Pyrethroid Resistance in a Major African Malaria Vector Anopheles arabiensis from Mamfene; Northern KwaZulu-Natal; South Africa

A population of Anopheles arabiensis; a major malaria vector in South Africa; was collected during 2005 from inside sprayed houses in Mamfene; northern KwaZulu-Natal; South Africa; using window exit traps. None of these specimens (n = 300 females) was found to be infected with Plasmodium falciparum. Insecticide susceptibility assays on 2-3 day old F1 progeny usingWHOsusceptibility kits revealed 100susceptibility to bendiocarb; resistance to deltamethrin (95.91) was suspected; while resistance to permethrin (78.05) was confirmed. The knockdown resistant (kdr) genotype was not found in the surviving mosquitoes. Biochemical analysis using enzyme assays showed elevated levels of monooxygenase that correlated with the permethrin bioassay data. While elevated levels of non-specific esterase were found in some families (11/12 for a- and 6/12 for Beta-esterases); the data did not show any correlation with the permethrin bioassay. Analysis of permethrin and bendiocarb tolerant lines; selected in the laboratory to characterise biochemical resistance profiles; showed increased levels of non-specific esterase and monooxygenase activity in the case of the permethrin-selected cohorts; and elevated glutathione S-transferases and general esterases in that of the bendiocarb-selected line. Synergist assays; using piperonyl butoxide; confirmed the involvement of monooxygenase and glutathione S-transferase in pyrethroid and bendiocarb resistance. This study underlines the importance of routine surveillance for insecticide susceptibility in wild anopheline populations

Donnees recentes sur la sensibilite d'Anopheles arabiensis et d'Anopheles funestus aux pyrethrinoides et au DDT sur les Hautes Terres Centrales de Madagascar -Resultats preliminaires montrant une absence de la mutation kdr chez An. arabiensis

"Recent observations on the sensitivity to pyrethroids and DDT of Anopheles arabiensis and Anopheles funestus in the central Highlands of Madagascar; preliminary resultson the absence of the kdr mutation in An. arabiensis"". Anopheles arabiensis and Anopheles funestus are the principal vectors of malaria on the central highlands of Madagascar. These two species of mosquito are directly or indirectly the targets of indoor insecticide spread. The survey of the susceptibility of these two vectors to insecticides is essential specifying for the anti-vectorial current directives and for the future programs. This paper describes : - the recent tests of susceptibility and the study of the knock-down effect of four pyrethroids (deltamethrin 0.50"

Efficacite et remanance de deux pyrethrinoides en impregnation de tulle moustiquaire sur deux moustiques du Sud-Cameroun

Des bio-essais ont permis d'evaluer les reactions immediates et retardees d'anopheles gambiae; souche Yaounde et de culex quinquefasciatus; souche Yaounde et souche Douala. La mise en contact force des moustiques a dure trois minutes. L'impregnation du tulle moustiquaire a ete effectuee avec la deltamethrine ou la permethrine; chacune avec trois concentrations differentes. Des resultats obtenus avec les moustiques testes; il ressort que la deltamethrine est un insecticide sensiblement superieur tant pour l'efficacite que pour la remanence. La deltamethrine est a preferer a la permethrine pour l'impregnation des moustiquaires dans le Sud-Cameroun

Influence of deltamethrin treatment of bed nets on malaria transmission in the Kou Valley, Burkina Faso

A 3-year entomological study was carried out on the transmission of malaria in a village of 900 inhabitants in a rice-growing area of Burkina Faso. In the study area inhabitants use bed nets to protect themselves from mosquito bites. In the first year of the study, baseline data were collected; in the second year, the village was divided in two parts and all the bed nets in the southern part were sprayed with deltamethrin (25 mg/m2); and in the third year, all the bed nets in both parts of the village were sprayed. The inoculation rate was estimated by hand collection of mosquitos on human volunteers who were not protected by bed nets. The overall inoculation rate in the first year was 55 infected bites per person and was higher in the southern than in the northern part of the village. During the second year the rate increased to 70 bites per person on average (but was slightly lower than this in the southern part of the village). During the third year, the inoculation rate fell to three infected bites per year, i.e., a reduction of 94% compared with the first year. This reduction arose primarily because of a marked decrease in the sporozoitic index and a lower density of vectors. Thus, use of pyrethroid-impregnated bed nets by all members of the community appears to be a major tool in preventing transmission of malaria

Control of tsetse and trypanosomiasis transmission in Uganda by a application of lambdacyhalothrin

The pyrethroid insecticide lambda-cyhalothrin was evaluated in field trials against Glossina f. fuscipes and sleeping sickness transmission in lyolwa sub-county; Tororo District; Eastern Uganda. The isnecticide was applied selectively to the resting-sites of tsetse; by bush-spraying; using 10vettable powder (10WP) formulation at an application rate of 11.6 g.a.i/ha over an area of 32km 2;215 pyramidal traps treated with lambda-cyhalothrin which eliminated tsetse within 1-2 months; whereas G.f.fuscipes persisted at very low density in part of the area treated with 2ED lambda-cyhalothrin. In both treated areas; the numbers of human sleeping sickness cases fell to no more than one per month; compared with four to twelve per month previously. The overall rate of cattle trypanosomiasis (T.brucei and T.vivax) was also reduced slightly. Insecticide-treatedtraps remained fully effective for at least 6 months under field conditions; and catches were reduced 20-90-fold. These results in the control of tsetse and trypanosomiasis transmission lead us to recommend lambda-cyhalothrin for tsetse control operations