Georgia’s Rapid Expansion of Mosquito Surveillance in Response to Zika Virus

Abstract

ObjectiveTo describe the Georgia Department of Public Health’s (DPH)mosquito surveillance capacity before and after Zika virus wasdeclared a public health emergency, review and compare mosquitosurveillance results from 2015 to 2016, and evaluate the risk ofautochthonous vector transmission of Zika virus based on 2016surveillance data ofAedes aegyptiandAedes albopictusmosquitoes.IntroductionZika virus was declared an international public health emergencyby the World Health Organization on February 1, 2016. WithGeorgia hosting the world’s busiest international airport and a sub-tropical climate that can support the primary Zika virus vector,Aedesaegypti,and secondary vector, Aedes albopictus,the CDC designatedGeorgia as a high risk state for vector transmission. Faced with alack of mosquito surveillance data to evaluate risk of autochthonoustransmission and a few counties statewide that provide comprehensivemosquito control, the DPH rapidly scaled up a response. DPH updatedexisting mosquito surveillance and response plans targeted for WestNile Virus (WNV) and expanded capacity to areas that lackedprevious surveillance targeting the Zika virus vector.MethodsMosquito surveillance data provided by DPH was analyzedfor years 2015 and 2016 to date. The geographical distribution ofcounties conducting surveillance, total number and percentage bymosquito species collected in 2015 were compared to 2016 data.The distribution of counties conducting surveillance was mappedusing ArcMap 10.4.1 for pre and post Zika response. Autochthonousvector transmission risk was evaluated based on the overall numbersand percentages ofAedes aegyptiandAedes albopictusmosquitoescollected for 2016.ResultsIn 2015, Georgia had 14 counties conducting mosquitosurveillance, with a DPH entomologist providing direct surveillancein 4 of these counties. In 2016, DPH expanded surveillance capacity to34 counties, a 142% increase, geographically dispersed across theState in urban and rural areas. A total of 76,052 mosquitoes weretrapped and identified in 2015 compared to 91,261 mosquitoes trappedto date in 2016, representing a 20% increase. A total of 37 mosquitospecies were identified in both years withCulex quinquefasciatus,Georgia’s primary WNV vector, representing the highest percentage(2015-79.45% and 2016-70.41%) of mosquitoes trapped overall.In addition,Aedes aegyptirepresented only 0.108% and 0.007% ofthe total mosquitoes trapped respectively each year and was found inone county.Aedes albopictusrepresented only 1.50% and 1.82% ofthe total mosquitoes trapped respectively each year and was found ina majority of the counties conducting surveillance.ConclusionsDPH was able to rapidly expand its surveillance capacity statewideby maximizing existing grant funds to hire new surveillance staffwhile also collaborating with academic institutions, military bases,Georgia Mosquito Control Association, and local health departmentsto provide training and funding for surveillance and data sharing. Thisexpanded surveillance network provided a clearer picture of the typesof mosquitoes potentially exposing the public to mosquito-bornedisease risks.Historical data for the primary vector of Zika virus,Aedesaegyptihas been isolated to just two counties in Georgia. Expandedsurveillance in 2016 confirmed a low abundance ofAedes aegypti,suggesting the primary vector for Zika has been displaced byAedesalbopictus. This may suggest a reduced risk of autochthonoustransmission of Zika virus in Georgia due toAedes albopictus’affinity for feeding on both humans and animals. This should beinterpreted with caution due to limitations in the data related tounstandardized reporting techniques for each county. DPH is workingwith all counties to improve the quality of data collected and reportedand continues to educate the public on ways they can reduce theirindividual risk of mosquito bites, which in turn reduces the risk ofother mosquito-borne diseases such as WNV.In conclusion, DPH’s response to Zika virus allowed it to rapidlyincrease its surveillance footprint and with new data, make soundpublic health decisions regarding mosquito-borne disease risks.