Reduced susceptibility to pyrethroid insecticide treated nets by the malaria vector Anopheles gambiae s.l . in western Uganda

• Published in: Malaria Journal
• Main Authors: Ephraim Tukesiga, John Rubaihayo, Andrew Abaasa
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2008
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/1475-2875-7-92; https://doaj.org/article/34470f3af4ed405db2c3ee778359d692

Abstract Background Pyrethroid insecticide-treated mosquito nets are massively being scaled-up for malaria prevention particularly in children under five years of age and pregnant mothers in sub-Saharan Africa. However, there is serious concern of the likely evolution of widespread pyrethroid resistance in the malaria vector Anopheles gambiae s.l . due to the extensive use of pyrethroid insecticide-treated mosquito nets. The purpose of this study was to ascertain the status of pyrethroid resistance in An. gambiae s.l . in western Uganda. Methods Wild mosquitoes (1–2 days old) were exposed in 10 replicates to new nets impregnated with K-othrine (Deltamethrin 25 mg/m 2 ), Solfac EW50 (Cyfluthrin 50 mg/m 2 ) and Fendona 6SC (Cypermethrin 50 mg/m 2 ) and observed under normal room temperature and humidity (Temperature 24.8°C���27.4°C, Humidity 65.9–45.7). A similar set of mosquitoes collected from the control area 80 km away were exposed to a deltamethrin 25 mg/m 2 impregnated net at the same time and under the same conditions. The 10-year mean KDT 50 and mortality rates for each of the three pyrethroid insecticides were compared using the Student t -test. Results A significant increase in the mean knockdown time (KDT 50 ) and mean mortality rate were observed in almost all cases an indication of reduced susceptibility. The overall results showed a four-fold increase in the mean knockdown time (KDT 50 ) and 1.5-fold decrease in mortality rate across the three pyrethroid insecticides. There was a significant difference in the 10-year mean KDT 50 between deltamethrin and cyfluthrin; deltamethrin and cypermethrin, but no significant difference between cyfluthrin and cypermethrin. The 10-year mean difference in KDT50 for mosquitoes exposed to deltamethrin from the control site was significantly different from that of mosquitoes from the intervention site (p<0.05, t=3.979, 9df). The 10-year mean difference in mortality rate between deltamethrin (84.64%); cyfluthrin (74.18%); cypermethrin (72.19%) and the control ...