Fighting mosquito bite during a crisis: capabilities of Florida mosquito control districts during the COVID-19 pandemic

Worldwide, mosquito-borne diseases continue to contribute to the global burden of infectious diseases, and produce epidemics of dengue, malaria, chikungunya, yellow fever and Zika that disturb health security and have wider socioeconomic impacts [1, 2]. Globally, mosquito-borne diseases account for more than 17% of all infectious diseases [3] and cause more than 700,000 deaths per year. In addition, mosquito-borne diseases pose a special challenge to public health practitioners and mosquito control districts [4‐6] owing to their complex nature (biological transmission complexity) [7, 8] and potential to produce epidemics, particularly in areas that institutionally struggle to sustain mosquito management [9]. This makes surveillance and control key aspects for preventing mosquito-borne diseases and emerging arboviruses [4].

In Florida, Aedes and Culex continue to be major vector genera [10‐12], with the state of Florida having been ground-zero for local transmission of Zika and dengue viruses [13]. The state is also in close proximity to Latin American where viruses such as Zika and dengue viruses are endemic [4, 14]. Therefore, surveillance as a key aspect of effective mosquito control and prevention [2, 15] is particularly important in economically depressed subtropical areas of the United States [1].

Now the stay-at-home orders imposed in early April 2020 in Florida due to the COVID-19 pandemic has complicated mosquito control activities [16], and raised questions about how we should manage mosquito control programs in the wake of pandemics or crises. The Centers for Disease Control and Prevention (CDC) underscore the importance of initiating or continuing the delivery of mosquito control and public health organization services during public health emergencies and responses to natural disasters in order to reduce the risk of mosquito-borne disease [17]. Despite the importance of mosquito control as a basic public health function, the National Association of County and City Health Officials (NACCHO) recently reported COVID-19 impacts on mosquito programs that operate under the auspices of local health departments [18].

This, coupled with major funding and capacity gaps, may put pressure on some already struggling programs, and may exacerbate timely and effective response to (re) emergent arboviral diseases in the future [9]. Therefore, to understand the challenges inherent in implementing mosquito activities during a pandemic, we assessed the capabilities of Florida state-approved mosquito control districts and open programs to carry out mosquito control activities at a time when Florida was still under heightened awareness of, stay-at-home orders and planning a phase 1 reopening over the COVID-19 pandemic. Our findings will shed light on the capabilities of Florida mosquito control programs, the first line of defense against mosquito-borne pathogens. It will also shed light on the challenges experienced by these programs to carry out mosquito control during a pandemic.

Our findings suggest that despite the imposed COVID-19 lockdown or stay-at-home orders, the vast majority of responding Florida mosquito districts and open programs did not cease mosquito control operations. Those that remained open were mostly programs operating under the auspice of the Board of County Commissioners (BOCC), municipal and independent tax district. The mandate for these programs is to not only fight pest mosquitoes but also fight species of mosquitoes that have potential to transmit mosquito-borne pathogens [24, 25]. Florida’s mosquito control capabilities during the initial months of the COVID-19 pandemic may be attributed to the very nature of the ongoing mosquito control programs with permanent personnel, including the lessons learned from several prior research projects on mosquitoes and mosquito-borne diseases [26].

The observed lack of arbovirus surveillance for serology and pool testing is of primary concern as it limits the generation of evidence about when programs can anticipate a surge in arbovirus infection and in mosquito control programs’ capability to detect or monitor arbovirus presence for timely control response. To note, in Florida, most arboviral surveillance (serology and pool testing) is conducted at a state laboratory located in Tampa, a laboratory that was redirected to COVID-19 testing at the time of this study. This finding is not unique to Florida. The National Association of County and City Health Officials (NACCHO) reported similar challenges among county and city programs during the lockdown [20]. This is a persistent problem that was also reported by Hadler and his colleagues when they assessed “arbovirus surveillance 13 years after the introduction of WNV in the US” [21]. To prevent nuisance mosquitoes or diseases, there is a need for real time information. For example, if a mosquito is carrying Zika virus, we want to know that today, not in 2 weeks or months from now. The first author’s previous co-authored study identified over 1000 mosquito control agencies in the continental United States; 152 had publicly available open access mosquito datasets, and 148 agencies had live data that can be leveraged with good effect [27].

Notably, despite the observed marked differences in the level of performed mosquito control activities in Florida, most mosquito programs (both state-approved and open programs) performed mosquito control activities either fully or partially for key surveillance activities (Larviciding and adulticiding) during a time when the world was facing great challenges due to the COVID-19 pandemic. The majority of programs also engaged in routine control of domestic mosquitoes such as Aedes species of mosquitoes that can cause Aedes-borne arboviruses like dengue virus (DENV), chikungunya virus (CHIKV), yellow fever virus (YFV), and Zika virus (ZIKV) as well as Culex species of mosquitoes that can cause Culex-arboviruses like SLEV and WNV. In addition, mosquito surveillance is enhanced by the existence of ongoing meteorological, climatological, and water table monitoring [28]. This demonstrates that although Florida mosquito control programs have a long history and experience with the Culex-arbovirus systems, they are also capable of providing mosquito control against Aedes species as evidenced by the quick mitigation of the 2016 ZIKV outbreak [29].

Our findings have implications for local and state mosquito programs including national associations as they work towards mitigating the impacts of COVID-19. More importantly, maintaining sustainable systems for arbovirus surveillance for serology and pool testing is vital as it can help define the nature and extent of circulating strains of arboviruses, provide a basis for evaluating the risk of transmission of mosquito-borne diseases, contain a potential mosquito-borne disease outbreak and reduce the cost of responding to emerging vector-borne pathogens. This can also aid in gauging the efficacy of control activities. There is also a need to build the capacity of mosquito control district and program laboratories and for the establishment of viral genomic databases as a reference for current and future research.