scholarly journals The dominant malaria vector, Anopheles funestus from rural south-eastern Tanzania, is more strongly resistant to insecticides than Anopheles arabiensis

2020 ◽  
Author(s):  
Polius Gerazi Pinda ◽  
Claudia Eichenberger ◽  
Halfan S Ngowo ◽  
Dickson S Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Pyrethroid Resistance ◽  
Mosquito Species ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Insecticide Treated Nets ◽  
South Eastern ◽  
Sub Saharan

Abstract Background: Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance in dominant malaria vectors. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus now transmit more than 80% of malaria infections even in villages where the species occurs at far lower densities than other vectors such as Anopheles arabiensis.Methods: To better understand the dominance of An. funestus in these settings and improve options for its control, this study compared intensities of resistance between females of this species and those of An. arabiensis , using WHO assays with 1×, 5× and 10× insecticide doses. Additional tests were done to assess the reversibility of such resistance using synergists. The mosquitoes were collected from villages across two districts in south-eastern Tanzania.Findings: Both species were resistant to the two pyrethroids (permethrin and deltamethrin) and the organochloride (DDT) but susceptible to the organophosphate (pirimiphos-methyl) at standard baseline doses (1×). However, An. funestus as opposed to An. arabiensis was also resistant to the carbamate (bendiocarb) at standard doses (1×). An. funestus showed strong resistance to pyrethroids, surviving the 5× doses and 10× doses except in one village. Pre-exposure to the synergist, piperonyl butoxide (PBO), reversed the pyrethroid-resistance in both An. arabiensis and An. funestus achieving mortalities >98%, except for An. funestus from two villages for which permethrin-associated mortalities exceeded 90% but not 98%.Conclusions : In these communities where An. funestus now dominates malaria transmission, the species also displays much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can readily survive more classes of insecticides, including carbamates. The resistance to pyrethroids in both mosquito species appears to be mostly metabolic and can be reversed significantly using synergists such as PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and will also inform future choices of interventions to tackle malaria transmission in this area and other similar settings. Such interventions may include PBO-based LLINs or improved IRS with compounds such as organophosphates against which the vectors are still susceptible.

scholarly journals Anopheles funestus mosquitoes from rural south-eastern Tanzania may have stronger resistance to pyrethroids than the other malaria vector, Anopheles arabiensis

2020 ◽  
Author(s):  
Polius Gerazi Pinda ◽  
Claudia Eichenberger ◽  
Halfan S Ngowo ◽  
Dickson S Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Anopheles Arabiensis ◽  
Pyrethroid Resistance ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
The Other ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Insecticide Treated Nets ◽  
South Eastern

Abstract Background: Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector species, Anopheles arabiensis. This study compared the intensities of resistance between the two malaria vectors, so as to improve options for control. Methods: The study used WHO assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from villages across two districts in south-eastern Tanzania and identified using morphological and molecular approaches.Findings: At baseline doses (1×), both species were resistant to the two pyrethroids (permethrin and deltamethrin) but susceptible to the organophosphate (pirimiphos-methyl). An. funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb) at baseline doses. Both species were generally resistant to DDT, except An.arabiensis from one village. An. funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses except in one village. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of pyrethroid in both An. arabiensis and An. funestus achieving mortalities >98%, except for An. funestus from two villages for which permethrin-associated mortalities exceeded 90% but not 98%. Conclusions: In these communities where An. funestus dominates malaria transmission, this study may suggest that the species also have much stronger resistance to pyrethroids than its counterpart, An. arabiensis and can survive more classes of insecticides, including carbamates. The pyrethroid resistance in both species appears to be mostly metabolic and may be temporarily addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new choices of interventions to tackle malaria transmission in such settings. These may include PBO-based LLINs or improved IRS with compounds to which the vectors are susceptible. Additional field validation of these indications will be necessary using age-synchronized mosquitoes.

scholarly journals Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Polius G. Pinda ◽  
Claudia Eichenberger ◽  
Halfan S. Ngowo ◽  
Dickson S. Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Malaria Transmission ◽  
Anopheles Arabiensis ◽  
Pyrethroid Resistance ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
World Health ◽  
Malaria Vectors ◽  
South Eastern

Abstract Background Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used. Methods The study used the World Health Organization (WHO) assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from three villages across two districts in south-eastern Tanzania and included four insecticide classes. Findings At baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (> 98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%. Conclusions In south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible.

scholarly journals Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania

2020 ◽  
Author(s):  
Polius Gerazi Pinda ◽  
Claudia Eichenberger ◽  
Halfan S Ngowo ◽  
Dickson S Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Malaria Transmission ◽  
Anopheles Arabiensis ◽  
Pyrethroid Resistance ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
World Health ◽  
Malaria Vectors ◽  
South Eastern

Abstract BackgroundLong-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used.MethodsThe study used the World Health Organization (WHO) assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from three villages across two districts in south-eastern Tanzania and included four insecticide classes.FindingsAt baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (>98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%.ConclusionsIn south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible.

scholarly journals Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania

2019 ◽  
Author(s):  
Betwel John Msugupakulya ◽  
Emmanuel W. Kaindoa ◽  
Halfan S. Ngowo ◽  
Japhet M. Kihonda ◽  
Najat F. Kahamba ◽  
...  
Keyword(s):  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Insecticide Treated Nets ◽  
Rural South ◽  
South Eastern ◽  
Malaria Mosquitoes ◽  
Common House ◽  
Contact Insecticides

Abstract Background Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis , inside four common house types in rural south-eastern Tanzania.Methodology The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6am-8am), evenings (6pm-8pm) and at night (11pm-12.00am) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets).Results Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33-55% of An. funestus and 43-50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16-20% of An. funestus and 8-30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47-53% of An. funestus ; 60-66% of An. arabiensis ).Conclusion While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.

scholarly journals Bionomics and ecology of Anopheles merus along the East and Southern Africa coast

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Brian Bartilol ◽  
Irene Omedo ◽  
Charles Mbogo ◽  
Joseph Mwangangi ◽  
Martin K. Rono
Keyword(s):  
Malaria Transmission ◽  
Mosquito Species ◽  
Scale Up ◽  
Indoor Residual Spraying ◽  
Temporal Distribution ◽  
Malaria Vectors ◽  
Behavioural Plasticity ◽  
Insecticide Treated Nets ◽  
Resting Behaviour ◽  
Residual Malaria Transmission

AbstractMalaria transmission persists despite the scale-up of interventions such as long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). Understanding the entomological drivers of transmission is key for the design of effective and sustainable tools to address the challenge. Recent research findings indicate a shift in vector populations from the notorious Anopheles gambiae (s.s.) as a dominant vector to other species as one of the factors contributing to the persistence of malaria transmission. However, there are gaps in the literature regarding the minor vector species which are increasingly taking a lead role in malaria transmission. Currently, minor malaria vectors have behavioural plasticity, which allows their evasion of vector control tools currently in use. To address this, we have reviewed the role of Anopheles merus, a saltwater mosquito species that is becoming an important vector of malaria transmission along the East and Southern African coast. We performed a literature review from PubMed and Google Scholar and reviewed over 50 publications relating to An. merus's bionomics, taxonomy, spatial-temporal distribution and role in malaria transmission. We found that An. merus is an important vector of malaria and that it contributes to residual malaria transmission because of its exophilic tendencies, insecticide resistance and densities that peak during the dry seasons as the freshwater mosquitoes decline. Spatial and temporal studies have also shown that this species has increased its geographical range, densities and vectorial capacity over time. In this review, we highlight the resting behaviour and breeding habitats of this mosquito, which could be targeted for surveillance studies and control interventions.

scholarly journals Laboratory and field evaluation of MAÏA®, an ointment containing N,N-diethyl-3-methylbenzamide (DEET) against mosquitoes in Burkina Faso

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Alphonse Traoré ◽  
Gérard Niyondiko ◽  
Antoine Sanou ◽  
Franck Langevin ◽  
N’Falé Sagnon ◽  
...  
Keyword(s):  
Burkina Faso ◽  
Laboratory Tests ◽  
Mosquito Species ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Negative Control ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
Insecticide Treated Nets ◽  
H 30

Abstract Background Malaria vector control relies upon the use of insecticide-treated nets and indoor residual spraying. However, as the emergency of insecticide resistance in malaria vectors grows, the effectiveness of these measures could be limited. Alternative tools are needed. In this context, repellents can play an important role against exophagic and exophilic mosquitoes. This study evaluated the efficacy of MAÏA®, a novel repellent ointment, in laboratory and field conditions in Burkina Faso. Methods For laboratory and field assessment, 20 volunteers were enrolled and trained for nocturnal collection of mosquitoes using human landing catches (HLC). In the laboratory tests, 2 mg/sq cm of treatment (either MAIA® or 20 % DEET) were used to assess median complete protection time (CPT) against two species: Anopheles gambiae and Aedes aegypti, following WHO guidelines. For both species, two strains consisting of susceptible and local strains were used. The susceptible strains were Kisumu and Bora Bora for An. gambiae and Ae. aegypti, respectively. For the field test, the median CPT of MAÏA® was compared to that of a negative (70 % ethanol) and positive (20 % DEET) after carrying out HLCs in rural Burkina Faso in both indoor and outdoor settings. Results Laboratory tests showed median Kaplan-Meier CPT of 6 h 30 min for An. gambiae (Kisumu), 5 h 30 min for An. gambiae (Goden, local strain), and 4 h for Ae. aegypti for both the local and sensitive strain. These laboratory results suggest that MAÏA® is a good repellent against the three mosquito species. During these field tests, a total of 3979 mosquitoes were caught. In this population, anophelines represented 98.5 %, with culicines (Aedes) making up the remaining 1.5 %. Among anopheline mosquitoes, 95 % belonged to the An. gambiae complex, followed by Anopheles funestus and Anopheles pharoensis. The median CPT of 20 % DEET and MAÏA® were similar (8 h) and much longer than that of the negative control (2 h). Conclusions Results from the present studies showed that MAÏA® offers high protection against anophelines biting indoors and outdoors and could play an important role in malaria prevention in Africa.

scholarly journals Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania

2019 ◽  
Author(s):  
Betwel John Msugupakulya ◽  
Emmanuel W. Kaindoa ◽  
Halfan S. Ngowo ◽  
Japhet M. Kihonda ◽  
Najat F. Kahamba ◽  
...  
Keyword(s):  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Insecticide Treated Nets ◽  
Rural South ◽  
South Eastern ◽  
Malaria Mosquitoes ◽  
Common House ◽  
Contact Insecticides

Abstract Background Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis , inside four common house types in rural south-eastern Tanzania.Methodology The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6am-8am), evenings (6pm-8pm) and at night (11pm-12.00am) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets).Results Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33-55% of An. funestus and 43-50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16-20% of An. funestus and 8-30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47-53% of An. funestus ; 60-66% of An. arabiensis ).Conclusion While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.

scholarly journals An increasing role of pyrethroid-resistant Anopheles funestus in malaria transmission in the Lake Zone, Tanzania

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nancy S. Matowo ◽  
Jackline Martin ◽  
Manisha A. Kulkarni ◽  
Jacklin F. Mosha ◽  
Eliud Lukole ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Anopheles Funestus ◽  
Sub Saharan Africa ◽  
North West ◽  
Vector Population ◽  
Lake Zone ◽  
Sub Saharan ◽  
Long Lasting Insecticidal Nets ◽  
Study District

AbstractAnopheles funestus is playing an increasing role in malaria transmission in parts of sub-Saharan Africa, where An. gambiae s.s. has been effectively controlled by long-lasting insecticidal nets. We investigated vector population bionomics, insecticide resistance and malaria transmission dynamics in 86 study clusters in North-West Tanzania. An. funestus s.l. represented 94.5% (4740/5016) of all vectors and was responsible for the majority of malaria transmission (96.5%), with a sporozoite rate of 3.4% and average monthly entomological inoculation rate (EIR) of 4.57 per house. Micro-geographical heterogeneity in species composition, abundance and transmission was observed across the study district in relation to key ecological differences between northern and southern clusters, with significantly higher densities, proportions and EIR of An. funestus s.l. collected from the South. An. gambiae s.l. (5.5%) density, principally An. arabiensis (81.1%) and An. gambiae s.s. (18.9%), was much lower and closely correlated with seasonal rainfall. Both An. funestus s.l. and An. gambiae s.l. were similarly resistant to alpha-cypermethrin and permethrin. Overexpression of CYP9K1, CYP6P3, CYP6P4 and CYP6M2 and high L1014S-kdr mutation frequency were detected in An. gambiae s.s. populations. Study findings highlight the urgent need for novel vector control tools to tackle persistent malaria transmission in the Lake Region of Tanzania.

scholarly journals Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons

2019 ◽  
Author(s):  
John Paliga Masalu ◽  
Marceline Finda ◽  
Gerry F. Killeen ◽  
Halfan S. Ngowo ◽  
Polius G. Pinda ◽  
...  
Keyword(s):  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Insecticide Treated Nets ◽  
Domestic Spaces ◽  
Host Seeking ◽  
Outdoor Spaces ◽  
Outdoor Biting ◽  
Outdoor Environments ◽  
Almost All

Abstract Background Residents of malaria-endemic communities spend several hours outdoors performing different activities, e.g. cooking, story-telling or eating, thereby exposing themselves to potentially-infectious mosquitoes. This compromises effectiveness of indoor interventions, notably long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). This study characterized common peri-domestic spaces in rural south-eastern Tanzania, and assessed protective efficacies of hessian fabric mats and ribbons treated with the spatial repellent, transfluthrin and respectively fitted to chairs and outdoor kitchens, against mosquitoes.Methods Two hundred households were surveyed, and their most-used peri-domestic spaces physically characterized. Protective efficacies of locally-made transfluthrin-emanating chairs and hessian ribbons were tested in outdoor environments of eight households using volunteer-occupied exposure-free double net traps. CDC light traps were used to estimate host-seeking mosquito densities within open-structure outdoor kitchens. Field-collected Anopheles arabiensis and Anopheles funestus mosquitoes were exposed underneath the chairs to estimate 24h-mortality. Finally, WHO insecticide susceptibility tests were conducted on wild-caught Anopheles from the villages.Results Approximately half (52%) of houses had verandas. Aside from these verandas, most houses also had peri-domestic spaces where residents stayed most times (67% of houses with verandas and 94% of non-veranda houses). Two-thirds of these spaces were sited under trees, and only one third (34.4%) were built-up. The outdoor structures were usually makeshift kitchens having roofs and partial walls. Transfluthrin-treated chairs reduced outdoor-biting An. arabiensis densities by 70-76% while transfluthrin-treated hessian ribbons fitted to the outdoor kitchens caused 81% reduction in the general peri-domestic area. Almost all the field-collected An. arabiensis (99.4%) and An. funestus (100%) exposed under transfluthrin-treated chairs died. The An. arabiensis were susceptible to non-pyrethroids (pirimiphos methyl & bendiocarb) but resistant to pyrethroids commonly used on LLINs (deltamethrin & permethrin).Conclusion Most houses had actively-used peri-domestic outdoor spaces where exposure to mosquitoes occurred. The transfluthrin-treated chair and ribbons reduced outdoor-biting malaria vectors in these peri-domestic spaces, and also elicited significant mortality among pyrethroid-resistant field-caught malaria vectors. These two new prototype formats for transfluthrin emanators, if developed further, may constitute new options for complementing LLINs and IRS with outdoor protection against malaria and other mosquito-borne pathogens in areas where peri-domestic human activities are common.

scholarly journals Impact of insecticide resistance in Anopheles arabiensis on malaria incidence and prevalence in Sudan and the costs of mitigation

2017 ◽  
Vol 114 (52) ◽  
pp. E11267-E11275 ◽  
Author(s):  
Hmooda Toto Kafy ◽  
Bashir Adam Ismail ◽  
Abraham Peter Mnzava ◽  
Jonathan Lines ◽  
Mogahid Shiekh Eldin Abdin ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Pyrethroid Resistance ◽  
Malaria Incidence ◽  
Disease Incidence ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Incidence And Mortality ◽  
Additional Protection ◽  
The Impact

Insecticide-based interventions have contributed to ∼78% of the reduction in the malaria burden in sub-Saharan Africa since 2000. Insecticide resistance in malaria vectors could presage a catastrophic rebound in disease incidence and mortality. A major impediment to the implementation of insecticide resistance management strategies is that evidence of the impact of resistance on malaria disease burden is limited. A cluster randomized trial was conducted in Sudan with pyrethroid-resistant and carbamate-susceptible malaria vectors. Clusters were randomly allocated to receive either long-lasting insecticidal nets (LLINs) alone or LLINs in combination with indoor residual spraying (IRS) with a pyrethroid (deltamethrin) insecticide in the first year and a carbamate (bendiocarb) insecticide in the two subsequent years. Malaria incidence was monitored for 3 y through active case detection in cohorts of children aged 1 to <10 y. When deltamethrin was used for IRS, incidence rates in the LLIN + IRS arm and the LLIN-only arm were similar, with the IRS providing no additional protection [incidence rate ratio (IRR) = 1.0 (95% confidence interval [CI]: 0.36–3.0; P = 0.96)]. When bendiocarb was used for IRS, there was some evidence of additional protection [interaction IRR = 0.55 (95% CI: 0.40–0.76; P < 0.001)]. In conclusion, pyrethroid resistance may have had an impact on pyrethroid-based IRS. The study was not designed to assess whether resistance had an impact on LLINs. These data alone should not be used as the basis for any policy change in vector control interventions.

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