| Ecological correlates of risk and incidence of West Nile virus in the United States | Allan, Brian F. | 2009 |
KeywordsWNV AbstractWest Nile virus, which was recently introduced to North America, is a mosquito-borne pathogen that infects a wide range of vertebrate hosts, including humans. Several species of birds appear to be the primary reservoir hosts, whereas other bird species, as well as other vertebrate species, can be infected but are less competent reservoirs. One hypothesis regarding the transmission dynamics of West Nile virus suggests that high bird diversity reduces West Nile virus transmission because mosquito blood-meals are distributed across a wide range of bird species, many of which have low reservoir competence. One mechanism by which this hypothesis can operate is that high-diversity bird communities might have lower community-competence, defined as the sum of the product of each species' abundance and its reservoir competence index value. Additional hypotheses posit that West Nile virus transmission will be reduced when either: (1) abundance of mosquito vectors is low; or (2) human population density is low. We assessed these hypotheses at two spatial scales: a regional scale near Saint Louis, MO, and a national scale (continental USA). We found that prevalence of West Nile virus infection in mosquito vectors and in humans increased with decreasing bird diversity and with increasing reservoir competence of the bird community. Our results suggest that conservation of avian diversity might help ameliorate the current West Nile virus epidemic in the USA. AuthorsAllan, Brian F., Langerhans, R. Brian, Ryberg, Wade A., Landesman, William J., Griffin, Nicholas W., Katz, Rachael S., Oberle, Brad J., Schutzenhofer, Michele R., Smyth, Kristina N., St. Maurice, Annabelle, Clark, Larry, Crooks, Kevin R., Hernandez, Daniel E., McLean, Robert G., Ostfeld, Richard S. and Chase, Jonathan M. Year Published2009 PublicationOecologia LocationsDOI10.1007/s00442-008-1169-9 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/18941794 |
| HEMATOLOGY, PLASMA BIOCHEMISTRY, AND ANTIBODIES TO SELECT VIRUSES IN WILD-CAUGHT EASTERN MASSASAUGA RATTLESNAKES (SISTRURUS CATENATUS CATENATUS) FROM ILLINOIS | Allender, Matthew C. | 2006 |
KeywordsBiochemistry, hematology, massasauga, ophidian paramyxovirus, rattlesnake, serology, Sistrurus catenatus catenatus, West Nile virus, WNV AbstractDuring the 2004 field season, blood was collected from Eastern massasauga rattlesnakes (Sistrurus catenatus catenatus) in the Carlyle Lake (Carlyle, Illinois, USA) and Allerton Park (Monticello, Illinois, USA) populations to derive baseline complete blood count and plasma biochemistry data and to assess the prevalence of antibodies to West Nile virus (WNV) and ophidian paramyxovirus (OPMV). Massasaugas were located for sampling through visual encounter surveys. Body weight, snout–vent length, total protein, globulins, sodium, and potassium were normally distributed among the survey population. Aspartate aminotransferase, creatine kinase, albumin, calcium, uric acid, white blood cell count, heterophils, lymphocytes, monocytes, eosinophils, and basophils were non-normally distributed within these animals. Female snakes had significantly shorter tail lengths; lower blood glucose, packed cell volumes, and absolute azurophil counts; and higher plasma calcium and phosphorus concentrations than did males. None of the snakes tested (n=21) were seropositive for WNV, whereas all (n=20) were seropositive for OPMV. AuthorsAllender, Matthew C., Mitchell, Mark A., Phillips, Christopher A., Gruszynski, Karen and Beasley, Val R. Year Published2006 PublicationJournal of Wildlife Diseases LocationsDOI10.7589/0090-3558-42.1.107 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16699153 |
| Wintering of Neurotropic Velogenic Newcastle Disease Virus and West Nile Virus in Double-Crested Cormorants (Phalacrocorax auritus) from the Florida Keys | Allison, A. B. | 2005 |
KeywordsNewcastle disease virus, double-crested cormorant, fusion protein, West Nile virus, Florida, wintering grounds, reservoir, WNV AbstractDuring November 2002, six double-crested cormorants (DCCs; Phalacrocorax auritus) were found moribund in Big Pine Key, FL, exhibiting clinical signs indicative of neurologic disease. Postmortem diagnostic evaluations were performed on two adult birds. Virulent Newcastle disease virus (NDV) was isolated from a cloacal swab from cormorant 1. West Nile virus (WNV) was isolated from the brain and lung of cormorant 2. Nucleotide sequence analysis of a portion of the fusion (F) protein gene of the NDV cormorant isolate revealed it shared a 100% deduced amino acid identity with only two viruses: the 1992 epizootic cormorant isolate from Minnesota and the 1992 turkey isolate from North Dakota. The epidemiologic significance of the recognition of virulent NDV on cormorant wintering grounds during a nonepizootic period, in addition to the potential implications of the concurrent isolation of NDV and WNV from cormorants, is discussed. AuthorsAllison, A. B., Gottdenker, N. L. and Stallknecht, D. E. Year Published2005 PublicationAvian Diseases LocationsDOI10.1637/7278-091304R Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16094838 |
| West Nile Virus from Female and Male Mosquitoes (Diptera: Culicidae) in Subterranean, Ground, and Canopy Habitats in Connecticut | Anderson, John F. | 2006 |
KeywordsWest Nile virus, Culex restuans, Culex salinarius, Aedes vexans, Culex pipiens, WNV AbstractIn total, 93,532 female mosquitoes (Diptera: Culicidae) were captured in traps placed in subterranean (catch basin), ground (≈ 1.5 m above ground), and canopy (≈7.0 m above ground) habitats in Stamford and Stratford, CT, during 2003–2005. Culex pipiens L. was the most abundant (64.8%) of the 31 species identified. Significantly greater numbers of Cx. pipiens were captured in canopy-placed mosquito magnet experimental traps, and significantly greater numbers were collected in catch basin-placed (Centers for Disease Control) CDC traps than in CDC traps placed elsewhere. Culex restuans Theobald was captured in significantly greater numbers in traps placed in catch basins. Aedes vexans (Meigen), Aedes cinereus Meigen, and Aedes cantator (Coquillett) were significantly more abundant in ground traps. In total, 429 isolations of West Nile virus (WNV) were made from seven species of mosquitoes from late June through the end of October during 2003 through 2005. Three hundred ninety-eight (92.8%) isolates were from Cx. pipiens. Others were from Cx. restuans (n = 16), Culex salinarius Coquillett (n = 5), Ae. vexans (n = 4), Ae. cantator (n = 3), Aedes triseriatus (Say) (n = 2), and Ae. cinereus (n = 1). Multiple isolates from Cx. pipiens were made each week, primarily during the later part of July through the end of September. Weekly minimum infection rates (MIRs) were lower in 2004 (highest weekly MIR = 7.1) when no human cases were reported in Connecticut in comparison with 2003 and 2005 (highest weekly MIR = 83.9) when human cases were documented. Frequencies of infected pools were significantly higher in Cx. pipiens captured in traps in the canopy and significantly higher in catch basin placed traps than in traps at ground level. The physiological age structure of Cx. pipiens captured in the canopy was significantly different from that of Cx. pipiens collected in catch basins. Invariably, Cx. pipiens captured in the canopy were nulliparous or parous with ovaries in Christophers’ stage 2, whereas 58.7% of the females captured in catch basins possessed ovaries filled with mature oocytes in Christophers’ stage 5. Our results suggest that females in the canopy are seeking hosts, and after digestion of the bloodmeal and development of mature oocytes, they descend to catch basins for shelter and deposition of eggs. WNV was isolated from three, one, and two pools of male Cx. pipiens captured in catch basin-, ground-, and canopy-placed traps, respectively, and from six nulliparous Cx. pipiens females collected in the canopy. Weekly MIR ranged from 1.2 to 31.1 per 1,000 male specimens. These data show that mosquitoes become infected by means other than by blood feeding, possibly by transovarial transmission. The placement of traps in tree canopies and in catch basins can be used to augment current practices of placement of traps near the ground for surveillance of mosquitoes infected with WNV and for studies of the ecology of WNV. AuthorsAndreadis, Theodore G., Anderson, John F., Vossbrinck, Charles R., Main, Andy J. and Ferrandino, Francis J. Year Published2006 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585(2006)43[1010:WNVFFA]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17017241 |
|
Importance of Vertical and Horizontal Transmission of West Nile Virus by
Culex pipiens
in the Northeastern United States
| Anderson, John F. | 2006 |
KeywordsWNV AbstractWest Nile virus (WNV) has become established in the northeastern United States, where mosquitoes are inactive during winter. There have been no documented studies to explain how this virus survives winter and reinitiates infection in spring. We report that WNV was vertically transmitted to 2 F1 female Culex pipiens from a naturally infected female collected in Stratford, Connecticut. One vertically infected F1 female, which was 168 days old, fed on a hamster that died 8 days later of West Nile disease. This suggests that WNV survives winter in unfed, vertically infected C. pipiens with amplification initiated in spring by horizontal transmission AuthorsAnderson, John F. and Main, Andy J. Year Published2006 PublicationThe Journal of Infectious Diseases LocationsDOI10.1086/508754 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17083043 |
| North American West Nile virus genotype isolates demonstrate differential replicative capacities in response to temperature | Andrade, C. C. | 2011 |
KeywordsWNV AbstractThe presence of West Nile virus (WNV) was first documented in California, USA, during the summer of 2003, and subsequently the virus has become endemic throughout the state. Sequence analysis has demonstrated that the circulating strains are representative of the North American (WN02) genotype that has displaced the East Coast genotype (NY99). A recent study has indicated that enhanced vector competence at elevated temperatures may have played a role in the displacement of the East Coast genotype by WN02. In the current study, four WN02 strains from California, including an initial 2003 isolate (COAV997), were compared to strain NY99 in growth curve assays in mosquito and duck embryonic fibroblast (DEF) cell lines at differing, biologically relevant temperatures to assess the relative temperature sensitivities of these natural isolates. COAV997 was significantly debilitated in viral replication in DEF cells at 44 °C. Full-length sequence comparison of COAV997 against the NY99 reference strain revealed non-synonymous mutations in the envelope glycoprotein (V159A), non-structural protein 1 (NS1) (K110N) and non-structural protein 4A (NS4A) (F92L), as well as two mutations in the 3' UTR: C→T at nt 10 772 and A→G at nt 10 851. These non-synonymous mutations were introduced into the NY99 viral backbone by site-directed mutagenesis. A mutant containing the NS1-K110N and NS4A-F92L mutations exhibited a debilitated growth phenotype in DEF cells at 44 °C, similar to that of COAV997. One explanation for the subsistence of this genotype is that COAV997 was obtained from an area of California where avian host species might not present elevated temperatures. These data indicate that the NS1 and NS4A mutations identified in some WN02 isolates could reduce thermal stability and impede replication of virus at temperatures observed in febrile avian hosts. AuthorsAndrade, C. C., Maharaj, P. D., Reisen, W. K. and Brault, A. C. Year Published2011 PublicationJournal of General Virology LocationsDOI10.1099/vir.0.032318-0 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21775581 |
|
Mosquito Surveillance for West Nile Virus in Connecticut, 2000: Isolation from
Culex pipiens
,
Cx. restuans
,
Cx. salinarius
, and
Cul | Andreadis, Theodore G. | 2001 |
KeywordsWNV AbstractFourteen isolations of West Nile (WN) virus were obtained from four mosquito species (Culex pipiens [5], Cx. restuans [4], Cx. salinarius [2], and Culiseta melanura [3]) in statewide surveillance conducted from June through October 2000. Most isolates were obtained from mosquitoes collected in densely populated residential locales in Fairfield and New Haven counties, where the highest rates of dead crow sightings were reported and where WN virus was detected in 1999. Minimum field infection rates per 1,000 mosquitoes ranged from 0.5 to 1.8 (county based) and from 1.3 to 76.9 (site specific). Cx. restuans appears to be important in initiating WN virus transmission among birds in early summer; Cx. pipiens appears to play a greater role in amplifying virus later in the season. Cs. melanura could be important in the circulation of WN virus among birds in sylvan environments; Cx. salinarius is a suspected vector of WN virus to humans and horses. AuthorsAndreadis, Theodore G., Anderson, John F. and Vossbrinck, Charles R. Year Published2001 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid0704.010413 |
| Discovery, Distribution, and Abundance of the Newly Introduced Mosquito Ochlerotatus japonicus (Diptera: Culicidae) in Connecticut, USA | Andreadis, Theodore G. | 2001 |
KeywordsWNV AbstractThe earliest documented specimen of an exotic east Asian mosquito Ochlerotatus (Finlaya) japonicis japonicus (Theobald) in the Western Hemisphere is reported along with the results of a state wide survey to determine the distribution and abundance of this mosquito in Connecticut. Ochlerotatus japonicus was collected from 87 locations in eight counties. It is established throughout the state and occurs in a variety of natural and artificial container habitats including discarded tire casings, bird baths, wooden barrels, porcelain bath tubs (used for watering animals), plastic milk cartons, toys, vinyl tarpaulins (covering wood piles and swimming pools), exposed rock holes in stream beds, tree holes, subterranean catch basins, surface water rain pools, and spring-fed depressions. Larvae were particularly common in containers with water, decaying leaves, and algae, in shaded and sunlit areas and, in rock-pool habitats along streambeds, in association with Ochlerotatus atropalpus (Coquillett). Adult females were collected in sod grass-infused gravid and CO2- baited light traps, from early June through October, with peak collections in September. Biting females were collected by human bait method augmented with CO2, verifying its capacity to feed on humans. The ovitraps used in this study were not effective for recovering this species. Our results suggest that Oc. japonicus was introduced into Connecticut between 1992 and 1998. Because of the ability of Oc. japonicus to transmit West Nile virus, and because of the recent detection of this virus in field-collected specimens, the introduction of Oc. japonicus is considered a significant public health development. AuthorsAndreadis, Theodore G., Anderson, John F., Munstermann, Leonard E., Wolfe, Roger J. and Florin, David A. Year Published2001 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-38.6.774 |
| 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 |
| A TWO-YEAR EVALUATION OF ELEVATED CANOPY TRAPPING FOR CULEX MOSQUITOES AND WEST NILE VIRUS IN AN OPERATIONAL SURVEILLANCE PROGRAM IN THE NORTHEASTERN UNITED STATES | Andreadis, Theodore G. | 2007 |
KeywordsWest Nile virus, Culex pipiens, Culex restuans, Culex salinarius, surveillance, light trap, gravid trap, elevation, WNV AbstractThe effectiveness of CO2-baited Centers for Disease Control and Prevention miniature light traps elevated in the tree canopy (7.6 m) was compared with light traps placed at ground level (1.5 m) and grass-sod infused gravid traps for collecting Culex pipiens, Culex restuans, and Culex salinarius and detecting West Nile virus (WNV) activity in an operational surveillance program that encompassed 12 ecologically diverse sites in Connecticut in 2004 and 2005. More than twice as many Cx. pipiens were collected on average in light traps suspended in the tree canopy than in either light or gravid traps placed at ground level. This difference was generally restricted to those collection sites where markedly greater numbers of Cx. pipiens were collected with all trapping methods but was not associated with site-specific urbanization indices. Culex restuans was not preferentially attracted to light traps suspended in the tree canopy. No differences in the overall abundance of this species were recorded with either of the 2 trapping procedures, but both light traps were more effective than the gravid traps. Culex salinarius was significantly more attracted to ground-based light traps than traps suspended in the tree canopy, while gravid traps were ineffective at all sites regardless of the level of urbanization or any other specific land-use characteristic. CO2-baited light traps placed in the tree canopy were generally superior to ground-based light traps for detecting WNV in Cx. pipiens. West Nile virus–infected females were collected more regularly, and the frequency of infected pools was significantly greater. Twofold higher minimum field infection rates (maximum likelihood estimation [MLE] = 6.7 vs. 3.0 per 1,000 mosquitoes) were also recorded from canopy collections of this species, and virus was detected in canopy-collected females several weeks before it was detected in collections from light traps at ground level. We conclude that the use of CO2-baited light traps placed in the tree canopy for targeted trapping of Cx. pipiens and subsequent detection of WNV are likely to yield better overall results than light traps placed at ground level in this region of the northeastern United States. The virus isolation data obtained from Cx. pipiens collected in gravid traps compared favorably both temporally and spatially with results from canopy trap collections. There were no significant differences in the overall frequency of WNV-infected pools or MLEs for Cx. pipiens, but fewer total WNV isolations were made from Cx. pipiens collected in the gravid traps and virus was detected more infrequently. Results reaffirmed the utility of gravid traps as effective surveillance tools for detection of WNV in Cx. pipiens in the northeastern United States. However, findings also demonstrated that CO2-baited light traps placed in the tree canopy provided more consistent results where weekly detection of virus amplification is a critical objective. The comparative effectiveness of ground- and canopy-based light traps for detection of WNV-infected Cx. restuans and Cx. salinarius was inconclusive owing to the limited number of virus isolations that were made from these species during the 2 years of study. However, WNV virus isolations were made several weeks earlier and more frequently from Cx. restuans collected in traps placed in the canopy rather than at ground level in 2004. Results support the view that ground-based light traps are more effective for detection of WNV in Cx. salinarius. AuthorsAndreadis, Theodore G. and ARMSTRONG, PHILIP M. Year Published2007 PublicationJournal of the American Mosquito Control Association LocationsDOI10.2987/8756-971X(2007)23[137:ATEOEC]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17847845 |
