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.

First report of Anopheles stephensi from southern Ethiopia.

BACKGROUND: Anopheles stephensi is an emerging exotic invasive urban malaria vector in East Africa. The World Health Organization recently announced an initiative to take concerted actions to limit this vector's expansion by strengthening surveillance and control in invaded and potentially receptive territories in Africa. This study sought to determine the invasion of An. stephensi in southern Ethiopia. METHODS: A targeted entomological survey, both larvae and adult, was conducted in Hawassa City, southern Ethiopia between November 2022 and February 2023. Anopheles larvae were reared to adults for species identification. CDC light traps and BG Pro traps were used indoors and outdoors overnight at selected houses to collect adult mosquitoes in the study area. Prokopack aspirator was employed to sample indoor resting mosquitoes in the morning. Adults of An. stephensi was identified using morphological keys and then confirmed by PCR. RESULTS: Larvae of An. stephensi were found in 28 (16.6%) of the 169 potential mosquito breeding sites surveyed. Out of 548 adult female Anopheles mosquitoes reared from larvae, 234 (42.7%) were identified as An. stephensi morphologically. A total of 449 female anophelines were caught, of which 53 (12.0%) were An. stephensi. Other anopheline species collected in the study area included Anopheles gambiae sensu lato (s.l.), Anopheles pharoensis, Anopheles coustani, and Anopheles demeilloni. CONCLUSION: This study confirmed the presence of An. stephensi in southern Ethiopia. The presence of both larval and adult stages of this mosquito attests that this species established sympatric colonization with native vector species such as An. gambiae (s.l.) in southern Ethiopia. The findings warrant further investigation on the ecology, behaviour, population genetics, and role of An. stephensi in malaria transmission in Ethiopia.

Asymptomatic and submicroscopic malaria infections in sugar cane and rice development areas of Ethiopia.

BACKGROUND: Water resource development projects, such as dams and irrigation schemes, have a positive impact on food security and poverty reduction. However, such projects could increase prevalence of vector borne disease, such as malaria. This study investigate the impact of different agroecosystems and prevalence of malaria infection in Southwest Ethiopia. METHODS: Two cross-sectional surveys were conducted in the dry and wet seasons in irrigated and non-irrigated clusters of Arjo sugarcane and Gambella rice development areas of Ethiopia in 2019. A total of 4464 and 2176 study participants from 1449 households in Arjo and 546 households in Gambella enrolled in the study and blood samples were collected, respectively. All blood samples were microscopically examined and a subset of microscopy negative blood samples (n = 2244) were analysed by qPCR. Mixed effect logistic regression and generalized estimating equation were used to determine microscopic and submicroscopic malaria infection and the associated risk factors, respectively. RESULTS: Prevalence by microscopy was 2.0% (88/4464) in Arjo and 6.1% (133/2176) in Gambella. In Gambella, prevalence was significantly higher in irrigated clusters (10.4% vs 3.6%) than in non-irrigated clusters (p < 0.001), but no difference was found in Arjo (2.0% vs 2.0%; p = 0.993). On the other hand, of the 1713 and 531 samples analysed by qPCR from Arjo and Gambella the presence of submicroscopic infection was 1.2% and 12.8%, respectively. Plasmodium falciparum, Plasmodium vivax, and Plasmodium ovale were identified by qPCR in both sites. Irrigation was a risk factor for submicroscopic infection in both Arjo and Gambella. Irrigation, being a migrant worker, outdoor job, < 6 months length of stay in the area were risk factors for microscopic infection in Gambella. Moreover, school-age children and length of stay in the area for 1-3 years were significant predictors for submicroscopic malaria in Gambella. However, no ITN utilization was a predictor for both submicroscopic and microscopic infection in Arjo. Season was also a risk factor for microscopic infection in Arjo. CONCLUSION: The study highlighted the potential importance of different irrigation practices impacting on submicroscopic malaria transmission. Moreover, microscopic and submicroscopic infections coupled with population movement may contribute to residual malaria transmission and could hinder malaria control and elimination programmes in the country. Therefore, strengthening malaria surveillance and control by using highly sensitive diagnostic tools to detect low-density parasites, screening migrant workers upon arrival and departure, ensuring adequate coverage and proper utilization of vector control tools, and health education for at-risk groups residing or working in such development corridors is needed.

Anopheles larval habitats seasonality and environmental factors affecting larval abundance and distribution in Arjo-Didessa sugar cane plantation, Ethiopia.

BACKGROUND: Water resource development projects are essential for increasing agricultural productivity and ensuring food security. However, these activities require the modification of pre-existing environmental settings, which may alter mosquito larval habitat availability and seasonality. The intensive utilization of current adult vector control tools results in insecticide resistance among the main vectors. When coupled with behavioural resistances, a shift in malaria vector feeding and resting behaviours could compromise the effectiveness of the current adult vector control strategies. Thus, it is important to look for new or alternative vector control interventions for immatures to complement adult control by focusing on different larval habitats and their seasonal availability. Thus, this study investigated larval habitat seasonality and seasonal larval abundance and distribution in irrigated sugar cane plantation settings in Ethiopia. METHODS: Anopheles mosquito larval habitats were surveyed and visited twice a month for a period of 14 months. Anopheline larvae and pupae were collected, reared, and fed finely ground fish food. Adults were provided with sucrose solution and kept under standard conditions. Female Anopheles mosquitoes were identified morphologically and using a species-specific PCR assay. Environmental parameters, which include habitats' physico-chemical characteristics, were assessed. Larval habitat diversity and larval abundance and distribution were determined across different seasons. RESULTS: The study revealed that Anopheles gambiae sensu lato (s.l.) was the most predominant 4197(57%) vector species, followed by Anopheles coustani complex 2388 (32.8%). Molecular analysis of sub-samples of An. gambiae s.l. resulted in Anopheles arabiensis (77.9%) and Anopheles amharicus (21.5%), and the remaining 1.1% (n = 7) sub-samples were not amplified. Physico-chemical parameters such as temperature (t = 2.22, p = 0.028), conductivity (t = 3.21, p = 0.002), dissolved oxygen (t = 7.96, p = 0.001), nitrate ion (t = 2.51, p = 0.013), and ammonium ion (t = 2.26, p = 0.025) showed a significant and direct association with mosquito larval abundance. Furthermore, mosquito larval abundance was correlated with distance to the nearest houses (r = - 0.42, p = 0.001), exposure to sunlight (r = 0.34, p = 0.001), during long and short rainy season animal hoof prints, truck tires/road puddles and rain pools were negatively correlated (r = - 0.22, p = 0.01) and types of habitat (r = - 0.20, p = 0.01). Significant habitat type productivity were observed in man-made pools (t = 3.881, P = 0.01163), rain pools, animal hoof prints, (t = - 4.332, P = 0.00749 in both short and long rainy season, whereas, during dry seasons habitat type productivity almost similar and have no significance difference. CONCLUSION: The study found that different larval habitats had variable productivity in different seasons, and that physical and physicochemical features like ammonium and nitrate, as well as the distance between larval habitats and households, are related to larval production. As a result, vector control should take into account the seasonality of Anopheles larval habitat as well as the impact of pesticide application on larval source management.

First report of Anopheles stephensi in Southern Ethiopia.

Background: Anopheles stephensi is an emerging exotic invasive urban vector of malaria in East Africa. The World Health Organization recently announced an initiative to take concerted actions to limit this vector's expansion by strengthening surveillance and control in invaded and potentially receptive territories in Africa. This study sought to determine the geographic distribution of An. stephensi in southern Ethiopia. Methods: A targeted entomological survey, both larvae and adult, was conducted in Hawassa city, Southern Ethiopia between November 2022 and February 2023. Anopheles Larvae were reared to adults for species identification. CDC light traps and BG Pro traps were used overnight both indoor and outdoor at selected houses to collect adult mosquitoes in the study area. Prokopack Aspirator was employed to sample indoor resting mosquitoes in the morning. Adults of An. stephensi was identified using morphological keys, and then confirmed by PCR. Results: Larvae of An. stephensi were found in 28 (16.6%) of the 169 potential mosquito breeding sites surveyed. Out of 548 adult female Anopheles mosquitoes reared from larvae, 234 (42.7%) were identified to be An. stephensi morphologically. A total of 449 female anophelines were caught, of which 53 (12.0%) were An. stephensi. Other anopheline species collected in the study area included An. gambiae (s.l.), An. pharoensis, An. coustani, and An. demeilloni. Conclusion: The study, for the first time, confirmed the presence of An. stephensi in southern Ethiopia. The presence of both larval and adult stages of this mosquito attest that this species established a sympatric colonization with native vector species such as An. gambiae (s.l.) in Southern Ethiopia. The findings warrant further investigation on the ecology, behavior, population genetics, and role of An. stephensi in malaria transmission in Ethiopia.

Increased malaria incidence following irrigation practices in the Endorheic Rift Valley Basin of Sidama Region, Ethiopia.

BACKGROUND: Water resource development practice such as irrigation is key to ensuring economic growth and food security in developing countries. However, unintended public health problems such as malaria linked to such development projects have been a concern. This study aimed to determine the impact of irrigation on malaria incidence and vector mosquito abundance in southern Ethiopia. METHODS: Eight years' malaria morbidity data were extracted from the medical registers of health facilities in both irrigated and non-irrigated settings. Additionally, adult and larval malaria vector surveys were carried out in both irrigated and non-irrigated villages. The trend of malaria incidence, case distribution across age and sex, seasonality, parasite species proportion, and mosquito density were analyzed and compared between irrigated and non-irrigated villages. RESULTS: The result showed that annual mean malaria incidence was 6.3 higher in the irrigated (95% CI: 0.7-33.6) than in the non-irrigated villages (95% CI: 1.2-20.6). Although a remarkable declining trend in malaria incidence was observed for four successive years (2013-2017), a significant resurgence between 2018 and 2020 was noted following the introduction of irrigation schemes. The densities of adult Anopheles mosquitoes were 15-fold higher in the irrigated compared to non-irrigated villages. Of the total potential mosquito-breeding habitats surveyed, the majority (93%) were from irrigated villages. CONCLUSION: Higher malaria incidence, adult Anopheles density, and mosquito-breeding habitat were recorded in the irrigated villages compared to non-irrigated villages. These observations have important implications for the effectiveness of existing malaria interventions. Environmental management could help reduce the breeding of malaria vector mosquitoes around irrigation schemes.

Asymptomatic and submicroscopic malaria infections in sugar cane and rice development areas of Ethiopia.

Background: Water resource development projects such as dams and irrigation schemes have a positive impact on food security and poverty reduction but might result in increased prevalence of malaria. Methods: Two cross-sectional surveys were conducted in the dry and wet seasons in irrigated and non-irrigated clusters of Arjo sugarcane and Gambella rice development areas of Ethiopia in 2019. A total of 4464 and 2176 blood samples were collected from Arjo and Gambella. A subset of 2244 microscopy negative blood samples were analyzed by PCR. Results: Prevalence by microscopy was 2.0% (88/4464) in Arjo and 6.1% (133/2176) in Gambella. In Gambella, prevalence was significantly higher in irrigated clusters (10.4% vs 3.6%) than in non-irrigated clusters (p < 0.001), but no difference was found in Arjo (2.0% vs 2.0%; p = 0.993). Level of education was an individual risk factors associated with infection in Arjo [AOR: 3.2; 95%CI (1.27-8.16)] and in Gambella [AOR: 1.7; 95%CI (1.06-2.82)]. While duration of stay in the area for < 6 months [AOR: 4.7; 95%CI (1.84-12.15)] and being a migrant worker [AOR: 4.7; 95%CI (3.01-7.17)] were risk factors in Gambella. Season [AOR: 15.9; 95%CI (6.01-42.04)], no ITN utilization [AOR: 22.3; 95%CI (7.74-64.34)] were risk factors in Arjo, and irrigation [AOR: 2.4; 95%CI (1.45-4.07)] and family size [AOR: 2.3; 95%CI (1.30-4.09)] risk factors in Gambella. Of the 1713 and 531 randomly selected smear negative samples from Arjo and Gambella and analyzed by PCR the presence of Plasmodium infection was 1.2% and 12.8%, respectively. P. falciparum, P. vivax, and P. ovale were identified by PCR in both sites. Conclusion: Strengthening malaria surveillance and control in project development areas and proper health education for at-risk groups residing or working in such development corridors is needed.

Susceptibility of primary, secondary and suspected vectors to Plasmodium vivax and Plasmodium falciparum infection in Ethiopia.

BACKGROUND: Insecticide-based vector control interventions in combination with case management with artemisinin-based combination therapy has reduced malaria incidence and prevalence worldwide. Current control methods focus on the primary malaria vectors, Anopheles gambiae sensu lato (s.l.) and the An. funestus group; however, the impact of secondary and suspected vectors has been either sidelined or received limited attention. Defining the susceptibility of secondary, suspected vector species to different parasites in time and space is essential for efficient malaria control and elimination programs. The aim of this study was to assess the susceptibility of An. gambiae s.l., An. coustani complex and An. pharoensis to Plasmodium vivax and P. falciparum infection in Ethiopia. METHODS: Larvae of Anopheles spp. were collected from different aquatic habitats and reared to adults under laboratory conditions, with the temperature and humidity maintained at 27 ± 1 °C and 75 ± 5%, respectively. Adult female mosquitoes were identified to species as An. gambiae s.l., An. coustani complex and An. pharoensis. Females of these three Anopheles spp. were allowed to feed in parallel feeding assays on infected blood containing the same gametocytes isolated from P. falciparum and P. vivax gametocyte-positive patients by indirect membrane feeding assays. All blood-fed mosquitoes were held under laboratory conditions. After 7 days, all surviving mosquitoes were dissected to detect mid-gut oocyst and enumerated under a microscope. RESULTS: Of 5915 female Anopheles mosquitoes exposed to gametocyte-infected blood, 2106 (35.6%)s fed successfully in the 32 independent infection experiments. There was a significant variation in feeding rates among An. gambiae s.l., An. pharoensis and An. coustani complex (G-test = 48.43, P = 3.049e-11). All three exposed mosquito species were receptive to P. vivax and P. falciparum infection development. The percentage of infected mosquitoes following feeding on an infected blood meal was significantly different among species (G-test = 6.49, P = 0.03886). The median infection intensity (II) for An. coustani complex, An. gambiae s.l. and An. pharoensis was 1.16, 2.00 and 1.25, respectively. Although the proportion of infected mosquitoes significantly differed in terms of II, infection rate (IR) and mean oocyst density among the species, mean oocyst density and IR were highly correlated with gametocyte density in all tests (P < 0.001). CONCLUSION: Primary, secondary and suspected vectors were experimentally susceptible to both P. vivax and P. falciparum infection. An effective malaria elimination program might include surveillance and control tools which target secondary and suspected vectors that might play an outdoor transmission role, possibly resulting in reduced focal malaria transmission. Comparison of the three species' mean infection rates with standard deviation.

Evidence of pyrethroid resistance in Anopheles amharicus and Anopheles arabiensis from Arjo-Didessa irrigation scheme, Ethiopia.

BACKGROUND: Indoor residual spraying and insecticide-treated nets are among the key malaria control intervention tools. However, their efficacy is declining due to the development and spread of insecticide resistant vectors. In Ethiopia, several studies reported resistance of An. arabiensis to multiple insecticide classes. However, such data is scarce in irrigated areas of the country where insecticides, pesticides and herbicides are intensively used. Susceptibility of An. gambiae s.l. to existing and new insecticides and resistance mechanisms were assessed in Arjo-Didessa sugarcane plantation area, southwestern Ethiopia. METHODS: Adult An. gambiae s.l. reared from larval/pupal collections of Arjo-Didessa sugarcane irrigation area and its surrounding were tested for their susceptibility to selected insecticides. Randomly selected An. gambiae s.l. (dead and survived) samples were identified to species using species-specific polymerase chain reaction (PCR) and were further analyzed for the presence of knockdown resistance (kdr) alleles using allele-specific PCR. RESULTS: Among the 214 An. gambiae s.l. samples analyzed by PCR, 89% (n = 190) were An. amharicus and 9% (n = 20) were An. arabiensis. Mortality rates of the An. gambiae s.l. exposed to deltamethrin and alphacypermethrin were 85% and 86.8%, respectively. On the other hand, mortalities against pirmiphos-methyl, bendiocarb, propoxur and clothianidin were 100%, 99%, 100% and 100%, respectively. Of those sub-samples (An. amharicus and An. arabiensis) examined for presence of kdr gene, none of them were found to carry the L1014F (West African) allelic mutation. CONCLUSION: Anopheles amharicus and An. arabiensis from Arjo-Didessa sugarcane irrigation area were resistant to pyrethroids which might be synergized by extensive use of agricultural chemicals. Occurrence of pyrethroid resistant malaria vectors could challenge the ongoing malaria control and elimination program in the area unless resistance management strategies are implemented. Given the resistance of An. amharicus to pyrethroids, its behavior and vectorial capacity should be further investigated.

Predicting distribution of malaria vector larval habitats in Ethiopia by integrating distributed hydrologic modeling with remotely sensed data.

Larval source management has gained renewed interest as a malaria control strategy in Africa but the widespread and transient nature of larval breeding sites poses a challenge to its implementation. To address this problem, we propose combining an integrated high resolution (50 m) distributed hydrological model and remotely sensed data to simulate potential malaria vector aquatic habitats. The novelty of our approach lies in its consideration of irrigation practices and its ability to resolve complex ponding processes that contribute to potential larval habitats. The simulation was performed for the year of 2018 using ParFlow-Common Land Model (CLM) in a sugarcane plantation in the Oromia region, Ethiopia to examine the effects of rainfall and irrigation. The model was calibrated using field observations of larval habitats to successfully predict ponding at all surveyed locations from the validation dataset. Results show that without irrigation, at least half of the area inside the farms had a 40% probability of potential larval habitat occurrence. With irrigation, the probability increased to 56%. Irrigation dampened the seasonality of the potential larval habitats such that the peak larval habitat occurrence window during the rainy season was extended into the dry season. Furthermore, the stability of the habitats was prolonged, with a significant shift from semi-permanent to permanent habitats. Our study provides a hydrological perspective on the impact of environmental modification on malaria vector ecology, which can potentially inform malaria control strategies through better water management.

Survivorship of Anopheles gambiae sensu lato in irrigated sugarcane plantation scheme in Ethiopia.

BACKGROUND: To ensure food security, sub-Saharan Africa has initiated massive water resource development projects, such as irrigated agriculture, in recent years. However, such environmental modifications affect the survivorship and development of mosquitoes, which are vectors of different diseases. This study aimed at determining the effects of irrigation practices on development and survivorship of Anopheles gambiae s.l. in Ethiopia. METHODS: A life table experiment was conducted to examine the effect of environmental modification on survivorship of both immature and adult An. gambiae s.l. in irrigated and non-irrigated areas. The pupation rate and development time of the immatures and adult longevity and fecundity were compared between the two settings. RESULTS: The estimated mean survival time of female An. gambiae s.l. in the irrigated and non-irrigated areas was 37.9 and 31.3 days, respectively. A survival analysis showed that adult females of An. gambiae s.l. placed in an irrigated area lived significantly longer than those in a non-irrigated area (χ2 = 18.3, df = 1, P <0.001), and An. gambiae s.l. females lived significantly longer than males in both areas (P < 0.001). CONCLUSIONS: Adult An. gambiae s.l. survivorship was found to be enhanced in the irrigated area compared to non-irrigated area. Longer survival of adult mosquitoes in irrigated areas could have important implications for vectorial capacity and hence malaria transmission.

Effects of rainfall, temperature and topography on malaria incidence in elimination targeted district of Ethiopia.

BACKGROUND: Climate and environmental factors could be one of the primary factors that drive malaria transmission and it remains to challenge the malaria elimination efforts. Hence, this study was aimed to evaluate the effects of meteorological factors and topography on the incidence of malaria in the Boricha district in Sidama regional state of Ethiopia. METHODS: Malaria morbidity data recorded from 2010 to 2017 were obtained from all public health facilities of Boricha District in the Sidama regional state of Ethiopia. The monthly malaria cases, rainfall, and temperature (minimum, maximum, and average) were used to fit the ARIMA model to compute the malaria transmission dynamics and also to forecast future incidence. The effects of the meteorological variables and altitude were assessed with a negative binomial regression model using R version 4.0.0. Cross-correlation analysis was employed to compute the delayed effects of meteorological variables on malaria incidence. RESULTS: Temperature, rainfall, and elevation were the major determinants of malaria incidence in the study area. A regression model of previous monthly rainfall at lag 0 and Lag 2, monthly mean maximum temperature at lag 2 and Lag 3, and monthly mean minimum temperature at lag 3 were found as the best prediction model for monthly malaria incidence. Malaria cases at 1801-1900 m above sea level were 1.48 times more likely to occur than elevation ≥ 2000 m. CONCLUSIONS: Meteorological factors and altitude were the major drivers of malaria incidence in the study area. Thus, evidence-based interventions tailored to each determinant are required to achieve the malaria elimination target of the country.

Impact of sugarcane irrigation on malaria vector Anopheles mosquito fauna, abundance and seasonality in Arjo-Didessa, Ethiopia.

BACKGROUND: Despite extensive irrigation development in Ethiopia, limited studies assessed the impact of irrigation on malaria vector mosquito composition, abundance and seasonality. This study aimed to evaluate the impact of sugarcane irrigation on species composition, abundance and seasonality of malaria vectors. METHODS: Adult Anopheles mosquitoes were collected using CDC light traps from three irrigated and three non-irrigated clusters in and around Arjo-Didessa sugarcane irrigation scheme in southwestern Ethiopia. Mosquitoes were surveyed in four seasons: two wet and two dry, in 2018 and 2019. Mosquito species composition, abundance and seasonality were compared between irrigated and non-irrigated clusters. Anopheles mosquitoes were sorted out to species using morphological keys and molecular techniques. Chi square was used to test the relationships between Anopheles species occurrence, and environmental and seasonal parameters. RESULTS: Overall, 2108 female Anopheles mosquitoes comprising of six species were collected. Of these, 92.7% (n = 1954) were from irrigated clusters and 7.3% (n = 154) from the non-irrigated. The Anopheles gambiae complex was the most abundant (67.3%) followed by Anopheles coustani complex (25.3%) and Anopheles pharoensis (5.7%). PCR-based identification revealed that 74.7% (n = 168) of the An. gambiae complex were Anopheles arabiensis and 22.7% (n = 51) Anopheles amharicus. The density of An. gambiae complex (both indoor and outdoor) was higher in irrigated than non-irrigated clusters. The overall anopheline mosquito abundance during the wet seasons (87.2%; n = 1837) was higher than the dry seasons (12.8%; n = 271). CONCLUSION: The ongoing sugarcane irrigation activities in Arjo-Didessa created conditions suitable for malaria transmitting Anopheles species diversity and abundance. This could drive malaria transmission in Arjo-Didessa and its environs in both dry and wet seasons. Currently practiced malaria vector interventions need to be strengthened by including larval source management to reduce vector abundance in the irrigated areas.

Effects of environmental modification on the diversity and positivity of anopheline mosquito aquatic habitats at Arjo-Dedessa irrigation development site, Southwest Ethiopia.

BACKGROUND: Irrigated agriculture is key to increase agricultural productivity and ensure food security in Africa. However, unintended negative public health impacts (e.g. malaria) of such environmental modification have been a challenge. This study assessed the diversity and distribution of breeding habitats of malaria vector mosquitoes around Arjo-Dedessa irrigation development site in Southwest Ethiopia. METHODS: Anopheline mosquito larvae were surveyed from two agroecosystems, 'irrigated' and 'non-irrigated' areas during the dry (December 2017-February 2018) and wet (June 2018-August 2018) seasons. Mosquito habitat diversity and larval abundance were compared between the irrigated and non-irrigated areas. The association between anopheline mosquito larvae occurrence and environmental parameters was analysed using Pearson chi-square. Multiple logistic regression analysis was used to determine primary parameters that influence the occurrence of anopheline larvae. RESULTS: Overall, 319 aquatic habitats were surveyed during the study period. Around 60% (n = 152) of the habitats were positive for anopheline mosquito larvae, of which 63.8% (n = 97) and 36.2% (n = 55) were from irrigated and non-irrigated areas, respectively. The number of anopheline positive habitats was two-fold higher in irrigated than non-irrigated areas. Anopheline larval abundance in the irrigated area was 16.6% higher than the non-irrigated area. Pearson's chi-square analysis showed that season (χ2 = 63.122, df = 1, P < 0.001), agroecosystem (being irrigated or non-irrigated) (χ2 = 6.448, df = 1, P = 0.011), and turbidity (χ2 = 7.296, df = 2, P = 0.025) had a significant association with larval anopheline occurrence. CONCLUSIONS: The study showed a higher anopheline mosquito breeding habitat diversity, larval occurrence and abundance in the irrigated than non-irrigated areas in both dry and wet seasons. This indicates that irrigation development activities contribute to proliferation of suitable mosquito breeding habitats that could increase the risk of malaria transmission. Incorporating larval source management into routine malaria vector control strategies could help reduce mosquito population density and malaria transmission around irrigation schemes.

Correction to: Ten years malaria trend at Arjo-Didessa sugar development site and its vicinity, Southwest Ethiopia: a retrospective study.

Following publication of the original article [1], it came to the authors' attention that unfortunately the last name of one of the authors is spelled incorrectly in the published article.

Ten years malaria trend at Arjo-Didessa sugar development site and its vicinity, Southwest Ethiopia: a retrospective study.

BACKGROUND: The trend analysis of malaria data from health facilities is useful for understanding dynamics of malaria epidemiology and inform for future malaria control planning. Changes in clinical malaria characteristics, like gender and age distribution are good indicators of declining malaria transmission. This study was conducted to determine the malaria trend at Arjo-Didessa sugar development site and its vicinity, southwest Ethiopia, from 2008 to 2017. METHODS: Monthly malaria confirmed case data from 2008 to 2017 was extracted from 11 health facilities based on clinical registers at Arjo sugar development site and its vicinity, southwest Ethiopia. Both positivity rate and malaria incidence rate were calculated. Changes in malaria parasite species and seasonality were analysed; age structure and gender distribution were compared between different study periods. Trend in malaria incidence and climatic impact were analysed and past LLIN and IRS campaigns were used as dynamics modifier. RESULTS: Over a period of 10 years, 54,020 blood film were collected for malaria diagnosis in the health facilities at the area, of which 18,049 (33.4%) were confirmed malaria cases by both microscopically and RDT. Plasmodium falciparum, Plasmodium vivax, and mixed infection (P. falciparum and P. vivax) accounted for 8660 (48%), 7649 (42.4%), and 1740 (9.6%) of the malaria cases, respectively. The study also revealed that P. vivax was the predominant over P. falciparum for 4 years (2010, 2014, 2015 and 2016). There was a remarkable reduction of overall malaria infection during the 10 years. Malaria has been reported in all age groups, but age distribution showed that vast majority of cases were adults age 15 years and above 13,305 (73.7%). In all age groups, males were more significantly affected than females (χ2 = 133.0, df = 2, P < 0.0001). Moreover, malaria positivity rate showed a strong seasonality (χ2 = 777.55, df = 11, P < 0.0001). However, malaria cases were reported in all seasons across 10 years in the study area. CONCLUSION: In general, malaria positivity showed a declining trend over 10 years period in the area. However, current prevalence shows it is public health burden and needs attention for further intensification of interventions. In the study area, both P. falciparum and P. vivax co-exist and P. vivax is more prevalent than P. falciparum in almost half of the years. Therefore, malaria interventions should be strengthened in the study area.

Timely initiation of postpartum contraceptive utilization and associated factors among women of child bearing age in Aroressa District, Southern Ethiopia: a community based cross-sectional study.

BACKGROUND: Globally, more than 90% of women during the first year of postpartum period want to either delay or avoid future pregnancies. The first year postpartum period is more crucial time to use modern contraceptives that enhance maternal and child health, so more attention should be given on time of initiating modern contraceptive utilization after delivery. Therefore, the aim of this study was to assess the magnitude and associated factors of timely initiation of postpartum contraceptive utilization among women of child bearing age in Aroressa district, Southern Ethiopia. METHODS: The study was conducted in Aroressa district from March 15 to April 15, 2017. A community based cross-sectional study design with interviewer administered structured and pretested questionnaire was used. Multistage sampling technique was employed involving a total of 695 women of child bearing age who delivered a child in the past 12 months prior to the study period. Data were cleaned, coded and entered into Epi data version 3.1, then exported to statistical package for social science version 20 for analysis. Descriptive statistics, Bivariate and Multivariate logistic regression analysis were done. p-value < 0.05 was used to consider significant variables. RESULTS: The magnitude of timely initiation of postpartum contraceptive utilization was found to be 31.7% [95% CI (28, 36)]. Antenatal care [AOR = 1.94, 95% CI (1.23, 3.01)], postnatal care [AOR = 1.90, 95%CI (1.23, 2.94)], spousal communication on contraceptive methods [AOR = 1.63, 95% CI (1.09, 2.41)] and resumption of menses after delivery [AOR = 2.6, 95% CI (1.47, 3.81)] were predictors positively associated with timely initiation of postpartum contraceptive utilization. CONCLUSION: The magnitude of timely initiation of postpartum contraceptive utilization was low. Strengthening integration of family planning information with antenatal and postnatal care follow up and encouraging spousal communication by promoting information, education and communication activities is important to enhance contraceptive use on timely manner.

Efficient attractants and simple odor-baited sticky trap for surveillance of Anopheles arabiensis Patton mosquito in Ethiopia.

INTRODUCTION: Many efforts have been made to ease the burden of malaria through vector control, among whichis the development of odor-baited traps and evaluation of efficient attractants that could replace host odor. However, most traps and evaluated attractants are expensive, which poor communities cannot afford. This study was conductedwith the aim to devise asimple and affordable odor-baited trap and to investigate effective but affordable attractants for trapping Anopheles arabiensis. METHODOLOGY: First, an odor-baited sticky trap was developed; next, an experimental study with randomized design was conducted to evaluate the efficacy of selected attractants for trapping Anopheles arabiensis using the designed trap from June to August 2014. Laboratory strain Anopheles arabiensis were obtainedfrom the Adama Malaria Research and Training Center Insectary. Wild Anopheline mosquito larvae were collected from a temporary breeding site, reared in Asendabo Vector Biology Laboratory, and tested. RESULTS: A simple odor-baited sticky trap was designed. Selected attractants were tested for attracting efficiency using the designed trap. Among the evaluated attractants, cow urine, which was kept for four days, attracted significantly more wild population and laboratory strains of the Anopheles arabiensisthan a worn sock alone and the combination of cow urine and a worn sock. CONCLUSIONS: Although further comparison studies with other standard traps are needed, the designed trap in conjunction with efficient attractant is shown to be effective for mosquito surveillance. Of the tested attractants, cow urine was anefficient attractant both for the wild population and the laboratory strain of Anohpeles arabiensis.