Endalew Zemene

The invasive urban malaria vector Anopheles stephensi threatens 126 million city dwellers in Africa. Controlling An. stephensi requires greater understanding of its origin, invasion dynamics, and insecticide resistance mechanisms. Analysis of 645 whole genomes sampled across Africa, the Middle East, and Asia supports an invasion scenario in which an initial South Asian introduction established a bridgehead population in Djibouti, which seeded distinct invasion fronts in Sudan, Ethiopia/Kenya, and Yemen. These incursions show contrasting rates and routes of spread shaped by landscape topology. Insecticide resistance is predominantly mediated by metabolic detoxification genes, with resistance haplotypes and copy-number amplifications introduced from South Asia. These findings, alongside a companion genomic resource, enable genomic surveillance of An. stephensi spread and resistance to aid control strategies.

Background Under-five children and women of reproductive age in developing countries face a high risk of morbidity from intestinal parasitic infections (IPIs). Maternal IPIs may increase the risk of infection of their children. This study aimed to determine the prevalence of intestinal parasites among mothers and their under-five children at Haro Health Center, Southwest Ethiopia. Methods A cross-sectional study involving under-five children and their mothers was conducted in Haro Health Center between March and June 2019. Socio-demographic data and factors associated with IPIs were collected using a semi-structured questionnaire. Stool samples from both the children and their mothers were examined for intestinal parasites using direct wet-mount microscopy and formol-ether concentration technique. Data were analyzed using STATA_MP version 12 (Stata Corp., TX, USA). Results A total of 209 mother–child pairs participated in the study. Intestinal parasitic infections were detected in 22% (46/209) of the mothers and 19.1% (40/209) of the children. Overall, Ascaris lumbricoides and Giardia lamblia were the predominant intestinal parasites recorded. Significant factors associated with maternal IPIs included source of drinking water (adjusted odds ratio [AOR] = 5.8, 95% CI 1.0–28.3), bathing in the river (AOR = 7.2, 95% CI 2.6–20.0) and having untrimmed fingernails (AOR = 28.0, 95% CI 7.5–105). Among the children, IPIs were significantly associated with having untrimmed fingernails (AOR = 2.6, 95% CI 1.0–6.5) and experiencing diarrhea in the two weeks prior to the survey (AOR = 9.4, 95% CI 2.2–40). Conclusions In this study, untrimmed fingernails were a predisposing factor for IPIs in both the children and their mothers. There is a need to improve personal hygiene and enhance the quality of drinking water for the local population.

The invasion of Africa by the Asian urban malaria vector, Anopheles stephensi, endangers 126 million people across a rapidly urbanising continent where malaria is primarily a rural disease. Control of An. stephensi requires greater understanding of its origin, invasion dynamics, and mechanisms of widespread resistance to vector control insecticides. We present a genomic surveillance study of 551 An. stephensi sampled across the invasive and native ranges in Africa and Asia. Our findings support a hypothesis that an initial invasion from Asia to Djibouti seeded separate incursions to Sudan, Ethiopia, and Yemen before spreading inland, aided by favourable temperature, vegetation cover, and human transit conditions. Insecticide resistance in invasive An. stephensi is conferred by detoxification genes introduced from Asia. These findings, and a companion genomic data catalogue, will form the foundation of an evidence base for surveillance and management strategies for An. stephensi .

Schistosomiasis and soil-transmitted helminth (STH) infections occurring during pregnancy may pose adverse health consequences to the mother and the developing baby. This study aims to determine the prevalence of Schistosoma mansoni and STHs, and their association with adverse birth outcomes among pregnant women in Jimma Town. A cross-sectional study involving 314 pregnant women was conducted in Jimma Town, Southwest Ethiopia. The pregnant women were recruited from selected public health facilities during their antenatal care (ANC) visits from August to December 2021. Data on demographic characteristics and factors associated with S. mansoni and STH infections were collected using a pretested questionnaire. Moreover, during the third trimester, stool specimen of each pregnant woman was examined using Kato-Katz technique, and hemoglobin was measured using a HemoCue analyzer. Data on adverse birth outcomes were collected during delivery. Data were analyzed using STATA-MP_12 (StataCorp., TX, USA). The overall prevalence of intestinal helminthic infections was 26.1%. Soil-transmitted helminths and S. mansoni were detected in 20.4% (95%CI: 15.9–24.8) and 5.7% (95%CI: 3.2–8.3) of the pregnant women, respectively. The magnitude of low birth weight was 6.4%, higher in those with late-term delivery and maternal anemia (p < 0.05). Maternal anemia was also associated with post-partum bleeding (p < 0.05). Pregnant women who carry out laundry activities in the river were significantly more infected by S. mansoni (AOR 10.7, 95% CI: 2.2–51.9). This study sheds light on the burden of maternal STH and S. mansoni infections in Jimma Town. A quarter of the pregnant women were infected with STHs and S. mansoni. It is recommended that pregnant women in the area avoid washing clothes in the river to reduce the risk of S. mansoni infection. Screening for intestinal parasitic infections should be conducted for pregnant women living in endemic areas during their ANC follow-up.

: 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.

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. 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). 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. 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.

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 (F_3,8: 1.982, P:0.195). However, the inter-annual total case count difference was statistically significant (F_11,132: 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.

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. Graphical

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.