Aedes Aegypti Density Monitoring and Reduction at Miami-Dade County
Mosquito-borne diseases are the most prevalent vector-borne diseases in the subtropics and in the entire world with over 30% of the global population at risk. Research has demonstrated the necessity of understanding the life cycle of Aedes aegypti mosquitoes because they are linked to prevalent mosquito-borne diseases such as Yellow fever, Dengue, Chikungunya, and Zika. As of this April 2016, incidences of Zika had been reported in Miami-Dade County following the importation of the virus from outside the country, particularly from Latin America. This paper explores the local surveillance of Aedes aegypti in Miami-Dade County and its implications in public health. Additionally, it reviews the policies and regulations on monitoring and reducing the mosquitos in the County. One of the outstanding modalities for reducing the density of Aedes aegypti mosquitoes is the use of Genetically Modified ones, which have the capacity to reduce the population of infectious (female) mosquitoes and limit the transmission of the pathogens.
Aedes aegypti mosquitoes are the leading transmitters of mosquito-borne viruses, including Chikungunya, Dengue 1-4, Zika, and Yellow fever (Fischer, Scott, & Margolis, 2015). Contrary to their counterparts, Aedes albopictus, which cause only Dengue and Chikungunya, the Aedes aegypti mosquitoes are the most efficient vectors for humans. Zika virus gained attention due to unprecedented growth of incidences of Guillain-Barré syndrome and microcephaly caused by Zika virus (Centers for Disease Control and Prevention, n.d.; European Centre for Disease Prevention and Control, 2016). The virus was also identified in Florida, New York, and Texas. The Florida Department of Health confirmed cases of Zika virus brought to the state by international traveler with Miami-Dade County leading in four cases (Chang, & Lima, 2016). Aedes aegypti is of particular concern due to high density and its link to the various tropical diseases, including Dengue and the more recently in the public domain, Zika. This paper explores the local surveillance of Aedes aegypti in Miami-Dade County and its implications in public health. In addition, it reviews the policies and regulations on monitoring and reducing Aedes aegypti mosquitoes in Miami-Dade County.
Significance of the Topic
Aedes Aegypti Mosquitoes and Host Relationship
Aedes aegypti belongs to the Aedes (Stegomyia) subgenus (Fischer, Scott, & Margolis, 2015). The mosquitoes are traced to Africa and have been transported worldwide throughout the temperate, tropical and subtropical world through international shipping and trade activities (Powell, & Tabachnick, 2013). They lay eggs in domestic water containers. Aedes aegypti is subject to scrutiny because it is more effectual vector for humans than the Aedes albopictus, which causes Chikungunya and Dengue, and it lives in and around households. Additionally, its peek feeding time is during the day. Only female Aedes aegypti mosquitoes feed on blood for egg development. They prefer human blood to animal one. The vector host relationship of these mosquitoes is that they bite during the day when humans are active. The frequency of bites increases the fitness of the mosquitoes in the sense that lay more eggs and live longer (Monaghan et al., 2016). Furthermore, a high frequency of bites increases the potential for virus infection.
Aedes Aegypti and the Associated Mosquito-Borne Diseases
With more than 30% of the world’s population residing in areas at risk of mosquito-borne diseases, Aedes aegypti is a leading cause of these maladies in subtropics. There are several mosquito-borne diseases, including Dengua, Chikungunya and Zika. According to CDC (Centers for Disease Control and Prevention, n.d.), Dengue is a leading cause of mosquito-based illnesses and deaths in the subtropics. The agency notes that approximately 400 million people are infected annually. According to WHO (World Health Organization, n.d.), Zika virus is a mild mosquito-borne disease, and most human hosts with the virus do not exhibit symptoms. However, following the recent rise in the spread of the virus in Latin America, particularly in Brazil, the virus has been accompanied by an unprecedented growth of number among children born with unusually small heads, a condition referred to as microcephaly. Additionally, there has been an increase in incidences of Guillain-Barré syndrome, which is one of the neurological disorders that tends to result in paralysis and death (World Health Organization, n.d.). Evidence is growing that Zika virus causes Guillain-Barré syndrome and microcephaly (Monaghan et al., 2016).
As of this writing, Zika was the most recent public health concern in the subtropics. CDC’s Incident Management System was activated on January 22, 2016, through the entity’s Emergency Operations Center (EOC) to respond to the occurrences of Zika in the Americas (Centers for Disease Control and Prevention, n.d.). The response was activated in in line with increased reports regarding Guillain-Barré syndrome and birth defects in areas affected. In the same context, the Word Health Organization declared a Public Health Emergency of International Concern (PHEIC) due to clusters of microcephaly and some neurological disorders in areas that reported Zika (Centers for Disease Control and Prevention, n.d.). Following the severity of Zika and its increased prevalence, the response efforts by CDC were elevated to Level 1, which is the highest response level at CDC. Based on the prevalence and outcomes of the Zika virus, it is evident that there is an urgent need to investigate and find solutions to the increasing density of Aedes aegypti mosquito in Miami-Dade County.
High Density of Aedes Aegypti and Public Health Outcome
On February 19, 2016, the Florida Health Department had confirmed 19 Zika cases; all of them were acquired outside the state (Chang, 2016). Out of the 19 Zika cases, 10 were reported in Miami-Dade County. It should be noted that there was not locally transmitted case that had been reported in the county. The primary concern among researchers, physicians and the public is the speculated connection between the virus and the resultant growth in cases of microcephaly. The concern is amplified by the knowledge regarding the growing density of Aedes aegypti in Miami-Dade County. A high density translates to more bites and increased potential for virus transmission. Additionally, Zika infection during pregnancy is linked to miscarriages as well as eye problems in the newborns. Two miscarriages in the US have been attributed to Zika virus (Chang, 2016). In both cases, the mothers had travelled outside the country and miscarried after returning following the infection of Zika virus. Additionally, a case of microcephaly was reported in Hawaii with the virus traced to Brazil where the mother had been living during pregnancy. Thus, lack of appropriate infrastructure in Miami-Dade County favors the growth of Aedes aegypti mosquitoes with high potential of Zika virus transmission.
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Environmental Conditions Affecting the Prevalence of the Zika Virus
The prevalence of Zika virus correlates to the density of the Aedes aegypti mosquitoes. Therefore, discussing the environmental conditions that have either a direct or an indirect impact on the diseases, it is essential to pay attention to the condition that favors these mosquitoes. Fischer, Scott, and Margolis (2015) state that Aedes aegypti mosquitoes are highly domesticated. In other words, they thrive around household and densely populated areas because they depend on the blood from humans in their life cycle. Stored or stagnant pools of water, as well as discarded non-biodegradable containers accumulate rainwater, creating mosquito breeding and development sites (Fischer, Scott, & Margolis, 2015). Rapid urban growth also favors the growth of mosquito densities due to the resultant substandard housing, poor solid waste disposal, and inadequate water supply. High human population density favors high mosquito densities marked by close biting contact. For that reason, high population density increases the potential for transmission.
Local Surveillance and Its Public Implication
Local surveillance of Aedes aegypti in Miami-Dale County falls under the mandate of the Florida Department of Health. The department works with other counties, states, as well as federal and non-governmental entities to protect, improve and promote the health of all residents in Florida through integrated community, county and state efforts (Miami-Dade County Emergency Operations Center, 2016). In the same context, the collection of surveillance data and the monitoring of the mosquito population density are conducted through integrated efforts.
Data on Aedes Aegypti Density in Miami-Dade County
The data regarding the density of Aedes aegypti in Miami-Dade County is of concern due to its significance in the formulation of strategies and policies meant to curb the growth of Aedes aegypti population and the prevention of the virus transmission. The geographic distribution of Aedes aegypti in Florida overlaps with environmental conditions and population density. In study about the influence of habitat on the predominance of mosquitoes in South Florida, it was noted that Aedes aegypti mosquitoes predominate in urban areas of the county (Rey et al., 2006). In line with this study, Florida Health Department and the CDC focus their data collection efforts in urbanized areas.
How Surveillance Data is Collected
In the United States, Miami-Dade in particular, mosquitoes transmit a variety of viruses. The surveillance data collection approaches is limited to the viruses transmitted by the Aedes aegypti as the principal vector of Zika, Dengue and Chikungunya. Data are collected from various sources both qualitatively and quantitatively. The key data sources for surveillance include environmental data, special surveys (disease registers, hospital admissions, and mosquito population density), demographic data, information on vectors, reports on epidemic investigations, and morbidity and mortality reports. The choice of either quantitative or qualitative method of data collection largely depends on the suitability of addressing the underlying problems or questions. The county makes use of the data collected by the CDC and the Florida Health Department. Additionally, data are obtained from research institutions, including public universities and health institutions. Overall, the data collection approach used depends on the data analysis technique used. Observably, most of the information obtained regarding the mosquito density in the county is collected through a mixed method approach (Miami-Dade County Emergency Operations Center, 2016), whereby a hybrid of qualitative and quantitative approaches of data collection and analysis are used (Bryman, 2006; Creswell, 2014). Qualitatively, interviews used to collect new information are guided by protocols, which center on the factors that favor the growth of mosquito populations in the county. Quantitatively, sampling and surveys are conducted by the Florida Health Department with the help of the CDC. Typically, the qualitative data are used to inform the information collected, improving findings, conclusions, recommendations, and the resultant strategies.
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How the Density of Aedes Aegypti Is Monitored in Miami-Dade County
The density of Aedes aegypti mosquitoes in the county are monitored through a public health surveillance program. It monitors health events to detect the changes in mosquito population densities and distributions, as well as disease occurrences. Additionally, Miami-Dade County monitors long-term (secular) trend and pattern of mosquito distribution in the county. In the same context, the changes in host and agent factors are identified. To a lesser degree than federal health agencies, county health agencies use the surveillance data to detect sudden increased in mosquito-borne disease incidences. In other words, state and national agencies are much more active than the county health agencies in investigating and initiating prevention and control activities.
Modalities of Improving Data Surveillance
Miami-Dade County should use an integrated public health surveillance mechanism to monitor the density of mosquito populations in the county. Its purpose is to appropriately set goals, plan data collection programs and take action where necessary. Ideally, surveillance should be an ongoing systematic collection, analysis, validation, interpretation, evaluation, and dissemination of the Aedes aegypti data. Both public and private agencies should be involved in the surveillance process to describe and monitor the mosquito density trends and the corresponding incidences of mosquito-borne diseases within Miami-Dale County. To improve efficiency, surveillance data should be used to set priorities and aid the county and agencies such as CDC to planning, execution and evaluation of public health policies, programs and interventions designed to curb the growth of mosquito populations. Additionally, the integrated surveillance system should be used as an information loop, involving public health agencies, healthcare providers, and the public. The cycle or loop is only completed when the collected information about the mosquito density and disease incidences is relayed to relevant entities for prevention and control, as well as for education and research purposes. The involvement of the public is in line with the observation that the public has a vital responsibility to play vector control and disease prevention. Therefore, all the stakeholders must be included in the reception of feedback regarding surveillance information.
Figure 1. The components of integrated surveillance system and the resultant public health action.
Figure 1 illustrates the key components of an integrated surveillance system. It follows that the county and responsible agencies should exploit the benefits of information technology, including centralized database, use of handheld devices in data collection, as well as websites for education and alert purposes (Cambie, & Ooi, 2009). At the center of this recommendation is the efficacy of IT solution as seen in the case of CDC. The latter makes use of social media and social networking sites, predominantly, Twitter and Facebook (Murthy, 2013). The viral nature of these tools can be used to educate the public or disseminate information regarding prevention of mosquito population growth as well as the spread transmission of viruses (Murthy, 2013). For example, since the elevation of the CDC alert level, the agency has warned many people of the risk zones using its official website and Twitter handles.
Review of the Existing Policies/ Standards, Regulation and Measures
The existing vector control policies, regulations and measures in Miami-Dade County are designed to reduce adult mosquito density, infections mosquitoes and human biting rate. Additionally, the policies and measures target both adult and larval stages. This section reviews policies and regulations on monitoring and reducing Aedes aegypti mosquitoes in Miami-Date County.
A handful of recent studies regarding health surveillance in Latin America, Asia and Africa have demonstrated that community mobilization can result in reduction mosquito breeding and disease spread (European Centre for Disease Prevention and Control, 2016; Miami-Dade County, n.d.). Following the outbreak, the government has engaged the public in keeping control efforts at high level (Miami-Dade County Emergency Operations Center, 2016). Government and community investment in mosquito prevention and virus prevention plays a critical role in the promotion of public health. Such public health investments would contribute not only to the well-being and health of the residents of Miami-Dade County but also improve the health of Florida and ultimately boost social welfare of all people in the country. Similarly, real-time information regarding mosquito density and Zika or Dengue incidence is achieved in the county through digitized health systems. This policy is achieved by setting up and running a low cost community mosquito density health surveillance system using volunteers in towns and homes, as well as and government-based health surveillance assistants to collate the collected data.
To demonstrate success in tracking mosquito population density, Miami-Dade County should develop new information systems, improve capacity for Big Data collection and data processing, and make good use of the analyzed data to formulate strategic policies (O’Carroll, Yasnoff, Ward, Ripp, & Martin, 2010). Additionally, the government supports a continuum of preventive public health services. It follows that government staff members are continuously trained on the public education and mosquito prevention strategies at community, county and national level (Centers for Disease Control and Prevention, n.d.). Additionally, the county ensures that there are well-functioning health facilities with the capacity to provide public education and high-quality care for the individual infected with the Zika or Dengue virus. Further, the county-based health facilities are equipped with essential mosquito-borne disease supplies such as the yellow fever vaccine. Effective prevention polices and strategies emphasize on improving public health education and the allocating resources to various agencies (Chang, 2016). Well-informed and educated communities are much likely to take responsibility for ensuring that their environment does not favor vector-borne diseases. Similarly, informed and educated communities will help the infected members of the community to seek medical care. Additionally, such communities can take precautions such as ensuring that their properties are clear of stagnant water pools and other breeding areas (Miami-Dade County, n.d.).
Private-Public Partnerships (PPPs) are necessary to strengthen the Florida health system. Effective NGO or donor partnership and government commitment are vital for effective mosquito prevention programs. Most importantly, sustained federal and state commitment provides paired investments of various sectors, including staff empowerment and community education as well as improvement in communication channels (Chang, 2016). In other words, federal support is important in the improvement of a combination of multi-sectorial strategies intended to improve public health in Florida. For example, the government works with the private sector in deploying ground level insecticide sprayers to kill both larval and adult mosquitoes.
Lastly, enhanced national capacity to carry out Aedes aegypti-based research as well as to evaluate and monitor mosquito prevention programs is essential to the success of the government’s fight against mosquito-borne diseases. Mosquito density data are indispensable in the analysis, formulation and implementation of strategic policies and programs intended to progress public health. Furthermore, data are essential in the development of programs that are not only adaptable to various counties but also sustainable for long-term improvement.
Modalities in Reducing Densities of Aedes Aegypti Mosquito
GMO mosquito. The conceptual foundation for the population-replacement paradigm of mosquito-borne vector control is that mosquito-borne diseases such as Zika, Dengue and Chikungunya will be reduced, following the introduction of a genetically modified gene into a mosquito population (Scott, & Morrison, 2013). The gene should be able to induce resistance to the pathogen. The logic is to replace the susceptible Aedes aegypti mosquitoes with a mosquito population that has refractory conspecifics by modifying vector competence, or the Aedes aegypti mosquitoes’ capacity to be infected with and transmit the disease-causing pathogens. Therefore, the eradication of Aedes aegypti mosquitoes is not feasible, and there is no commercially available vaccine for Zika, Dengue and Chikungunya (Fischer, Scott, & Margolis, 2015). Genetically modified mosquitoes provide a feasible method for reducing the density and transmission of mosquito-borne pathogens. As of this writing, the vaccine status for Dengue and Chikungunya were at Phase 3 and Phase 1-2 clinical trials respectively (Fischer, Scott, & Margolis, 2015). In the same line, Zika had no vaccine. The Yellow fever had a licensed vaccine.
Aedes aegypti is the most prevalent vector during mosquito-borne disease outbreaks. The mosquitos are the primary transmitters of the Zika virus. The recent increased incidence and spread of Zika virus in Miami-Dade County has called for amplified attention regarding data collection, surveillance, monitoring, and modalities for reducing the density of the Aedes aegypti mosquitoes. Chikungunya and dengue vaccine are in the process of development. As of this writing, there was no vaccine for the Zika virus. Primary prevention measure was to reduce mosquito exposure, but the existing vector-control modalities were difficult to maintain. The existing vector control as well as monitoring policies and measures in Miami-Dade target both adult and larval stages of Aedes aegypti mosquito development and lessen human biting rate and adult mosquito population density. As aforementioned, the efficiency of vector control measures depends on the ability to reduce mosquito population. The investigation of local mosquito population density is essential because it will help the county, state and federal government mosquito control entities interested in identifying specific population locations for control. Consequently, the county and relevant entities can protect the public and minimize the use of insecticides.