Mosquito Species Composition And Insecticide Resistance Status of Anopheles Arabiensis In Itang Special Woreda, Gambella, Southwestern Ethiopia

Abstract Introduction: Anopheles arabiensis, member species of the Anopheles gambiae complex, is the primary vector of malaria widely distributed in Ethiopia. Anopheles funestus, An. pharoensis and An. nili are secondary vectors occurring with limited distribution in the country. Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are pillars for the interventions against malaria control and elimination efforts in Ethiopia. However, the emergence and widespread of insecticide resistance in the major malaria vector, An. arabiensis, might compromise the efforts of the country. The aim of this study was to investigate composition of mosquito species and insecticide resistance status of An. arabiensis in Itang special woreda (district), Gambella, southwestern Ethiopia.Materials and methods: Adult mosquitoes were sampled from September 2020 to Feburary 2021 using Centers for Disease Control and Prevention (CDC) light trap and Pyrethrum Spray Catch (PSC). Moreover, mosquito larvae were also collected from different breeding sites and reared to adults to assess susceptibility status of populations of An. gambiae s.l. in the study area. Susceptibility tests were conducted on two to three days old non blood fed female An. gambiae s.l using insecticide impregnated papers with deltamethrin (0.05%), alpha-cypermethrin (0.05%), propoxur (0.1%), pirimiphos-methyl (0.25%) and bendiocarb (0.1%) following World Health Organization (WHO) standard susceptibility test procedure. Molecular diagnostics were done for the identification of member species of An. gambiae s.l and detection of knockdown resistance (kdr) allele using species specific polymerase chain reaction (PCR) and allele specific PCR. Results: In total, 468 adult mosquitoes were collected from different houses. Culex mosquitoes were the most dominant (80.4%) followed by Anopheles mosquitoes. Three species of Anopheles mosquitoes (An. coustani, An. pharoensis, and An. gambiae (s.l.)) were identified, of which An. coustani was the dominant (8.1%) species. WHO bioassay tests revealed that the populations of An. gambiae s.l in the study area are resistant against alpha-cypermethrin and deltamethrin whereas, susceptible to bendiocarb, pirimiphos-methyl and propoxur. Out of the total 86 An. gambiae s.l specimens assayed, 79 (92%) successfully amplified and identified as An. arabiensis. West African Kdr (L1014F) mutation was detected with high Kdr allele frequency ranging from 67-88%.Conclusion: The detection of target site mutation, kdr L1014F allele, coupled with the phenotypic resistance against alpha-cypermethrin and deltamethrin call for continuous resistance monitoring.

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Composition of Mosquito Fauna and Insecticide Resistance Status of Anopheles gambiae complex in Itang special woreda, Gambella, Southwestern Ethiopia

10.21203/rs.3.rs-739196/v1 ◽

2021 ◽

Author(s):

Tebiban Chanyalew ◽

Delenasaw Yewhalaw ◽

Eba Alemayehu Simma

Keyword(s):

Insecticide Resistance ◽

Anopheles Gambiae ◽

Light Trap ◽

Test Procedure ◽

World Health ◽

Site Mutation ◽

African Countries ◽

Breeding Sites ◽

Phenotypic Resistance ◽

Pirimiphos Methyl

Abstract IntroductionMalaria is a leading cause of morbidity and mortality mainly in sub-Saharan African countries. Plasmodium falciparum and P. vivax are the dominant malaria parasites responsible for the majority of malaria cases in Africa. The aim of this study was to investigate composition of mosquito fauna and insecticide resistance status of Anopheles mosquito in Itang special woreda (district), Gambella, southwestern Ethiopia.Materials and methodsAdult mosquitoes were sampled from September 2020 to Feburary 2021 using Centers for Disease Control and Prevention (CDC) light trap and Pyrethrum Spray Catch (PSC). Moreover, mosquito larvae were collected from different breeding sites and reared to adults. Susceptibility tests were conducted on adult two to three days old non blood fed female Anopheles gambiae s.l following world health organization (WHO) standard susceptibility test procedure. Insecticide impregnated papers with deltamethrin (0.05%), alpha-cypermethrin (0.05%), propoxur (0.1%), pirimiphos-methyl (0.25%) and bendiocarb (0.1%) were used to assess susceptibility status of Anopheles gambiae s.l populations in the study area. Moreover, molecular diagnostics were done for the identification of member species of Anopheles gambiae s.l and detection of knockdown resistance (kdr) using species specific polymerase chain reaction (PCR) and allele specific PCR.ResultsIn total, 468 adult mosquitoes were collected from different houses. Culex mosquitoes were the most dominant (80.4%) followed by Anopheles mosquitoes. Three species of Anopheles mosquitoes (An. coustani, An. pharoensis, and An. gambiae (s.l.)) were identified, of which An. coustani was the dominant (8.1%) species. Out of 468 adult mosquitoes, 294 were blood fed while 46 were half-gravid and gravid. The WHO bioassay tests revealed that the populations of An. gambiae s.l in the study area are resistant against alpha-cypermethrin and deltamethrin whereas, susceptible to bendiocarb, pirimiphos-methyl and propoxur. Out of the total 86 An. gambiae s.l specimens assayed, 79 (92%) successfully amplified and all were identified as An. arabiensis. West African Kdr (L1014F) mutation was detected with high Kdr allele frequency ranging from 67–88%.ConclusionThe detection of target site mutation, kdr L1014F allele, coupled with the phenotypic resistance against alpha-cypermethrin and deltamethrin call for continuous resistance monitoring.

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

Malaria Journal ◽

10.1186/s12936-020-03483-3 ◽

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.

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

10.21203/rs.3.rs-19762/v3 ◽

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.

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Insecticide resistance status of malaria vectors Anopheles gambiae (s.l.) of southwest Burkina Faso and residual efficacy of indoor residual spraying with microencapsulated pirimiphos-methyl insecticide

Parasites & Vectors ◽

10.1186/s13071-020-04563-8 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Dieudonné Diloma Soma ◽

Barnabas Zogo ◽

Domonbabele François de Sales Hien ◽

Aristide Sawdetuo Hien ◽

Didier Alexandre Kaboré ◽

...

Keyword(s):

Insecticide Resistance ◽

Burkina Faso ◽

Anopheles Gambiae ◽

Local Population ◽

Residual Activity ◽

Indoor Residual Spraying ◽

Susceptible Strain ◽

Malaria Vectors ◽

Pirimiphos Methyl ◽

Residual Efficacy

Abstract Background The rapid spread of insecticide resistance in malaria vectors and the rebound in malaria cases observed recently in some endemic areas underscore the urgent need to evaluate and deploy new effective control interventions. A randomized control trial (RCT) was conducted with the aim to investigate the benefit of deploying complementary strategies, including indoor residual spraying (IRS) with pirimiphos-methyl in addition to long-lasting insecticidal nets (LLINs) in Diébougou, southwest Burkina Faso. Methods We measured the susceptibility of the Anopheles gambiae (s.l.) population from Diébougou to conventional insecticides. We further monitored the efficacy and residual activity of pirimiphos-methyl on both cement and mud walls using a laboratory susceptible strain (Kisumu) and the local An. gambiae (s.l.) population. Results An. gambiae (s.l.) from Diébougou was resistant to DDT, pyrethroids (deltamethrin, permethrin and alphacypermethrin) and bendiocarb but showed susceptibility to organophosphates (pirimiphos-methyl and chlorpyrimiphos-methyl). A mixed-effect generalized linear model predicted that pirimiphos-methyl applied on cement or mud walls was effective for 210 days against the laboratory susceptible strain and 247 days against the local population. The residual efficacy of pirimiphos-methyl against the local population on walls made of mud was similar to that of cement (OR = 0.792, [0.55–1.12], Tukey’s test p-value = 0.19). Conclusions If data on malaria transmission and malaria cases (as measured trough the RCT) are consistent with data on residual activity of pirimiphos-methyl regardless of the type of wall, one round of IRS with pirimiphos-methyl would have the potential to control malaria in a context of multi-resistant An. gambiae (s.l.) for at least 7 months.

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Insecticide resistance status of Anopheles arabiensis in irrigated and non-irrigated areas in western Kenya

Parasites & Vectors ◽

10.1186/s13071-021-04833-z ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Pauline Winnie Orondo ◽

Steven G. Nyanjom ◽

Harrysone Atieli ◽

John Githure ◽

Benyl M. Ondeto ◽

...

Keyword(s):

Insecticide Resistance ◽

Vector Control ◽

Anopheles Arabiensis ◽

Crop Protection ◽

Indoor Residual Spraying ◽

Malaria Vectors ◽

Western Kenya ◽

Animal Protection ◽

Selection Of ◽

Selection Of Resistance

Abstract Background Malaria control in Kenya is based on case management and vector control using long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). However, the development of insecticide resistance compromises the effectiveness of insecticide-based vector control programs. The use of pesticides for agricultural purposes has been implicated as one of the sources driving the selection of resistance. The current study was undertaken to assess the status and mechanism of insecticide resistance in malaria vectors in irrigated and non-irrigated areas with varying agrochemical use in western Kenya. Methods The study was carried out in 2018–2019 in Homa Bay County, western Kenya. The bioassay was performed on adults reared from larvae collected from irrigated and non-irrigated fields in order to assess the susceptibility of malaria vectors to different classes of insecticides following the standard WHO guidelines. Characterization of knockdown resistance (kdr) and acetylcholinesterase-inhibiting enzyme/angiotensin-converting enzyme (Ace-1) mutations within Anopheles gambiae s.l. species was performed using the polymerase chain reaction (PCR) method. To determine the agricultural and public health insecticide usage pattern, a questionnaire was administered to farmers, households, and veterinary officers in the study area. Results Anopheles arabiensis was the predominant species in the irrigated (100%, n = 154) area and the dominant species in the non-irrigated areas (97.5%, n = 162), the rest being An. gambiae sensu stricto. In 2018, Anopheles arabiensis in the irrigated region were susceptible to all insecticides tested, while in the non-irrigated region reduced mortality was observed (84%) against deltamethrin. In 2019, phenotypic mortality was decreased (97.8–84% to 83.3–78.2%). In contrast, high mortality from malathion (100%), DDT (98.98%), and piperonyl butoxide (PBO)-deltamethrin (100%) was observed. Molecular analysis of the vectors from the irrigated and non-irrigated areas revealed low levels of leucine-serine/phenylalanine substitution at position 1014 (L1014S/L1014F), with mutation frequencies of 1–16%, and low-frequency mutation in the Ace-1R gene (0.7%). In addition to very high coverage of LLINs impregnated with pyrethroids and IRS with organophosphate insecticides, pyrethroids were the predominant chemical class of pesticides used for crop and animal protection. Conclusion Anopheles arabiensis from irrigated areas showed increased phenotypic resistance, and the intensive use of pesticides for crop protection in this region may have contributed to the selection of resistance genes observed. The susceptibility of these malaria vectors to organophosphates and PBO synergists in pyrethroids offers a promising future for IRS and insecticide-treated net-based vector control interventions. These findings emphasize the need for integrated vector control strategies, with particular attention to agricultural practices to mitigate mosquito resistance to insecticides. Graphic abstract

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Insecticide resistance in Anopheles stephensi in Somali Region, eastern Ethiopia

10.21203/rs.2.18020/v3 ◽

2020 ◽

Author(s):

Solomon Yared ◽

Araya Gebressielasie ◽

Lambodhar Damodaran ◽

Victoria Bonnell ◽

Karen Lopez ◽

...

Keyword(s):

Insecticide Resistance ◽

Anopheles Stephensi ◽

Mortality Rates ◽

Resistance Mechanisms ◽

World Health ◽

Malaria Vectors ◽

Resistance Locus ◽

Eastern Ethiopia ◽

Pyrethroid Insecticides ◽

Pirimiphos Methyl

Abstract Background The movement of malaria vectors into new areas is a growing concern in the efforts to control malaria. The recent report of Anopheles stephensi in eastern Ethiopia has raised the necessity to understand the insecticide resistance status of the vector in the region to better inform vector-based interventions. The aim of this study was to evaluate insecticide resistance in An. stephensi in eastern Ethiopia using two approaches: 1) World Health Organization (WHO) bioassay tests in An. stephensi; and 2) genetic analysis of insecticide resistance genes in An. stephensi in eastern Ethiopia. Methods Mosquito larvae and pupae were collected from Kebri Dehar. Insecticide susceptibility of An. stephensi was tested withmalathion 5%, bendiocarb 0.1%, propoxur 0.1%, deltamethrin 0.05%, permethrin 0.75%, Pirimiphos-methyl 0.25% and DDT 4%, according to WHO standard protocols. In this study, the knockdown resistance locus (kdr) in the voltage gated sodium channel (vgsc) and ace1R locus in the acetylcholinesterase gene (ace-1) were analysed in An. stephensi. Results All An. stephensi samples were resistant to carbamates, with mortality rates of 23% and 21% for bendiocarb and propoxur, respectively. Adult An. stephensi was also resistant to pyrethroid insecticides with mortality rates 67% for deltamethrin and 53% for permethrin. Resistance to DDT and malathion was detected in An. stephensi with mortality rates of 32% as well as An. stephensi was resistance to pirimiphos-methyl with mortality rates 14%. Analysis of the insecticide resistance loci revealed the absence of kdr L1014F and L1014S mutations and the ace1R G119S mutation. Conclusion Overall, these findings support that An. stephensi is resistant to several classes of insecticides, most notably pyrethroids. However, the absence of the kdr L1014 gene may suggest non-target site resistance mechanisms. Continuous insecticide resistance monitoring should be carried out in the region to confirm the documented resistance and exploring mechanisms conferring resistance in An. stephensi in Ethiopia.

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Insecticide Resistance in Anopheles stephensi in Somali Region, Eastern Ethiopia

10.21203/rs.2.18020/v2 ◽

2020 ◽

Cited By ~ 1

Author(s):

Solomon Yared ◽

Araya Gebressielasie ◽

Lambodhar Damodaran ◽

Victoria Bonnell ◽

Karen Lopez ◽

...

Keyword(s):

Insecticide Resistance ◽

Anopheles Stephensi ◽

Mortality Rates ◽

Resistance Mechanisms ◽

World Health ◽

Malaria Vectors ◽

Eastern Ethiopia ◽

Pyrethroid Insecticides ◽

Pirimiphos Methyl ◽

Health Organization

Abstract Background: The movement of malaria vectors into new areas is a growing concern in the efforts to control malaria. The recent report of Anopheles stephensi in eastern Ethiopia has raised the necessity to understand the insecticide resistance status of the vector in the region to better inform vector-based interventions. The aim of this study was to evaluate insecticide resistance in An. stephensi in eastern Ethiopia using two approaches: 1) World Health Organization (WHO) bioassay tests in An. stephensi and 2) genetic analysis of insecticide resistance genes in An. stephensi in eastern Ethiopia. Methods: Mosquito larvae and pupae were collected from Kebridehar. Insecticide susceptibility of An. stephensi was tested with malathion 5%, bendiocarb 0.1%, propoxur 0.1%, deltamethrin 0.05%, permethrin 0.75%, Pirimiphos-methyl 0.25% and DDT 4%, according to WHO standard protocols. Results: All An. stephensi samples were resistant to carbamates, with mortality rates 23% and 21% for bendiocarb and propoxur, respectively. Adult An. stephensi was also resistant to pyrethroid insecticides with mortality rates 67% for deltamethrin and 53% for permethrin. Resistance to DDT and malathion was detected in An. stephensi with mortality rates of 32% as well as An. stephensi was resistance to pirimiphos-methyl with mortality rates 14%. Analysis of the voltage gate sodium channel gene (vgsc) revealed the absence of kdr L1014 mutations. Conclusion: Overall, these findings support that An. stephensi is resistant to several classes of insecticides, most notably pyrethroids. However, the absence of the kdr L1014 gene may suggest non-target site resistance mechanisms. Continuous insecticide resistance monitoring should be carried out in the region to confirm the documented resistance and exploring mechanisms conferring resistance in An. stephensi in Ethiopia.

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Multiple insecticide resistance target sites in adult field strains of An. gambiae s.l. from southeast Senegal.

10.21203/rs.3.rs-44879/v3 ◽

2020 ◽

Author(s):

El hadji Diouf ◽

El hadji Amadou Niang ◽

Badara Samb ◽

Cheikh Tidiane Diagne ◽

Mbaye Diouf ◽

...

Keyword(s):

Insecticide Resistance ◽

Control Strategies ◽

Mosquito Species ◽

Indoor Residual Spraying ◽

Malaria Prevention ◽

Mortality Rates ◽

Malaria Vectors ◽

Public Health Issue ◽

Genetic Mutations ◽

African Countries

Abstract Background: Malaria prevention strategies are based on the use of long-lasting insecticide-treated mosquito nets (LLINs), indoor residual spraying of insecticides (IRS) and seasonal malaria chemoprevention (SMC). The combination of these strategies with artemisinin-based combination therapy (ACTs) has led to a significant reduction in malaria cases. However, malaria remains a major public health issue in most sub-Saharan African countries. Indeed, the resistance of vectors to most WHO-approved insecticides could jeopardize vector-control strategies. This study examines insecticide resistance and associated genetic mutations among malaria vectors in southeast Senegal. Methods: The study was conducted in October and November 2014 in two sites in southeast Senegal. An. gambiae s.l. populations were sampled from Kedougou (Kedougou district) and Wassadou-Badi (Tambacounda district) and were evaluated for insecticide resistance according to WHO susceptibility tests. Specimens were 3 to 5-day-old adults raised from collected larvae. Eleven insecticides belonging to the four known classes of insecticides were assessed. Mosquito species were identified and mutations associated with insecticide resistance (ace-1, rdl (A296S or A296G), Vgsc-1014F and Vgsc-1014S) were determined. Results: A total of 3,742 An. gambiae s.l. were exposed to insecticides (2,439 from Kedougou and 1,303 from Wassadou-Badi). In both sites, mosquitoes showed high levels of resistance to all the five pyrethroids tested (mortality rates ranged from 42.8 to 81.4% in Kedougou and 52.4 to 86.4% in Wassadou-Badi) as well as to dieldrin (67.8 and 83%) and DDT (12.7 and 55%). The mosquitoes were susceptible to pirimiphos-methyl (mortality rate 100%) and malathion (mortality rates 100% and 99% in Kedougou and Wassadou-Badi respectively). An. gambiae s.l. populations from Kedougou were also resistant to bendiocarb and fenitrothion. Of the 745 An. gambiae s.l. genotyped An. gambiae s.s. (71.6%) was the predominant species, followed by An. arabiensis (21.7%), An. coluzzii (6.3%) and hybrids (An. gambiae s.s./An. coluzzii; 0.4%). The Vgsc-1014F mutation was widely distributed and is predominant in An. gambiae s.s. and An. coluzzii in comparison to An. arabiensis. Vgsc-1014S was present in An. gambiae s.l. populations in Wassadou but not in Kedougou. The ace-1 and rdl mutations were more frequent in An. gambiae s.s. compared to An. arabiensis whereas they were detected weakly in An. coluzzii populations.Conclusions: The present study demonstrates the resistance of malaria vectors to pyrethroids and organo chlorines in southeast Senegal as well as the presence of genetic mutations associated with this resistance in An. gambiae s.l. No Vgsc-1014S mutation was detected in An. gambiae s.s. population in Kedougou. These findings are key for monitoring and managing the resistance of vectors to insecticides in this region.

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The Current Insecticide Resistance in Main Malaria Vector Anopheles arabiensis in Yemen

Journal of Tropical Medicine ◽

10.1155/2020/5625019 ◽

2020 ◽

Vol 2020 ◽

pp. 1-5

Author(s):

Zalalham Al-Koleeby ◽

Ahmed El Aboudi ◽

Mithaq Assada ◽

Mohamed Al-Hadi ◽

Mohammed Abdalr Ahman ◽

...

Keyword(s):

Insecticide Resistance ◽

Malaria Vector ◽

Anopheles Arabiensis ◽

Resistance Management ◽

Indoor Residual Spraying ◽

Malaria Vectors ◽

Test Procedures ◽

Phenotypic Resistance ◽

Lambda Cyhalothrin ◽

Susceptibility Tests

Control of malaria vectors in Yemen relies on both indoor residual spraying using carbamate (bendiocarb) and long-lasting pyrethroids-treated nets. This paper reports the results of studies conducted to monitor the insecticide resistance of the main malaria vector, Anopheles arabiensis, to the insecticides currently used in the vector control in four different locations. Susceptibility tests were performed following the WHO test procedures. Two pyrethroids (lambda-cyhalothrin 0.05% and deltamethrin 0.05%) and one carbamate (bendiocarb 0.1%) were tested at diagnostic doses (DD). The five-fold DD of lambda-cyhalothrin and deltamethrin (0.25%) were also used to yield information on the intensity of resistance. Besides, tests with synergists were performed to assess the involvement of detoxifying enzyme in the phenotypic resistance of the populations of An. arabiensis to pyrethroids. The results of the performed susceptibility bioassay showed that the vector is susceptible to bendiocarb and resistant to lambda-cyhalothrin and deltamethrin in the four studied areas. The pyrethroids resistance is solely metabolic. This information could help policy-makers to plan insecticide resistance management. Bendiocarb is still an effective insecticide in the form of IRS. Concerning LLINS, it would be interesting to assess their effectiveness, combining a pyrethroid with PBO for the control of the pyrethroid-resistant malaria vector.

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Status of insecticide susceptibility in Anopheles arabiensis and detection of the knockdown resistance mutation (kdr) concerning agricultural practices from Northern Sudan state, Sudan

Journal of Genetic Engineering and Biotechnology ◽

10.1186/s43141-021-00142-1 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

M. Y. Korti ◽

T. B. Ageep ◽

A. I. Adam ◽

K. B. Shitta ◽

A. A. Hassan ◽

...

Keyword(s):

Insecticide Resistance ◽

Vector Control ◽

Anopheles Arabiensis ◽

Resistance Mutation ◽

Indoor Residual Spraying ◽

Mortality Rates ◽

Malaria Vectors ◽

Bed Nets ◽

Knockdown Resistance ◽

Insecticide Susceptibility

Abstract Background Chemical control has been the most efficient method in mosquito control, the development of insecticide resistance in target populations has a significant impact on vector control. The use of agricultural pesticides may have a profound impact on the development of resistance in the field populations of malaria vectors. Our study focused on insecticide resistance and knockdown resistance (kdr) of Anopheles arabiensis populations from Northern Sudan, related to agricultural pesticide usage. Results Anopheles arabiensis from urban and rural localities (Merowe and Al-hamadab) were fully susceptible to bendiocarb 0.1% and permethrin 0.75% insecticides while resistant to DDT 4% and malathion 5%. The population of laboratory reference colony F189 from Dongola showed a mortality of 91% to DDT (4%) and fully susceptible to others. GLM analysis indicated that insecticides, sites, site type, and their interaction were determinant factors on mortality rates (P < 0.01). Except for malathion, mortality rates of all insecticides were not significant (P > 0.05) according to sites. Mortality rates of malathion and DDT were varied significantly (P < 0.0001 and P < 0.05 respectively) by site types, while mortality rates of bendiocarb and permethrin were not significant (P >0.05). The West African kdr mutation (L1014F) was found in urban and rural sites. Even though, the low-moderate frequency of kdr (L1014F) mutation was observed. The findings presented here for An. arabiensis showed no correlation between the resistant phenotype as ascertained by bioassay and the presence of the kdr mutation, with all individuals tested except the Merowe site which showed a moderate association with DDT (OR= 6 in allelic test), suggesting that kdr genotype would be a poor indicator of phenotypic resistance. Conclusion The results provide critical pieces of information regarding the insecticide susceptibility status of An. arabiensis in northern Sudan. The usage of the same pesticides in agricultural areas seemed to affect the Anopheles susceptibility when they are exposed to those insecticides in the field. The kdr mutation might have a less role than normally expected in pyrethroids resistance; however, other resistance genes should be in focus. These pieces of information will help to improve the surveillance system and The implication of different vector control programs employing any of these insecticides either in the treatment of bed nets or for indoor residual spraying would achieve satisfactory success rates.

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