Insect vector control

DDT, discovered by Dr. Mueller in Switzerland, and used for insect vector control during World War II, quickly found a place in forestry, as well as agriculture. The material proved highly effective in the control of such insects as the spruce budworm, tussock moth, hemlock looper, and many others. It was widely used in the Northeast for control of the introduced Gypsy moth during these early years. The low toxicity of DDT to mammals made it to appear to be an excellent insecticide for forestry use. It was only after subsequent studies revealed the impact on other species that reservations about its use was raised. 

When DDT was widely used, it was released into the environment in a number of different ways. The spraying of crops, and the spraying of water surfaces and land to control insect vectors of diseases, were major sources of environmental contamination. Waterways were sometimes contaminated with effluents from factories where DDT was used. Sheep-dips containing DDT were discharged into water courses. Thus, it is not surprising that DDT residues became so widespread in the years after the war. It should also be remembered that, because of their stability, DDT residues can be circulated by air masses and ocean currents to reach remote parts of the globe. Very low levels have been detected even in Antarctic snow ... 

For those infectious diseases that are transmitted to humans via insect vectors the onset and decline phases of epidemics are rarely observed other than as a reflections of the seasonal variation in the prevalence of the insect. Rather, the disease is endemic within the population group and has a steady incidence of new cases. Diseases such as these are generally controlled by public health measures and environmental control of the vector with vaccination and immunization being deployed to protect individuals (e.g. yellow fever vaccination). 

All of us have witnessed developments of the past decade when a second world war engulfed most of the civilized world. Insect control was of prime importance to the protection of the armed forces against insect vectors of disease organisms as well as to the pro-... 

The limiting factor in tomato production in the tropics is more apt to be a virus disease than a fungus disease of the foliage. The control of virus disease by control of the insect vector has been investigated in Mexico on potatoes (leaf roll, purple top), tomatoes (several unidentified viruses, one of which perhaps is curly top), and corn (corn stunt). Virus control in this way has been variable but usually negligible. This lack of control perhaps is due to slow kill of the insect vector, or to the continuous entry of the vector into the field. 

Viruses are too small to be seen with conventional microscopy, so they are usually named after the plant In which they were first discovered and the symptoms they cause. Control is restricted to planting virus-free material, the use of resistant varieties, and controlling the insect vectors of the virus. 

WHOPES is currently evaluating seven insecticide products for indoor residual spraying and insecticide treatment of mosquito nets for malaria and/or Chagas vector control, two insect repellents, and two insect growth regulator mosquito larvicides, with ongoing trials in 14 countries. 

Insects were the first major focus of pest control, whether to prevent the destruction of food or fiber crops or to limit the spread of insect vectors of disease. There is little doubt that the use of insecticides had a profound impact on the further development of civilization. The control of anopheline mosquitoes and malarial infection, as well as vectors for typhus. 

At that lime pyre dim m was considered to be the strategic insecticide for the control of mosquitoes and other insect vectors, Japan was the major producer of pyrethrum, with East Africa under active development. The possibility of imports being disrupted in a future war was regarded as a serious risk, as existing supplies of the insecticide were barely adequate for public health uses. 

The chemical is being considered for inclusion or is included in the WHO Pesticide Evaluation Scheme (WHOPES) programme (approval programme for direct appHcation of pesticides to drinking water for control of insect vectors of disease). 

Preliminary evidence suggest that piquerol A (26a) can be a potential resource in the control of Chagas disease (American trypanosomiasis), an endemic illness which afflicts millions of people in Latin America [116]. The causal agent is the protozoan Trypanosoma cruzi, which is transmitted by insect vectors. 

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