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Fairbanks EL, Saeung M, Pongsiri A, Vajda E, Wang Y, McIver DJ, Richardson JH, Tatarsky A, Lobo NF, Moore SJ, Ponlawat A, Chareonviriyaphap T, Ross A, Chitnis N. Inference for entomological semi-field experiments: Fitting a mathematical model assessing personal and community protection of vector-control interventions. Comput Biol Med 2024; 168:107716. [PMID: 38039890 DOI: 10.1016/j.compbiomed.2023.107716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/19/2023] [Accepted: 11/15/2023] [Indexed: 12/03/2023]
Abstract
The effectiveness of vector-control tools is often assessed by experiments as a reduction in mosquito landings using human landing catches (HLCs). However, HLCs alone only quantify a single characteristic and therefore do not provide information on the overall impacts of the intervention product. Using data from a recent semi-field study which used time-stratified HLCs, aspiration of non-landing mosquitoes, and blood feeding, we suggest a Bayesian inference approach for fitting such data to a stochastic model. This model considers both personal protection, through a reduction in biting, and community protection, from mosquito mortality and disarming (prolonged inhibition of blood feeding). Parameter estimates are then used to predict the reduction of vectorial capacity induced by etofenpox-treated clothing, picaridin topical repellents, transfluthrin spatial repellents and metofluthrin spatial repellents, as well as combined interventions for Plasmodium falciparum malaria in Anopleles minimus. Overall, all interventions had both personal and community effects, preventing biting and killing or disarming mosquitoes. This led to large estimated reductions in the vectorial capacity, with substantial impact even at low coverage. As the interventions aged, fewer mosquitoes were killed; however the impact of some interventions changed from killing to disarming mosquitoes. Overall, this inference method allows for additional modes of action, rather than just reduction in biting, to be parameterised and highlights the tools assessed as promising malaria interventions.
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Affiliation(s)
- Emma L Fairbanks
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland.
| | - Manop Saeung
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Arissara Pongsiri
- Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand
| | - Elodie Vajda
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland; Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Yuqian Wang
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
| | - David J McIver
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Allison Tatarsky
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Sarah J Moore
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland; Vector Control Product Testing Unit, Ifakara Health Institute, Bagamoyo, United Republic of Tanzania; The Nelson Mandela, African Institution of Science and Technology, School of Life Sciences and Bio Engineering, Tengeru, Arusha, United Republic of Tanzania
| | - Alongkot Ponlawat
- Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand
| | | | - Amanda Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
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Chen I, Doum D, Mannion K, Hustedt J, Sovannaroth S, McIver D, Macdonald M, Lobo N, Tatarsky A, Handley MA, Neukom J. Applying the COM-B behaviour change model to a pilot study delivering volatile pyrethroid spatial repellents and insecticide-treated clothing to forest-exposed populations in Mondulkiri Province, Cambodia. Malar J 2023; 22:251. [PMID: 37658337 PMCID: PMC10472618 DOI: 10.1186/s12936-023-04685-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 08/22/2023] [Indexed: 09/03/2023] Open
Abstract
BACKGROUND Southeast Asia is making tremendous progress towards their 2030 malaria elimination goal but needs new interventions to stop forest malaria. This study trials two new vector control tools, a volatile pyrethroid spatial repellent (VPSR) and insecticide-treated clothing (ITC), amongst forest-exposed populations in Mondulkiri Province Cambodia to inform their potential use for eliminating forest malaria. METHODS 21 forest-exposed individuals were given a questionnaire on their perceptions of malaria and preventive practices used, after which they trialed two products sequentially. Clothes was treated with ITC by the study team. Mixed methods were used to understand their experience, attitudes, and preferences regarding the products trialed. Quantitative data was summarized and qualitative insights were analysed using thematic analysis, applying the Capability, Opportunity, and Motivation Behaviour Change (COM-B) model and Behaviour Change Wheel Framework to identify intervention functions to support tailored product rollout amongst these populations. RESULTS Study participants reported a need for protection from mosquito bites in outdoor and forest-exposed settings and perceived both products trialed to be effective for this purpose. The VPSR product was preferred when travel was not required, whereas ITC was preferred for ease of use when going to the forest, especially in rainy conditions. COM-B analysis identified that key enablers for use of both products included their perceived efficacy and ease of use, which required no skill or preparation. For barriers to use, the odour of ITC was sometimes perceived as being toxic, as well as its inability to protect uncovered skin from mosquito bites, while the perceived usefulness of the VPSR product trialed was limited by its water sensitivity in rainy forest settings. Intervention components to encourage appropriate and sustained use of these products include education about how to use these products and what to expect, persuasion to use them from community leaders and targeted channels, and enablement to facilitate convenient and affordable access. CONCLUSION The rollout of VPSRs and ITC amongst forest-exposed populations can be useful for eliminating malaria in Southeast Asia. Study findings can be applied to increase product uptake among forest exposed populations in Cambodia, while manufacturers can aim to develop products that are rainproof, easy to use in forest settings, and have favourable odour profiles to target users.
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Affiliation(s)
- Ingrid Chen
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA.
| | - Dyna Doum
- Health Forefront Organization, Phnom Penh, Cambodia
| | - Kylie Mannion
- Menzies School of Health Research, Charles Darwin University, Casuarina, Australia
| | - John Hustedt
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Siv Sovannaroth
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - David McIver
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Neil Lobo
- University of Notre Dame, Notre Dame, IN, USA
| | - Allison Tatarsky
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Margaret A Handley
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Josselyn Neukom
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
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Swai JK, Kibondo UA, Ntabaliba WS, Ngoyani HA, Makungwa NO, Mseka AP, Chura MR, Mascari TM, Moore SJ. CDC light traps underestimate the protective efficacy of an indoor spatial repellent against bites from wild Anopheles arabiensis mosquitoes in Tanzania. Malar J 2023; 22:141. [PMID: 37120518 PMCID: PMC10148989 DOI: 10.1186/s12936-023-04568-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 04/20/2023] [Indexed: 05/01/2023] Open
Abstract
BACKGROUND Methods for evaluating efficacy of core malaria interventions in experimental and operational settings are well established but gaps exist for spatial repellents (SR). The objective of this study was to compare three different techniques: (1) collection of blood-fed mosquitoes (feeding), (2) human landing catch (HLC), and (3) CDC light trap (CDC-LT) collections for measuring the indoor protective efficacy (PE) of the volatile pyrethroid SR product Mosquito Shield™ METHODS: The PE of Mosquito Shield™ against a wild population of pyrethroid-resistant Anopheles arabiensis mosquitoes was determined via feeding, HLC, or CDC-LT using four simultaneous 3 by 3 Latin squares (LS) run using 12 experimental huts in Tanzania. On any given night each technique was assigned to two huts with control and two huts with treatment. The LS were run twice over 18 nights to give a sample size of 72 replicates for each technique. Data were analysed by negative binomial regression. RESULTS The PE of Mosquito Shield™ measured as feeding inhibition was 84% (95% confidence interval (CI) 58-94% [Incidence Rate Ratio (IRR) 0.16 (0.06-0.42), p < 0.001]; landing inhibition 77% [64-86%, (IRR 0.23 (0.14-0.36) p < 0.001]; and reduction in numbers collected by CDC-LT 30% (0-56%) [IRR 0.70 (0.44-1.0) p = 0.160]. Analysis of the agreement of the PE measured by each technique relative to HLC indicated no statistical difference in PE measured by feeding inhibition and landing inhibition [IRR 0.73 (0.25-2.12) p = 0.568], but a significant difference in PE measured by CDC-LT and landing inhibition [IRR 3.13 (1.57-6.26) p = 0.001]. CONCLUSION HLC gave a similar estimate of PE of Mosquito Shield™ against An. arabiensis mosquitoes when compared to measuring blood-feeding directly, while CDC-LT underestimated PE relative to the other techniques. The results of this study indicate that CDC-LT could not effectively estimate PE of the indoor spatial repellent in this setting. It is critical to first evaluate the use of CDC-LT (and other tools) in local settings prior to their use in entomological studies when evaluating the impact of indoor SR to ensure that they reflect the true PE of the intervention.
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Affiliation(s)
- Johnson Kyeba Swai
- Vector Control Product Testing unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo, Tanzania.
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Ummi Abdul Kibondo
- Vector Control Product Testing unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo, Tanzania
| | - Watson Samuel Ntabaliba
- Vector Control Product Testing unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo, Tanzania
| | - Hassan Ahamad Ngoyani
- Vector Control Product Testing unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo, Tanzania
| | - Noely Otto Makungwa
- Vector Control Product Testing unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo, Tanzania
| | - Antony Pius Mseka
- Vector Control Product Testing unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo, Tanzania
| | | | | | - Sarah Jane Moore
- Vector Control Product Testing unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo, Tanzania
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
- The Nelson Mandela, African Institution of Science and Technology, School of Life Sciences and Bio Engineering, Tengeru, Arusha, United Republic of Tanzania
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Tambwe MM, Kibondo UA, Odufuwa OG, Moore J, Mpelepele A, Mashauri R, Saddler A, Moore SJ. Human landing catches provide a useful measure of protective efficacy for the evaluation of volatile pyrethroid spatial repellents. Parasit Vectors 2023; 16:90. [PMID: 36882842 PMCID: PMC9993701 DOI: 10.1186/s13071-023-05685-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 01/25/2023] [Indexed: 03/09/2023] Open
Abstract
BACKGROUND The human landing catch (HLC) method, in which human volunteers collect mosquitoes that land on them before they can bite, is used to quantify human exposure to mosquito vectors of disease. Comparing HLCs in the presence and absence of interventions such as repellents is often used to measure protective efficacy (PE). Some repellents have multiple actions, including feeding inhibition, whereby mosquitoes may be unable to bite even if they land on a host. A comparison was made between the PE of the volatile pyrethroid spatial repellent (VPSR) transfluthrin determined using a landing method (HLC) and a biting method (allowing the mosquitoes that landed to blood-feed) to evaluate whether HLC is a suitable method for the estimation of the personal PE of a VPSR. METHODS A fully balanced, two-arm crossover design study was conducted using a 6 × 6 × 2-m netted cage within a semi-field system. Hessian strips (4 m × 0.1 m) treated with a 5-, 10-, 15-, or 20-g dose of transfluthrin were evaluated against a paired negative control for three strains of laboratory-reared Anopheles and Aedes aegypti mosquitoes. Six replicates were performed per dose using either the landing or the biting method. The number of recaptured mosquitoes was analysed by negative binomial regression, and the PEs calculated using the two methods were compared by Bland-Altman plots. RESULTS For Anopheles, fewer mosquitoes blood-fed in the biting arm than landed in the landing arm (incidence rate ratio = 0.87, 95% confidence interval 0.81-0.93, P < 0.001). For Ae. aegypti, biting was overestimated by around 37% with the landing method (incidence rate ratio = 0.63, 95% confidence interval 0.57-0.70, P = 0.001). However, the PEs calculated for each method were in close agreement when tested by the Bland Altman plot. CONCLUSIONS The HLC method led to underestimation of mosquito feeding inhibition as a mode of action of transfluthrin, and there were species- and dose-dependent differences in the relationship between landing and biting. However, the estimated PEs were similar between the two methods. The results of this study indicate that HLC can be used as a proxy for personal PE for the evaluation of a VPSR, especially when the difficulties associated with enumerating blood-fed mosquitoes in a field setting are taken into consideration.
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Affiliation(s)
- Mgeni Mohamed Tambwe
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania. .,Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwill, Basel, Switzerland. .,University of Basel, Petersplatz 1, 4001, Basel, Switzerland.
| | - Ummi Abdul Kibondo
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Olukayode Ganiu Odufuwa
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania.,Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwill, Basel, Switzerland.,University of Basel, Petersplatz 1, 4001, Basel, Switzerland.,London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Jason Moore
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania.,Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwill, Basel, Switzerland.,University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Ahmed Mpelepele
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Rajabu Mashauri
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | | | - Sarah Jane Moore
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania.,Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwill, Basel, Switzerland.,University of Basel, Petersplatz 1, 4001, Basel, Switzerland.,Nelson Mandela African Institution of Science and Technology (NM-AIST), P.O. Box 447, Tengeru, Tanzania
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Tambwe MM, Moore S, Hofer L, Kibondo UA, Saddler A. Transfluthrin eave-positioned targeted insecticide (EPTI) reduces human landing rate (HLR) of pyrethroid resistant and susceptible malaria vectors in a semi-field simulated peridomestic space. Malar J 2021; 20:357. [PMID: 34461911 DOI: 10.1186/s12936-021-03880-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 08/15/2021] [Indexed: 02/07/2023] Open
Abstract
Background Volatile pyrethroids (VPs) are proven to reduce human–vector contact for mosquito vectors. With increasing resistance to pyrethroids in mosquitoes, the efficacy of VPs, such as transfluthrin, may be compromised. Therefore, experiments were conducted to determine if the efficacy of transfluthrin eave-positioned targeted insecticide (EPTI) depends on the resistance status of malaria vectors. Methods Ribbons treated with 5.25 g transfluthrin or untreated controls were used around the eaves of an experimental hut as EPTI inside a semi-field system. Mosquito strains with different levels of pyrethroid resistance were released simultaneously, recaptured by means of human landing catches (HLCs) and monitored for 24-h mortality. Technical-grade (TG) transfluthrin was used, followed by emulsifiable concentrate (EC) transfluthrin and additional mosquito strains. Generalized linear mixed models with binomial distribution were used to determine the impact of transfluthrin and mosquito strain on mosquito landing rates and 24-h mortality. Results EPTI treated with 5.25 g of either TG or EC transfluthrin significantly reduced HLR of all susceptible and resistant Anopheles mosquitoes (Odds Ratio (OR) ranging from 0.14 (95% Confidence Interval (CI) [0.11–0.17], P < 0.001) to 0.57, (CI [0.42–0.78] P < 0.001). Both TG and EC EPTI had less impact on landing for the resistant Anopheles arabiensis (Mbita strain) compared to the susceptible Anopheles gambiae (Ifakara strain) (OR 1.50 [95% CI 1.18–1.91] P < 0.001) and (OR 1.67 [95% CI 1.29–2.17] P < 0.001), respectively. The EC EPTI also had less impact on the resistant An. arabiensis (Kingani strain) (OR 2.29 [95% CI 1.78–2.94] P < 0.001) compared to the control however the TG EPTI was equally effective against the resistant Kingani strain and susceptible Ifakara strain (OR 1.03 [95% CI 0.82–1.32] P = 0.75). Finally the EC EPTI was equally effective against the susceptible An. gambiae (Kisumu strain) and the resistant An. gambiae (Kisumu-kdr strain) (OR 0.98 [95% CI 0.74–1.30] P = 0.90). Conclusions Transfluthrin-treated EPTI could be useful in areas with pyrethroid-resistant mosquitoes, but it remains unclear whether stronger resistance to pyrethroids will undermine the efficacy of transfluthrin. At this dosage, transfluthrin EPTI cannot be used to kill exposed mosquitoes. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03880-2.
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Yang X, Zhou Y, Sun Y, Liu J, Jiang D. Multiple insecticide resistance and associated mechanisms to volatile pyrethroid in an Aedes albopictus population collected in southern China. Pestic Biochem Physiol 2021; 174:104823. [PMID: 33838716 DOI: 10.1016/j.pestbp.2021.104823] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 02/07/2021] [Accepted: 03/01/2021] [Indexed: 06/12/2023]
Abstract
Conventional and volatile pyrethroids are widely used to control the vectors of dengue arboviral diseases, Aedes albopictus in China. The development of resistance to conventional pyrethroids has become an increasing problem, potentially affecting the use of volatile pyrethroid. The Ae. albopictus dimefluthrin-resistant (R) strain by selecting the field population with dimefluthrin were investigated the multiple and cross-resistance levels between conventional and volatile pyrethroids and analyzed both target-site and metabolic resistant mechanisms to dimefluthrin compared with three volatile pyrethroids metofluthrin, meperfluthrin and esbiothrin and type II pyrethroid deltamethrin. The R strain displayed moderate to low resistance to selected pyrethroids (dimefluthrin, metofluthrin, meperfluthrin, esbiothrin and deltamethrin) associated with metabolic enzymes, but less distinctly to selected pyrethroids (dimefluthrin and metofluthrin) associated with a high frequency of sodium channel gene mutation (F1534S). Profiles of the multiple and cross-resistance of the R strain to other three volatile pyrethroids and type II pyrethroid deltamethrin were detected. Both synergistic and enzyme activity studies indicated that multifunctional oxidase (MFO) played an important role in this resistance.
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Affiliation(s)
- Xiaodong Yang
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, Laboratory of Insect Toxicology, South China Agricultural University, Guangzhou 510642, PR China
| | - Yulei Zhou
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, Laboratory of Insect Toxicology, South China Agricultural University, Guangzhou 510642, PR China
| | - Yanan Sun
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, Laboratory of Insect Toxicology, South China Agricultural University, Guangzhou 510642, PR China
| | - Jiali Liu
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, Laboratory of Insect Toxicology, South China Agricultural University, Guangzhou 510642, PR China
| | - Dingxin Jiang
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, Laboratory of Insect Toxicology, South China Agricultural University, Guangzhou 510642, PR China.
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