Impact of a large-scale fruit and vegetable irrigation scheme on the micro-epidemiology of malaria in southwest Ethiopia.

BACKGROUND: Malaria continues to represent an important public health problem in Ethiopia. The expansion of irrigated agricultural development projects turns out to be a major impediment to long-lasting and sustainable malaria prevention and control efforts in the country. The aim of this study was to determine the micro-epidemiology of malaria and associated risk factors in and around Gojeb Horizon Irrigation Plantation in southwest Ethiopia. METHODS: A community-based comparative cross-sectional study was conducted from May to June 2018 in Gimbo District, southwest Ethiopia. A total of 186 households (94 from irrigated village and 92 from non-irrigated village) were randomly selected from among the communities living around the Gojeb Horizon plantation. In total, 718 individuals (368 from irrigated village and 350 from non-irrigated village) were recruited from the selected households. A finger-prick blood sample was obtained from each participant. Socio-demographic data from the households and individual study participants were collected using a semi-structured questionnaire. Multivariate regression was used to assess factors associated with micro-epidemiology of malaria. P-value < 0.05 was considered statistically significant. RESULTS: The prevalence of malaria in irrigated and non-irrigated villages was 8.2% and 3.4%, respectively. Plasmodium falciparum, Plasmodium vivax and mixed infections accounted for 57.1%, 38.1%, and 4.8% of the cases, respectively. Individuals living in the irrigated villages were 2.53 (95% CI: 1.23-5.20) times at higher risk of Plasmodium infection as compared to those living in the non-irrigated village. Age (AOR = 1.03, 95% CI: 1.01-1.06) and non-use of long-lasting insecticidal net (AOR = 2.72, 95% CI: 1.03-7.22) were co-predictors of malaria infection in the area. CONCLUSION: This study revealed that communities living in irrigation village were at a higher risk of Plasmodium infection than those living in non-irrigated village, which necessitates the development of tailored interventions that are both targeted and customized.

Urban malaria and its determinants in Eastern Ethiopia: the role of Anopheles stephensi and urbanization.

BACKGROUND: Malaria prevention and control strategies have been hampered by urbanization and the spread of Anopheles stephensi. The spread of this vector into Africa further complicates the already complex malaria situation, that could put about 126 million Africans at risk of infection. Hence, this study aimed to assess the determinants of urban malaria, focusing on the role of urbanization and the distribution of An. stephensi in Eastern Ethiopia. METHODS: A matched case control study was conducted among febrile urban residents of Dire Dawa (malaria positive as cases and negative as a control). A capillary blood sample was collected for parasite identification using microscopic examination and an interviewer administered questionnaire was used to collect additional data. Centers for Disease Control and Prevention miniature light traps (CDC-LT) and Prokopack aspirator were used to collect adult mosquito vectors from the selected cases and control houses to identify the mosquito vector species. Then, the data were exported to STATA for analysis. Conditional logistic regression was done to identify determinants, and principal component Analysis (PCA) was done for some independent variables. RESULTS: This study enrolled 132 cases and 264 controls from urban setting only. Of the 132 cases, 90 cases were positive for Plasmodium falciparum, 34 were positive for Plasmodium vivax and 8 had mixed infections. All cases and controls were similar with regard to their respective age and sex. Travel history (AOR: 13.1, 95% CI 2.8-61.4), presence of eves and holes on walls (AOR: 2.84, 95% CI 1.5-5.5), history of malaria diagnosis (AOR: 2.4, 95% CI 1.1-5.3), owning any livestock (AOR: 7.5, 95% CI 2.4-22.8), presence of stagnant water in the area (AOR: 3.2, 95% CI 1.7-6.1), sleeping under bed net the previous night (AOR: 0.21, 95% CI 0.1-0.6) and knowledge on malaria and its prevention (AOR: 2.2, 95% CI 1.2-4.1) were determinants of urban malaria infection. About 34 adult Anopheles mosquitoes were collected and identified from those selected cases and control houses and 27 of them were identified as An. stephensi. CONCLUSION: Among the cases, the dominant species were P. falciparum. This study identified travel history, house condition, past infection, livestock ownership, stagnant water, bed net use, and malaria knowledge as determinants of infection. This study also found the dominance of the presence of An. stephensi among the collected mosquito vectors. This suggests that the spread of An. stephensi may be impacting malaria infection in the study area. Hence, strengthening urban-targeted malaria interventions should be enhanced to prevent and control further urban malaria infection and spread.

Mapping the distribution of tuberculosis cases and associated factors identified through routine program implementation and community-based active screening in Central Ethiopia.

BACKGROUND: Smear-positive TB patients greatly contribute to community-level transmission of this disease. Locating hotspots would make it easier to prioritize and target control interventions. This study aimed to assess the spatial distribution of smear-positive index TB cases and their secondary cases and the predictors of clustering of smear-positive TB cases. METHODS: This study was conducted in the Silti Zone of Central Ethiopia from 2020 to 2022. The data of smear-positive index TB patients were collected from the unit TB registries of healthcare facilities. Contacts of all index TB patients were screened in the community and tested to identify secondary TB patients. We performed spatial analysis, including Moran's I statistic, the Getis-Ord Gi* statistic and geographically weighted regression (GWR), to assess the global distribution, local clustering and predictors of clustering of smear-positive TB patients, respectively. Additionally, we used inverse distance weighting (IDW) interpolation to predict the distribution of smear-positive TB cases and develop a continuous raster map for places with no data. RESULTS: Spatial autocorrelation analysis revealed that the distribution of smear-positive TB patients exhibited significant clustering (Moran's I = 0.70029; p value < 0.000). The Getis-Ord Gi* output indicated the presence of statistically significant hotspots as well as cold spots in the study area. Significant hotspots were found in 11 Kebeles of the Silti, Dalocha and Misrak Silti districts. Significant coldspots were also found in five kebeles of the Silti and Misrak districts. GWR analysis revealed that no education, primary education, family size and thatched roof houses were significant predictors of the spatial clustering of smear-positive TB cases. We also found that the majority of the secondary TB cases were found in hotspots identified through spatial analysis. CONCLUSION: The study revealed a heterogenous distribution of smear positive TB in the study area and it could act as a model that can be replicated in other regions. The identified hotspots of TB could be targeted through location-based interventions such as systematic active screening in the form of outreach programs to improve the performance of TB prevention and control, including reducing the transmission of TB. Educational status, family size and housing type were some of the factors that significantly influenced the spatial distribution of smear-positive TB in the study area. The distribution of secondary TB cases found through household contact screening coincided with the identified hotspots, indicating greater transmission of the disease in these places.

Genotype distribution and allele frequency of thioester-containing protein 1(Tep1) and its effect on development of Plasmodium oocyst in populations of Anopheles arabiensis in Ethiopia.

BACKGROUND: Thioester-containing protein 1 (TEP1) is a crucial component of mosquitoes' natural resistance to parasites. To effectively combat malaria, there is a need to better understand how TEP1 polymorphism affects phenotypic traits during infections. Therefore, the purpose of this study was to determine the Tep1 genotype frequency in malaria vector populations from south-western Ethiopia and investigate its effect on Plasmodium oocyst development in Anopheles arabiensis populations. METHODS: Using standard dippers, Anopheles mosquito larvae were collected from aquatic habitats in Asendabo, Arjo Dedessa, and Gambella in 2019 and 2020. Collected larvae were reared to adults and identified morphologically. Female An. gambiae s.l. were allowed to feed on infected blood containing the same number of gametocytes obtained from P. falciparum and P. vivax gametocyte-positive individuals using indirect membrane feeding methods. Polymerase Chain Reaction (PCR) was used to identify An. gambiae s.l. sibling species. Three hundred thirty An. gambiae s.l. were genotyped using Restricted Fragment Length Polymorphism (RFLP) PCR and sub samples were sequenced to validate the TEP1 genotyping. RESULTS: Among the 330 samples genotyped, two TEP1 alleles, TEP1*S1 (82% frequency) and TEP1*R1 (18% frequency), were identified. Three equivalent genotypes, TEP1*S1/S1, TEP1*R1/R1, and TEP1*S1/R1, had mean frequencies of 65.15%, 2.12%, and 32.73%, respectively. The nucleotide diversity was ranging from 0.36554 to 0. 46751 while haplotype diversity ranged from 0.48871 to 0.63161, across all loci. All sample sites had positive Tajima's D and Fu's Fs values. There was a significant difference in the TEP1 allele frequency and genotype frequency among mosquito populations (p < 0.05), except populations of Anopheles arabiensis from Asendabo and Gambella (p > 0.05). In addition, mosquitoes with the TEP1 *RR genotype were susceptible and produced fewer Plasmodium oocysts than mosquitoes with the TEP1 *SR and TEP1 *SS genotypes. CONCLUSION: The alleles identified in populations of An. arabiensis were TEP1*R1 and TEP1*S1. There was no significant variation in TEP1*R1 allele frequency between the high and low transmission areas. Furthermore, An. arabiensis carrying the TEP1*R1 allele was susceptible to Plasmodium infection. Further studies on vector-parasite interactions, particularly on the TEP1 gene, are required for vector control techniques.

Tsetse fly density and trypanosoma infection rate in Bedele and Dabo Hana districts of Buno Bedele Zone, Southwest Ethiopia.

BACKGROUND: Trypanosomiasis is an infectious disease caused by parasitic protozoa of the genus Trypanosome and primarily transmitted by tsetse flies. This study aimed to determine the density of tsetse flies and the rate of trypanosome infection in the Bedele and Dabo Hana districts of the Buno Bedele Zone in Ethiopia. RESULTS: A cross-sectional study was conducted from January to February 2023 to catch tsetse flies, determine tsetse density, and estimate the trypanosome infection rate. We used 100 traps (40 NGU, 30 pyramidal, and 30 biconical) to catch the flies. The following standard procedures were followed to identify the specific trypanosome species in the collected tsetse flies: The flies were dissected, and the salivary glands were removed. We placed the salivary glands in a drop of saline solution on a microscope slide. A coverslip was placed over the salivary glands, the slide was examined under a microscope, and the trypanosomes were identified based on their morphology. A total of 3,740 tsetse flies were captured from 100 traps, resulting in an overall apparent density of 18.7 flies per trap per day. Within the study area, only one species of tsetse fly, Glossina tachinoides, was identified. Of the 1,320 dissected Glossina tachinoides, 1.82% were found to be infected with trypanosome parasites. Among these infections, 58.33% were attributed to Trypanosoma congolense, while the remaining 41.67% were caused by Trypanosoma brucei. The infection rate of trypanosomes was significantly higher in female tsetse flies (87.5%) as compared to male flies (12.5%). Furthermore, a significantly higher infection rate was observed in flies older than 20 days (83.33%) and in hunger stage 1 flies (58.33%) compared to hunger stages 2, 3, and 4. CONCLUSIONS: This study highlights the necessity of implementing control and suppression measures targeting the vector (tsetse flies) and the parasite (trypanosomes) to effectively manage and prevent pathogenic animal trypanosomiasis.

Investigating the association between household exposure to Anopheles stephensi and malaria in Sudan and Ethiopia: A case-control study protocol.

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.

Assembled genome of an Ethiopian Plasmodium vivax isolate generated using GridION long-read technology.

Plasmodium vivax causes ~20% of malaria cases in Ethiopia. Here, we report a long-read genome assembly generated from an individual collected in 2022. P. vivax is genetically diverse across endemic regions; thus, the genome assembly of an African isolate is an important resource for the malaria research community.

Resurgence of Clinical Malaria in Ethiopia and Its Link to Anopheles stephensi Invasion.

The invasion of Anopheles stephensi into Africa poses a potential threat to malaria control and elimination on the continent. However, it is not clear if the recent malaria resurgence in Ethiopia has linked to the expansion of An. stephensi. We obtained the clinical malaria case reports and malaria intervention data from the Ethiopian Ministry of Health (MoH) for the period 2001-2022. We analyzed clinical malaria hotspots and investigated the potential role of An. stephensi in the 2022 malaria outbreaks. Clinical malaria cases in Ethiopia decreased by 80%, from 5.2 million cases in 2004 to 1.0 million cases in 2018; however, cases increased steadily to 2.6 million confirmed cases in 2022. Plasmodium vivax cases and proportion have increased significantly in the past 5 years. Clinical malaria hotspots are concentrated along the western Ethiopian border areas and have grown significantly from 2017 to 2022. Major malaria outbreaks in 2022/2023 were detected in multiple sites across Ethiopia, and An. stephensi was the predominant vector in some of these sites, however, it was absence from many of the outbreak sites. The causes of recent upsurge in malaria in Ethiopia may be multi-factorial and it is a subject of further investigation.

Copy Number Variations of Plasmodium vivax DBP1, EBP/DBP2, and RBP2b in Ethiopians Who Are Duffy Positive and Duffy Negative.

Recent evidence challenges the belief that individuals who are Duffy-negative are resistant to Plasmodium vivax due to lacking the Duffy antigen receptor for chemokines. Erythrocyte-binding protein (EBP/DBP2) has shown moderate binding to Duffy-negative erythrocytes in vitro. Reticulocyte-binding protein 2b (RBP2b) interactions with transferrin receptor 1 suggest involvement in Duffy-negative infections. Gene copy number variations in PvDBP1, PvEBP/DBP2, and PvRBP2b were investigated in Duffy-positive and Duffy-negative P vivax infections from Ethiopia. Among Duffy-positive samples, 34% displayed PvDBP1 duplications (Cambodian type). In Duffy-negative infections, 30% showed duplications, mostly Cambodian type. For PvEBP/DBP2 and PvRBP2b, Duffy-positive samples exhibited higher duplication rates (1-8 copies for PvEBP/DBP2, 46%; 1-5 copies for PvRBP2b, 43%) as compared with Duffy-negative samples (20.8% and 26%, respectively). The range of copy number variations was lower in Duffy-negative infections. Demographic and clinical factors associated with gene multiplications in both Duffy types were explored, enhancing understanding of P vivax evolution in Africans who are Duffy negative.

The effect of single low-dose primaquine treatment for uncomplicated Plasmodium falciparum malaria on haemoglobin levels in Ethiopia: a longitudinal cohort study.

BACKGROUND: To interrupt residual malaria transmission and achieve successful elimination of Plasmodium falciparum in low-transmission settings, the World Health Organization (WHO) recommends the administration of a single dose of 0.25 mg/kg (or 15 mg/kg for adults) primaquine (PQ) combined with artemisinin-based combination therapy (ACT), without glucose-6-phosphate dehydrogenase (G6PD) testing. However, due to the risk of haemolysis in patients with G6PD deficiency (G6PDd), PQ use is uncommon. Thus, this study aimed to assess the safety of a single low dose of PQ administered to patients with G6PD deficiency. METHODS: An observational cohort study was conducted with patients treated for uncomplicated P. falciparum malaria with either single-dose PQ (0.25 mg/kg) (SLD PQ) + ACT or ACT alone. Microscopy-confirmed uncomplicated P. falciparum malaria patients visiting public health facilities in Arjo Didessa, Southwest Ethiopia, were enrolled in the study from September 2019 to November 2022. Patients with uncomplicated P. falciparum malaria were followed up for 28 days through clinical and laboratory diagnosis, such as measurements of G6PD levels and haemoglobin (Hb) concentrations. G6PD levels were measured by a quantiative CareSTART™ POCT S1 biosensor machine. Patient interviews were also conducted, and the type and frequency of clinical complaints were recorded. Hb data were taken on days (D) 7, 14, 21, and 28 following treatment with SLD-PQ + ACT or ACT alone. RESULTS: A total of 249 patients with uncomplicated P. falciparum malaria were enrolled in this study. Of these, 83 (33.3%) patients received ACT alone, and 166 (66.7%) received ACT combined with SLD-PQ treatment. The median age of the patients was 20 (IQR 28-15) years. G6PD deficiency was found in 17 (6.8%) patients, 14 males and 3 females. There were 6 (7.2%) and 11 (6.6%) phenotypic G6PD-deficient patients in the ACT alone and ACT + SLD-PQ arms, respectively. The mean Hb levels in patients treated with ACT + SLD-PQ were reduced by an average of 0.45 g/dl (95% CI = 0.39 to 0.52) in the posttreatment phase (D7) compared to a reduction of 0.30 g/dl (95% CI = 0.14 to - 0.47) in patients treated with ACT alone (P = 0.157). A greater mean Hb reduction was observed on day 7 in the G6PDd ACT + SLD-PQ group (- 0.60 g/dL) than in the G6PDd ACT alone group (- 0.48 g/dL); however, there was no statistically significant difference (P = 0.465). Overall, D14 losses were 0.10 g/dl (95% CI = - 0.00 to 0.20) and 0.05 g/dl (95% CI = - 0.123 to 0.22) in patients with and without SLD-PQ, respectively (P = 0.412). CONCLUSIONS: This study's findings indicate that using SLD-PQ in combination with ACT is safe for uncomplicated P. falciparum malaria regardless of the patient's G6PD status in Ethiopian settings. Caution should be taken in extrapolating this finding in other settings with diverse G6DP phenotypes.

Asymptomatic malaria in pregnancy and associated risk factors in Majang Zone, Gambella Region, Southwest Ethiopia: a hard-to-reach malaria hotspot.

BACKGROUND: Asymptomatic malaria in pregnancy (AMiP) is a daunting public health problem with multifaceted adverse outcomes for mothers, fetuses, newborns and beyond. This study aimed to assess the prevalence and risk factors of AMiP and anaemia in Majang Zone, Gambella, Southwest Ethiopia. METHODS: A facility-based cross-sectional study was conducted among 425 pregnant women attending the antenatal care (ANC) clinics of five health facilities in the Majang Zone from November 2022 to February 2023. Sociodemographic, obstetric, and anti-malarial intervention data were collected using an interviewer-administered questionnaire. A capillary blood specimen was collected to diagnose malaria and anaemia as well as determine the blood group. Malaria was diagnosed by rapid diagnostic test (RDT), microscopy, and quantitative polymerase chain reaction (qPCR). Statistical analyses were done by Statistical Package for Social Science (SPSS) version 26.0. The association between dependent and independent variables was assessed by multivariable binary logistic regression, considering P < 0.05 statistically significant. The magnitude of associations was quantified with the adjusted odds ratio (AOR) along with the corresponding 95% confidence interval (CI). RESULTS: The overall prevalence of AMiP was 15.3% (95% CI 12.1, 18.9). It was 11.3% (95% CI 8.4, 14.7) by RDT, 11.8% (95% CI 8.9, 15.2) by microscopy and 17.6% (95% CI 11.7, 24.9) by qPCR. Plasmodium falciparum, moderate parasitaemia and submicroscopic infection accounted for 55.4% of the AMiP prevalence, 50.8% of the parasite density, and 41.6% of the qPCR-positive AMiP, respectively. Nearly 32.3% of pregnant women with AMiP carried gametocytes. Risk factors of AMiP were: not utilizing insecticide-treated net (ITN) within the previous week (AOR: 9.43 95% CI 1.57, 56.62), having a history of malaria within the previous year (AOR: 2.26 95% CI 1.16, 4.42), lack of indoor residual spraying (IRS) within the previous year (AOR: 3.00 95% CI 1.50, 6.00), and ANC contact below two rounds (AOR: 4.28 95% CI 2.06, 8.87). The prevalence of anaemia was 27.7% (95% CI 23.6, 32.1), and it was higher among AMiP-positives (56.9%) than the negatives (22.5%) (P: 000). CONCLUSION: The prevalence of AMiP and anaemia was high, and remained as a critical public health problem in the study area. Focus on the identified risk factors and introduction of more sensitive diagnostic tools should be considered to mitigate AMiP in the study area.

Correction: Beyond eves and cracks: An interdisciplinary study of socio-spatial variation in urban malaria transmission in Ethiopia.

[This corrects the article DOI: 10.1371/journal.pgph.0000173.].

Resurgence of Clinical Malaria in Ethiopia in the Era of Anopheles stephensi Invasion.

Background: The invasion of Anopheles stephensi into Africa poses a potential threat to malaria control and elimination on the continent. However, it is not clear if the recent malaria resurgence in Ethiopia has linked to the expansion of An. stephensi. We aimed to summarize the major achievements and lesson learnt in malaria control in Ethiopia from 2001 to 2022, to assess the new challenges and prospects for the control of An. stephensi. Methods and findings: We obtained the clinical malaria case reports, antimalarial drug treatment records, insecticide-treated and long-lasting insecticidal net (ITN/LLIN) distribution and utilization records, and indoor residual spraying (IRS) coverage data from the Ethiopian Ministry of Health (MoH) for the period 2001-2022. We analyzed clinical malaria hotspots using spatially optimized hotspot analysis. We investigated malaria outbreaks in 2022 and examined the potential role of An. stephensi in the outbreaks.Clinical malaria cases in Ethiopia decreased by 80%, from 5.2 million cases (11% confirmed) in 2004 to 1.0 million cases (92% confirmed) in 2018; however, cases increased steadily to 2.6 million confirmed cases (98% confirmed) in 2022. Plasmodium vivax cases and proportion have increased significantly in the past 5 years. Clinical malaria hotspots are concentrated along the western Ethiopian border areas and have grown significantly from 2017 to 2022. Major malaria outbreaks in 2022/23 were detected in multiple sites across Ethiopia, and An. stephensi was the predominant vector in some of these sites, however, it was absence from many of the outbreak sites. Conclusions: The malaria burden has been significantly reduced in Ethiopia in the past two decades, but in recent years it has increased substantially, and the cause of such increase is a subject of further investigation. Major gaps exist in An. stephensi research, including vector ecology, surveillance, and control tools, especially for adult mosquito control.

Detection of Duffy blood group genotypes and submicroscopic Plasmodium infections using molecular diagnostic assays in febrile malaria patients.

BACKGROUND: Malaria remains a severe parasitic disease, posing a significant threat to public health and hindering economic development in sub-Saharan Africa. Ethiopia, a malaria endemic country, is facing a resurgence of the disease with a steadily rising incidence. Conventional diagnostic methods, such as microscopy, have become less effective due to low parasite density, particularly among Duffy-negative human populations in Africa. To develop comprehensive control strategies, it is crucial to generate data on the distribution and clinical occurrence of Plasmodium vivax and Plasmodium falciparum infections in regions where the disease is prevalent. This study assessed Plasmodium infections and Duffy antigen genotypes in febrile patients in Ethiopia. METHODS: Three hundred febrile patients visiting four health facilities in Jimma town of southwestern Ethiopia were randomly selected during the malaria transmission season (Apr-Oct). Sociodemographic information was collected, and microscopic examination was performed for all study participants. Plasmodium species and parasitaemia as well as the Duffy genotype were assessed by quantitative polymerase chain reaction (qPCR) for all samples. Data were analysed using Fisher's exact test and kappa statistics. RESULTS: The Plasmodium infection rate by qPCR was 16% (48/300) among febrile patients, of which 19 (39.6%) were P. vivax, 25 (52.1%) were P. falciparum, and 4 (8.3%) were mixed (P. vivax and P. falciparum) infections. Among the 48 qPCR-positive samples, 39 (13%) were negative by microscopy. The results of bivariate logistic regression analysis showed that agriculture-related occupation, relapse and recurrence were significantly associated with Plasmodium infection (P < 0.001). Of the 300 febrile patients, 85 (28.3%) were Duffy negative, of whom two had P. vivax, six had P. falciparum, and one had mixed infections. Except for one patient with P. falciparum infection, Plasmodium infections in Duffy-negative individuals were all submicroscopic with low parasitaemia. CONCLUSIONS: The present study revealed a high prevalence of submicroscopic malaria infections. Plasmodium vivax infections in Duffy-negative individuals were not detected due to low parasitaemia. In this study, an improved molecular diagnostic tool was used to detect and characterize Plasmodium infections, with the goal of quantifying P. vivax infection in Duffy-negative individuals. Advanced molecular diagnostic techniques, such as multiplex real-time PCR, loop-mediated isothermal amplification (LAMP), and CRISPR-based diagnostic methods. These techniques offer increased sensitivity, specificity, and the ability to detect low-parasite-density infections compared to the employed methodologies.

The effect of single low-dose primaquine treatment for uncomplicated Plasmodium falciparum malaria on hemoglobin levels in Ethiopia: a longitudinal cohort study.

Background: To interrupt residual malaria transmission and achieve successful elimination of P. falciparum in low-transmission settings, the World Health Organization (WHO) recommends the administration of a single dose of 0.25 mg/kg (or 15 mg/kg for adults) primaquine (PQ) combined with artemisinin-based combination therapy (ACT) without glucose-6-phosphate dehydrogenase (G6PD) testing. However, due to the risk of hemolysis in patients with G6PD deficiency (G6PDd), PQ use is not as common. Thus, this study aimed to assess the safety of a single low dose of PQ administered to patients with G6PD deficiency. Methods: An observational cohort study was conducted with patients treated for uncomplicated P. falciparum malaria with either single-dose PQ (0.25 mg/kg) (SLD PQ) + ACT or ACT alone. Microscopy-confirmed uncomplicated P. falciparum malaria patients visiting public health facilities in Arjo Didessa, Southwest Ethiopia, were enrolled in the study from September 2019 to November 2022. Patients with uncomplicated P. falciparum malaria were followed up for 28 days through clinical and laboratory diagnosis, such as measurements of G6PD levels and hemoglobin (Hb) concentrations. G6PD levels were masured by a quantiative biosensor machine. Patient interviews were also conducted, and the type and frequency of clinical complaints were recorded. Hb data were taken on days (D) 7, 14, 21, and 28 following treatment with SLD-PQ + ACT or ACT alone. Results: A total of 249 patients with uncomplicated P. falciparum malaria were enrolled in this study. Of these, 83 (33.3%) patients received ACT alone, and 166 (66.7%) received ACT combined with SLD-PQ treatment. The median age of the patients was 20 (IQR 14) years. G6PD deficiency was found in 17 (6.8%) patients, 14 males and 3 females. There were 6 (7.2%) and 11 (6.6%) phenotypic G6PD-deficient patients in the ACT alone and ACT + SLD-PQ arms, respectively. The mean Hb levels in patients treated with ACT + SLD-PQ were reduced by an average of 0.45 g/dl (95% CI = 0.39 to 0.52) in the posttreatment phase (D7) compared to a reduction of 0.30 g/dl (95% CI = 0.14 to -0.47) in patients treated with ACT alone (P = 0.157). A greater mean Hb reduction was observed on day 7 in the G6PD deficiency group (-0.56 g/dL) than in the G6PD normal group (-0.39 g/dL); however, there was no statistically significant difference (P = 0.359). Overall, D14 losses were 0.10 g/dl (95% CI = -0.00 to 0.20) and 0.05 g/dl (95% CI = -0.123 to 0.22) in patients with and without SLD-PQ, respectively (P = 0.412). Conclusions: Our findings showed that single low-dose primaquine (SLD-PQ) treatment for uncomplicated P. falciparum malaria is safe and does not increase the risk of hemolysis in G6PDd patients. This evidence suggests that the wider deployment of SLD-PQ for P. falciparum is part of a global strategy for eliminating P. falciparum malaria.

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.

Comparison of the yield of two tuberculosis screening approaches among household contacts in a community setting of Silti Zone, Central Ethiopia: a prospective cohort study.

BACKGROUND: Household contacts of tuberculosis (TB) patients are at a greater risk of infection and developing TB as well. Despite recommendations to actively screen such high-risk groups for TB, it is poorly implemented in Ethiopia. A community-based household contact screening was conducted to compare the yield of two different screening approaches and to identify factors associated with TB occurrence. METHODS: Smear-positive pulmonary TB index cases from six health facilities in six districts of Silti Zone were identified and enrolled prospectively between September 2020 and December 2022. Trained healthcare workers conducted house visits to screen household contacts for TB. WHO (World Health Organization) recommended symptom-based screening algorithms were used. The yield of screening was compared between a two-time screening at study site I and a single baseline screening at study site II, which is the current programmatic approach. Generalized estimating equation was used to run multivariate logistic regression to identify factors associated with TB occurrence. RESULTS: A total of 387 index TB cases (193 at site I and 194 at site II) with 1,276 eligible contacts were included for analysis. The TB yield of repeat screening approach did not show a significant difference compared to a single screening (2.3% at site I vs. 1.1% at site II, p < 0.072). The number needed to screen was 44 and 87 for the repeat and single screening, respectively, indicating a high TB burden in both settings. The screening algorithm for patients with comorbidities of asthma and heart failure had a 100% sensitivity, 19.1% specificity and a positive predictive value of 5.6%. Cough [AOR: 10.9, 95%CI: 2.55,46.37], fatigue [AOR: 6.1, 95%CI: 1.76,21.29], daily duration of contact with index case [AOR: 4.6, 95%CI; 1.57,13.43] and age of index cases [AOR: 0.9, 95%CI; 0.91-0.99] were associated with the occurrence of TB among household contacts. CONCLUSION: Our study showed that the yield of TB was not significantly different between one-time screening and repeat screening. Although repeat screening has made an addition to case notification, it should be practiced only if resources permit. Cough, fatigue, duration of contact and age of index cases were factors associated with TB. Further studies are needed to establish the association between older age and the risk of transmitting TB.

Methods of sampling malaria vectors and their reliability in estimating entomological indices in Africa.

In efforts to intensify malaria control through vector control and hasten the progress towards elimination, the impact of control interventions needs to be evaluated. This requires sampling vector population using appropriate trapping methods. The aim of this article is to critically review methods of sampling malaria vectors and their reliability in estimating entomological indicators of malaria transmission in Africa. The standard methods are human landing catch (HLC), pyrethrum spray catch, and pit shelter for sampling host-seeking, indoor resting, and outdoor resting malaria vectors, respectively. However, these methods also have drawbacks such as exposure of collectors to infective mosquito bites, sampling bias, and feasibility issue. Centers for Disease Control and Prevention (CDC) light traps placed beside human-occupied bed nets have been used as an alternative to the HLC for sampling host-seeking malaria vectors. Efforts have been made to evaluate the CDC light traps against HLC to generate a conversion factor in order to use them as a proxy estimator of human biting rate and entomological inoculation rates in Africa. However, a reproducible conversion factor was not found, indicating that the trapping efficiency of the CDC light traps varies between different geographical locations. Several other alternative traps have also been developed and evaluated in different settings but most of them require further standardization. Among these, human-baited double net trap/CDC light trap combination and mosquito electrocuting trap have the potential to replace the HLC for routine malaria vector surveillance. Further research is needed to optimize the alternative sampling methods and/or develop new surveillance tools based on vector behavior.

Plasmodium falciparum transmission in the highlands of Ethiopia is driven by closely related and clonal parasites.

Malaria cases are frequently recorded in the Ethiopian highlands even at altitudes above 2000 m. The epidemiology of malaria in the Ethiopian highlands, and, in particular, the role of importation by human migration from the highly endemic lowlands is not well understood. We sequenced 187 Plasmodium falciparum samples from two sites in the Ethiopian highlands, Gondar (n = 159) and Ziway (n = 28), using a multiplexed droplet digital PCR (ddPCR)-based amplicon sequencing method targeting 35 microhaplotypes and drug resistance loci. Here, we characterize the parasite population structure and genetic relatedness. We identify moderate parasite diversity (mean HE : 0.54) and low infection complexity (74.9% monoclonal). A significant percentage of infections share microhaplotypes, even across transmission seasons and sites, indicating persistent local transmission. We identify multiple clusters of clonal or near-clonal infections, highlighting high genetic relatedness. Only 6.3% of individuals diagnosed with P. falciparum reported recent travel. Yet, in clonal or near-clonal clusters, infections of travellers were frequently observed first in time, suggesting that parasites may have been imported and then transmitted locally. 31.1% of infections are pfhrp2-deleted and 84.4% pfhrp3-deleted, and 28.7% have pfhrp2/3 double deletions. Parasites with pfhrp2/3 deletions and wild-type parasites are genetically distinct. Mutations associated with resistance to sulphadoxine-pyrimethamine or suggested to reduce sensitivity to lumefantrine are observed at near-fixation. In conclusion, genomic data corroborate local transmission and the importance of intensified control in the Ethiopian highlands.