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Healy J.M.,University of California at Davis | Reisen W.K.,University of California at Davis | Kramer V.L.,Vector Borne Disease Section | Fischer M.,Centers for Disease Control and Prevention | And 8 more authors.
Vector-Borne and Zoonotic Diseases | Year: 2015

Surveillance systems for West Nile virus (WNV) combine several methods to determine the location and timing of viral amplification. The value of each surveillance method must be measured against its efficiency and costs to optimize integrated vector management and suppress WNV transmission to the human population. Here we extend previous comparisons of WNV surveillance methods by equitably comparing the most common methods after standardization on the basis of spatial sampling density and costs, and by estimating optimal levels of sampling effort for mosquito traps and sentinel chicken flocks. In general, testing for evidence of viral RNA in mosquitoes and public-reported dead birds resulted in detection of WNV approximately 2-5 weeks earlier than serological monitoring of sentinel chickens at equal spatial sampling density. For a fixed cost, testing of dead birds reported by the public was found to be the most cost effective of the methods, yielding the highest number of positive results per 1000. Increased spatial density of mosquito trapping was associated with more precise estimates of WNV infection prevalence in mosquitoes. Our findings also suggested that the most common chicken flock size of 10 birds could be reduced to six to seven without substantial reductions in timeliness or sensitivity. We conclude that a surveillance system that uses the testing of dead birds reported by the public complemented by strategically timed mosquito and chicken sampling as agency resources allow would detect viral activity efficiently in terms of effort and costs, so long as susceptible bird species that experience a high mortality rate from infection with WNV, such as corvids, are present in the area. © 2015 Mary Ann Liebert, Inc. Source

Bingham A.M.,University of South Florida | Graham S.P.,Pennsylvania State University | Burkett-Cadena N.D.,University of South Florida | White G.S.,Coachella Valley Mosquito and Vector Control District | And 2 more authors.
American Journal of Tropical Medicine and Hygiene | Year: 2012

The role of non-avian vertebrates in the ecology of eastern equine encephalomyelitis virus (EEEV) is unresolved, but mounting evidence supports a potential role for snakes in the EEEV transmission cycle, especially as overwintering hosts. To determine rates of exposure and infection, we examined serum samples from wild snakes at a focus of EEEV in Alabama for viral RNA using quantitative reverse transcription polymerase chain reaction. Two species of vipers, the copperhead (Agkistrodon contortrix) and the cottonmouth (Agkistrodon piscivorus), were found to be positive for EEEV RNA using this assay. Prevalence of EEEV RNA was more frequent in seropositive snakes than seronegative snakes. Positivity for the quantitative reverse transcription polymerase chain reaction in cottonmouths peaked in April and September. Body size and sex ratios were not significantly different between infected and uninfected snakes. These results support the hypothesis that snakes are involved in the ecology of EEEV in North America, possibly as over-wintering hosts for the virus. Copyright © 2012 by The American Society of Tropical Medicine and Hygiene. Source

Dieckmann R.,Coachella Valley Mosquito and Vector Control District | Drees B.M.,Texas AgriLife Research Center
Southwestern Entomologist | Year: 2013

The effect of surface soil temperature on attraction of foraging red imported fire ants, Solenopsis invicta Buren, to a food lure in centrifuge vials with access 2.54, 5.08, and 7.62 cm below the surface compared with vials horizontally at the soil surface or in the soil with the opening at the soil surface was monitored in the Coachella Valley of California. Analysis of variance showed no significant differences in the mean numbers of ants collected in the three strata, indicating a 2.54-cm opening as preferable, or when compared with vials horizontally placed at the soil surface or with the opening at the soil surface. However, during summer days, vials baited with subsurface food lure attracted 10-30 more foraging worker ants compared with vials horizontally placed at the soil surface or with the opening at the soil surface. Use of this method could provide more consistent data on monitoring ant foraging and result in fewer false negatives. Source

White G.,Coachella Valley Mosquito and Vector Control District | Ottendorfer C.,Centers for Disease Control and Prevention | Graham S.,Auburn University | Unnasch T.R.,University of South Florida
American Journal of Tropical Medicine and Hygiene | Year: 2011

Eastern equine encephalitis virus (EEEV) is endemic throughout most of the eastern United States. Although it is transmitted year round in Florida, transmission elsewhere is seasonal. The mechanism that enables EEEV to overwinter in seasonal foci remains obscure. In previous field studies, early season EEEV activity was detected in mosquito species that feed primarily upon ectothermic hosts, suggesting that reptiles and amphibians might represent overwintering reservoir hosts for EEEV. To determine if this might be possible, two commonly fed upon amphibian and reptile species were evaluated as hosts for the North American subtype I strain of EEEV. Neither amphibian species was a competent host. However, circulating viremias were detected in both reptile species examined. Hibernating infected garter snakes remained viremic after exiting hibernation. These data suggest that snakes may represent an overwintering host for North American EEEV. Copyright © 2011 by The American Society of Tropical Medicine and Hygiene. Source

Britch S.C.,U.S. Department of Agriculture | Linthicum K.J.,U.S. Department of Agriculture | Wynn W.W.,U.S. Department of Agriculture | Walker T.W.,U.S. Navy | And 7 more authors.
Military Medicine | Year: 2010

Treating perimeters of vegetation with residual insecticides for protection from mosquito vectors has potential for U.S. military force health protection. However, for current U.S. military operations in hot-arid environments with little or no vegetation, residual applications on portable artifi cial materials may be a viable alternative. We evaluated bifenthrin residual treatments of U.S. military camoufl age netting under hot-arid field conditions in a desert area in southern California exposed to abundant wild Culex tarsalis mosquitoes. We assessed the ability of the treatment to reduce the numbers of mosquitoes penetrating perimeters of netting and reaching CO2 -baited mosquito traps. Treated camouflage netting barriers reduced mosquitoes by =50% for 7-14 days and by 20-35% for 21-28 days compared to untreated barriers. Although reductions may be translated into reductions in risk of exposure to mosquito-borne diseases, we emphasize that barrier treatments should be a component in a suite of insect control measures to be effective. Source

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