Last data update: May 06, 2024. (Total: 46732 publications since 2009)
Records 1-4 (of 4 Records) |
Query Trace: Churcher TS[original query] |
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A new WHO bottle bioassay method to assess the susceptibility of mosquito vectors to public health insecticides: results from a WHO-coordinated multi-centre study
Corbel V , Kont MD , Ahumada ML , Andréo L , Bayili B , Bayili K , Brooke B , Pinto Caballero JA , Lambert B , Churcher TS , Duchon S , Etang J , Flores AE , Gunasekaran K , Juntarajumnong W , Kirby M , Davies R , Lees RS , Lenhart A , Lima JBP , Martins AJ , Müller P , N'Guessan R , Ngufor C , Praulins G , Quinones M , Raghavendra K , Verma V , Rus AC , Samuel M , Ying KS , Sungvornyothin S , Uragayala S , Velayudhan R , Yadav RS . Parasit Vectors 2023 16 (1) 21 BACKGROUND: The continued spread of insecticide resistance in mosquito vectors of malaria and arboviral diseases may lead to operational failure of insecticide-based interventions if resistance is not monitored and managed efficiently. This study aimed to develop and validate a new WHO glass bottle bioassay method as an alternative to the WHO standard insecticide tube test to monitor mosquito susceptibility to new public health insecticides with particular modes of action, physical properties or both. METHODS: A multi-centre study involving 21 laboratories worldwide generated data on the susceptibility of seven mosquito species (Aedes aegypti, Aedes albopictus, Anopheles gambiae sensu stricto [An. gambiae s.s.], Anopheles funestus, Anopheles stephensi, Anopheles minimus and Anopheles albimanus) to seven public health insecticides in five classes, including pyrethroids (metofluthrin, prallethrin and transfluthrin), neonicotinoids (clothianidin), pyrroles (chlorfenapyr), juvenile hormone mimics (pyriproxyfen) and butenolides (flupyradifurone), in glass bottle assays. The data were analysed using a Bayesian binomial model to determine the concentration-response curves for each insecticide-species combination and to assess the within-bioassay variability in the susceptibility endpoints, namely the concentration that kills 50% and 99% of the test population (LC(50) and LC(99), respectively) and the concentration that inhibits oviposition of the test population by 50% and 99% (OI(50) and OI(99)), to measure mortality and the sterilizing effect, respectively. RESULTS: Overall, about 200,000 mosquitoes were tested with the new bottle bioassay, and LC(50)/LC(99) or OI(50)/OI(99) values were determined for all insecticides. Variation was seen between laboratories in estimates for some mosquito species-insecticide combinations, while other test results were consistent. The variation was generally greater with transfluthrin and flupyradifurone than with the other compounds tested, especially against Anopheles species. Overall, the mean within-bioassay variability in mortality and oviposition inhibition were < 10% for most mosquito species-insecticide combinations. CONCLUSION: Our findings, based on the largest susceptibility dataset ever produced on mosquitoes, showed that the new WHO bottle bioassay is adequate for evaluating mosquito susceptibility to new and promising public health insecticides currently deployed for vector control. The datasets presented in this study have been used recently by the WHO to establish 17 new insecticide discriminating concentrations (DCs) for either Aedes spp. or Anopheles spp. The bottle bioassay and DCs can now be widely used to monitor baseline insecticide susceptibility of wild populations of vectors of malaria and Aedes-borne diseases worldwide. |
Review and meta-analysis of the evidence for choosing between specific pyrethroids for programmatic purposes
Lissenden N , Kont MD , Essandoh J , Ismail HM , Churcher TS , Lambert B , Lenhart A , McCall PJ , Moyes CL , Paine MJI , Praulins G , Weetman D , Lees RS . Insects 2021 12 (9) Pyrethroid resistance is widespread in malaria vectors. However, differential mortality in discriminating dose assays to different pyrethroids is often observed in wild populations. When this occurs, it is unclear if this differential mortality should be interpreted as an indication of differential levels of susceptibility within the pyrethroid class, and if so, if countries should consider selecting one specific pyrethroid for programmatic use over another. A review of evidence from molecular studies, resistance testing with laboratory colonies and wild populations, and mosquito behavioural assays were conducted to answer these questions. Evidence suggested that in areas where pyrethroid resistance exists, different results in insecticide susceptibility assays with specific pyrethroids currently in common use (deltamethrin, permethrin, α-cypermethrin, and λ-cyhalothrin) are not necessarily indicative of an operationally relevant difference in potential performance. Consequently, it is not advisable to use rotation between these pyrethroids as an insecticide-resistance management strategy. Less commonly used pyrethroids (bifenthrin and etofenprox) may have sufficiently different modes of action, though further work is needed to examine how this may apply to insecticide resistance management. |
Anopheles stephensi Mosquitoes as Vectors of Plasmodium vivax and falciparum, Horn of Africa, 2019
Tadesse FG , Ashine T , Teka H , Esayas E , Messenger LA , Chali W , Meerstein-Kessel L , Walker T , Wolde Behaksra S , Lanke K , Heutink R , Jeffries CL , Mekonnen DA , Hailemeskel E , Tebeje SK , Tafesse T , Gashaw A , Tsegaye T , Emiru T , Simon K , Bogale EA , Yohannes G , Kedir S , Shumie G , Sabir SA , Mumba P , Dengela D , Kolaczinski JH , Wilson A , Churcher TS , Chibsa S , Murphy M , Balkew M , Irish S , Drakeley C , Gadisa E , Bousema T . Emerg Infect Dis 2021 27 (2) 603-607 Anopheles stephensi mosquitoes, efficient vectors in parts of Asia and Africa, were found in 75.3% of water sources surveyed and contributed to 80.9% of wild-caught Anopheles mosquitoes in Awash Sebat Kilo, Ethiopia. High susceptibility of these mosquitoes to Plasmodium falciparum and vivax infection presents a challenge for malaria control in the Horn of Africa. |
A diagnostics platform for the integrated mapping, monitoring, and surveillance of neglected tropical diseases: rationale and target product profiles
Solomon AW , Engels D , Bailey RL , Blake IM , Brooker S , Chen JX , Chen JH , Churcher TS , Drakeley CJ , Edwards T , Fenwick A , French M , Gabrielli AF , Grassly NC , Harding-Esch EM , Holland MJ , Koukounari A , Lammie PJ , Leslie J , Mabey DC , Rhajaoui M , Secor WE , Stothard JR , Wei H , Willingham AL , Zhou XN , Peeling RW . PLoS Negl Trop Dis 2012 6 (7) e1746 Control and elimination strategies for trachoma, lymphatic filariasis, onchocerciasis, schistosomiasis, ascariasis, trichuriasis and hookworm infection have striking similarities, including the use of periodic mass drug administration (MDA). Because these diseases tend to be co-endemic in the poorest communities of the poorest countries, such that multiple NTDs are frequently found not just in the same populations but within the same individuals [1], it has been suggested that mapping, treatment, impact monitoring, and post-elimination surveillance could be coordinated to better utilise limited human and financial resources. Although many programmes now distribute multiple anthelmintics simultaneously, progress in integrating mapping [2], [3], [4], monitoring, and surveillance [5] activities has been slow [6]. Ideally, population sampling strategies, fieldwork protocols, and sample types (e.g., blood or urine) could all be harmonised between diseases to increase population compliance, simplify overall survey procedures, and decrease costs. | For each of these diseases, current diagnostic tools are imperfect (Table S1A), especially for areas with low prevalence. A cost-effective strategy for improved tool development would incorporate integration of diagnostic strategies from the outset [7], [8]. |
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