Mosquitoes control measures

S. S. Yamamoto, V. R. Louis, A. Sie, and R. Sauerborn. The effects of zooprophylaxis and other mosquito control measures against malaria in Nouna, Burkina Faso, Malaria Journal, 8, 2009. 

Measures taken to control sources of larval emergence of sanitary pests are limited, and excessive treatments frequently induce the development of resistance in disease-transmitting insects. On the other hand, control measures by individuals are becoming a trend. For example, patients with malaria have decreased by the popularization of Olyset mosquito nets, which were developed by Sumitomo Chemical Co., Ltd. to deal with noctumally-active blood-sucking anopheles. 

Caution Humans are infectious for mosquitoes for at least seventy-two hours after the onset of symptoms, so mosquito control can provide an important measure of control to ensure prevention of secondary Venuzuelan equine encephalitis following either intentional or natural outbreaks of VEE. 

Because of the nondrifting qualities of the granular materials, they can be applied under conditions of greater air movement than fine sprays or dusts. This means that airplanes are not limited to operating a few hours at dawn or dusk but can be used many more hours a day. This in turn should permit more efficient use of airplanes. Each of the above factors should result in lower costs of application of mosquito control materials and make practical the use of control measures over greater areas. 

Out of Doors. Control measures against adult mosquitoes out of doors have been discussed by Ginsburg ( 1), Coveil et al. (P), Russell and Knipe (45), and others. These workers used pyrethrum in oil sprays and were instrumental in reducing malaria or mosquito annoyance. 

A single dose of primaquine (45 mg base) can be used as a control measure to render P falciparum gametocytes noninfective to mosquitoes. This therapy is of no clinical benefit to the patient but will disrupt transmission. 

Several species and populations from other Anopheles complexes have been discriminated based on CHC patterns. Examples include all five species of the An. quad-rimaculus complex (Carlson et al., 1997), some species of the An. maculipennis complex (Phillips et al., 1990a), malaria-vector and non-vector forms of the An. maculates complex (Kittayapong et al., 1990, 1993), and An. Stephensi strains susceptible or resistant to DDT and malathion (Anyanwu et al., 1993, 1997). CHCs have been used in combination with isoenzyme analysis to successfully differentiate populations of An. darlingi (Rosa-Freitas et al., 1992). All these findings demonstrate that hydrocarbon analysis is a powerful tool for distinguishing mosquito species and populations. This is particularly important for disease vectors, since it can facilitate interpretation of epidemiological data and assist implementation of control measures. 

At present, there is no vaccine to protect against dengue. The most effective method of prevention is to eliminate the mosquito that causes the disease. This requires removal of the mosquito breeding sites, a process known as source reduction. Proper disposal of solid waste helps to reduce the collection of water in discarded articles. Other control measures include preventing mosquito bites with screens, protective clothing, and insect repellents in epidemic risk areas, application of insecticide is practiced through an application method known as fogging to decrease the mosquito population. 

Mosquito-transmitted pathogens were not detected in either disaster area, and emergency mosquito control was primarily intended to provide relief from high mosquito densities that hampered recovery efforts. Surveillance after control measures were implemented indicated that mosquito populations had decreased markedly. 

It is important to apply control measures to all horses in a group rather than only treating those that demonstrate clinical signs of fly, mosquito or tick problems. 

M. K. Aikins et al. Attitudes to malaria, traditional practices and bednets (mosquito nets) as vector control measures A comparative study in five West African conntries. J Trop Med Hyg, 97, 81, 1994. 

The value of insecticides in controlling human and animal diseases spread by insects has been dramatic. It has been shown that between 1942 and 1952, the use of DDT in pubHc health measures to control the mosquito vectors of malaria and the human body louse vector of typhus saved five million hves and prevented 100 million illnesses (4). Insecticides have provided the means to control such important human diseases as filariasis transmitted by Culex mosquitoes and onchocerciasis transmitted by Simulium blackflies. 

Biological larvicides have been introduced for malaria and dengue control in many countries. Locally manufactured biological larvicides are available. Personal protection measures have been promoted by control programmes, including the use of insect repellents, mosquito coils, mats and aerosols. Household pesticide use is increasing in India, Indonesia, Sri Lanka and Thailand. 

Malaria is caused by several species of Plasmodium parasites which enter the human bloodstream after penetration of the skin by anopheline mosquitos. Nishina et al. have reported 270 MHz Wand lactate concentration measurements on the blood sera from 20 Nigerians seropositive to Plasmodium, 13 seronegative Nigerians and six healthy Japanese controls. Significantly lower W values and high lactate concentrations were reported for the sera of the malaria-positive group than for the other two groups. 

Investigations on the efficacy of repellents in a static-air apparatus, which measures 9 X 60 cm (Figure 5.4), allow the measurement of spatial repellency and contact avoidance frequency. A potential repellent is made up in a carrier solvent (acetone or hexane), 1 mL of the solution is applied to a 9 cm filter paper (63.6 cm ), and the solvent is allowed to evaporate before testing. A treated filter paper (test compound or solvent control) is then secured to each end of the repellency apparatus. Then, 20-25 adult female mosquitoes are added into the middle of the apparatus, and their distribution is recorded at various time points throughout the experiment. Spatial repellency can be calculated as follows percentage repellency = (number of mosquitoes in the untreated half -number of mosquitoes in the treated half)/(total number of mosquitoes) x 100%. 

Advantages of the static-air repellency chamber are the measurement of mosquito movement in a highly controlled environment, allowance for the quantification of spatial distribution of mosquitoes over time, and determination for residual repellency. Disadvantages of this method include the lack of an attracting source and that some highly volatile and toxic compounds can cause mosquito knockdown or mosquito death. 

Y-tube olfactometers (Figure 6.4) are generally used to measure the level of attraction or repulsion of host-seeking mosquitoes to volatile stimuli in choice experiments. " Clean and conditioned air constantly runs through the tube system to the end of the base leg, where mosquitoes are connected. During stimulus application, mosquitoes are allowed to fly upwind into a decision chamber to choose between a test cage that holds the test stimulus and a control cage with clean air. 

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