| Epidemiology of West Nile Virus in Connecticut: A Five-Year Analysis of Mosquito Data 1999–2003 | Andreadis, Theodore G. | 2004 |
KeywordsWNV AbstractTwo hundred and ten isolations of West Nile virus (WNV) were obtained from 17 mosquito species in six genera in statewide surveillance conducted in Connecticut from June through October, 1999–2003. Culex pipiens (86), Culex salinarius (32), Culex restuans (26), Culiseta melanura (32), and Aedes vexans (12) were implicated as the most likely vectors of WNV in the region based on virus isolation data. Culex pipiens was abundant from July through September and is likely involved in early season enzootic transmission and late season epizootic amplification of the virus in wild bird populations. Epidemic transmission of WNV to humans in urban locales is probable. The abundance of Cx. restuans in June and July and isolations of WNV in early July suggest that this species may play an important role as an enzootic vector involved in early amplification of WNV virus among wild birds. Its involvement as a bridge vector to humans is unlikely. Culex salinarius was the most frequently captured Culex species and was abundant in August and September when virus activity was at its height. Frequent isolations of WNV from this species in September when the majority of human cases were reported in union with its abundance at this time of the year, demonstrated vector competence, and broad feeding habits, make Cx. salinarius a likely bridge vector to humans, horses and other mammals. Multiple isolations WNV from Cs. melanura collected in more rural locales in late August and September, provide supportive evidence to suggest that this predominant avian feeder may play a significant role in epizootic amplification of the virus among wild bird populations in these environs. Aedes vexans was the only species of Aedes or Ochlerotatus from which multiple isolations of WNV were made in more than one year and was among the most frequently trapped and abundant species throughout the season. Since Ae. vexans predominately feeds on mammals it is unlikely to play a significant role in epizootic amplification of WNV, however, because of its abundance and aggressive mammalian and human biting behavior it must receive strong consideration as a bridge vector to humans and horses. The occasional virus isolations obtained from Aedes cinereus (4), Uranotaenia sapphirina (3), Ochlerotatus canadensis (2), Ochlerotatus trivittatus (2), Ochlerotatus sollicitans (2), Ochlerotatus sticticus (2), Psorophora ferox (2), Anopheles punctipennis, Anopheles walkeri, Ochlerotatus cantator, Ochlerotatus taeniorhynchus, and Ochlerotatus triseriatus in conjunction with their inefficient vector competency and host feeding preferences indicate that these species likely play a very minor role in either the enzootic maintenance or epizootic transmission of WNV in this region. The principal foci of WNV activity in Connecticut were identified as densely populated (>3,000 people/mi2) residential communities in coastal Fairfield and New Haven Counties, and in the case of 2002, similar locales in proximity of the city of Hartford in central Hartford County. In almost all instances we observed a correlation both temporally and spatially between the isolation of WNV from field-collected mosquitoes and subsequent human cases in these locales. In most years the incidence of human cases closely paralleled the number of virus isolations made from mosquitoes with both peaks falling in early September. We conclude that the isolation of WNV from fieldcollected mosquitoes is a sensitive indicator of virus activity that is associated with the risk of human infection that habitually extends from early August through the end of October in Connecticut.Vector-Borne Zoonotic Dis. 4, 360–378. AuthorsAndreadis, Theodore G., Anderson, John F., Vossbrinck, Charles R. and Main, Andrew J. Year Published2004 PublicationVector-Borne and Zoonotic Diseases LocationsDOI10.1089/vbz.2004.4.360 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15682518 |
| Year-round West Nile Virus Activity, Gulf Coast Region, Texas and Louisiana | Tesh, Robert B. | 2004 |
KeywordsWNV AbstractWest Nile virus (WNV) was detected in 11 dead birds and two mosquito pools collected in east Texas and southern Louisiana during surveillance studies in the winter of 2003 to 2004. These findings suggest that WNV is active throughout the year in this region of the United States. AuthorsTesh, Robert B., Parsons, Ray, Siirin, Marina, Randle, Yvonne, Sargent, Chris, Guzman, Hilda, Wuithiranyagool, Taweesak, Higgs, Stephen, Vanlandingham, Dana L., Bala, Adil A., Haas, Keith and Zerinque, Brian Year Published2004 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1009.040203 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15498169 |
| Antibody Prevalence of West Nile Virus in Birds, Illinois, 2002 | Ringia, Adam M. | 2004 |
KeywordsWNV AbstractAntibodies to West Nile virus were detected in 94 of 1,784 Illinois birds during 2002. Captive and urban birds had higher seropositivity than did birds from natural areas, and northern and central Illinois birds’ seropositivity was greater than that from birds from the southern sites. Adult and hatch-year exposure rates did not differ significantly. AuthorsRingia, Adam M., Blitvich, Bradley J., Koo, Hyun-Young, Van de Wyngaerde, Marshall, Brawn, Jeff D. and Novak, Robert J. Year Published2004 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1006.030644 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15207067 |
| Investigation of an outbreak of encephalomyelitis caused by West Nile virus in 136 horses | Ward, Michael P. | 2004 |
KeywordsWNV AbstractNo abstract available AuthorsWard, Michael P., Levy, Michel, Thacker, H. Leon, Ash, Marianne, Norman, Sandra K. L., Moore, George E. and Webb, Paul W. Year Published2004 PublicationJournal of the American Veterinary Medical Association LocationsDOI10.2460/javma.2004.225.84 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15239478 |
| Mosquito and Arbovirus Activity During 1997–2002 in a Wetland in Northeastern Mississippi | Cupp, E. W. | 2004 |
KeywordsSaint Louis encephalitis, eastern equine encephalomyelitis virus, Culex erraticus, Culiseta melanura, blood meal identification, WNV AbstractThe species composition and population dynamics of adult mosquitoes in a wetland near Iuka, MS, were analyzed over a 6-yr period (1997–2002) and reverse transcription-polymerase chain reaction (PCR) detection rates of arboviruses determined during five of those years. Blood meals of three likely vector species were identified using a PCR-based method that allows identification of the host to species. Culex erraticus (Dyar & Knab) composed 51.9% of the population during the 6-yr period with 295 females collected per trap night. Eastern equine encephalomyelitis (EEE) virus was detected in six genera of mosquitoes [Coquillettidia perturbans (Walker), Culex restuans Theobald, Culex salinarius Coquillett, Culex erraticus (Dyar & Knab), Anopheles crucians Wiedemann, Anopheles quadrimaculatus Say, Aedes vexans (Meigen), Ochlerotatus triseriatus Say, and Psorophora ferox Humboldt) with positive pools occurring in 1998, 1999, and 2002. Culiseta melanura Coquillett occurred at a low level (<1%) and was not infected. Saint Louis encephalitis virus was detected once in a single pool of Cx. erraticus in 1998. Neither West Nile virus nor LaCrosse virus was found. Minimum infection rates per 1000 females tested of competent vectors of EEE virus were variable and ranged from 0.14 for Cx. erraticus to 40.0 for Oc. triseriatus. Thirty-nine species of birds were identified in the focus with blood-engorged mosquitoes found to contain meals (n = 29) from eight avian species. The majority of meals was from the great blue heron, Ardea herodias L. (n = 55%), but when bird abundance data were adjusted for avian mass, the brown-headed cowbird, Molothrus ater (Boddaert); blue jay, Cyanocitta cristata (L.); and northern mockingbird, Mimus polyglottos (L.), were overrepresented as hosts. AuthorsCupp, E. W., Tennessen, K. J., Oldland, W. K., Hassan, H. K., Hill, G. E., Katholi, C. R. and Unnasch, T. R. Year Published2004 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-41.3.495 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15185956 |
| Pesticide Spraying for West Nile Virus Control and Emergency Department Asthma Visits in New York City, 2000 | Karpati, Adam M. | 2004 |
KeywordsWNV AbstractNo abstract available AuthorsKarpati, Adam M., Perrin, Mary C., Matte, Tom, Leighton, Jessica, Schwartz, Joel and Barr, R. Graham Year Published2004 PublicationEnvironmental Health Perspectives LocationsDOI10.1289/ehp.6946 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15289164 |
| West Nile Virus Surveillance: A Simple Method for Verifying the Integrity of RNA in Mosquito (Diptera: Culicidae) Pools | Hoffmann, Peter R. | 2004 |
KeywordsWest Nile virus, reverse transcriptase-polymerase chain reaction, mosquito, arbovirus, 18S rRNA, WNV AbstractIn a West Nile virus (WNV)-free ecosystem, it is essential to verify the integrity of RNA before concluding that RNA extracted from mosquito specimens is negative for WNV gene sequences. The primary objective of our study was to develop a rapid molecular assay to rapidly screen mosquitoes for the presence of 18S RNA and WNV gene sequences. Mosquitoes, collected from multiple sites on the island of O‘ahu, were pooled into groups of 1–50 mosquitoes according to capture site, date, and species. Using primer design software and the GenBank database, generic oligonucleotide primer pairs were designed to amplify mosquito18S rRNA gene sequences from different species. RNA was extracted from mosquito pools, and reverse transcriptase-polymerase chain reaction (RT-PCR) was performed for the presence of mosquito18S rRNA and WNV gene sequences. Three of the seven primer pairs successfully detected 18S rRNA sequences for both Aedes and Culex by RT-PCR, and one primer pair successfully amplified 18S rRNA sequences for 15 different mosquito species. All 64 mosquito pools from 10 different sites on the island of Oahu, Hawaii, were negative for WNV nonstructural protein-5 gene sequences. This simple, one-step RT-PCR method for screening mosquito pools for arboviruses will become an increasingly valuable tool as WNV becomes endemic throughout the Americas. AuthorsHoffmann, Peter R., Woodrow, Robert J., Calimlim, Precilia S., Sciulli, Rebecca, Effler, Paul V., Miyamoto, Vernon, Imrie, Allison, Yanagihara, Richard and Nerurkar, Vivek R. Year Published2004 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-41.4.731 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15311468 |
| SYNERGISTIC IMPACTS OF MALATHION AND PREDATORY STRESS ON SIX SPECIES OF NORTH AMERICAN TADPOLES | Relyea, Rick A. | 2004 |
KeywordsPredation;Stress;Synergy;Frog;Toad, WNV AbstractThe decline of many amphibian populations is associated with pesticides, but for most pesticides we know little about their toxicity to amphibians. Malathion is a classic example; it is sprayed over aquatic habitats to control mosquitoes that carry malaria and the West Nile virus, yet we know little about its effect on amphibians. I examined the survival of six species of tadpoles (wood frogs, Rana sylvatica; leopard frogs, R. pipiens; green frogs, R. clamitans; bullfrogs, R. catesbeiana; American toads, Bufo americanus; and gray tree frogs, Hyla versicolor) for 16 d in the presence or absence of predatory stress and six concentrations of malathion. Malathion was moderately toxic to all species of tadpoles (median lethal concentration [LC50] values, the concentration estimated to kill 50% of a test population, ranged from 1.25–5.9 mg/L). These values are within the range of values reported for the few amphibians that have been tested (0.2–42 mg/L). In one of the six species, malathion became twice as lethal when combined with predatory stress. Similar synergistic interactions have been found with the insecticide carbaryl, suggesting that the synergy may occur in many carbamate and organophosphate insecticides. While malathion has the potential to kill amphibians and its presence is correlated with habitats containing declining populations, its actual role in amphibian declines is uncertain given the relatively low concentration in aquatic habitats. AuthorsRelyea, Rick A. Year Published2004 PublicationEnvironmental Toxicology and Chemistry LocationsDOI10.1897/03-259 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15095908 |
| Alligators as West Nile Virus Amplifiers | Klenk, Kaci | 2004 |
KeywordsWNV AbstractRecent evidence suggests that American alligators (Alligator mississippiensis) may be capable of transmitting West Nile virus (WNV) to other alligators. We experimentally exposed 24 juvenile alligators to WNV parenterally or orally. All became infected, and all but three sustained viremia titers >5.0 log10 PFU/mL (a threshold considered infectious for Culex quinquefasciatus mosquitoes) for 1 to 8 days. Noninoculated tankmates also became infected. The viremia profiles and multiple routes of infection suggest alligators may play an important role in WNV transmission in areas with high population densities of juvenile alligators. AuthorsKlenk, Kaci, Snow, Jamie, Morgan, Katrina, Bowen, Richard, Stephens, Michael, Foster, Falicia, Gordy, Paul, Beckett, Susan, Komar, Nicholas, Gubler, Duane and Bunning, Michel Year Published2004 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1012.040264 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15663852 |
| Drought-Induced Amplification and Epidemic Transmission of West Nile Virus in Southern Florida | Shaman, Jeffrey | 2005 |
KeywordsWest Nile virus, amplification, transmission, Culex nigripalpus, drought, WNV AbstractWe show that the spatial-temporal variability of human West Nile (WN) cases and the transmission of West Nile virus (WNV) to sentinel chickens are associated with the spatial-temporal variability of drought and wetting in southern Florida. Land surface wetness conditions at 52 sites in 31 counties in southern Florida for 2001–2003 were simulated and compared with the occurrence of human WN cases and the transmission of WNV to sentinel chickens within these counties. Both WNV transmission to sentinel chickens and the occurrence of human WN cases were associated with drought 2–6 mo prior and land surface wetting 0.5–1.5 mo prior. These dynamics are similar to the amplification and transmission patterns found in southern Florida for the closely related St. Louis encephalitis virus. Drought brings avian hosts and vector mosquitoes into close contact and facilitates the epizootic cycling and amplification of the arboviruses within these populations. Southern Florida has not recorded a severe, widespread drought since the introduction of WNV into the state in 2001. Our results indicate that widespread drought in the spring followed by wetting during summer greatly increase the probability of a WNV epidemic in southern Florida. AuthorsDay, Jonathan F., Shaman, Jeffrey and Stieglitz, Marc Year Published2005 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585(2005)042[0134:DAAETO]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15799522 |
