EARLY theories of health and medicine have posited mysterious origins for numerous diseases as scientists have tried various experiments and theories in order to curtail the spread of infectious illnesses.

In the 18th century mosquito-borne diseases such as malaria were thought to be caused by bad air (“mala aria”) from marshlands, however in later years other scientists made new discoveries and realised that infectious illnesses were caused by a germ, giving rise to the germ theory. This theory of an infectious disease being caused by a germ was the construct for a new approach to managing infectious diseases globally. However, as time evolves, more empirical evidence has been found and used in various fields of medicine to reduce the public health burden through the implementation of evidence-based interventions and strategies.

Mosquito-borne diseases have continued to be a grave global public health issue, contributing to considerable economic cost in many countries. Diseases such as malaria, yellow fever and dengue are endemic in most of the tropical and subtropical parts of the world, and since January 2023 there have been more than 1,000 confirmed cases of dengue in Jamaica. Many Caribbean states have also experienced increased numbers of mosquito-borne diseases since the beginning of the year, despite the implementation of numerous mosquito-control strategies.

Strengthen entomological capacities through better use of environmental data

Many factors such as climate change, unplanned urbanisation, human behaviour, and globalisation are contributing to the emergence and re-emergence of mosquito-borne diseases in recent years. Using data captured from environmental surveillance is therefore necessary to combat these challenges and ensure the effective implementation of mosquito-control programmes. Mosquito-control programmes devoid of scientifically gathered data are often plagued with repeated problems and ineffective use of resources. Constant gathering and use of data, such as the mosquito index — in particular breteau and container indices), identification of potential and common sites for mosquito breeding, distribution of wetlands, levels of precipitation, atmospheric temperatures and wind speed — allow for implementation of effective strategies necessary to curtail incidents of mosquito-borne diseases. Dengue fever is a major public health problem throughout most tropical and some subtropical regions worldwide, and so is Zika fever and other arboviral infections such as chikungunya. Malaria is endemic to many Caribbean countries and remains a major killer of children, particularly in sub-Saharan Africa where it results in the death of a child every two minutes. Environmental data, if captured and used properly, can strengthen entomological capacities as the information provides an understanding of patterns, causes and effects of mosquito-borne diseases, as well as areas that require priority attention to avert possible outbreaks of mosquito-borne diseases.

Common failings of mosquito-control programmes:

1. Failure to capture and incorporate environmental data such as atmospheric temperatures, levels of precipitation, wind speed and land cover conditions when planning and implementing mosquito-control strategies.

The atmospheric temperature of an area and land cover conditions are useful pieces of information that can be used to predict the likelihood of mosquito proliferation atmospheric temperatures within particular ranges that encourage the reproduction of mosquitoes. Female mosquitoes cannot develop eggs at temperatures below 50°F (10°C). Atmospheric temperatures of 27-32 °C are favourable for the rapid completion of the mosquito life cycle. The condition of land cover also has a direct bearing on the effectiveness of mosquito-control strategies. In urban areas of Brazil, environmental surveillance data shows a positive relationship between environmental temperatures, land cover, and Aedes agypti mosquito breeding. In Brazil, roofs made of asbestos and concrete have also been proven to provide favourable sites for Aedes aeygptyi breeding. Mosquitoes are biting nuisances, resulting in cases of urticarial rashes and other dermatological infections. Effective programmes are therefore necessary for a multiplicity of reasons.

2. Failure to adequately incorporate and use technology when implementing mosquito-control strategies.

It is a proven fact that GIS (geographic information systems) technology has significantly transformed mosquito-control strategies in many countries worldwide. GIS enables the visualisation and analysis of geographical data, thereby providing valuable insights into mosquito population dynamics. GIS can be used to map mosquito larvae and adult habitats as well as human populations which are at a greater risk for mosquito exposure and mosquito-borne infections. Through GIS mapping, areas of priority that require ongoing entomological management can be easily identified. Using GIS technology permits the development and use of mosquito-control treatment area maps and leads to better schedules for mosquito-control activities — all of which are necessary to ensure proper management and use of programme resources.

3. Relaxing mosquito-control activities in dry months.

At no time should mosquito-control activities be relaxed. While it is a known fact that some species of female mosquitoes lay their eggs above the waterline in water-holding containers it is also proven scientifically that other species will lay their eggs on damp soil — even when there is no flooding. Water levels on land of 12.7 mm (1/2 inch) or above can cause mosquito eggs to hatch. GIS technology provides data that enables consistent monitoring for timely and proactive implementation of larviciding and adulticiding activities so as to avert increases in indices.

4. Failure to use evidenced-based data in conducting adultidicing (fogging) activities.

If desired mosquito-control targets, such as those set by the World Health Organization, are to be met then the natural behaviour of a particular mosquito specie must be considered. For example, research shows that the Aedes aegyptyi mosquito is diurnal and engages in peak biting activities in the environment approximately two hours after sunrise and several hours before sunset. It is therefore advisable that for rapid reduction in adult mosquito population, adulticiding activities should be done in the same area at dusk and at dawn; wind speed should also be less than 1.6 km/h. Wind speed directly impacts the proper dispersal and effectiveness of insecticides in the atmosphere.

What else is needed for effective mosquito control?

• Mosquito-control programmes require increased investment to strengthen programmatic capacity. The provision of tools and equipment that capture environmental data is mandatory for the success of any mosquito-control programme. Installation and monitoring of rain gauges throughout communities will provide data to identify when increased mosquito control activities are required. Installation and monitoring of light traps and Ovi traps provide useful data to guide mosquito-control activities in areas such as ports of entry. According to International Health Regulations (IHR), a minimum of 400-meter zones around seaports, airports, and ground crossings are to be maintained as a vector-free zone so that the transmission risk of pathogens imported with vectors or reservoirs can be minimised or nullified.

• The use of chemicals, including insecticides, is the first line control for mosquitoes all over the world, however many of these chemicals are known to have damaging effects on the environment. To minimise the need for the use of chemicals in mosquito control, consistent education strategies geared towards environmental sanitation are required. Capturing and using environmental data — such as the sanitary status of a particular community — will identify conditions which are likely to support mosquito-breeding activities in domestic and other settings so that strategies geared towards source reduction can be implemented in a timely manner. Strategies such as community clean-up days implemented ahead of expected seasons of rainfall can prove useful in reducing mosquito indices.

It is a proven fact that much has been done to curtail the incidence and prevalence of mosquito-borne diseases in Jamaica. Amidst these achievements, better use of environmental data as a tool for reducing mosquito-borne diseases can benefit the nation vastly by ensuring more efficient use of resources and reduction of many public health burdens associated with mosquito-borne diseases nationally.

Dr Karlene Atkinson is a public health specialist and lecturer at the School of Public Health, University of Technology, Jamaica.