Utilizing mosquito surveillance to prevent West Nile virus infection—Indiana, 2012
Tuesday, November 12, 2013
Exhibit Hall 4 (Austin Convention Center)
Bryan Price
,
Indiana State Department of Health, Indianapolis, IN
Jennifer House
,
Indiana State Department of Health, Indianapolis, IN
Pam Pontones
,
Indiana State Department of Health, Indianapolis, IN
Mark Glazier
,
Indiana State Department of Health, Indianapolis, IN
Lee Green
,
Indiana State Department of Health, Indianapolis, IN
Doug Ginder
,
Indiana State Department of Health, Indianapolis, IN
Nikki Collins
,
Indiana State Department of Health, Indianapolis, IN
Michael Denton
,
Indiana State Department of Health, Indianapolis, IN
Chris Waldron
,
Indiana State Department of Health, Indianapolis, IN
West Nile Virus (WNV) can cause encephalitis or meningoencephalitis. From May-October 2012, the Indiana State Department of Health (ISDH) conducted mosquito surveillance to determine the emergence and extent of viral activity statewide. Female mosquitoes were collected from every county using gravid traps. Specimens were identified and grouped into pools of up to 100 mosquitoes. Each pool was tested for WNV RNA by real-time reverse transcription polymerase chain reaction (rRT-PCR). Positive laboratory reports indicating human infection with WNV were investigated. All persons meeting the National Notifiable Diseases Surveillance System (NNDSS) case definition for either probable or confirmed arboviral disease (including neuroinvasive and non-neuroinvasive) were counted as cases. The minimum infection rate (MIR) of mosquito pools was calculated and compared to the emergence of human infection.
Of the 1941 mosquito pools tested, WNV was confirmed in 577 (29.7%) pools. Of the 92 counties sampled, 91 (98.9%) had positive rRT-PCR results at least once during the season. Illness investigations identified 77 human cases of WNV. Comparison of mosquito MIR with onset dates for cases revealed that a rapid and steep increase in positive mosquito populations preceded an outbreak of disease. As the MIR in mosquito populations decreased there was a corresponding decrease in the number of new WNV cases.
Utilizing mosquito surveillance is an effective tool for public health. Rapid testing of specimens provides quantifiable evidence of viral activity in communities prior to the onset of illness. This early warning allows communities to take action to prevent infection. Communications to residents with scientific evidence of risk can motivate citizens to take precautions against exposure. Targeted vector control based on evidence of viral activity can assist communities with resource management while taking action to control infectious disease vectors.
