLEV strain were not statistically significant. However, only the House sparrows that were infected with the epidemic strain achieved infectious-level viremia titers sufficient to infect Cx. spp. mosquitoes vectors. Furthermore, the vertebrate reservoir competence index values indicated an approximately 3-fold increase in amplification potential of House sparrows infected with the epidemic strain when pre-existing flavivirus-reactive antibodies were present, suggesting the possibility that antibody-dependent enhancement may increase the risk of avian-amplified transmission of SLEV in South America. St. Louis encephalitis virus (SLEV, Flavivirus, Flaviviridae) is an emerging arbovirus in South America, with human SLEV encephalitis cases reported in Argentina and Brazil. Genotype III strains of SLEV were isolated from mosquitoes during the largest SLEV outbreak ever reported in South America (Córdoba, Argentina, 2005). These strains are related to a non-epidemic genotype III SLEV strain isolated in 1979 in Santa Fe Province, Argentina. There is currently no clear explanation for the reemergence of SLEV in Argentina. This study tested the hypothesis that the epidemic strain exhibited greater virulence compared to a non-epidemic genotype III strain in an avian model, the House sparrow (Passer domesticus). House sparrows were susceptible to infection with Argentinean SLEV strains; however, the proportion of birds that became detectably viremic was low for both strains. Although no significant difference was detected between both strains, House sparrows inoculated with epidemic strain developed higher and longer viremias than those inoculated with non-epidemic strain. The virus amplification role of House sparrows was apparently enhanced when they had previous flavivirus immunity. The evolutionary/introduction process of a more viremogenic SLEV strain and the immunological interactions among antigenically-related flaviviruses will undoubtedly affect the continued reemergence of SLEV in Argentina.
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Affiliation(s)
- Luis Adrián Diaz
- Laboratorio Arbovirus, Instituto de Virología Dr. J. M. Vanella, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina.
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15
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Abstract
The linkages between human health and ecosystems are complex, dynamic, and political. For millennia ecosystems have provided humans with essential services such as food, water, shelter and medicine. At the same time, they have mediated the transmission of many diseases and posed a number of health risks. The vitality of ecosystem services for human health and well-being is well captured by Bernard Abraham, President of Weskit-Chi Aboriginal Trappers Association, when he commented on the importance of forest ecosystems to Aboriginal people. He observed that many Aboriginal people consider the forest as: “their food bank, drugstore, meat market, bakery, fruit and vegetable stand, building material centre, beverage supply, and the habitat for all of the creator’s creatures.”1
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Burkett-Cadena ND, Ligon RA, Liu M, Hassan HK, Hill GE, Eubanks MD, Unnasch TR. Vector-host interactions in avian nests: do mosquitoes prefer nestlings over adults? Am J Trop Med Hyg 2010; 83:395-9. [PMID: 20682889 DOI: 10.4269/ajtmh.2010.10-0048] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The hypothesis that nestlings are a significant driver of arbovirus transmission and amplification is based upon findings that suggest nestlings are highly susceptible to being fed upon by vector mosquitoes and to viral infection and replication. Several previous studies have suggested that nestlings are preferentially fed upon relative to adults in the nest, and other studies have reported a preference for adults over nestlings. We directly tested the feeding preference of nestling and adult birds in a natural setting, introducing mosquitoes into nesting boxes containing eastern bluebirds (Sialia sialis), collecting blood-fed mosquitoes, and matching the source of mosquito blood meals to individual birds using microsatellite markers. Neither nestlings nor adults were fed upon to an extent significantly greater than would be predicted based upon their relative abundance in the nests, although feeding upon mothers decreased as the age of the nestlings increased.
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17
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O'Brien VA, Meteyer CU, Reisen WK, Ip HS, Brown CR. Prevalence and pathology of West Nile virus in naturally infected house sparrows, western Nebraska, 2008. Am J Trop Med Hyg 2010; 82:937-44. [PMID: 20439979 DOI: 10.4269/ajtmh.2010.09-0515] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Nestling birds are rarely sampled in the field for most arboviruses, yet they may be important in arbovirus amplification cycles. We sampled both nestling and adult house sparrows (Passer domesticus) in western Nebraska for West Nile virus (WNV) or WNV-specific antibodies throughout the summer of 2008 and describe pathology in naturally infected nestlings. Across the summer, 4% of nestling house sparrows were WNV-positive; for the month of August alone, 12.3% were positive. Two WNV-positive nestlings exhibited encephalitis, splenomegaly, hepatic necrosis, nephrosis, and myocarditis. One nestling sparrow had large mural thrombi in the atria and ventricle and immunohistochemical staining of WNV antigen in multiple organs including the wall of the aorta and pulmonary artery; cardiac insufficiency thus may have been a cause of death. Adult house sparrows showed an overall seroprevalence of 13.8% that did not change significantly across the summer months. The WNV-positive nestlings and the majority of seropositive adults were detected within separate spatial clusters. Nestling birds, especially those reared late in the summer when WNV activity is typically greatest, may be important in virus amplification.
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Affiliation(s)
- Valerie A O'Brien
- Department of Biological Sciences, University of Tulsa, Tulsa, Oklahoma, USA.
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18
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Abstract
Landscape epidemiology describes how the temporal dynamics of host, vector, and pathogen populations interact spatially within a permissive environment to enable transmission. The spatially defined focus, or nidus, of transmission may be characterized by vegetation as well as by climate, latitude, elevation, and geology. The ecological complexity, dimensions, and temporal stability of the nidus are determined largely by pathogen natural history and vector bionomics. Host populations, transmission efficiency, and therefore pathogen amplification vary spatially, thereby creating a heterogeneous surface that may be defined by remote sensing and statistical tools. The current review describes the evolution of landscape epidemiology as a science and exemplifies selected aspects by contrasting the ecology of two different recent disease outbreaks in North America caused by West Nile virus, an explosive, highly virulent mosquito-borne virus producing ephemeral nidi, and Borrelia burgdorferi, a slowly amplifying chronic pathogen producing semipermanent nidi.
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Affiliation(s)
- William K Reisen
- Center for Vectorborne Diseases and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California-Davis, CA 95616, USA.
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19
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Kent R, Juliusson L, Weissmann M, Evans S, Komar N. Seasonal blood-feeding behavior of Culex tarsalis (Diptera: Culicidae) in Weld County, Colorado, 2007. JOURNAL OF MEDICAL ENTOMOLOGY 2009; 46:380-90. [PMID: 19351092 DOI: 10.1603/033.046.0226] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Studies on Culex tarsalis Coquillett in Colorado have shown marked seasonal variation in the proportion of blood meals from birds and mammals. However, limitations in the specificity of antibodies used in the precipitin test and lack of vertebrate host availability data warrant revisiting Cx. tarsalis blood feeding behavior in the context of West Nile virus (WNV) transmission. We characterized the host preference of Cx. tarsalis during peak WNV transmission season in eastern Colorado and estimated the relative contribution of different avian species to WNV transmission. Cx. tarsalis preferred birds to mammals each month, although the proportion of blood meals from mammals increased in July and August. The distribution of blood meals differed significantly across months, in part because of changes in the proportion of blood meals from American robins, a preferred host. The estimated proportion of WNV-infectious vectors derived from American robins declined from 60 to 1% between June and August. The majority of avian blood meals came from doves, preferred hosts that contributed 25-40% of the WNV-infectious mosquitoes each month. Active WNV transmission was observed in association with a large house sparrow communal roost. These data show how seasonal patterns in Cx. tarsalis blood feeding behavior relate to WNV transmission in eastern Colorado, with the American robin contributing greatly to early-season virus transmission and a communal roost of sparrows serving as a focus for late-season amplification.
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Affiliation(s)
- Rebekah Kent
- Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases, Arbovirus Diseases Branch, 3150 Rampart Rd., Fort Collins, CO 80521, USA.
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20
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Savage HM, Aggarwal D, Apperson CS, Katholi CR, Gordon E, Hassan HK, Anderson M, Charnetzky D, McMillen L, Unnasch EA, Unnasch TR. Host choice and West Nile virus infection rates in blood-fed mosquitoes, including members of the Culex pipiens complex, from Memphis and Shelby County, Tennessee, 2002-2003. Vector Borne Zoonotic Dis 2008; 7:365-86. [PMID: 17767413 PMCID: PMC2580743 DOI: 10.1089/vbz.2006.0602] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The source of bloodmeals in 2,082 blood-fed mosquitoes collected from February 2002 through December 2003 in Memphis and surrounding areas of Shelby County, Tennessee were determined. Members of the genus Culex and Anopheles quadrimaculatus predominated in the collections. Members of the Cx. pipiens complex and Cx. restuans were found to feed predominately upon avian hosts, though mammalian hosts made up a substantial proportion of the bloodmeals in these species. No significant difference was seen in the host class of bloodmeals in mosquitoes identified as Cx. pipiens pipiens, Cx. p. quinquefasciatus, or hybrids between these two taxa. Anopheles quadrimaculatus and Cx. erraticus fed primarily upon mammalian hosts. Three avian species (the American Robin, the Common Grackle, and the Northern Cardinal) made up the majority of avian-derived bloodmeals, with the American Robin representing the most frequently fed upon avian host. An analysis of these host feeding data using a modification of a transmission model for Eastern Equine encephalitis virus suggested that the American Robin and Common Grackle represented the most important reservoir hosts for West Nile virus. A temporal analysis of the feeding patterns of the dominant Culex species did not support a shift in feeding behavior away from robins to mammals late in the summer. However, a significant degree of temporal variation was noted in the proportion of robin-derived bloodmeals when the data were analyzed by semi-monthly periods throughout the summers of 2002 and 2003. This pattern was consistent with the hypothesis that the mosquitoes were preferentially feeding upon nesting birds.
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Affiliation(s)
- Harry M Savage
- Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA.
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21
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Loss SR, Hamer GL, Goldberg TL, Ruiz MO, Kitron UD, Walker ED, Brawn JD. Nestling passerines are not important hosts for amplification of West Nile Virus in Chicago, Illinois. Vector Borne Zoonotic Dis 2008; 9:13-8. [PMID: 18759639 DOI: 10.1089/vbz.2008.0042] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nestling birds have been hypothesized to be important hosts for mosquito-borne arboviruses, but the role of nestlings for West Nile virus (WNV) amplification remains unclear. We sampled open-cup and cavity-nesting passerines in Chicago, Illinois, an area of intense WNV transmission, to determine infection rates in nestlings and mosquitoes, and to test whether mosquitoes are attracted to nesting birds. Analysis of Culex pipiens mosquito populations demonstrated WNV amplification to high mosquito infection rates during both years of the study near the locations where nestlings were sampled. Nevertheless, of 194 nestlings representing 12 species, only one 8-day-old house wren was positive for WNV RNA, and only one 10-day-old mourning dove was seropositive for antibodies to WNV, but at a low titer (1:20). The number of mosquitoes captured in nest box traps and control traps was not significantly different. These combined results suggest that nestling passerines play no evident role in WNV amplification and transmission in the Chicago area.
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Affiliation(s)
- Scott R Loss
- Department of Natural Resources and Environmental Sciences, Shelford Vivarium, Urbana, IL, USA.
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22
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Hamer GL, Walker ED, Brawn JD, Loss SR, Ruiz MO, Goldberg TL, Schotthoefer AM, Brown WM, Wheeler E, Kitron UD. Rapid amplification of West Nile virus: the role of hatch-year birds. Vector Borne Zoonotic Dis 2008; 8:57-67. [PMID: 18237262 DOI: 10.1089/vbz.2007.0123] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Epizootic transmission of West Nile virus (WNV) often intensifies rapidly leading to increasing risk of human infection, but the processes underlying amplification remain poorly understood. We quantified epizootic WNV transmission in communities of mosquitoes and birds in the Chicago, Illinois (USA) region during 2005 and 2006. Using quantitative polymerase chain reaction (PCR) methods, we detected WNV in 227 of 1195 mosquito pools (19%) in 2005 and 205 of 1685 (12%) in 2006; nearly all were Culex pipiens. In both years, mosquito infection rates increased rapidly in the second half of July to a peak of 59/1000 mosquitoes in 2005 and 33/1000 in 2006, and then declined slowly. Viral RNA was detected in 11 of 998 bird sera (1.1%) in 2005 and 3 of 1285 bird sera (<1%) in 2006; 11 of the 14 virus-positive birds were hatch-year birds. Of 540 hatch-year birds, 100 (18.5%) were seropositive in 2005, but only 2.8% (14/493) tested seropositive in 2006 for WNV antibodies using inhibition enzyme-linked immunosorbent assay (ELISA). We observed significant time series cross-correlations between mosquito infection rate and proportion of virus-positive birds, proportion of hatch-year birds captured in mist nets (significant in 2006 only), seroprevalence of hatch-year birds, and number of human cases in both seasons. These associations, coupled with the predominance of WNV infection and seropositivity in hatch-year birds, indicate a key role for hatch-year birds in the amplification of epizootic transmission of WNV, and in increasing human infection risk by facilitating local viral amplification.
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Affiliation(s)
- Gabriel L Hamer
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA.
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23
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Strong AC, Kondratieff BC, Doyle MS, Black WC. Resistance to permethrin in Culex tarsalis in northeastern Colorado. JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION 2008; 24:281-288. [PMID: 18666537 DOI: 10.2987/5593.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Resistance to permethrin and the activity of metabolic enzymes were monitored in field-collected Culex tarsalis from northeastern Colorado during 2005 and 2006 and compared with a lab strain from Bakersfield, CA. Collections were made from 13 different sites within and outside of the mosquito abatement area. Resistance levels by year and early vs. late season were examined and median lethal time values and 95% confidence intervals were compared with the lab strain. Mosquitoes collected in 2005 were more resistant to permethrin than either the lab strain or mosquitoes collected in 2006. Glutathione S-transferase levels recorded in 2005 were 9-12x higher than either the lab strain or 2006 mosquitoes; activity of mixed-function oxidases was also greater. Both mechanisms may play a role in permethrin resistance or reflect nontarget exposure to other pesticides in Cx. tarsalis in northeastern Colorado.
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Affiliation(s)
- Adam C Strong
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523, USA
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24
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Reisen WK, Lothrop HD, Wheeler SS, Kennsington M, Gutierrez A, Fang Y, Garcia S, Lothrop B. Persistent West Nile virus transmission and the apparent displacement St. Louis encephalitis virus in southeastern California, 2003-2006. JOURNAL OF MEDICAL ENTOMOLOGY 2008; 45:494-508. [PMID: 18533445 PMCID: PMC2435167 DOI: 10.1603/0022-2585(2008)45[494:pwnvta]2.0.co;2] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
West Nile virus (family Flaviviridae, genus Flavivirus, WNV) invaded the Colorado Desert biome of southern California during summer 2003 and seemed to displace previously endemic St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus, SLEV, an antigenically similar Flavivirus in the Japanese encephalitis virus serocomplex). Western equine encephalomyelitis virus (family Togaviridae, genus Alphavirus, WEEV), an antigenically distinct Alphavirus, was detected during 2005 and 2006, indicating that conditions were suitable for encephalitis virus introduction and detection. Cross-protective "avian herd immunity" due to WNV infection possibly may have prevented SLEV reintroduction and/or amplification to detectable levels. During 2003-2006, WNV was consistently active at wetlands and agricultural habitats surrounding the Salton Sea where Culex tarsalis Coquillett served as the primary enzootic maintenance and amplification vector. Based on published laboratory infection studies and the current seroprevalence estimates, house sparrows, house finches, and several Ardeidae may have been important avian amplifying hosts in this region. Transmission efficiency may have been dampened by high infection rates in incompetent avian hosts, including Gamble's quail, mourning doves, common ground doves, and domestic pigeons. Early season WNV amplification and dispersal from North Shore in the southeastern portion of the Coachella Valley resulted in sporadic WNV incursions into the urbanized Upper Valley near Palm Springs, where Culex pipiens quinquefasciatus Say was the primary enzootic and bridge vector. Although relatively few human cases were detected during the 2003-2006 period, all were concentrated in the Upper Valley and were associated with high human population density and WNV infection in peridomestic populations of Cx. p. quinquefasciatus. Intensive early mosquito control during 2006 seemed to interrupt and delay transmission, perhaps setting the stage for the future reintroduction of SLEV.
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Affiliation(s)
- William K Reisen
- Arbovirus Research Unit, Center for Vectorborne Diseases, School of Veterinary Medicine, University of California, Old Davis Rd., Davis, CA 95616, USA.
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25
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Diaz LA, Occelli M, Almeida FL, Almirón WR, Contigiani MS. Eared Dove (Zenaida Auriculata, Columbidae) as Host for St. Louis Encephalitis Virus (Flaviviridae, Flavivirus). Vector Borne Zoonotic Dis 2008; 8:277-82. [DOI: 10.1089/vbz.2007.0168] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Luis A. Diaz
- Laboratorio Arbovirus, Instituto de Virología “Dr. J. M. Vanella,” Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Maricel Occelli
- Laboratorio Arbovirus, Instituto de Virología “Dr. J. M. Vanella,” Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Francisco Ludueña Almeida
- Centro de Investigaciones Entomológicas de Córdoba, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Walter R. Almirón
- Centro de Investigaciones Entomológicas de Córdoba, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Marta S. Contigiani
- Laboratorio Arbovirus, Instituto de Virología “Dr. J. M. Vanella,” Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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26
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Savage HM, Anderson M, Gordon E, McMillen L, Colton L, Delorey M, Sutherland G, Aspen S, Charnetzky D, Burkhalter K, Godsey M. Host-seeking heights, host-seeking activity patterns, and West Nile virus infection rates for members of the Culex pipiens complex at different habitat types within the hybrid zone, Shelby County, TN, 2002 (Diptera: Culicidae). JOURNAL OF MEDICAL ENTOMOLOGY 2008; 45:276-288. [PMID: 18402144 DOI: 10.1603/0022-2585(2008)45[276:hhhapa]2.0.co;2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Host-seeking heights, host-seeking activity patterns, and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection rates were assessed for members of the Culex pipiens complex from July to December 2002, by using chicken-baited can traps (CT) at four ecologically different sites in Shelby County, TN. Host-seeking height was assessed by CT placed at elevations of 3.1, 4.6, and 7.6 m during one 24-h period per month. Host-seeking activity was assessed by paired CT placed at an elevation of 4.6 m. Can traps were sampled at one 10-h daytime interval and at seven 2-h intervals during the evening, night, and morning. Cx. pipiens complex mosquitoes accounted for 87.1% of collected mosquitoes. Culex (Melanoconion) erraticus (Dyar & Knab) accounted for 11.9% of specimens. The average number of Cx. pipiens complex mosquitoes collected per 24-h CT period from July to September was lowest at a rural middle income site (1.7), intermediate at an urban middle income site (11.3), and highest at an urban low income site (47.4). Can traps at the forested site failed to collect Cx. pipiens complex mosquitoes. From July to September at urban sites, Culex pipiens pipiens L. was the rarest of the three complex members accounting for 11.1-25.6% of specimens. At the rural site, Culex pipiens quinquefasciatus Say was the rarest member of the complex. Cx. p. pipiens was not collected after September. Mean abundance of Cx. pipiens complex mosquitoes was higher in traps at 7.6 m than in traps at 4.6 m. Abundances at 3.1 m were intermediate and not significantly different from abundances at the other heights. Initiation of host-seeking activity was associated with the end of civil twilight and activity occurred over an extended nighttime period lasting 8-10 h. All 11 WNV-positive mosquitoes were Cx. pipiens complex mosquitoes collected from urban sites in traps placed at elevations of 4.6 and 7.6 m. Infection rates were marginally nonsignificant by height. Infection rates, host-seeking heights, and activity patterns were not significantly different among members of the Cx. pipiens complex.
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Affiliation(s)
- Harry M Savage
- Centers for Disease Control and Prevention, P.O. Box 2087, Fort Collins, CO 80522, USA.
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27
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Kilpatrick AM, LaDeau SL, Marra PP. Ecology of West Nile Virus Transmission and its Impact on Birds in the Western Hemisphere. ACTA ACUST UNITED AC 2007. [DOI: 10.1093/auk/124.4.1121] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- A. Marm Kilpatrick
- Consortium for Conservation Medicine, 460 West 34th Street, 17th floor, New York, New York 10001, USA
| | - Shannon L. LaDeau
- Smithsonian Migratory Bird Center, National Zoological Park, P.O. Box 37012, MRC 5508, Washington, D.C. 20013, USA
| | - Peter P. Marra
- Smithsonian Migratory Bird Center, National Zoological Park, P.O. Box 37012, MRC 5508, Washington, D.C. 20013, USA
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28
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Reisen WK, Martinez VM, Fang Y, Garcia S, Ashtari S, Wheeler SS, Carroll BD. Role of California (Callipepla californica) and Gambel's (Callipepla gambelii) quail in the ecology of mosquito-borne encephalitis viruses in California, USA. Vector Borne Zoonotic Dis 2007; 6:248-60. [PMID: 16989564 DOI: 10.1089/vbz.2006.6.248] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Gambel's and California quail were infected repeatedly whenever western equine encephalomyelitis virus (WEEV), St. Louis encephalitis virus (SLEV), and (WNV) West Nile virus were active during summer in California. The timing of virus appearance and quail infection coincided well with the appearance of chicks in nature, leading us to hypothesize that large coveys containing these non-immune birds could be important in focal virus amplification in rural settings. However, experimental infection studies with chicks, juveniles, and adults of both quail species using sympatric strains of WEEV, SLEV, and WNV indicated that only immature birds were competent hosts for WEEV, producing viremias sufficiently elevated to efficiently infect Culex tarsalis mosquitoes. Quail were less competent hosts for WNV and were incompetent for SLEV. Large populations of quail that frequently are infected with SLEV or WNV, but produce low to moderate viremias, may serve as dead end hosts for these viruses. Due to their abundance and repeated infection, these birds may attenuate virus amplification in rural areas of California and possibly could be one reason why WNV epidemics seem to occur more frequently in urban and periurban than in rural landscapes.
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Affiliation(s)
- William K Reisen
- Center for Vectorborne Diseases, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
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