Bio-efficacy of deltamethrin based durable wall lining against wild populations of Anopheles gambiae s.l. in Northern Tanzania

Abstract

BackgroundIndoor residual spraying (IRS) is one of the preferred tools used for control of malaria in many settings in the world. However, this control tool still faces challenges that include lack of long lasting active ingredient, limited number of well-trained personal, and need of repeated treatment which increases operational costs and reduces acceptability by residents. As a result there is need to develop and validate other methods which can complement the existing controls. The current study compared the bio-efficacy of durable wall lining (DL) (treated with deltamethrin 265 mg/m2) and IRS (with deltamethrin 5% WP at 20 mg/m2) on indoor mosquitoes densities and biting behaviour of mosquitoes in comparison with control houses without either DL or IRS.MethodsA study with two treatment arms and a control was conducted in Magugu ward, Northern Tanzania. Overall, a total of 60 houses were selected for the study with 20 houses per treatment arm and control. From each arm and control five houses were selected for mosquitoes trapping. Mosquitoes were sampled from 18:00 to 07:00 hourly every month for a period of 6 months. Mosquitoes were sampled using CDC miniature light traps.ResultsA total of 14,400 female wild mosquitoes were used for contact bioassays in the control arm. 20 houses were sprayed, additionally walls of 20 houses were installed with wall liners, and walls of 20 unsprayed houses were used as control. Also, a total of 946 mosquitoes were sampled with traps in 60 houses during the hourly sampling for 6 months. A total of 3000 unfed females of An. gambiae s.l. wild population raised from larvae were collected from natural habitats in the same village for bioassays. The decline in indoor mosquitoes densities observed in this study did not lead to a shift in the biting cycles (P = 0.712). The number of mosquitoes caught indoors in houses with DL and IRS was significantly lower (P < 0.001) compared to control houses. When the comparisons were done between DL and IRS houses, the densities were significantly lower in DL houses compared to IRS houses (P = 0.021). In the DL installed houses, indoor mosquito density declined notably and sustained throughout the 6 months of the study. However, in those houses sprayed with deltamethrin 5% WP (PALI™5 WP), the density noted to start to increase within four months after spraying(do you mean to say that the densities declined up to 4 months post spraying and thereafter increased.ConclusionsConsidering the efficacy duration of DL against IRS with deltamethrin 5% WP on mosquito densities decline indoors. The results of this study suggest that DL is more effective in malaria control as its efficacy lasted more than that of IRS.

Novel Indoor Residual Spray Insecticide With Extended Mortality Effect: A Case of SumiShield 50WG Against Wild Resistant Populations of Anopheles arabiensis in Northern Tanzania

“…arabiensis . These findings demonstrate a better efficacy of SumiShield 50WG than that previously observed in studies with pyrethroids, organophosphates, carbamates, and organophosphates 5 , 13 , 16 , 38 – 40 . The efficacy of SumiShield 50WG against wild populations of An.…”

“…The bio-efficacy and residual effect of SumiShield 50WG reported from this field study in Tanzania has shown that the product retains maximum mortality efficacy for 6 months while other IRS compounds used in Tanzania were found to have sharply decreased mortality from the fourth to the sixth month 5 , 29 , 32 – 34 , 40 . Therefore, SumiShield 50WG provides the potential for longer residual protection as it consistently maintains its residual activity once applied.…”

“…Despite the general decline in malaria transmission, malaria remains a major cause of morbidity and mortality in many tropical countries including Tanzania 1 , 2 . Malaria vector control campaigns have been advocating the use of indoor residual spray (IRS) and long-lasting insecticidal bed nets (LLINs) to reduce malaria transmission 3 – 5 . The scale-up of LLINs in Tanzania has been successful, with coverage of 75% and up to 100% in some parts of the country, mostly in the Lake Zone regions (Kagera, Mara, Mwanza, and Shinyanga) 6 – 8 .…”

Dynamics and monitoring of insecticide resistance in malaria vectors across mainland Tanzania from 1997 to 2017: a systematic review

“…gambiae s.l.–1 Kdr mutation[25]2013/2014 An. gambiae s.l.Permethrin, deltamethrin, lambdacyhalothrin, DDT, bendiocarb and pirimiphos methyl1Susceptibility[26]2012/2014 An. gambiae s.l.Permethrin, deltamethrin, DDT1Susceptibility[11]2015 An.…”

Insecticide-treated durable wall lining (ITWL): future prospects for control of malaria and other vector-borne diseases

“…1 ). Initial small-scale studies across multiple African and Asian countries demonstrated consistently high levels of user acceptability, entomological efficacy and no significant loss of insecticidal activity over 1 year of household use [ 53 , 54 ]. However, no phase III evaluation of this product was ever conducted due to the emergence of widespread pyrethroid resistance among vector populations across sub-Saharan Africa [ 6 , 7 ].…”