Spatiotemporal distribution and bionomics of Anopheles stephensi in different eco-epidemiological settings in Ethiopia.

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.

Epidemiology of Plasmodium vivax in Duffy negatives and Duffy positives from community and health centre collections in Ethiopia.

BACKGROUND: Malaria remains a significant cause of morbidity and mortality in Ethiopia with an estimated 3.8 million cases in 2021 and 61% of the population living in areas at risk of malaria transmission. Throughout the country Plasmodium vivax and Plasmodium falciparum are co-endemic, and Duffy expression is highly heterogeneous. The public health significance of Duffy negativity in relation to P. vivax malaria in Ethiopia, however, remains unclear. This study seeks to explore the prevalence and rates of P. vivax malaria infection across Duffy phenotypes in clinical and community settings. METHODS: A total of 9580 and 4667 subjects from community and health facilities from a malaria endemic site and an epidemic-prone site in western Ethiopia were enrolled and examined for P. vivax infection and Duffy expression from February 2018 to April 2021. Association between Duffy expression, P. vivax and P. falciparum infections were examined for samples collected from asymptomatic community volunteers and symptomatic subjects from health centres. RESULTS: Infection rate of P. vivax among Duffy positives was 2-22 fold higher than Duffy negatives in asymptomatic volunteers from the community. Parasite positivity rate was 10-50 fold higher in Duffy positives than Duffy negatives among samples collected from febrile patients attending health centres and mixed P. vivax and P. falciparum infections were significantly more common than P. vivax mono infections among Duffy negative individuals. Plasmodium vivax parasitaemia measured by 18sRNA parasite gene copy number was similar between Duffy positives and Duffy negatives. CONCLUSIONS: Duffy negativity does not offer complete protection against infection by P. vivax, and cases of P. vivax in Duffy negatives are widespread in Ethiopia, being found in asymptomatic volunteers from communities and in febrile patients from health centres. These findings offer evidence for consideration when developing control and intervention strategies in areas of endemic P. vivax and Duffy heterogeneity.

Determination of Plasmodium vivax and Plasmodium falciparum Malaria Exposure in Two Ethiopian Communities and Its Relationship to Duffy Expression.

Despite historical dogma that Duffy blood group negativity of human erythrocytes confers resistance to Plasmodium vivax blood stage infection, cases of P. vivax malaria and asymptomatic blood stage infection (subclinical malaria) have recently been well documented in Duffy-negative individuals throughout Africa. However, the impact of Duffy negativity on the development of naturally acquired immunity to P. vivax remains poorly understood. We examined antibody reactivity to P. vivax and P. falciparum antigens at two field sites in Ethiopia and assessed Duffy gene expression by polymerase chain reaction amplification and sequencing of the GATA-1 transcription factor-binding site of the Duffy antigen receptor for chemokines (DARC) gene promotor region that is associated with silencing of erythroid cell transcription and absent protein expression. Antibodies to three of the four P. vivax blood stage antigens examined, RBP2b, EBP2, and DBPIISal-1, were significantly lower (P < 0.001) in Duffy-negative individuals relative to Duffy-positive individuals. In stark contrast, no clear pattern was found across Duffy-negative and Duffy-positive genotypes for P. falciparum antibodies. We conclude that lack of erythroid Duffy expression is associated with reduced serologic responses, indicative of less naturally acquired immunity and less cumulative exposure to blood stage P. vivax parasites relative to Duffy positive individuals living in the same communities.

Comparison of Plasmodium Vivax Infections in Duffy Negatives From Community and Health Center Collections in Ethiopia.

Background: Malaria remains a significant cause of morbidity and mortality in Ethiopia with an estimated 4.2 million annual cases and 61% of the population living in areas at risk of malaria transmission. Throughout the country Plasmodium vivax and P. falciparum are co-endemic, and Duffy expression is highly heterogeneous. The public health significance of Duffy negativity in relation to P. vivax malaria in Ethiopia, however, remains unclear. Methods: A total of 9,580 and 4,667 subjects from community and health facilities from a malaria endemic site and an epidemic-prone site in western Ethiopia were enrolled and examined for P. vivax infection and Duffy expression. Association between Duffy expression, P. vivax and P. falciparum infections were examined for samples collected from asymptomatic community volunteers and symptomatic subjects from health centers. Results: Among the community-based cross-sectional samples, infection rate of P. vivax among the Duffy positives was 2-22 fold higher than among the Duffy negatives. Parasite positivity rate was 10-50 fold higher in Duffy positive than Duffy negatives among samples collected from the health center settings and mixed P. vivax and P. falciparum infections were significantly more common than P. vivax mono infections among Duffy negative individuals. P. vivax parasitemia measured by 18sRNA parasite gene copy number was similar between Duffy positives and Duffy negatives. Conclusions: Duffy negativity does not offer complete protection against infection by P. vivax, and cases of P. vivax in Duffy negatives are widespread in Ethiopia, being found in asymptomatic volunteers from communities and in febrile patients from health centers. These findings offer evidence for consideration when developing control and intervention strategies in areas of endemic P. vivax and Duffy heterogeneity.

Schistosoma mansoni Infections and Morbidities Among School Children in Hotspot Areas of Jimma Town, Southwest Ethiopia: A Cross-Sectional Study.

Background: Schistosoma mansoni is endemic in all regions of Ethiopia. School-age children are highly vulnerable to schistosomiasis-related morbidities. This study aimed to determine the prevalence of S. mansoni and morbidities among schoolchildren in schistosomiasis hotspot areas of Jimma Town. Methods: Cross-sectional study was conducted among schoolchildren in Jimma Town. Stool sample was examined using Kato-Katz for the detection of S. mansoni. Results: A total of 332 schoolchildren were included in the study. The prevalence of S. mansoni and STHs was 20.2% and 19.9%, respectively. Males (adjusted odds ratio (AOR) = 4.9; 95% CI: 2.4-10.1; p = .001), swimming habits (AOR = 3.0; 95% CI: 1.1-8.3; p = .033) and schools attended (AOR = 4.3; 95% CI: 1.4-13.6; p = .012, AOR = 3.8; 95% CI: 1.3-10.9; p = .014) were associated factors for S. mansoni infections. Blood in stool (AOR = 2.0; CI: 1.0-4.1; p = .045) and feeling general malaise (AOR = 4.0; CI: 1.4-11.3; p = .007) were significantly associated with S. mansoni infection-related morbidities. Moreover, prevalence of stunting among schoolchildren 6 to 11 years of age was 29.7% (71/239). Conclusion: The transmission of S. mansoni among schoolchildren is moderate. Sex, swimming habits and schools attended were associated with S. mansoni infections. Blood in stool and general malaise were clinical characteristics associated with S. mansoni infections. Integration of health promotion is needed to achieve control and elimination goals. Attention should also be given to stunted growth of the children.

Residual efficacy of SumiShield™ 50WG for indoor residual spraying in Ethiopia.

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.

An experimental hut study evaluating the impact of pyrethroid-only and PBO nets alone and in combination with pirimiphos-methyl-based IRS in Ethiopia.

BACKGROUND: Pyrethroid resistance observed in populations of malaria vectors is widespread in Ethiopia and could potentially compromise the effectiveness of insecticide-based malaria vector control interventions. In this study, the impact of combining indoor residual spraying (IRS) and insecticide-treated nets (ITNs) on mosquito behaviour and mortality was evaluated using experimental huts. METHODS: A Latin Square Design was employed using six experimental huts to collect entomological data. Human volunteers slept in huts with different types of nets (pyrethroid-only net, PBO net, and untreated net) either with or without IRS (Actellic 300CS). The hut with no IRS and an untreated net served as a negative control. The study was conducted for a total of 54 nights. Both alive and dead mosquitoes were collected from inside nets, in the central rooms and verandah the following morning. Data were analysed using Stata/SE 14.0 software package (College Station, TX, USA). RESULTS: The personal protection rate of huts with PermaNet® 2.0 alone and PermaNet® 3.0 alone was 33.3% and 50%, respectively. The mean killing effect of huts with PermaNet® 2.0 alone and PermaNet® 3.0 alone was 2% and 49%, respectively. Huts with PermaNet® 2.0 alone and PermaNet® 3.0 alone demonstrated significantly higher excito-repellency than the control hut. However, mosquito mortality in the hut with IRS + untreated net, hut with IRS + PermaNet® 2.0 and hut with IRS + PermaNet® 3.0 were not significantly different from each other (p > 0.05). Additionally, pre-exposure of both the susceptible Anopheles arabiensis laboratory strain and wild Anopheles gambiae sensu lato to PBO in the cone bioassay tests of Actellic 300CS sprayed surfaces did not reduce mosquito mortality when compared to mortality without pre-exposure to PBO. CONCLUSION: Mosquito mortality rates from the huts with IRS alone were similar to mosquito mortality rates from the huts with the combination of vector control intervention tools (IRS + ITNs) and mosquito mortality rates from huts with PBO nets alone were significantly higher than huts with pyrethroid-only nets. The findings of this study help inform studies to be conducted under field condition for decision-making for future selection of cost-effective vector control intervention tools.

High-throughput Plasmodium falciparum hrp2 and hrp3 gene deletion typing by digital PCR to monitor malaria rapid diagnostic test efficacy.

Most rapid diagnostic tests for Plasmodium falciparum malaria target the Histidine-Rich Proteins 2 and 3 (HRP2 and HRP3). Deletions of the hrp2 and hrp3 genes result in false-negative tests and are a threat for malaria control. A novel assay for molecular surveillance of hrp2/hrp3 deletions was developed based on droplet digital PCR (ddPCR). The assay quantifies hrp2, hrp3, and a control gene with very high accuracy. The theoretical limit of detection was 0.33 parasites/µl. The deletion was reliably detected in mixed infections with wild-type and hrp2-deleted parasites at a density of >100 parasites/reaction. For a side-by-side comparison with the conventional nested PCR (nPCR) assay, 248 samples were screened in triplicate by ddPCR and nPCR. No deletions were observed by ddPCR, while by nPCR hrp2 deletion was observed in 8% of samples. The ddPCR assay was applied to screen 830 samples from Kenya, Zanzibar/Tanzania, Ghana, Ethiopia, Brazil, and Ecuador. Pronounced differences in the prevalence of deletions were observed among sites, with more hrp3 than hrp2 deletions. In conclusion, the novel ddPCR assay minimizes the risk of false-negative results (i.e., hrp2 deletion observed when the sample is wild type), increases sensitivity, and greatly reduces the number of reactions that need to be run.

Burden of malaria, impact of interventions and climate variability in Western Ethiopia: an area with large irrigation based farming.

BACKGROUND: Land use change has increasingly been expanding throughout the world in the past decades. It can have profound effects on the spatial and temporal distribution of vector borne diseases like malaria through ecological and habitat change. Understanding malaria disease occurrence and the impact of prevention interventions under this intense environmental modification is important for effective and efficient malaria control strategy. METHODS: A descriptive ecological study was conducted by reviewing health service records at Abobo district health office. The records were reviewed to extract data on malaria morbidity, mortality, and prevention and control methods. Moreover, Meteorological data were obtained from Gambella region Meteorology Service Center and National Meteorology Authority head office. Univariate, bivariate and multivariate analysis techniques were used to analyze the data. RESULTS: For the twelve-year time period, the mean annual total malaria case count in the district was 7369.58. The peak monthly malaria incidence was about 57 cases per 1000 people. Only in 2009 and 2015 that zero death due to malaria was recorded over the past 12 years. Fluctuating pattern of impatient malaria cases occurrence was seen over the past twelve years with an average number of 225.5 inpatient cases. The data showed that there is a high burden of malaria in the district. Plasmodium falciparum (Pf) was a predominant parasite species in the district with the maximum percentage of about 90. There was no statistically significant association between season and total malaria case number (F3,8: 1.982, P:0.195). However, the inter-annual total case count difference was statistically significant (F11,132: 36.305, p < 0001). Total malaria case count had shown two months lagged carry on effect. Moreover, 3 months lagged humidity had significant positive effect on total malaria cases. Malaria prevention interventions and meteorological factors showed statistically significant association with total malaria cases. CONCLUSION: Malaria was and will remain to be a major public health problem in the area. The social and economic impact of the disease on the local community is clearly pronounced as it is the leading cause of health facility visit and admission including the mortality associated with it. Scale up of effective interventions is quite important. Continuous monitoring of the performance of the vector control tools needs to be done.

The effect of irrigation on malaria vector bionomics and transmission intensity in western Ethiopia.

BACKGROUND: Irrigation schemes may result in subsequent changes in malaria disease dynamics. Understanding the mechanisms and effects of irrigation on malaria vector bionomics and transmission intensity is essential to develop new or alternative surveillance and control strategies to reduce or control malaria risk. This study was designed to assess the effect of rice irrigation on malaria vector bionomics and transmission intensity in the Gambella Region, Ethiopia. METHODS: Comparative cross-sectional study was conducted in Abobo District of the Gambella Region, Ethiopia. Accordingly, clusters (kebeles) were classified into nearby and faraway clusters depending on their proximity to the irrigation scheme. Adult mosquito survey was conducted in February, August and November 2018 from three nearby and three faraway clusters using Centers for Disease Control and Prevention (CDC) light traps (LTs). During the November survey, human landing catch (HLC) and pyrethrum spray catch (PSC) were also conducted. The collected mosquitoes were morphologically identified to species and tested for Plasmodium infection using circumsporozoite protein enzyme-linked immunosorbent assay (CSP-ELISA). Furthermore, species-specific polymerase chain reaction (PCR) was performed to identify member species of the Anopheles gambiae complex. Chi-square and t-tests were used to analyze the data using the SPSS version 20 software package. RESULTS: A total of 4319 female anopheline mosquitoes comprising An. gambiae sensu lato, An. funestus group, An. pharoensis, An. coustani complex and An. squamosus were collected. Overall, 84.5% and 15.5% of the anopheline mosquitoes were collected from the nearby and faraway clusters, respectively. Anopheles gambiae s.l. was the predominant (56.2%) anopheline species in the area followed by An. pharoensis (15.7%). The density of anopheline mosquitoes was significantly higher in the nearby clusters in both HLCs [t(3) = 5.14, P = 0.0143] and CDC LT catches [t(271.97) = 7.446, P < 0.0001). The overall sporozoite rate of anopheline species from the nearby clusters was 10-fold higher compared to the faraway clusters. CONCLUSIONS: Significantly higher mosquito population density was observed in areas close to the irrigation sites. Sporozoite infection rate in the mosquito population was also markedly higher from the nearby clusters. Therefore, the irrigation scheme could increase the risk of malaria in the area.

Malaria vector dynamics and utilization of insecticide-treated nets in low-transmission setting in Southwest Ethiopia: implications for residual transmission.

BACKGROUND: Understanding the behaviour of local malaria vectors is essential as effectiveness of the commonly used vector-targeted malaria control tools heavily relies on behaviour of the major malaria vectors. This study was conducted to determine species composition, biting behaviour, host preference and infectivity of anopheline mosquitoes, and assess utilization of insecticide-treated nets (ITNs) in a low transmission setting in Southwest Ethiopia. METHODS: Adult anopheline mosquitoes were collected using human landing catches (HLCs), Centers for Disease Control and Prevention (CDC) light traps (LTs) and Pyrethrum Spray Catches (PSCs) from June 2016 to May 2018 in Kishe, Jimma Zone, Southwest Ethiopia. The anopheline mosquitoes were morphologically identified. Moreover, sub-sample of An. gambiae s.l. was identified to species using polymerase chain reaction (PCR). Circum-sporozoite proteins (CSPs) and blood meal sources of the anopheline mosquitoes were tested using enzyme-linked immunosorbent assay (ELISA). In addition, a cross-sectional survey was conducted to assess ITN utilization by the inhabitants. RESULTS: A total of 3659 anopheline mosquitoes comprising An. coustani complex (84.4%), An. gambiae s.l. (11.3%), and An. pharoensis and An. squamosus comprising less than 5% were collected. The anopheline mosquitoes showed marked outdoor (67%) and early evening (63%) biting behaviour. An. coustani complex and An. gambiae s.l. were predominantly zoophilic and anthropophilic, respectively. None of the sampled anopheline were CSP-positive. Most of the households (97.8%) owned at least one ITN, with modest usage by the inhabitants (73.4%). ITN usage was significantly higher among under-five children (AOR = 7.9, 95% CI: 4.41-14.03), household heads and spouses (AOR = 4.8, 95% CI: 3.0-7.59), those with sufficient access to ITNs (AOR = 1.8, 95% CI: 1.39-2.35), and who were not utilizing alternative mosquito repellents (AOR = 2.2, 95% CI: 1.58-2.99). CONCLUSION: The anopheline mosquito species exhibited predominantly outdoor and early evening biting activity. Household ITN coverage was high with slight gap in usage. Vector control interventions should target outdoor and early biting vectors to further suppress the local mosquito population. Moreover, sensitization of the community on consistent use of ITNs is required.

Strongyloidiasis: the most neglected tropical disease in Ethiopia.

BACKGROUND: Strongyloidiasis is the most neglected of the neglected tropical diseases (NTDs). The aim of this commentary is to describe the possible reasons why strongyloidiasis is so overlooked in Ethiopia, and shed light on better ways of control and elimination of the disease. MAIN BODY: This commentary highlights three points why strongyloidiasis is the most neglected of the NTDs in Ethiopia. Firstly, lack of clear category within the NTDs resulted in omission of the disease from reports, intervention programs, and preventive chemotherapy guidelines. Secondly, magnitude of the disease is underestimated due to paucity of studies and low sensitivity of diagnostic methods coupled with asymptomatic nature of most of the infections. Finally, ivermectin (the drug of choice for treatment of strongyloidiasis) is not in use for control of the other soil-transmitted helminthiasis, nor is there ivermectin mass drug administration for control of strongyloidiasis. This might have created gap in control and elimination of the disease in Ethiopia and possibly elsewhere. CONCLUSION: Strongyloidiasis appears to be the most neglected of the NTDs mainly due to nature of the infection, low sensitivity of the routine diagnostic tools and it's exclusion from strategic plans and intervention programs. Moreover, studies on strongyloidiasis should use sensitive diagnostic tools. Strongyloidiasis control and elimination programs should be based on reliable evidence of epidemiology of the disease in Ethiopia.

Soil-transmitted helminth infections and nutritional status of school children in government elementary schools in Jimma Town, Southwestern Ethiopia.

INTRODUCTION: Soil-transmitted helminth infections and malnutrition are major health problems of school-age children in developing countries. Malnutrition and soil-transmitted helminth infections often co-exist with synergetic consequences. OBJECTIVE: The aim of this study was to determine the prevalence and intensity of soil-transmitted helminths and its association with nutritional status of school-age children. METHODS: School-based cross-sectional study was carried out from April to May 2014 among 404 elementary school-age children in Jimma Town, Southwest Ethiopia. Data on background characteristics were collected using structured interviewer administered questionnaire. Anthropometric measurements were taken according to World Health Organization standard. Fresh single stool sample was collected from each study participant and examined using direct wet mount and McMaster techniques. Anthropometric indices were generated using WHO AnthroPlus software. Multivariable logistic regression models were fitted to isolate independent predictors of intestinal parasitic infection and nutritional status using STATA-MP software. All tests were two-sided and P < 0.05 was used to declare statistical significance. RESULTS: The overall prevalence of intestinal parasites and soil-transmitted helminths were 68.6% (n = 277) and 55.0% (n = 222), respectively. A total of eight species of intestinal parasites were identified in this study, Trichuris trichiura being the most common parasite identified followed by Ascaris lumbricoides. Study participants who had a habit of open defecation were two times more likely to be infected with soil-transmitted helminths (adjusted odds ratio = 1.9, 95% confidence interval: 1.0-3.4). The overall prevalence of stunting and thinness were 21.0% (n = 85) and 6.9% (n = 28), respectively. The odds of stunting was significantly high (adjusted odds ratio = 4.0, 95% confidence interval: 1.7-9.7) among children who had fathers working as daily labourers and children with personal dietary diversity score of ⩽3 (adjusted odds ratio = 3.5, 95% confidence interval: 1.5-8.0). T. trichiura infection (adjusted odds ratio = 9.4, 95% confidence interval: 2.0-44.8) was identified as an independent predictor of stunting among school-age children. CONCLUSION: Both the prevalence of soil-transmitted helminths and stunting are high among school-age children in Jimma Town. Although there was no statistically significant association between the STHs, in general, T. trichiura was reported as predictor of stunting. The results imply the need for strengthening strategies for reduction of parasitic infection to curb the pervasively high prevalence of stunting.

Identification of transmission foci of Schistosoma mansoni: narrowing the intervention target from district to transmission focus in Ethiopia.

BACKGROUND: Schistosoma mansoni (S. mansoni) infection is a significant public health problem in Ethiopia, and has wide distribution in the country. The impact of the disease is particularly high on school-age children. Nationwide 385 endemic districts were identified, whereby control and elimination interventions are underway using school-based annual mass drug administration (MDA) with praziquantel. The national elimination program targets endemic districts as a whole. The aim of this study was to identify the transmission foci of Schistosoma mansoni and determine prevalence of soil-transmitted helminths (STHs) in Abeshge district. METHODS: The study was conducted from April to May, 2019 among school-age children randomly selected from public elementary schools in Abeshge district, South-central Ethiopia. Demographic information and data on risk factors of S. mansoni infection were gathered using pre-tested questionnaire. Moreover, a stool sample was collected from each child and examined using Kato-Katz thick smear technique. The data were analyzed using STATA_MP version 12. RESULTS: A total of 389 school-age children from five public elementary schools were included in the study. The overall prevalence of S. mansoni and STHs was 19.3% (75/389) and 35% (136/389), respectively. The prevalence of S. mansoni was 60.6% in Kulit Elementary school, while it was zero in Geraba. The prevalence of S. mansoni was significantly higher among males (AOR = 2.6, 95% CI 1.3-5.1), those with habit of swimming and/or bathing in rivers (AOR = 2.9, 95%CI 1.3-5.1) and involved in irrigation activities (AOR = 2.9, 95% CI 1.0-8.3). Overall, the prevalence of S. mansoni was significantly higher among school children attending Kulit Elementary School compared to those attending the remaining schools (AOR = 12.5, 95%CI 6.2-25.1). CONCLUSION: A wide variation of S. mansoni prevalence was observed among the school children in the different schools. Control interventions better identify and target foci of S. mansoni transmission, instead of targeting the district homogenously.

Detection of foci of residual malaria transmission through reactive case detection in Ethiopia.

BACKGROUND: Sub-microscopic and asymptomatic infections could be bottlenecks to malaria elimination efforts in Ethiopia. This study determined the prevalence of malaria, and individual and household-level factors associated with Plasmodium infections obtained following detection of index cases in health facilities in Jimma Zone. METHODS: Index malaria cases were passively detected and tracked in health facilities from June to November 2016. Moreover, family members of the index houses and neighbours located within approximately 200 m from the index houses were also screened for malaria. RESULTS: A total of 39 index cases initiated the reactive case detection of 726 individuals in 116 households. Overall, the prevalence of malaria using microscopy and PCR was 4.0% and 8.96%, respectively. Seventeen (43.6%) of the index cases were from Doyo Yaya kebele, where parasite prevalence was higher. The majority of the malaria cases (90.74%) were asymptomatic. Fever (AOR = 12.68, 95% CI 3.34-48.18) and history of malaria in the preceding 1 year (AOR = 3.62, 95% CI 1.77-7.38) were significant individual-level factors associated with detection of Plasmodium infection. Moreover, living in index house (AOR = 2.22, 95% CI 1.16-4.27), house with eave (AOR = 2.28, 95% CI 1.14-4.55), area of residence (AOR = 6.81, 95% CI 2.49-18.63) and family size (AOR = 3.35, 95% CI 1.53-7.33) were main household-level predictors for residual malaria transmission. CONCLUSION: The number of index cases per kebele may enhance RACD efforts to detect additional malaria cases in low transmission settings. Asymptomatic and sub-microscopic infections were high in the study area, which need new or improved surveillance tools for malaria elimination efforts.

Epidemiology of soil-transmitted helminths and Schistosoma mansoni: a base-line survey among school children, Ejaji, Ethiopia.

INTRODUCTION: School children are among the high risk groups for soil-transmitted helminths (STHs) and Schistosoma mansoni (S. mansoni) infections in developing countries. The aim of this study was to determine the prevalence and associated factors of STHs and S. mansoni among primary school children. METHODOLOGY: A cross-sectional study was conducted from February 15 to March 30, 2016, involving a total of 340 primary school children (age range 6 to 19 years). Socio-demographic and related data were collected using interviewer-administered questionnaire. Stool samples were collected from each study participant and examined using direct wet mount and modified Kato-Katz thick smear technique. Intensity of the STHs and S. mansoni were determined by estimating the eggs per gram (EPG) of stool. Factors associated with STH and S. mansoni infections were analyzed using multivariable logistic regression model. RESULTS: Prevalence of the STHs and S. mansoni were 38.2% and 12.94%, respectively. The main predictors of STH infections among the children studied were being in the age group of 16-19 years, untrimmed finger nail and household latrine unavailability. Moreover, male children, children with habit of swimming and bathing in the river had significantly higher odds of S. mansoni infection. Most of the children infected with the parasites had light infection. CONCLUSIONS: The burden of STHs and S. mansoni was high among the school children. Deworming intervention should be strengthened, along with awareness creation on proper disposal of human excreta and personal hygiene. Regular monitoring of the burden of the parasites and mass drug administration is required.

Insecticide resistance in Anopheles arabiensis from Ethiopia (2012-2016): a nationwide study for insecticide resistance monitoring.

BACKGROUND: Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) remain the cornerstones of malaria vector control. However, the development of insecticide resistance and its implications for operational failure of preventative strategies are of concern. The aim of this study was to characterize insecticide resistance among Anopheles arabiensis populations in Ethiopia and describe temporal and spatial patterns of resistance between 2012 and 2016. METHODS: Between 2012 and 2016, resistance status of An. arabiensis was assessed annually during the long rainy seasons in study sites from seven of the nine regions in Ethiopia. Insecticide resistance levels were measured with WHO susceptibility tests and CDC bottle bioassays using insecticides from four chemical classes (organochlorines, pyrethroids, organophosphates and carbamates), with minor variations in insecticides tested and assays conducted between years. In selected sites, CDC synergist assays were performed by pre-exposing mosquitoes to piperonyl butoxide (PBO). In 2015 and 2016, mosquitoes from DDT and deltamethrin bioassays were randomly selected, identified to species-level and screened for knockdown resistance (kdr) by PCR. RESULTS: Intense resistance to DDT and pyrethroids was pervasive across Ethiopia, consistent with historic use of DDT for IRS and concomitant increases in insecticide-treated net coverage over the last 15 years. Longitudinal resistance trends to malathion, bendiocarb, propoxur and pirimiphos-methyl corresponded to shifts in the national insecticide policy. By 2016, resistance to the latter two insecticides had emerged, with the potential to jeopardize future long-term effectiveness of vector control activities in these areas. Between 2015 and 2016, the West African (L1014F) kdr allele was detected in 74.1% (n = 686/926) of specimens, with frequencies ranging from 31 to 100% and 33 to 100% in survivors from DDT and deltamethrin bioassays, respectively. Restoration of mosquito susceptibility, following pre-exposure to PBO, along with a lack of association between kdr allele frequency and An. arabiensis mortality rate, both indicate metabolic and target-site mutation mechanisms are contributing to insecticide resistance. CONCLUSIONS: Data generated by this study will strengthen the National Malaria Control Programme's insecticide resistance management strategy to safeguard continued efficacy of IRS and other malaria control methods in Ethiopia.

Transmission dynamics of co-endemic Plasmodium vivax and P. falciparum in Ethiopia and prevalence of antimalarial resistant genotypes.

Ethiopia is one of the few African countries where Plasmodium vivax is co-endemic with P. falciparum. Malaria transmission is seasonal and transmission intensity varies mainly by landscape and climate. Although the recent emergence of drug resistant parasites presents a major issue to malaria control in Ethiopia, little is known about the transmission pathways of parasite species and prevalence of resistant markers. This study used microsatellites to determine population diversity and gene flow patterns of P. falciparum (N = 226) and P. vivax (N = 205), as well as prevalence of drug resistant markers to infer the impact of gene flow and existing malaria treatment regimes. Plasmodium falciparum indicated a higher rate of polyclonal infections than P. vivax. Both species revealed moderate genetic diversity and similar population structure. Populations in the northern highlands were closely related to the eastern Rift Valley, but slightly distinct from the southern basin area. Gene flow via human migrations between the northern and eastern populations were frequent and mostly bidirectional. Landscape genetic analyses indicated that environmental heterogeneity and geographical distance did not constrain parasite gene flow. This may partly explain similar patterns of resistant marker prevalence. In P. falciparum, a high prevalence of mutant alleles was detected in codons related to chloroquine (pfcrt and pfmdr1) and sulfadoxine-pyrimethamine (pfdhps and pfdhfr) resistance. Over 60% of the samples showed pfmdr1 duplications. Nevertheless, no mutation was detected in pfK13 that relates to artemisinin resistance. In P. vivax, while sequences of pvcrt-o were highly conserved and less than 5% of the samples showed pvmdr duplications, over 50% of the samples had pvmdr1 976F mutation. It remains to be tested if this mutation relates to chloroquine resistance. Monitoring the extent of malaria spread and markers of drug resistance is imperative to inform policy for evidence-based antimalarial choice and interventions. To effectively reduce malaria burden in Ethiopia, control efforts should focus on seasonal migrant populations.