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Environmental Surveillance

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Environmental Surveillance

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    1. Environmental Surveillance Nick Komar, ScD CDC – DVBID Fort Collins, CO

    3. Environmental Surveillance Modalities Vector density and infection rate Sentinel captive birds Sentinel free-ranging birds Avian mortality surveillance Non-human morbidity & mortality surveillance

    4. Environmental Surveillance Modalities Vector density and infection rate Sentinel captive birds Sentinel free-ranging birds Avian mortality surveillance Non-human morbidity & mortality surveillance

    5. Vector Surveillance Purpose Monitor populations of mosquitoes Estimate risk of infectious mosquito bites Monitor risk in long-term surveillance sites In traditional transmission foci In population centers Determine local risk in response to other indicators of virus activity (such as a human case or a WNV+ dead bird)

    6. Number of USA counties reporting vector data to ArboNET is stable at about 28% (poster #27) Advantages Provides a relative measure of risk PPV of an infected mosquito is about 50% for human cases (poster #27) Disadvantages Mosquito ID is labor intensive Effort is Active, not Passive Data geographically limited by trapping effort Vector Surveillance

    7. Advances in Vector Surveillance Culex vectors well characterized throughout the US and Canada, permitting targeted collection practices Gravid traps for Cx. pipiens complex CO2-baited light traps for Cx. salinarius and Cx. tarsalis Molecular techniques now widely available for: Culex species ID Bloodmeal source ID Vectorial risk indices have been developed More user-friendly than vectorial capacity equation Improved mosquito traps

    8. Vector Indices Nasci Vector Index Infection rate (IR) x Trap index (TI) units = number of infected Culex pipiens per trap night Kilpatrick modified vector index IR x TI x competence x human feeding index Units=number of infectious Cx. pipiens that will bite humans per trap night Requires more resources but theoretically provides a better estimate of local risk

    9. Trap Improvements Updraft gravid trap Propane-powered mosquito magnet trap CDC Resting Trap (poster # 77)

    10. Avian Mortality Surveillance PURPOSE Early detection of transmission foci Confirmation of ongoing local transmission In some cases, quantify transmission risk (e.g. see Poster #35) Not the original purpose, but numerous studies across the country have found ways to use dead bird reports and avian carcass testing to quantify transmission and predict risk; more details will be presented and discussed in breakout session Friday evening. Indirect objectives: Cooperate with other surveillance systems (e.g. H5N1 AI) Detect novel pathogens

    11. Trends in Data Reporting

    12. Advantages Temporally sensitive when effort is intensive early in the season (multiple species targetted) Spatially sensitive No longer requires specialized laboratory facilities or skills Highly cost-efficient due to very high detection rates

    13. Disadvantages Triage systems need constant attention Utility of crows has diminished as predicted Success depends on strong support and participation from the public and strong interagency cooperation Poor fit with public health culture

    14. Selected advances WNV-pos carcasses (mainly corvids) predicted human cases in Colorado (Patnaik et al. EID 2007) DYCAST model effective for predicting human risk in California (poster #35) Sample collection facilitated by using immature feathers (Docherty et al. EID 2004) and mature feathers (poster #13)

    15. Mature breast feathers Reduction in sensitivity (52% in WNV-pos. corvid carcasses) offset by ease of sample collection Cold chain obsolete No infectious fluids

    16. The Big Picture WNV HAS BECOME ENDEMIC Diminishing resources Learning to live with WNV does not mean complacency Creative and cost efficient strategies needed to mitigate an omnipresent risk Environmental surveillance is crucial to this challenge

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