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Examining Mosquito and Tick Surveillance and Control Capacity at the Local Level

Roy, Angana MPH

Author Information
Journal of Public Health Management and Practice: November/December 2021 - Volume 27 - Issue 6 - p 618-620
doi: 10.1097/PHH.0000000000001435
Erratum

In the November/December 2021 issue of the Journal of Public Health Management and Practice, in the article by Roy, A, “Examining Mosquito and Tick Surveillance and Control Capacity at the Local Level,” under the heading, “Preliminary Findings From the 2020 Vector Assessment,” in the last sentence of the second paragraph, the word “million” should have been removed after “$500.” The sentence should read, “The funding ranged from $500 to $35 million across programs.”

The author regrets the error.

Journal of Public Health Management and Practice. 28(1):24, January/February 2022.

Vector Control at the Local Level

Even as the COVID-19 pandemic affected public health activity at every state and territory in the United States, vector control programs throughout the country continued operating at the local level. These local vector programs play a vital role in protecting public health as ticks and mosquitoes are the 2 most common vectors for disease in the country. Moreover, the Centers for Disease Control and Prevention (CDC) reports that between 2004 and 2016, 9 novel vector-borne human diseases were reported.1 Climate change may also affect the prevalence of vector-borne disease as warming temperatures may cause species habitats to shift, bringing an increased risk of vector-borne disease to areas that have not dealt with a significant risk before.2 Most vector-borne diseases present in the United States do not have available vaccines and many of these diseases can cause serious or even life-threatening symptoms, so minimizing the risk of mosquito and tick bites remains the key strategy for vector-borne disease prevention. As the risk of vector-borne disease continues to grow and change, it is more important than ever to understand the capacity of local vector control programs and to help improve their function as needed.

The risk of vector-borne disease varies by region and as such vector control activity is expected to vary as well. Gulf states such as Florida face a greater risk of mosquito-borne illness than states further north, while states in the Northeast experience a greater risk of Lyme disease. Mosquito-borne diseases reported in the United States include West Nile virus fever, dengue fever, chikungunya, and Zika virus disease. West Nile virus transmission has been reported throughout much of the continental United States every year for the past decade. In 2019, there were a total of 971 cases reported to the CDC.3 An estimated 80% of cases do not result in any symptoms. In rare cases, the disease can be serious, particularly for older adults.4 Chikungunya and dengue are more commonly reported in the US territories than in the continental United State. Most cases of chikungunya do cause some symptoms, though repeat infections are less likely, while an estimated 25% of dengue infections result in an illness and around 5% in severe illness. Reinfections can occur with dengue and are more likely to cause severe illness.5,6 As of 2019, no Zika virus transmission was reported anywhere in the United States.7 While mosquitoes can be found throughout the continental United States and across all the territories, only some species are known to transmit diseases to humans. The Aedes, Culex, and Anopheles families of mosquitoes carry most of the diseases of concern in the United States.

Tick-borne diseases in the United States include Lyme disease, Rocky Mountain spotted fever, and Powassan virus disease, among others. Of all the vector-borne diseases reported, Lyme disease is the most prevalent, with the CDC estimating around 476000 cases of Lyme disease being treated per year.8 Lyme disease is caused primarily by the Borrelia burgdorferi bacteria and most likely to be transmitted to humans through bites from Ixodes scapularis in the nymph stage or females in the adult stage. As of 2020, the habitat for I scapularis, commonly known as the blacklegged tick, includes the entire eastern half of the United States.9 However, not all areas are at equal risk for Lyme disease. While reported cases of Lyme disease have increased and spread over a wider area between 2001 and 2019,10 the habits of ticks vary by region, which affects their likelihood of carrying the B burgdorferi bacteria.11 Southern states remain at a lower risk than states in the Northeast and Mid-Atlantic. Rocky Mountain spotted fever virus can be transmitted by a variety of ticks, some of which have habitats that reach across the continental United States, but the disease is most commonly reported in just a handful of states, with Arizona reporting case counts well above the national average and reporting 21 fatalities between 2003 and 2016.12

Preliminary Findings From the 2020 Vector Assessment

The National Association of County and City Health Officials (NACCHO), supported by a cooperative agreement from the CDC, conducted the 2020 Vector Assessment to evaluate the capacity of local vector control programs across the country. The assessment was sent to 1664 verified vector control programs. The assessment was conducted from November 2020 through January 2021. This is the second iteration of the assessment, following the very first Vector Assessment in 2017,13 and the first time the assessment has included items related to ticks. The results of this assessment provide invaluable information about the current state of local vector control programs, showing a marked improvement in program capacity over the past 3 years.

Out of a database of 2213 programs, a total of 1664 programs could be verified as operational vector control organizations prior to the launch of the 2020 assessment. The response rate among verified programs was 29.5% (n = 491). Most respondents were vector control programs serving populations of less than 100 000. Most programs reported dedicated funding, with local funding being the most reported source of funding. The funding ranged from $500 million to $35 million across programs.

In terms of core capacities for mosquito programs,14,15 most respondents were engaged in both mosquito surveillance and control, and of the programs engaged in control activities, most programs reported larviciding and adulticiding activities, as well as pesticide resistance testing. In terms of capacity, a total of 39.7% programs (195 programs) were determined to be fully capable based on these criteria, while 15.5% (76 programs) were determined to be competent and 44.8% (220 programs) were determined to be in the needs improvement category. Of programs engaged in control activities, 22.6% reported species specific control for A aegypti, 31.2% for A albopictus, 44.4% for C pipiens, and 30.6% for any Anopheles species (Table).

TABLE - Core and Supplemental Mosquito Program Capacity
Five Core Capacities % n Five Supplemental Capacities % n
Routine mosquito surveillance, standardized trapping, and species identification 68.0 491 Licensed pesticide application requirements (of program that apply pesticides) 92.8 371
Treatment decisions using surveillance data 89.2 334 Nonchemical vector control (of programs that control) 67.3 385
Larviciding (l) or adulticiding (a) capabilities 75.8 (l), 94.5 (a) 385 Community outreach and education activities 82.3 491
Routine vector control (eg, chemical, biological, source reduction, or environmental management) 78.4 491 Communication with LHDs on surveillance and epidemiology 86.2 491
Pesticide resistance testing 69.8 484 Cooperation with nearby/partner vector control programs 65.4 491
Abbreviation: LHD, local health department.

When compared with the results from 2017, 155 of the organizations that completed both assessments showed measurable improvement, with 66% moving from needs improvement to fully capable, 27% from needs improvement to competent, and 6% from competent to fully capable. Of the programs that moved from needs improvement to fully capable between 2017 and 2020, 28 were based in Illinois or Ohio. All other states that reported improvement at the local level had between 1 and 6 programs with similar improvement over the same period.

In terms of tick-related activities, 21.4% of respondents reported tick surveillance while 3.3% reported any tick control activity. Out of all survey respondents, 35.4% engage in community outreach and education on tick-borne disease transmission and prevention. Of the programs engaged in surveillance activities, a majority of the programs are targeting I scaplularis, but most do not report their surveillance data to the public. While a much lower number of programs are engaged in any tick-related activity than mosquito-related activity, these data provide an important baseline for future studies.

It should be noted that the 2020 Vector Assessment was fielded during the COVID-19 outbreak and during a period of notably high case counts and fatalities from the pandemic. As local health departments have played a substantial role in the pandemic response, this may have affected the overall response rate. In 2017, the response rate was 53%, while in 2020, the response rate was 29.5%. Anecdotally, NACCHO staff contacted several organizations as part of routine follow-up activities during the assessment period and some organizations reported limited availability for staff due to COVID-19 activities. While the assessment did not ask about the effect of COVID-19 on vector control activities, NACCHO is continuing to try and better understand the effects of the pandemic on these programs through its work groups and other programs to identify any critical interruptions or changes to vector control activities.

In terms of next steps, NACCHO will continue to analyze the data from this assessment and identify any trends that can help build surveillance and control capacity at the local level. In addition, NACCHO will use the results from this assessment to support the activities of the Vector Surveillance and Control Work Group, a group of local vector control experts that advises and guides NACCHO activities to help respond to critical needs in the field, as well as the activities of the Vector Control Collaborative, a mentorship program that pairs experienced local vector programs with programs that are seeking to learn and improve upon their surveillance and control capacity. Finally, NACCHO plans to field another iteration of the assessment in 2023.

References

1. Centers for Disease Control and Prevention. Vital Signs: trends in reported vectorborne disease cases—United States and territories, 2004-2016. https://www.cdc.gov/mmwr/volumes/67/wr/mm6717e1.htm. Accessed August 12, 2021.
2. Kraemer MUG, Reiner RC Jr, Brady OJ, et al. Past and future spread of the arbovirus vectors Aedes aegypti and Aedes albopictus. Nat Microbiol. 2019;4(5):854–863.
3. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Final cumulative maps & data for 1999-2019. https://www.cdc.gov/westnile/statsmaps/cumMapsData.html#one. Accessed August 12, 2021.
4. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. West Nile virus: symptoms, diagnosis, & treatment. https://www.cdc.gov/westnile/symptoms/index.html. Accessed August 12, 2021.
5. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Chikungunya virus: symptoms, diagnosis, & treatment. https://www.cdc.gov/chikungunya/symptoms/index.html. Accessed August 12, 2021.
6. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Dengue: symptoms and treatment. https://www.cdc.gov/dengue/symptoms/index.html. Accessed August 12, 2021.
7. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Zika virus: statistics and maps. https://www.cdc.gov/zika/reporting/index.html. Accessed August 12, 2021.
8. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Lyme disease: data and surveillance. https://www.cdc.gov/lyme/datasurveillance/index.html. Accessed August 12, 2021.
9. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Ticks: regions where ticks live. https://www.cdc.gov/ticks/geographic_distribution.html. Accessed August 12, 2021.
10. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Lyme disease: Lyme disease maps: historical data. https://www.cdc.gov/lyme/stats/maps.html. Accessed August 12, 2021.
11. Ginsberg HS, Hickling GJ, Burke RL, et al. Why Lyme disease is common in the northern US, but rare in the south: the roles of host choice, host-seeking behavior, and tick density. PLoS Biol. 2021;19(1):e3001066.
12. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Tickborne diseases of the United States: Rocky Mountain spotted fever (RMSF). https://www.cdc.gov/ticks/tickbornediseases/rmsf.html. Accessed August 12, 2021.
13. NACCHO. Mosquito control capabilities in the US. https://www.naccho.org/uploads/downloadable-resources/Mosquito-control-in-the-U.S.-Report.pdf. Published 2017. Accessed July 7, 2021.
14. AMCA. Best practices for integrated mosquito management: a focused update. https://cdn.ymaws.com/www.mosquito.org/resource/resmgr/docs/Resource_Center/Training_Certification/12.21_amca_guidelines_final_.pdf. Published 2017. Accessed July 7, 2021.
15. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. Mosquito control for professionals. https://www.cdc.gov/mosquitoes/mosquito-control/professionals/index.html. Published 2020. Accessed August 12, 2021.
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