Malaria vector control

Since the Expert Committee last considered the chemistry and specifications of pesticides in 1989, 12 pesticide products have been fully evaluated for vector control, mainly for indoor residual spraying and insecticide treatment of mosquito nets for malaria vector control WHO specifications have been published for these products. 

Malaria vector control accounts for 80-90% of total pesticide use for public health purposes. Residual spraying uses the greatest volume of insecticides. However, the treatment of mosquito nets and other materials with pyrethroid inseetieides is becoming an additional important method for personal protection and reduction of transmission of malaria. 

DDT continues to be the pesticide most used in malaria vector control programmes in the Region with no significant decrease in overall quantities, although in some countries use has declined considerably. The introduction of insecticide-treated mosquito nets and the replacement of DDT by synthetic pyrethroids for indoor residual spraying have contributed to an increase in the public health use of pyrethroids. 

Chester, G., N.N. Sabapathy and B.H. WooUen (1992). Exposure and Health Assessment During Application of Lambda-Cyhalothrin for Malaria Vector Control in Pakistan, Bull. World Health Org., 70, 615-619. 

Figure 2. Types and quantities of insecticides applied annually for malaria vector control in Pakistan during 1960-86 year of first report of resistance to each insecticide and incidence of malaria based on SPR ...

D. R. Roberts, Insecticide Repellency in Malaria Vector Control A Position Paper. VBC Report No. 81131, VBC Project, Tropical Disease Control for Development, Arlington, VA Medical Service Corporation International, 1993. 

World Health Organization, The use of DDT in malaria vector control, WHO position statement. Global Malaria Programme, WHO/HTM/GMP/2011,2011. 

The prototypical organochlorine insecticide is DDT. It was first used in World War II for vector control of malaria. The organochlorine insecticides are very stable in the environment. This persistence allows toxic concentrations to build up in nontarget organisms. 

Malaria rates have bounced back, as explained above. Some health specialists have asserted a linkage between global warming and this resurgence.21 But according to world expert Dr. Paul Reiter, former head of Vector Control at the U.S. Centers for Disease Control in Puerto Rico and now at Harvard University s School of Public Health ... 

Most people cannot believe that DDT is still the best pesticide to control malaria vectors, even though its use began nearly sixty years ago. 

DDT (1,1,1 -trichloro-2,2-bis(/i-chlorophenyl)ethane) was first synthesized by Othmar Zeidle in Germany in 1874. Its insecticidal properties were not discovered until 1939 by the Swiss chemist Paul Muller. It was widely used in the Second World War to protect the troops against malaria, typhus and other vector borne diseases (Smith, 1991). After the war, DDT was widely used on agricultural crops and in disease vector control (Van Metre et al., 1997). 

Suroso, T., Sianturi, B., Pramono, B., 2000. Vector control policy in malaria control programme in Indonesia. Proceedings of Workshop on Sustainable Approaches for Pest and Vector Management and Opportunities for Collaboration in Replacing POPs Pesticides, Bangkok, March 6-10, 2000, UNEP/FAO/WHO. 

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. 

DDT is available and used in different formulations (e.g., aerosols, dustable powders, emulsifiable concentrates, granules, wettable powders). It is used mainly to control mosquito-borne malaria. Its use on crops has decreased because of its persistent residues. DDT was extensively used during World War II among Allied troops and certain civilian populations to control insect typhus and malaria vectors, and was extensively used as an agricultural insecticide after 1945. DDT was banned for use in Sweden in 1970 and in the United States in 1972. In view of its large-scale use over the decades, many insect pests may have developed... 

The annual global use of DDT for disease vector control is now running at about 66% (40,000 tons) of the I960 level and is expected to remain constant for the next decade (47) Major DDT resistance exists in about 1% of the area treated for malaria control and although a limited number of organophosphate and carbamate alternatives are available, their use is so much more costly that total DDT replacement seems economically impossible. Many of the less prosperous countries regard DDT as the most important life-saver known to man. Use of the other OC is more limited and resistance to them generally more intractable when it occurs ... 

There has been a major shift in the quantities and types of pesticides used in vector control programmes, especially for malaria control. The number of houses sprayed each year for malaria control has decreased from a high of 15 million in 1964 to 1.6 million in 1997. The house spraying rate (number of houses sprayed per 1000 inhabitants) has also decreased from 100 in 1964 to 9 in 1997. The number of cases of malaria has increased from a low of 241462 in 1964 to just over one million cases in 1997. 

Except for malaria, only limited information is available on the quantities of insecticides used for particular vector-borne disease control programmes and other public health purposes, but it has been observed that large amounts are being used for dengue vector control. 

Vector control for malaria and other mosquito-borne diseases. 

The most reliable study of POPs in breast milk samples from developing countries comes from work carried out by Kunisue and colleagues [103-105,155-157]. Here, samples were collected from across Asia and analyzed within the same laboratory using the same analytical procedures. Their studies revealed that relatively high concentrations of DDT, for example, were found in mothers from Vietnam, China, Cambodia and Malaysia, more than from other countries included in their studies. To compare levels in Asia with other developing countries, selected data from other published studies [103-105,155-164] from the literature have been compiled in Table 5.7. Other countries with elevated levels of DDT in breast milk, as shown in Table 5.7, are Zimbabwe, Mexico and Pakistan, aU countries with a history of widespread usage of DDT in malaria vector and pest control. 

The first organochlorine synthesized was DDT. Although it was first synthesized by Zeidler in 1874, it was not produced or used for many years. Mueller rediscovered DDT in 1939 and won the Nobel Prize for his efforts in 1948. The first major uses for DDT were vector control of typhus and malaria and control of lice and other pests during World War II. 

Vector borne diseases are the major problem in South East Asia region too. About 1 billion people are living in malaria endemic areas with about 3 min cases of malaria annually. Epidemics are common. All basic chemicals are used for vector control. In 1990, DDT was used in 7 countries, but after 1997 only 3 continue to use it against malaria, while Bangladesh reserved DDT only against kala-azar. 

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