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Examining Mosquito Surveillance and Control Capacity in the Top 10 Areas at Risk for Zika Virus Exposure in the United States

Gridley-Smith, Chelsea L. PhD

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Journal of Public Health Management and Practice: September/October 2017 - Volume 23 - Issue 5 - p 515-517
doi: 10.1097/PHH.0000000000000646
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Zika virus (ZIKV) disease is a mosquito-borne disease spread to humans mainly through the bite of infected Aedes mosquitoes (Ae. aegypti and Ae. albopictus). Ae. aegypti is also the main vector for viruses that cause dengue, yellow fever, and chikungunya. These mosquitoes typically remain close to human dwellings, often indoors, for their entire lives. This close proximity to humans increases the likelihood that diseases carried by Aedes mosquitoes, including ZIKV, will infect humans. The spread of ZIKV poses a serious health risk, primarily due to how the virus can impact pregnant women. More specifically, ZIKV disease can be passed from a pregnant woman to her fetus, potentially causing severe birth defects.1 In the United States, nearly 6000 ZIKV cases were reported since May 2016, with more infections predicted to occur throughout the remainder of 2017. As a result, local public health departments are increasingly focusing on preventing, preparing for, and responding to ZIKV-related health threats.2

While local health departments (LHDs) are on the front lines of defense against ZIKV infection, almost no data exist on whether or not local agencies are adequately prepared for a mosquito-borne virus outbreak. Without access to this information, federal and state efforts to support local response needs and address capacity gaps are significantly limited. To better align federal resources with local needs, the Centers for Disease Control and Prevention (CDC) Zika State Coordination Task Force and the National Association of County & City Health Officials (NACCHO) assessed ZIKV response capacity among local vector control programs.

The evaluation targeted agencies operating vector control programs in 10 ZIKV priority jurisdictions identified as high risk for infection based on the presence and abundance of the Ae. aegypti mosquito, one risk factor for locally acquired ZIKV infections. Focusing on mosquito control activities is one of the most effective ways to limit the spread of mosquito-borne viruses such as ZIKV. The goal was to assess capabilities and competencies of local vector control programs to determine what, if any, gaps or needs exist and to inform decision making about future ZIKV resources and technical assistance. The majority of vector control programs are conducted at the local level, operating through LHDs, stand-alone mosquito abatement districts, or other entities (eg, public works departments, contractors). As the organization representing nearly 3000 LHDs, NACCHO was uniquely equipped to access local vector control programs for this assessment.

NACCHO assessed mosquito surveillance and control activities across 10 high-risk jurisdictions (Alabama, Arizona, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, Texas, and Los Angeles County), each identified as potentially vulnerable to ZIKV infection. In coordination with the CDC, NACCHO developed and distributed an electronic quantitative tool to measure vector control competency for LHDs and vector control agencies serving these localities. Competency was measured according to the CDC guidance, “Zika Virus Mosquito Control for Professionals,” and guidelines from the American Mosquito Control Association (AMCA).3,4

The competencies, or activities required for sufficient mosquito control to prevent the spread of disease, were broken into 10 questions. Five questions covered core competencies, including the following:

  1. Routine mosquito surveillance, standardized trapping, and species identification;
  2. Larviciding and/or adulticiding capabilities;
  3. Routine vector control (eg, chemical, biological, source reduction, or environmental management);
  4. Species-specific activities; and
  5. Pesticide resistance testing.

Five questions covered supplemental competencies, including the following:

  1. Licensed pesticide application requirements;
  2. Nonchemical vector control;
  3. Community outreach and education activities;
  4. Communication with LHDs on surveillance and epidemiology; and
  5. Cooperation with nearby/partner vector control programs.

The competency framework, as derived from CDC and AMCA guidance, was used to develop a scoring matrix. The 5 core competencies correspond to essential activities of any competent (ie, capable or satisfactory) vector control program. Thus, the core competencies were weighed to rank each organization as fully capable, competent, or needs improvement. A “competent” organization or program performed at least the 5 core competency activities. A “fully capable” program performed all core and supplemental competencies. Any organization that failed to perform any of the core competencies was ranked as “needs improvement.”

In the 10 priority jurisdictions, NACCHO identified 381 local vector control organizations. NACCHO attempted to contact all 381 vector control organizations to verify vector control activities and identify an appropriate contact (ie, name and e-mail) to participate in the assessment. Even with these prescreening efforts, NACCHO was unable to reach 30 of these organizations. The final database contained 351 local vector control organizations and was composed of LHDs (24%), mosquito abatement districts (47%), and other organizations (29%). Examples of other organizations include public works departments, environmental health services, parish police juries, street works departments, and parishes. Of the 351 local vector control organizations assessed, 190 responses were received (54% response rate) and analyzed for competency.

The majority (68%) of local vector control organizations that responded to this assessment were ranked as “needs improvement.” Just over one-fifth of respondents (21%) were ranked as “fully capable,” and 9% fell into the “competent” ranking category. The 129 organizations that were ranked “needs improvement” were further analyzed on the basis of the number of core competency questions that were answered negatively. Forty-three percent (56 of 129) were missing only 1 core competency; of these 56 organizations, 91% would be competent if they performed pesticide resistance testing. This represents one opportunity for vector control improvement that could be addressed through targeted resources and technical assistance aimed at identifying the obstacles to increasing pesticide resistance testing at the local level.

Both NACCHO and the CDC compiled the findings and implications of the assessment into a slide deck to further advance LHD, local vector control, and ZIKV response planning.5 Collectively, the responses illustrate that mosquito control programs, expertise, activities, and financial resources are highly variable throughout the 10 jurisdictions. The assessment revealed a wide range of capacity, including agencies with zero to minimal capabilities and others with fully operational programs, equipped with advanced integrated mosquito management resources.

Many of the local mosquito control organizations that NACCHO contacted to participate in this assessment described a disorganization of vector control activities. Respondents expressed concern or lack of knowledge about who is responsible for mosquito abatement in different towns, counties, jurisdictions, and parishes; what resources are available from neighboring organizations in the event their assistance is needed; understaffing issues; and a significant lack of resources. Many organizations, particularly in smaller towns or jurisdictions, contract out all of their mosquito abatement activities. The results of this assessment can help inform opportunities to facilitate the sharing of promising practices and lessons learned among mosquito control jurisdictions. For example, organizations assessed as “needs improvement” or “competent” may benefit from lessons learned and best practices from “fully capable” organizations' programs.

The results of the assessment represent an initial attempt to classify mosquito control competency across the United States, starting in high-priority areas that may be at a heightened risk for local ZIKV transmission. While most ZIKV infections are mild or without symptoms, the tragic and costly effect to infants requires enhanced efforts to prevent the spread of disease. Mosquito control is one of the main ways to prevent the spread of ZIKV, including personal protection against mosquito bites.6 Mosquito control organizations play an important role in monitoring the mosquito population, identifying ZIKV within the mosquito population, and treating breeding grounds to eliminate mosquitoes. LHDs are key players in educating the public and providing information on how private property owners can eliminate mosquito breeding habitats in and around homes and residences (ie, the preferred breeding grounds for Ae. aegypti).

NACCHO's next steps include expanding the assessment to cover the remaining 41 states and jurisdictions to get a more comprehensive status of vector control competency across the United States. In addition, NACCHO has formed a Vector Surveillance and Control Workgroup composed of local vector control organizations and subject matter experts. This workgroup will inform and develop NACCHO's vector control technical assistance program, create and update relevant policy statements, and develop strategies to address the gaps identified by the assessment. Through these activities, NACCHO will continue to seek to minimize the health threats posed by the ZIKV.


1. Centers for Disease Control and Prevention. Zika virus: health effects & risks. Updated August 9, 2016. Accessed May 4, 2017.
2. Centers for Disease Control and Prevention. Zika virus: 2017 case counts in the US. Updated May 4, 2017. Accessed May 4, 2017.
3. Centers for Disease Control and Prevention. Zika virus: mosquito control for professionals. Updated November 17, 2016. Accessed May 4, 2017.
4. American Mosquito Control Association. Best practices for integrated mosquito management: a focused update. Updated January 2017. Accessed May 4, 2017.
5. National Association of County & City Health Officials. Mosquito surveillance and control assessment in Zika virus priority jurisdictions. Updated December 2016. Accessed May 8, 2017.
6. Centers for Disease Control and Prevention. Zika virus: mosquito control. Updated April 25, 2017. Accessed May 10, 2017.
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