Abstract Background The establishment of the invasive malaria vector Anopheles stephensi in Ethiopia threatens existing malaria control efforts. Unlike native vectors, An. stephensi thrives in both urban and rural areas, lacks clear seasonal peaks of abundance, and often breeds in artificial water containers. SumiLarv ™ 2MR containing the larvicide pyriproxyfen (PPF) offers a promising method for controlling the immature stages of An. stephensi in such habitats. This habitat-randomised controlled trial evaluated the efficacy of SumiLarv ™ 2MR against An. stephensi in Danan town, Somali region, Ethiopia. Methods Entomological surveillance identified 102 large artificial containers (“ birkas ”) which were randomly allocated in a 1:1 ratio to receive either SumiLarv ™ 2MR (treatment arm) or no treatment (control arm). SumiLarv ™ 2MR was introduced into the birkas at a dose of one disc per 200 L of water. Morphological identification was performed on adult mosquitoes emerging from control containers, while molecular analysis was conducted on both morphologically identified adult mosquitoes and dead pupae collected from the control and treatment arm. The residual efficacy of PPF content of the remaining discs was also analysed. Inhibition of adult mosquito emergence was assessed every 2 weeks for 40 weeks to determine the duration of efficacy. Results The number of SumiLarv ™ 2MR remained constant in the treatment arm throughout the study period. No significant differences were observed in water volume, pH, or temperature between the two study arms. Introduction of SumiLarv ™ 2MR resulted in complete (100%) inhibition of adult emergence throughout the 40 weeks’ study period (t = 6.26, p < 0.05). Morphological identification of a sub-samples of adult mosquitoes emerging from control containers at different time points confirmed the presence of An. stephensi (99.85%) and An. gambiae s.l. (0.15%). Molecular analysis of morphologically identified adults from control containers and dead pupae from treatment containers confirmed that 98.91% were An.stephensi . Post-trial analysis showed that approximately 82.20% of the original PPF had been released from SumiLarv ™ 2MR during study period. Conclusions The high and sustained efficacy of SumiLarv ™ 2MR demonstrated in this study suggests that it is a suitable tool for controlling An. stephensi in large artificial water storage containers.

The rotational use of insecticides with diverse modes of action in indoor residual spraying (IRS) is pivotal for enhancing malaria vector control and addressing insecticide resistance. A key factor in national malaria vector control/elimination programmes is the rate at which these insecticides decay. VECTRON™ T500, with broflanilide as its active ingredient, is a recently developed candidate insecticide formulation which has shown promising results in certain phase II experimental hut trials. However, its residual efficacy across different settings has not been thoroughly investigated. This study evaluated the efficacy of VECTRON™ T500 on various wall surfaces (mud, dung, paint, and cement) and assessed its decay rates over time in Ethiopia. Insectary-reared Anopheles arabiensis Sekoru strain mosquitoes were used to evaluate the residual efficacy of VECTRON™ T500. Female mosquitoes, aged three to five days were used for the bioassays. Seven 'tukul' type test huts, each hut with a distinct wall type (mud, dung, painted, and cemented) were used for the study. Three huts received VECTRON™ T500; three huts were sprayed with Actellic 300CS, and one hut served as a negative control (sprayed with water only). VECTRON™ T500 induced over 80

Malaria remains a significant global health challenge, particularly in sub-Saharan Africa, despite advances in control measures. In 2023, there were an estimated 263 million malaria cases and 597,000 deaths, with most occurring in Africa. This study presents a temperature-dependent, two-class age-structured malaria model using partial differential equations and optimal control strategies to assess their impact on malaria transmission. We analyze the existence and stability of equilibria, determined by the basic reproduction number R0, and demonstrate global stability through Lyapunov functionals. Numerical simulations show the effects of temperature variations and optimal controls on transmission dynamics, providing actionable insights for malaria management. Empirical validation of the model was performed using six years of infection prevalence data from the Jimma zone, revealing an [Formula: see text] of 0.68 and an adjusted [Formula: see text] of 0.63, indicating a good fit to observed data. Furthermore, comparison with an existing age-structured malaria model from the literature showed superior predictive accuracy, with our model demonstrating better performance in capturing temperature-dependent malaria trends. These results underscore the robustness and practical relevance of the model, offering improved prediction and control strategies under varying environmental conditions.

Background Malaria control in Ethiopia relies mainly on case management with ACT and vector control interventions, notably long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Anopheles arabiensis is the predominant vector, while the invasive An. stephensi is rapidly spreading across multiple regions, intensifying challenges for malaria elimination. Insecticide resistance further complicates control efforts. Methods This study assessed the susceptibility of An. gambiae s.l. and An. stephensi to commonly used and new public health insecticides at two sites: Awash Sabhat Kilo, where An. stephensi is established, and an area dominated by An. gambiae s.l. WHO tube bioassays tested pirimiphos-methyl (0.25%), propoxur (0.1%), bendiocarb (0.1%), deltamethrin (0.25%), alpha-cypermethrin (0.05%), and clothianidin (2%). CDC bottle bioassays examined susceptibility to pirimiphos-methyl, deltamethrin, chlorfenapyr, clothianidin, and broflanilide. Molecular identification and allele-specific PCR targeted resistant alleles, particularly mutations in the voltage-gated sodium channel (VGSC) gene. Data were analyzed with SPSS v20. Results Results showed An. gambiae s.l. populations were susceptible to propoxur and pirimiphos-methyl but resistant to bendiocarb, deltamethrin, alpha-cypermethrin, and clothianidin. An. stephensi displayed broader resistance, including to pirimiphos-methyl, propoxur, bendiocarb, deltamethrin, alpha-cypermethrin, and clothianidin. Both species remained fully susceptible to chlorfenapyr, clothianidin (at higher doses), and broflanilide across tested concentrations. Resistance to deltamethrin and pirimiphos-methyl was dose-dependent. Molecular identification confirmed An. arabiensis as the major species within the An. gambiae complex. Knockdown resistance ( kdr ) mutations were detected in An. arabiensis with a genotypic frequency of 22.8%. Conclusion These findings highlight the serious threat insecticide resistance poses to Ethiopia’s malaria control efforts. The persistence of resistance in both An. arabiensis and An. stephensi raises concerns about the long-term sustainability of insecticide-based strategies and underscores the need for alternative or integrated approaches.

The study was conducted to evaluate the in vitro efficacy of amitraz 12.5 % and diazinon 60 % against Amblyomma cohaerens and Rhipicephalus (Boophilus) decoloratus, and also to assess acaricide resistance using the Adult Immersion Test (AIT) in Jimma town, Oromia region, southwest Ethiopia. A total of 180 engorged adult female ticks of the two species (90 A. cohaerens and 90 R. decoloratus) were collected from local and crossbred cattle managed under extensive and semi-intensive systems. The ticks were immersed in amitraz 12.5 % and diazinon 60 % at field-recommended concentrations, and in distilled water for the control groups, for two minutes. Afterward, they were placed in an incubator at 27°C and 85 % RH for seven days. The oviposition responses of A. cohaerens and R. decoloratus were monitored regularly. The efficacy of each acaricide was assessed by comparing the mean egg mass laid by treated and untreated tick groups. The study results showed that ticks treated with amitraz 12.5 % died and did not lay eggs, while some ticks treated with diazinon 60 % survived and laid eggs after a seven-day incubation period. There was a significant difference (p < 0.05) between the two acaricides in controlling egg-laying in both species of ticks. The ticks in the control group that were treated with water survived and laid eggs. Amitraz 12.5 % at the field-recommended concentration achieved 100 % control, whereas diazinon 60 % achieved 91.3 % control. The study shows that both amitraz 12.5 % and diazinon 60 % significantly reduced egg laying in A. cohaerens and R. decoloratus ticks. The results also demonstrate that amitraz 12.5 % is more effective in controlling ticks and that there is a sign of emerging resistance of ticks to diazinon 60 %.

The study evaluated the efficacy and residual activity of SumiLarv 2MR, SumiLarv 0.5G, and Abate 1SG (used as a positive control) against Anopheles stephensi larvae in Awash Subath Kilo, Afar Regional State, Ethiopia, using a semi-field experimental setup. Plastic containers with capacities of 100L and 250L were used to assess the residual efficacy of SumiLarv 2MR. Specifically, four 100L containers were each treated with one disc of SumiLarv 2MR, compared to two untreated controls. Similarly, four 250L containers received one disc each, with two untreated controls. Additionally, eight 250L containers were treated with a half-dose to match one disc per 500L, alongside four untreated controls. For SumiLarv 0.5G and Abate 1SG, four 100L containers were treated with each larvicide, with two untreated controls for each. Each container received 20-25 third and fourth instar An. stephensi larvae. Observations of adult emergence were conducted until all pupae either emerged or died. Results showed that SumiLarv 2MR demonstrated a nine-month residual efficacy, SumiLarv 0.5G provided seven weeks of efficacy, and Abate 1SG showed a five-week efficacy. Additionally, SumiLarv 2MR discs retained nearly 50% of their initial pyriproxyfen content after nine months, suggesting potential for extended residual activity. This study highlights the long-term effectiveness of SumiLarv 2MR's as a larvicide against An. stephensi in Ethiopia.

Mosquitoes, notorious vectors of numerous diseases transmitted through bites, pose a significant public health threat, particularly in tropical and subtropical regions. Climate change may affect the risk of mosquito-borne diseases. This study investigated how temperature affects the population dynamics of all stages of Anopheles arabiensis mosquitoes, including eggs, larvae, pupae, and adults. We developed and analyzed a mathematical model that incorporates logistic growth and temperature. The well-posedness of the proposed model was proved. We demonstrated that if the non-autonomous basic reproduction number is less than unity, the disease-free equilibrium is locally asymptotically stable. Conversely, if it is greater than unity, there exists at least one positive periodic solution, as established by applying the comparison theorem and the theory of uniform persistence. Furthermore, the model parameters were fitted to real-world data conducted in the Tropical and Infectious Diseases Research Center (TIDRC) in Sekoru, Jimma University. The model presents the population dynamics of both immature and adult An. Arabiensis, which is similar to the observed experimental data obtained from TIDRC. Therefore, our model suggests that using the results obtained, it can be used to predict the impact of various intervention strategies on An. arabiensis distribution.

Malaria, a major vector-borne disease transmitted by female Anopheles mosquitoes, remains a critical public health challenge in tropical and subtropical regions. Climate change influences vector distribution, abundance, and disease transmission patterns. This study examined the influence of temperature and humidity on the development, abundance, and survival of Anopheles arabiensis , a key malaria vector in Ethiopia. Laboratory reared susceptible An. arabiensis strain mosquitoes were reared under varying conditions, with 400 eggs exposed to temperatures of 14.5–34.35°C and relative humidity (RH) levels of 64–84% and compared with the ones that reared under standard insectary conditions. Development and survival rates were analyzed across 20 temperature-humidity regimes using SPSS 26, with linear regression, OLS, and quadratic regression models. Results showed optimal egg hatchability (80%) at 25.3–34.35°C and 64–68% RH. Adult emergence peaked (80%) at 28.37–29.65°C and 70% RH, but declined significantly below 16°C and 64% RH. The longest larval development (13 days) occurred at 14.55–15.62°C and 83–86% RH, while adult survival reached 25 days at 23.65–24.72°C and 68–69% RH. These findings highlight the profound influence of temperature and humidity on An. arabiensis life stages, emphasizing their role in mosquito population dynamics. Further research is needed to explore how these factors affect malaria parasite development within vectors, offering insights to improve malaria control strategies. ### Competing Interest Statement The authors have declared no competing interest.

Ethiopia has been progressing very well in controlling malaria in the past few years. However, shortly after the COVID-19 pandemic, an unpredictable malaria resurgence was observed in almost all malaria-endemic areas of the country, although the exact cause of which has not yet been identified. Therefore, this study aimed to investigate malaria burden and associated risk factors in one of the endemic zones of Ethiopia. A health facility-based retrospective and cross-sectional study design was conducted in the Kaffa zone, southwest of Ethiopia. Hence, a seven-year retrospective data on malaria positivity rate, interventional activities undertaken in the area, and climatic variables were collected from the patient's medical records, district health bureau, and meteorological institute, respectively. For the cross-sectional study, all malaria-suspected patients seeking medication at the health facilities in the Kaffa Zone administrative centre, Bonga town, during the study period (January–June 2024), were recruited in the study. Data on the patient's socio-demographic, socio-economic, behavioural, health facilities and environmental factors were collected using a structured face-to-face interview questionnaire. Data was analysed using Statistical Package for Social Science software (SPSS) (version 26) and the statistical tools used were descriptive statistics and logistic regression models. A significant level was considered at p < 0.05. The study findings revealed a significant increment in malaria positivity trend (39.43

Abstract Background Malaria is a major public health concern in Ethiopia, and its incidence could worsen with the spread of the invasive mosquito species Anopheles stephensi in the country. This study aimed to provide updates on the distribution of An. stephensi and likely household exposure in Ethiopia. Methods Entomological surveillance was performed in 26 urban settings in Ethiopia from 2021 to 2023. A kilometer-by-kilometer quadrant was established per town, and approximately 20 structures per quadrant were surveyed every 3 months. Additional extensive sampling was conducted in 50 randomly selected structures in four urban centers in 2022 and 2023 to assess households’ exposure to An. stephensi. Prokopack aspirators and CDC light traps were used to collect adult mosquitoes, and standard dippers were used to collect immature stages. The collected mosquitoes were identified to species level by morphological keys and molecular methods. PCR assays were used to assess Plasmodium infection and mosquito blood meal source. Results Catches of adult An. stephensi were generally low (mean: 0.15 per trap), with eight positive sites among the 26 surveyed. This mosquito species was reported for the first time in Assosa, western Ethiopia. Anopheles stephensi was the predominant species in four of the eight positive sites, accounting for 75–100% relative abundance of the adult Anopheles catches. Household-level exposure, defined as the percentage of households with a peridomestic presence of An. stephensi, ranged from 18% in Metehara to 30% in Danan. Anopheles arabiensis was the predominant species in 20 of the 26 sites, accounting for 42.9–100% of the Anopheles catches. Bovine blood index, ovine blood index and human blood index values were 69.2%, 32.3% and 24.6%, respectively, for An. stephensi, and 65.4%, 46.7% and 35.8%, respectively, for An. arabiensis. None of the 197 An. stephensi mosquitoes assayed tested positive for Plasmodium sporozoite, while of the 1434 An. arabiensis mosquitoes assayed, 62 were positive for Plasmodium (10 for P. falciparum and 52 for P. vivax). Conclusions This study shows that the geographical range of An. stephensi has expanded to western Ethiopia. Strongly zoophagic behavior coupled with low adult catches might explain the absence of Plasmodium infection. The level of household exposure to An. stephensi in this study varied across positive sites. Further research is needed to better understand the bionomics and contribution of An. stephensi to malaria transmission. Graphical Abstract

Background Endemic African malaria vectors are poorly adapted to typical urban ecologies. However, Anopheles stephensi, an urban malaria vector formerly confined to South Asia and the Persian Gulf, was recently detected in Africa and may change the epidemiology of malaria across the continent. Little is known about the public health implications of An. stephensi in Africa. This study is designed to assess the relative importance of household exposure to An. stephensi and endemic malaria vectors for malaria risk in urban Sudan and Ethiopia. Methods Case-control studies will be conducted in 3 urban settings (2 in Sudan, 1 in Ethiopia) to assess the association between presence of An. stephensi in and around households and malaria. Cases, defined as individuals positive for Plasmodium falciparum and/or P. vivax by microscopy/rapid diagnostic test (RDT), and controls, defined as age-matched individuals negative for P. falciparum and/or P. vivax by microscopy/RDT, will be recruited from public health facilities. Both household surveys and entomological surveillance for adult and immature mosquitoes will be conducted at participant homes within 48 hours of enrolment. Adult and immature mosquitoes will be identified by polymerase chain reaction (PCR). Conditional logistic regression will be used to estimate the association between presence of An. stephensi and malaria status, adjusted for co-occurrence of other malaria vectors and participant gender. Conclusions Findings from this study will provide evidence of the relative importance of An. stephensi for malaria burden in urban African settings, shedding light on the need for future intervention planning and policy development.

The study assessed the efficacy and residual activity of SumiLarv™ 2MR, SumiLarv™ 0.5G, and Abate®1SG (as a positive control) against Anopheles stephensi larvae in Awash Subath Kilo, Afar Regional State, Ethiopia. A semi-field experiment used plastic containers with capacities of 100L, 250L, and 500L. For SumiLarv 2MR, four 100L containers were treated with one disc each, compared to two untreated controls. Similarly, four 250L containers were treated with one disc each with two untreated controls. Eight 250L containers were treated with a half-dose to match one disc per 500L, alongside four untreated controls. For SumiLarv 0.5G and Abate 1SG, four 100L containers were treated with each larvicide, with two untreated controls. Each container received 20–25 third and fourth instar An. stephensi larvae. Observations of adult emergence were conducted until all pupae either emerged or died. The result revealed that SumiLarv 2MR had a nine-month residual efficacy, SumiLarv 0.5G had a seven-week efficacy, and Abate 1SG had a five-week efficacy. SumiLarv 2MR discs retained nearly 50% of their initial pyriproxyfen content after nine months, indicating potential for extended residual activity. The study highlights SumiLarv 2MR's long-term efficacy as a larvicide against An. stephensi in Ethiopia.

Plasmodium vivax is the second most common malaria parasite in Ethiopia. It has been treated with chloroquine (CQ) for the past seven decades. However, the emergence of CQ-resistant strains in the nation urged the Federal Ministry of Health of Ethiopia to review its national malaria treatment guideline in 2018. In the revised guideline, the first-line treatment for uncomplicated P. vivax infection is a combination of CQ and primaquine (PQ). Thus, the present study was designed to evaluate the in vivo efficacy of CQ and PQ combination therapy against clinical P. vivax mono-infection in one of the malaria-endemic areas of Ethiopia. An open-label prospective clinical trial was conducted in the Limmu Kossa District, Jimma zone, Southwest Ethiopia, from September 2023 to March 2024. A total of 108 patients were recruited for the study. All participants received treatment with CQ at a dosage of 25 mg/kg over three days, followed by PQ at 0.25 mg/kg for 14 consecutive days. Patients were monitored for 42 days for any signs of treatment failure and malaria clinical symptoms, as per the World Health Organization (WHO) guidelines for anti-malarial drug evaluation. Additionally, haemoglobin (Hb) levels, body temperature, any adverse events, and signs of haemolysis were assessed. Data was analysed using R-software (version 4.0.0) and a significant level was considered at p < 0.05. The median age of the patients was 23 years, ranging from 2.5 to 62 years. Of the 108 patients initially recruited, 100 completed the 42-day follow-up period. The combination therapy of CQ and PQ for uncomplicated clinical P. vivax malaria demonstrated excellent therapeutic efficacy, with a 100

The molecular mechanisms of amitraz and chlorfenapyr resistance remain only poorly understood for major agricultural pests and vectors of human diseases. This study focusses on a multi-resistant field strain of the crop pest Tetranychus urticae, which could be readily selected in the laboratory to high levels of amitraz and chlorfenapyr resistance. Toxicity experiments using tralopyril, the active toxophore of chlorfenapyr, suggested decreased activation as a likely mechanism underlying resistance. Starting from the same parental strain, transcriptome profiling revealed that a cluster of detoxifying genes was upregulated after amitraz selection, but unexpectedly downregulated after chlorfenapyr selection. Further functional validation associated the upregulation of CYP392A16 with amitraz metabolism and the downregulation of CYP392D8 with reduced activation of chlorfenapyr to tralopyril. Genetic mapping (QTL analysis by BSA) was conducted in an attempt to unravel the genetic mechanisms of expression variation and resistance. This revealed that chlorfenapyr resistance was associated with a single QTL, while 3 QTLs were uncovered for amitraz resistance. Together with the observed contrasting gene expression patterns, we argue that transcriptional regulators most likely underly the distinct expression profiles associated with resistance, but these await further functional validation.

Pesticide resistance represents a clear and trackable case of adaptive evolution with a strong societal impact. Understanding the factors associated with the evolution and spread of resistance is imperative to develop sustainable crop management strategies. The two-spotted spider mite Tetranychus urticae, a major crop pest with worldwide distribution and a polyphagous lifestyle, has evolved resistance to most classes of pesticides. Tetranychus urticae exists as either a green- or a red-coloured morph. However, the extent of genetic divergence and reproductive compatibility vary across populations of these colour morphs, complicating their taxonomic resolution at the species level. Here, we studied patterns of genetic differentiation and barriers to gene flow within and between morphs of T. urticae in order to understand the factors that influence the spread of resistance mutations across its populations. We derived multiple iso-female lines from Tetranychus populations collected from agricultural crops. We generated genomic and morphological data, characterized their bacterial communities and performed controlled crosses. Despite morphological similarities, we found large genomic differentiation between the morphs. This pattern was reflected in the incomplete, but strong postzygotic incompatibility in crosses between colour morphs, while crosses within morphs from different geographical locations were largely compatible. In addition, our results suggest recent/on-going gene flow between green-coloured T. urticae and T. turkestani. By screening the sequences of 10 resistance genes, we found evidence for multiple independent origins and for single evolutionary origins of target-site resistance mutations. Our results indicate that target-site mutations mostly evolve independently in populations on different geographical locations, and that these mutations can spread due to incomplete barriers to gene flow within and between populations.

The development of insecticide resistance in malaria vectors is a challenge for the global effort to control and eradicate malaria. Glutathione S-transferases (GSTs) are multifunctional enzymes involved in the detoxification of many classes of insecticides. For mosquitoes, it is known that overexpression of an epsilon GST, GSTe2, confers resistance towards DDT and pyrethroids. In addition to GSTe2, consistent overexpression of a delta class GST, GSTd3, has been observed in insecticide resistant populations of different malaria vector species. However, the functional role of GSTd3 towards DDT resistance has not yet been investigated. Here, we recombinantly expressed both GSTe2 and GSTd3 from Anopheles arabiensis and compared their metabolic activities against DDT. Both AaGSTd3 and AaGSTe2 exhibited CDNB-conjugating and glutathione peroxidase activity and DDT meta-bolism was observed for both GSTs. However, the DDT dehydrochlorinase activity exhibited by AaGSTe2 was much higher than for AaGSTd3, and AaGSTe2 was also able to eliminate DDE although the metabolite could not be identified. Molecular modeling revealed subtle differences in the binding pocket of both enzymes and a better fit of DDT within the H-site of AaGSTe2. The overexpression but much lower DDT metabolic activity of AaGSTd3, might suggest that AaGSTd3 sequesters DDT. These findings highlight the complexity of insecticide resistance in the major malaria vectors and the difficulties associated with control of the vectors using DDT, which is still used for indoor residual spraying.

Background Anopheles arabiensis, member species of the Anopheles gambiae complex, is the primary vector of malaria and is widely distributed in Ethiopia. Anopheles funestus, Anopheles pharoensis and Anopheles 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 An. gambiae sensu lato (s.l.), might compromise the control efforts of the country. The aim of this study was to investigate composition of mosquito fauna and insecticide resistance status of An. gambiae s.l. in Itang special district ( woreda), Gambella, southwestern Ethiopia. Methods Adult mosquitoes were sampled from September 2020 to February 2021 using the CDC light trap and pyrethrum spray catch (PSC). CDC light traps were placed in three selected houses for two consecutive days per month to collect mosquitoes indoor and outdoor from 6:00 P.M. to 06:00 A.M. and PSC was used to collect indoor resting mosquitoes from ten selected houses once in a month from October 2020 to February 2021. 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 (Anopheles coustani, An. pharoensis, and An. gambiae s.l.) were identified, of which An. coustani was the dominant (8.1%) species. Higher number of mosquitoes (231) were collected outdoor by CDC light traps. Out of 468 adult mosquitoes, 294 were blood fed, 46 were half-gravid and gravid whereas the remaining 128 were unfed. WHO bioassay tests revealed that the populations of An. gambiae s.l. in the study area are resistant against alpha-cypermethrin and deltamethrin, but susceptible to bendiocarb, pirimiphos-methyl and propoxur. 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 to 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.

Malaria is a widespread vector-borne disease in the tropics and subtropics causing nearly half a million deaths every year. Malaria vector control intervention mainly rely on the control of adults using Indoor residual sprayings (IRS) and long lasting insecticidal nets (LLINs). The purpose of this study was to assess the species composition of Anopheles mosquitoes and determine the environmental and physicochemical parameters of their breeding habitats in Bambasi district, Benshangul Gumuz regional state, northwestern Ethiopia. Three major Anopheles breeding habitats were identified in three Kebeles namely; drainage ditch (Keshmando), swamp (Amba 46), and stagnant water (Amba 47). Anopheles mosquito larvae were sampled twice a month from September 2020 to November 2020. A total of 2185 Anopheles mosquito larvae were collected. Of those collected larvae three Anopheles species (Anopheles gambiae s.l. An. funestus and An. coustani complex) were identified. Anopheles gambiae s.l was the most abundant whereas An. funestus and An. coustani were the least in all the study kebeles. Of the three kebeles, Amba 47 was found the most productive for Anopheles followed by Amba 46 and Keshmando. The highest mean density of larvae per dip was sampled in September in all the study sites. The three sampling sites varied in physicochemical characteristics. The findings of this study showed that dissolved oxygen (DO) was highest (7.07 $$\pm$$ 0.55 mg/L) in the swamps and lowest (0.32 $$\pm$$ 0.04 mg/L) in the drainage ditches. Conductivity across different habitats showed wide variations. There were slight variations in temperature between different habitats. Higher total dissolved solids (TDS) 12.19 $$\pm$$ 0.26 mg/L was recorded from the drainage ditches; whereas TDS 9.49 $$\pm$$ 1.62 mg/L was recorded from the swamp. Salinity in the drainage ditches and stagnant water was 5.54 $$\pm$$ 1.00PSU and 3.30 $$\pm$$ 0.97 PSU respectively. There were negative strong correlation between the larval density with temperature and EC but positive correlation between larval density with salinity. However, there was no significant correlation between Anopheles larval density with TDS and DO. In conclusion this study suggested that environmental and physicochemical factors could play an important role in the development of mosquito larvae. Therefore, characterizing mosquito larval habitats is important for targeted control of malaria vectors in Ethiopia.

Abstract Background The rate of decay of the biological efficacy of insecticides used for indoor residual spraying (IRS) is an important factor when making decisions on insecticide choice for national malaria control programmes. A key roadblock to IRS programme is insecticide resistance. If resistance is detected to most of the existing insecticides used for IRS (DDT, pyrethroids, organophosphates and carbamates), the logical next choice could be neonicotinoid insecticides, as pyrethroids are used to treat nets. SumiShield™ 50WG belongs to the neonicotinoid class of insecticides and has shown promising results in several phase I, II and III trials in different settings. The aim of this study was to assess the persistence of SumiShield™ 50WG by spraying on different wall surfaces and determine its decay rates over time in Ethiopia. Methods Five huts with different wall surface types (mud, dung, paint and cement) which represented the Ethiopian house wall surfaces were used to evaluate the residual efficacy of SumiShield™ 50WG. Actellic 300CS sprayed on similar wall surfaces of another five huts was used as a comparator insecticide and two huts sprayed with water were used as a control. All huts were sprayed uniformly by an experienced spray operator; non-stop starting from the door and moving clockwise to cover the entire wall surface of the hut. The treatments were assigned to huts randomly. The residual efficacy of the insecticide formulations was evaluated against a susceptible insectary-reared population of Anopheles arabiensis using WHO cone bioassays. Results SumiShield™ 50WG resulted in mortality rates of over 80% at 120 h post-exposure on all surface types for up to nine months post-spray, while Actellic 300CS yielded mortality rates of over 80% for eight months after spray. Conclusions The results of this trial demonstrated that the residual efficacy of SumiShield™ 50WG extends up to nine months on all treated wall surface types. The long-lasting residual efficacy and unique mode of action of the SemiShield™ 50WG shows that it could be an ideal product to be considered as a potential candidate insecticide formulation for IRS in malaria endemic countries such as Ethiopia or other sub-Saharan countries where the transmission season lasts up to four months or longer.