Mosquitoes are vectors of malaria and dengue both. Annually there are an estimated 50–100 million cases of dengue fever, and 250,000–500,000 cases of dengue hemorrhagic fever throughout the world. The severity of mosquito-borne diseases is often a function of the amount and extent of rainfall within a region affecting the area in which the larvae can breed. The larval stage of dengue vectors can develop in quite small volumes of water in various man-made containers, such as discarded bottles, vases, and stacks of tires, etc. Management of aquatic environments with predatory fish and reduction of areas suitable for larvae is required to reduce breeding in ponds, canals and other areas of permanent water. The urban environment in many developing countries has deteriorated, with densely packed housing in shanty towns or slums and inadequate drinking-water supplies, garbage collection services, and surface-water drainage. Thus, the habitat has become favorable for the vectors of disease, such as malaria and dengue.
Insects are responsible for the transmission of several extremely harmful diseases suffered by humans including malaria and dengue. Controlling the vector by different techniques is increasingly important as the malarial parasite, Plasmodium spp. continues to develop resistance to drugs. A single bite from an infected female Anopheles mosquito can transmit the disease, with children under 5 years of age being the most susceptible. The control of Anopheline mosquitoes the vectors of malaria is crucial to the prevention of the infection while environmental management and insecticide application are the main methods of controlling the vector to reduce dengue. As the female mosquitoes need to have a blood meal, preventing access to dwellings by having netting across windows and other openings is also crucial, but chemical control is still the main tool to reduce mosquito populations, and thus the transmission of disease. Emphasize school-based programs targeting children and parents to eliminate vector breeding at home and at school.
Effective malaria control programs prevent transmission by promoting personal protection measures and effective vector control strategies and providing appropriate case management with early diagnosis and effective treatment. However, malaria control in complex emergency situations is often difficult because of the breakdown of existing health services and programs, displacement of health care workers and field staff with malaria expertise, movement of non-immune people to endemic areas, and concentrations of people, often already in poor health, in high-risk, high exposure settings. Local health workers may be unaccustomed to the dangers of malaria infection for non-immune older children and adults and must be instructed about timely and adequate diagnosis and treatment of these patients. In areas where mosquitoes bite early in the evening before people go to sleep under nets, the use of insecticide-treated curtains over openings such as windows, doors and eave gaps may provide some protection.
Malaria prevention strategies include vector control and personal protection against mosquito bites, in addition to intermittent preventive treatment during pregnancy to avert severe anemia and low birth weight. Treating nets with a suitable insecticide increases the level of protection: the insecticide kills or repels mosquitoes before they can enter the net or bite the person sleeping under the net. Insecticide treatment of nets provides personal protection for all those who sleep under them. Effective vector control against dengue remains elusive. Currently, no licensed dengue vaccine exists. Therefore, the current main strategy to protect travelers against dengue is limited to avoidance of mosquito bites with the use of insect repellents, protective clothing, and insecticides. Avoidance of litter and containers with stagnant water is also advised. Protective measures need to be taken during the day as Aedes mosquitoes are daytime biters; night-time measures such as insecticide-treated bed nets have only very limited effectiveness.
Clothing reduces the risk of mosquito biting if the cloth is sufficiently thick or loosely fitting. Long sleeves and trousers with stockings may protect the arms and legs, the preferred sites for mosquito bites. Schoolchildren should adhere to these practices whenever possible. Impregnating clothing with chemicals such as permethrin can be especially effective in preventing mosquito bites. Household insecticidal products, namely mosquito coils, pyrethrum space spray and aerosols have been used extensively for personal protection against mosquitoes. Electric vaporizer mats and liquid vaporizers may also be used for this purpose. Repellents are a common means of personal protection against mosquitoes and other biting insects. Permethrin is an effective repellant when impregnated in cloth. At the individual level, encourage each household to adopt routine health measures that will help in the control of mosquito-borne diseases. At the community level, organize “cleanup” campaigns two or more times a year to control the larval habitats of the vectors in public and private areas of the community.
Kill adult mosquitoes by making use of commercially-available safe aerosols (pyrethroid-based). Spray bedrooms including closets, bathrooms, and kitchens for a few seconds and close the rooms for 15-20 minutes. The timing of spray should coincide with the peak biting times of the early morning or late afternoon.
- Intensify efforts to reduce actual or potential larval habitats.
- Cover water containers in the house to prevent fresh egg-laying.
- Have infants sleep under bed nets during the day.
- Wear protective clothing, preferably sprayed with a repellent.
- Use commonly-available repellents during the day time and also make liberal use of mats and coils, etc. during night and day.
School children should be provided with health education on all aspects of dengue fever, i.e. what it is, how it spreads, the role of mosquitoes, how they breed, and how they can be controlled. I now hope that since you know how and why malaria and dengue spread, and persist; and being fully aware of the danger they bring to us and our loved ones, you would now adopt every measure possible to slay the mosquitos and stay safe.