Genetic Control

Genetic control refers to any method that reduces an insect’s reproductive or disease-transmitting potential through alteration of its hereditary material. The oldest form of genetic control is sterile insect technology (SIT), a proven strategy in past campaigns against screw worm, tsetse flies, and Mediterranean fruitflies. Unfortunately, when mass hybrid sterility was tried against A. gambiae in Burkina Faso, West Africa, few matings actually took place between the sterile males and wild female anophelines. Producing large numbers of sterile yet competitive male mosquitoes, and successfully releasing them in the wild remain major operational hurdles.

First predicted decades ago by Curtis (Curtis, 1968), genetically modified mosquitoes are now another potential means of vector control. The reasoning is as follows. Since only some anopheline mosquitoes transmit malaria, genes encoding the nontransmitting phenotype, or genes that prevent malaria parasites from developing within mosquitoes altogether, could be inserted into vector genomes (Collins, 1994; James et al., 1999). The feasibility of this approach was recently shown when a synthetic gene inserted into A. stephensi almost fully prevented its ability to transmit a strain of rodent malaria (Ito et al., 2002). However, the same practical obstacle facing SIT—namely, the rapid replacement of native mosquito populations—affects genetically modified mosquitoes. Concerns also have been raised about the fitness of genetically modified mosquitoes, the negative consequences of unstable genetic modifications, and public reservations regarding deployment of genetically altered organisms (Clarke, 2002).

TREATMENT AND CHEMOPREVENTION

The primary aim of malaria treatment is saving lives. Prompt, effective treatment in the early stages of falciparum malaria reduces the risk of death as much as 50-fold, whereas effective treatment after progression to severe illness produces only a five-fold reduction in the risk of dying (White, 1999). However, malaria treatment also can reduce malaria transmission in endemic areas. This section reviews the role of treatment as a control measure capable of reducing malaria transmission, as well as past and present chemoprevention strategies in residents of malaria-endemic areas. (See Chapter 9 for more detailed information regarding antimalarial drugs, drug resistance, and treatment protocols.)

Antimalarials and Reduction of Malaria Transmission

A key objective of many early studies of widespread antimalarial distribution was interrupting malaria transmission (Greenwood, 2004). Two approaches were tried: treatment of symptomatic cases; and mass drug



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