scholarly journals High level of resistance in Anopheles arabiensis mosquito to pyrethroid insecticides from low malaria transmission zone of Moroto district, Karamoja region, Uganda: Implication for malaria vector control

2020 ◽  
Author(s):  
Richard Echodu ◽  
Juliet Anena ◽  
Tereza Iwiru ◽  
Paul Mireji ◽  
Geoffrey Maxwell Malinga ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Malaria Vector ◽  
Malaria Control ◽  
Anopheles Arabiensis ◽  
Natural Habitats ◽  
Transmission Zone ◽  
Pirimiphos Methyl ◽  
The Impact ◽  
Karamoja Region ◽  
Low Malaria Transmission

Abstract Background: Karamoja region of Uganda previously classified as low malaria transmission zone is currently experiencing significant upsurge of malaria incidences. Long lasting insecticidal nets (LLINs) impregnated with pyrethroids constitute a major tool for malaria control in this region. Efficacy of this tool can be hampered by resistance to the pyrethroids in the Anopheles mosquito vectors. Resistance status of these mosquitoes in this region is poorly understood, effectively hampering better understanding of the impact of LLINs in the malaria control initiative. Here, we assessed susceptibility of the Anopheles arabiensis from the region to deltamethrin, permethrin (pyrethroids) and pirirmiphos-methyl (organophosphate) insecticides.Method: We collected anopheline mosquito larvae from their natural habitats and reared them to adult emergence in situ field insectary in Karamoja region. We then identified them morphological to species level and exposed 513 emerge adult female An gambiae s.l., mosquitoes to diagnostic dosages of deltamethrin (0.05%), permethrin (0.75%) and pirimiphos-methyl (0.25%) pyrethroids exposure using the standard WHO insecticide susceptibility test assay. Synergic assays using piperonyl butoxide (PBO) were done to check for the involvement of detoxification enzymes in pyrethroid resistant populations. We then screened for knockdown resistance (KDR) and mosquito species diversity using Polymerase Chain Reaction (PCR).Results: Majority (96%) of the mosquitoes we sampled were identified as An. arabiensis and 4% as An. gambiae sensu stricto. We observed cross-resistance to both deltamethrin (11.9%) and permethrin (47%) but susceptibility (100% mortality) to pirimiphos-methyl in An. arabiensis. The pre-exposure to PBO ameliorated the resistance to both pyrethroids. We detected homozygous KDR -eastern variant in 1.8 and 50% of the An. arabiensis and An. gambiae s.s. respectively.Conclusion: Anopheles arabiensis and An. gambiae s.s. are the malaria vector in Karamoja region with An. arabiensis predominating. Both species are susceptible to pirimiphos-methyl but resistant to both deltamethrin and permethrin, through a metabolic process (phenotype). Mosquotoes with genetic (kdr) mutations for resistance were minimal and hence have minimal contribution to the pyrethroid resistance profile. An. arabiensis can thus be controled in Karamoja region using deltamethrin and/or permethrin impregnated mosquito nets integrated with PBO and/or through indoor residual spraying of sprayable human dwellings with pirimiphos-methyl.

scholarly journals High level of resistance in the mosquito Anopheles arabiensis to pyrethroid insecticides from low malaria transmission zone of Moroto district, Karamoja region, Uganda: Implication for malaria vector control

2020 ◽  
Author(s):  
Richard Echodu ◽  
Juliet Anena ◽  
Tereza Iwiru ◽  
Paul Mireji ◽  
Geoffrey Maxwell Malinga ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Malaria Vector ◽  
Malaria Control ◽  
Anopheles Arabiensis ◽  
Natural Habitats ◽  
Transmission Zone ◽  
Pirimiphos Methyl ◽  
The Impact ◽  
Karamoja Region ◽  
Low Malaria Transmission

Abstract Background Karamoja region of Uganda previously classified as low malaria transmission zone is currently experiencing significant upsurge of malaria incidences. Long lasting insecticidal nets (LLINs) impregnated with pyrethroids constitute a major tool for malaria control in this region. Efficacy of this tool can be hampered by resistance to the pyrethroids in the Anopheles mosquito vectors. Resistance status of these mosquitoes in this region is poorly understood, effectively hampering better understanding of the impact of LLINs in the malaria control initiative. Here, we assessed susceptibility of the Anopheles arabiensis from the region to deltamethrin, permethrin (pyrethroids) and pirirmiphos-methyl (organophosphate) insecticides. Method We collected anopheline mosquito larvae from their natural habitats and reared them to adult emergence in situ field insectary in Karamoja region. We then identified them morphological to species level and exposed 513 emerge adult female An gambiae s.l., mosquitoes to diagnostic dosages of deltamethrin (0.05%), permethrin (0.75%) and pirimiphos-methyl (0.25%) pyrethroids exposure using the standard WHO insecticide susceptibility test assay. Synergic assays using piperonyl butoxide (PBO) were done to check for the involvement of detoxification enzymes in pyrethroid resistant populations. We then screened for knockdown resistance (KDR) and mosquito species diversity using Polymerase Chain Reaction (PCR). Results Majority (96%) of the mosquitoes we sampled were identified as An. arabiensis and 4% as An. gambiae sensu stricto . We observed cross-resistance to both deltamethrin (11.9%) and permethrin (47%) but susceptibility (100% mortality) to pirimiphos-methyl in An. arabiensis . The pre-exposure to PBO ameliorated the resistance to both pyrethroids. We detected homozygous KDR -eastern variant in 1.8 and 50% of the An. arabiensis and An. gambiae s.s. respectively. Conclusion Anopheles arabiensis and An. gambiae s.s. are the malaria vector in Karamoja region with An. arabiensis predominating. Both species are susceptible to pirimiphos-methyl but resistant to both deltamethrin and permethrin, through a metabolic process (phenotype). Mosquotoes with genetic (kdr) mutations for resistance were minimal and hence have minimal contribution to the pyrethroid resistance profile. An. arabiensis can thus be controled in Karamoja region using deltamethrin and/or permethrin impregnated mosquito nets integrated with PBO and/or through indoor residual spraying of sprayable human dwellings with pirimiphos-methyl.

scholarly journals The Impact of 3 Years of Targeted Indoor Residual Spraying With Pirimiphos-Methyl on Malaria Parasite Prevalence in a High-Transmission Area of Northern Zambia

2019 ◽  
Vol 188 (12) ◽  
pp. 2120-2130 ◽  
Author(s):  
Marisa A Hast ◽  
Mike Chaponda ◽  
Mbanga Muleba ◽  
Jean-Bertin Kabuya ◽  
James Lupiya ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Malaria Control ◽  
Malaria Parasite ◽  
Control Measure ◽  
Indoor Residual Spraying ◽  
Parasite Prevalence ◽  
Organophosphate Insecticide ◽  
Malaria Burden ◽  
Pirimiphos Methyl ◽  
The Impact

Abstract Malaria transmission in northern Zambia has increased in the past decade, despite malaria control activities. Evidence-based intervention strategies are needed to effectively reduce malaria transmission. Zambia’s National Malaria Control Centre conducted targeted indoor residual spraying (IRS) in Nchelenge District, Luapula Province, from 2014 to 2016 using the organophosphate insecticide pirimiphos-methyl. An evaluation of the IRS campaign was conducted by the Southern Africa International Centers of Excellence for Malaria Research using actively detected malaria cases in bimonthly household surveys carried out from April 2012 to July 2017. Changes in malaria parasite prevalence after IRS were assessed by season using Poisson regression models with robust standard errors, controlling for clustering of participants in households and demographic, geographical, and climatological covariates. In targeted areas, parasite prevalence declined approximately 25% during the rainy season following IRS with pirimiphos-methyl but did not decline during the dry season or in the overall study area. Within targeted areas, parasite prevalence declined in unsprayed households, suggesting both direct and indirect effects of IRS. The moderate decrease in parasite prevalence within sprayed areas indicates that IRS with pirimiphos-methyl is an effective malaria control measure, but a more comprehensive package of interventions is needed to effectively reduce the malaria burden in this setting.

scholarly journals Predicting distribution of malaria vector larval habitats in Ethiopia by integrating distributed hydrologic modeling with remotely sensed data

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ai-Ling Jiang ◽  
Ming-Chieh Lee ◽  
Guofa Zhou ◽  
Daibin Zhong ◽  
Dawit Hawaria ◽  
...  
Keyword(s):  
Malaria Vector ◽  
Malaria Control ◽  
Remotely Sensed ◽  
Larval Habitat ◽  
Validation Dataset ◽  
Significant Shift ◽  
Remotely Sensed Data ◽  
Larval Habitats ◽  
Common Land Model ◽  
The Impact

AbstractLarval source management has gained renewed interest as a malaria control strategy in Africa but the widespread and transient nature of larval breeding sites poses a challenge to its implementation. To address this problem, we propose combining an integrated high resolution (50 m) distributed hydrological model and remotely sensed data to simulate potential malaria vector aquatic habitats. The novelty of our approach lies in its consideration of irrigation practices and its ability to resolve complex ponding processes that contribute to potential larval habitats. The simulation was performed for the year of 2018 using ParFlow-Common Land Model (CLM) in a sugarcane plantation in the Oromia region, Ethiopia to examine the effects of rainfall and irrigation. The model was calibrated using field observations of larval habitats to successfully predict ponding at all surveyed locations from the validation dataset. Results show that without irrigation, at least half of the area inside the farms had a 40% probability of potential larval habitat occurrence. With irrigation, the probability increased to 56%. Irrigation dampened the seasonality of the potential larval habitats such that the peak larval habitat occurrence window during the rainy season was extended into the dry season. Furthermore, the stability of the habitats was prolonged, with a significant shift from semi-permanent to permanent habitats. Our study provides a hydrological perspective on the impact of environmental modification on malaria vector ecology, which can potentially inform malaria control strategies through better water management.

scholarly journals Heterogeneous exposure and hotspots for malaria vectors at three study sites in Uganda

2018 ◽  
Vol 2 ◽  
pp. 32 ◽  
Author(s):  
Su Yun Kang ◽  
Katherine E. Battle ◽  
Harry S. Gibson ◽  
Laura V. Cooper ◽  
Kilama Maxwell ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Malaria Vector ◽  
Malaria Control ◽  
Negative Binomial ◽  
Indoor Residual Spraying ◽  
Housing Quality ◽  
Environmental Covariates ◽  
Vector Density ◽  
Vector Abundance ◽  
Study Sites

Background: Heterogeneity in malaria transmission has household, temporal, and spatial components. These factors are relevant for improving the efficiency of malaria control by targeting heterogeneity. To quantify variation, we analyzed mosquito counts from entomological surveillance conducted at three study sites in Uganda that varied in malaria transmission intensity. Mosquito biting or exposure is a risk factor for malaria transmission. Methods: Using a Bayesian zero-inflated negative binomial model, validated via a comprehensive simulation study, we quantified household differences in malaria vector density and examined its spatial distribution. We introduced a novel approach for identifying changes in vector abundance hotspots over time by computing the Getis-Ord statistic on ratios of household biting propensities for different scenarios. We also explored the association of household biting propensities with housing and environmental covariates. Results: In each site, there was evidence for hot and cold spots of vector abundance, and spatial patterns associated with urbanicity, elevation, or other environmental covariates. We found some differences in the hotspots in rainy vs. dry seasons or before vs. after the application of control interventions. Housing quality explained a portion of the variation among households in mosquito counts. Conclusion: This work provided an improved understanding of heterogeneity in malaria vector density at the three study sites in Uganda and offered a valuable opportunity for assessing whether interventions could be spatially targeted to be aimed at abundance hotspots which may increase malaria risk. Indoor residual spraying was shown to be a successful measure of vector control interventions in Tororo, Uganda.  Cement walls, brick floors, closed eaves, screened airbricks, and tiled roofs were features of a house that had shown reduction of household biting propensity. Improvements in house quality should be recommended as a supplementary measure for malaria control reducing risk of infection.

scholarly journals Risk of Plasmodium falciparum infection in south-west Burkina Faso - potential impact of expanding eligibility for seasonal malaria chemoprevention

2021 ◽  
Author(s):  
Anne L Wilson ◽  
Steve W Lindsay ◽  
Alfred Tiono ◽  
Jean Baptiste Yaro ◽  
Hilary Ranson ◽  
...  
Keyword(s):  
Risk Factors ◽  
Plasmodium Falciparum ◽  
Burkina Faso ◽  
Malaria Transmission ◽  
Malaria Control ◽  
Control Measures ◽  
Sub Saharan Africa ◽  
South West ◽  
Seasonal Malaria Chemoprevention ◽  
The Impact

Abstract Background Burkina Faso has one of the highest malaria burdens in sub-Saharan Africa despite the mass deployment of insecticide-treated nets (ITNs) and use of seasonal malaria chemoprevention (SMC) in children aged up to 5 years. Identification of risk factors for Plasmodium falciparum infection in rural Burkina Faso could help to identify and target malaria control measures. Methods A cross-sectional survey of 1,199 children and adults was conducted during the peak malaria transmission season in south-west Burkina Faso in 2017. Logistic regression was used to identify risk factors for microscopically confirmed P. falciparum infection. A malaria transmission dynamic model was used to determine the impact on malaria cases averted of administering SMC to children aged 5–15 year old. Results P. falciparum prevalence was 32.8% in the study population. Children aged 5 to < 10 years old were at 3.74 times the odds (95% CI = 2.68–5.22, p < 0.001) and children aged 10 to 15 years old at 3.14 times the odds (95% CI = 1.20–8.21, p = 0.02) of P. falciparum infection compared to children aged less than 5 years old. Administration of SMC to children aged up to 10 years is predicted to avert an additional 57 malaria cases per 1000 population per year (9.4% reduction) and administration to children aged up to 15 years would avert an additional 89 malaria cases per 1000 population per year (14.6% reduction) in the Cascades Region, assuming coverage of pyrethroid-piperonyl butoxide ITNs. Conclusion Malaria infections were high in all age strata, although highest in children aged 5 to 15 years, despite roll out of core malaria control interventions. Given the burden of infection in school-age children, extension of the eligibility criteria for SMC could help reduce the burden of malaria in Burkina Faso and other countries in the region.

scholarly journals Mass Drug Administration With High-Dose Ivermectin and Dihydroartemisinin-Piperaquine for Malaria Elimination in an Area of Low Transmission With High Coverage of Malaria Control Interventions: Protocol for the MASSIV Cluster Randomized Clinical Trial

10.2196/20904 ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. e20904
Author(s):  
Edgard Diniba Dabira ◽  
Harouna M Soumare ◽  
Steven W Lindsay ◽  
Bakary Conteh ◽  
Fatima Ceesay ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Malaria Transmission ◽  
Randomized Clinical Trial ◽  
Drug Administration ◽  
Malaria Control ◽  
Mass Drug Administration ◽  
High Coverage ◽  
River Region ◽  
Cluster Randomized ◽  
The Impact

Background With a decline in malaria burden, innovative interventions and tools are required to reduce malaria transmission further. Mass drug administration (MDA) of artemisinin-based combination therapy (ACT) has been identified as a potential tool to further reduce malaria transmission, where coverage of vector control interventions is already high. However, the impact is limited in time. Combining an ACT with an endectocide treatment that is able to reduce vector survival, such as ivermectin (IVM), could increase the impact of MDA and offer a new tool to reduce malaria transmission. Objective The study objective is to evaluate the impact of MDA with IVM plus dihydroartemisinin-piperaquine (DP) on malaria transmission in an area with high coverage of malaria control interventions. Methods The study is a cluster randomized trial in the Upper River Region of The Gambia and included 32 villages (16 control and 16 intervention). A buffer zone of ~2 km was created around all intervention clusters. MDA with IVM plus DP was implemented in all intervention villages and the buffer zones; control villages received standard malaria interventions according to the Gambian National Malaria Control Program plans. Results The MDA campaigns were carried out from August to October 2018 for the first year and from July to September 2019 for the second year. Statistical analysis will commence once the database is completed, cleaned, and locked. Conclusions This is the first cluster randomized clinical trial of MDA with IVM plus DP. The results will provide evidence on the impact of MDA with IVM plus DP on malaria transmission. Trial Registration ClinicalTrials.gov NCT03576313; https://clinicaltrials.gov/ct2/show/NCT03576313 International Registered Report Identifier (IRRID) DERR1-10.2196/20904

scholarly journals Mass Drug Administration With High-Dose Ivermectin and Dihydroartemisinin-Piperaquine for Malaria Elimination in an Area of Low Transmission With High Coverage of Malaria Control Interventions: Protocol for the MASSIV Cluster Randomized Clinical Trial (Preprint)

2020 ◽  
Author(s):  
Edgard Diniba Dabira ◽  
Harouna M Soumare ◽  
Steven W Lindsay ◽  
Bakary Conteh ◽  
Fatima Ceesay ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Malaria Transmission ◽  
Randomized Clinical Trial ◽  
Drug Administration ◽  
Malaria Control ◽  
Mass Drug Administration ◽  
High Coverage ◽  
River Region ◽  
Cluster Randomized ◽  
The Impact

BACKGROUND With a decline in malaria burden, innovative interventions and tools are required to reduce malaria transmission further. Mass drug administration (MDA) of artemisinin-based combination therapy (ACT) has been identified as a potential tool to further reduce malaria transmission, where coverage of vector control interventions is already high. However, the impact is limited in time. Combining an ACT with an endectocide treatment that is able to reduce vector survival, such as ivermectin (IVM), could increase the impact of MDA and offer a new tool to reduce malaria transmission. OBJECTIVE The study objective is to evaluate the impact of MDA with IVM plus dihydroartemisinin-piperaquine (DP) on malaria transmission in an area with high coverage of malaria control interventions. METHODS The study is a cluster randomized trial in the Upper River Region of The Gambia and included 32 villages (16 control and 16 intervention). A buffer zone of ~2 km was created around all intervention clusters. MDA with IVM plus DP was implemented in all intervention villages and the buffer zones; control villages received standard malaria interventions according to the Gambian National Malaria Control Program plans. RESULTS The MDA campaigns were carried out from August to October 2018 for the first year and from July to September 2019 for the second year. Statistical analysis will commence once the database is completed, cleaned, and locked. CONCLUSIONS This is the first cluster randomized clinical trial of MDA with IVM plus DP. The results will provide evidence on the impact of MDA with IVM plus DP on malaria transmission. CLINICALTRIAL ClinicalTrials.gov NCT03576313; https://clinicaltrials.gov/ct2/show/NCT03576313 INTERNATIONAL REGISTERED REPORT DERR1-10.2196/20904

scholarly journals Exploring the Influence of Daily Climate Variables on Malaria Transmission and Abundance of Anopheles arabiensis over Nkomazi Local Municipality, Mpumalanga Province, South Africa

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Gbenga J. Abiodun ◽  
Kevin Y. Njabo ◽  
Peter J. Witbooi ◽  
Abiodun M. Adeola ◽  
Trevon L. Fuller ◽  
...  
Keyword(s):  
South Africa ◽  
Malaria Transmission ◽  
Anopheles Arabiensis ◽  
Climatic Factors ◽  
Time Lag ◽  
Wavelet Coherence ◽  
Study Region ◽  
Mosquito Abundance ◽  
The Impact ◽  
Wavelet Coherence Analysis

The recent resurgence of malaria incidence across epidemic regions in South Africa has been linked to climatic and environmental factors. An in-depth investigation of the impact of climate variability and mosquito abundance on malaria parasite incidence may therefore offer useful insight towards the control of this life-threatening disease. In this study, we investigate the influence of climatic factors on malaria transmission over Nkomazi Municipality. The variability and interconnectedness between the variables were analyzed using wavelet coherence analysis. Time-series analyses revealed that malaria cases significantly declined after the outbreak in early 2000, but with a slight increase from 2015. Furthermore, the wavelet coherence and time-lagged correlation analyses identified rainfall and abundance of Anopheles arabiensis as the major variables responsible for malaria transmission over the study region. The analysis further highlights a high malaria intensity with the variables from 1998–2002, 2004–2006, and 2010–2013 and a noticeable periodicity value of 256–512 days. Also, malaria transmission shows a time lag between one month and three months with respect to mosquito abundance and the different climatic variables. The findings from this study offer a better understanding of the importance of climatic factors on the transmission of malaria. The study further highlights the significant roles of An. arabiensis on malaria occurrence over Nkomazi. Implementing the mosquito model to predict mosquito abundance could provide more insight into malaria elimination or control in Africa.

scholarly journals Evaluating Putative Repellent ‘Push’ and Attractive ‘Pull’ Components for Manipulating the Odour-orientation of Host-seeking Malaria Vectors in the Peri-domestic Space

2020 ◽  
Author(s):  
Margaret Mendi Njoroge ◽  
Ulrike Fillinger ◽  
Adam Saddler ◽  
Sarah Moore ◽  
Willem Takken ◽  
...  
Keyword(s):  
Malaria Vector ◽  
Anopheles Arabiensis ◽  
Chemical Constituents ◽  
Domestic Space ◽  
Human Volunteer ◽  
Malaria Vectors ◽  
Human Being ◽  
Host Seeking ◽  
Spatial Repellent ◽  
The Impact

Abstract Background Novel malaria vector control approaches aim to combine tools to work in synergy for maximum protection. This study aimed to evaluate novel and re-evaluate existing, putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour-orientation of malaria vectors in the peri-domestic space. Methods Anopheles arabiensis outdoor human landing catches and trap comparisons were implemented in large semi-field systems to (1) test the efficacy of citriodiol or transfluthrin-treated fabric strips positioned in house eave gaps as push components for preventing bites; (2) understand the efficacy of an MB5-baited Suna-trap in attracting vectors in the presence of a human being; (3) assess 2-butanone as a CO2 replacement for trapping; and (4) determine the protection provided by a full push-pull set up. The air-concentrations of the chemical constituents of the push-pull mosquito control tool were quantified.Results Microencapsulated citriodiol eave strips did not provide any outdoor protection against host-seeking An. arabiensis. Transfluthrin-treated strips significantly reduced the odds of a mosquito landing on the human volunteer (OR 0.17; 95% CI 0.12-0.23). This impact was lower (OR 0.59; 95% CI 0.52-0.66) during the push-pull experiment which was associated with low night-time temperatures likely affecting the transfluthrin vaporisation. The MB5-baited Suna trap supplemented with CO2 attracted only a third of the released mosquitoes in the absence of a human being, however, with a human volunteer in the same system, the trap caught less than 1% of all released mosquitoes. The volunteer consistently attracted over two-thirds of all mosquitoes released. This was the case in the absence (‘pull’ only) and in the presence of a spatial repellent (‘push-pull’), indicating that in its current configuration the tested ‘pull’ does not provide a valuable addition to a spatial repellent. The chemical 2-butanone was ineffective in replacing CO2. Transfluthrin was detectable in the air space but with a strong linear reduction in concentrations over 5 metres from release. The MB5 constituent chemicals were only irregularly detected, potentially suggesting insufficient release and concentration in the air for attraction.Conclusion This step-by-step evaluation of the selected ‘push’ and ‘pull’ components led to a better understanding of their ability to affect host-seeking behaviours of the malaria vector Anopheles arabiensis in the peri-domestic space and helps to gauge the impact such tools would have when used in the field for monitoring or control.

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