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PubMed1956

Susceptibility of malaria vectors to DDT in Greece; laboratory findings.

The authors describe an investigation, started in Greece in the autumn of 1953 and continued during the 1954 malaria-transmission season, to determine the variations in the susceptibility to DDT of the anophelines in different localities, with a view to establishing a point of departure which would make it possible to follow any future changes in susceptibility to this insecticide.The degree of susceptibility of the mosquitos to DDT was assessed numerically by both the technique of topical application of microdoses of the insecticide and the technique devised by Busvine & Nash. The villages of Elos and Asterion (Skála area), the Agoulinitsa area, and the Georgioupolis (Crete) area were chosen for the investigation.The findings disclosed considerable differences in the susceptibility to DDT in the above areas, but showed that, on the whole, the tendency for anophelines to acquire resistance to DDT seemed to be continuing in Greece.

Animals↗
PubMed1956

A malaria-control experiment in the interior of Borneo.

A first experiment on malaria control in the interior of Borneo by spraying with residual insecticides is described. The work was carried out in the isolated, sparsely populated valleys of the Baram River and its tributary, the Tinjar, in northern Sarawak. The experimental area was divided into three parts: a DDT test area, where a 75% suspension of wettable powder was applied at the rate of 2 g of DDT per m(2) of surface; a BHC test area, where a 50% suspension of wettable powder was applied at the rate of 0.10 g of gamma isomer per m(2); and a check area.Entomological investigations made before the spraying operations were started showed that Anopheles leucosphyrus Dönitz, 1901 was the main malaria vector in both the test and the check areas. Out of a total of 7568 A. leucosphyrus dissected, 30 gland infections were detected-a sporozoite-rate of 0.40%. A. barbirostris was found to be a secondary vector throughout the experimental area.THE RESULTS OF INSECTICIDE SPRAYING WERE SATISFACTORY: in the DDT test area, the spleen-rate fell from 51.8% to 25.1%, and the parasite-rate from 35.6% to 1.6%, in 21 months, and a similar reduction in the rates was observed in the BHC test area. In the check area, the spleen- and parasite-rates rose during the period of observations. It is considered that if such a degree of control can be obtained in 21 months, complete eradication can be expected in the near future.Although BHC spraying proved effective, the fact that it has to be repeated every three months makes it impracticable in the interior of Sarawak, where communications are very poor and difficulties of transport very great. DDT spraying, which need only be done twice a year, is therefore to be preferred. The cost of the DDT operations-US$ 0.45 per person protected per year-is comparatively high, owing to the difficulty of communications and to the necessity for spraying not only the village "longhouses", but also the temporary shelters which the semi-nomadic people in the interior of Sarawak build each year in the rice-fields.

Animals↗