Epidemiological Mapping of Human Onchocerciasis in Transmission Suspected Districts of Bale, Borena, and West Arsi Zones of Eastern Ethiopia

Onchocerciasis is mainly found in western part of Ethiopia and there is no evidence of transmission in the east ward. However, some zones (Bale, Borena, and West Arsi) are suspected for transmission given the area has fast flowing rivers and is covered with vegetation. Therefore, this study was conducted to map onchocerciasis transmission in those zones. About 19 villages were selected based on proximity to the rivers, representation of districts, zones, and vegetation covers, whereas the study participants, all village residents of age > 5 years with good health condition, were skin sniped and examined using microscopy. In this study a total of 2560 study participants were surveyed of which 1332 were female (52%) and 122 were male (48%). The age group of 21–30 years was highest (34.4%) and that of age > 51 years was the lowest (3.1%) study participants. The survey result revealed that none of the study participants regardless of age, sex, and location demonstrated skin snip Onchocerca microfilariae. The prevalence of microfilariae and community microfilarial load (CMFL) were 0% and 0 mf/s, respectively. The finding implied that there is no onchocerciasis in the area and, therefore, there is no need for interventions. Black fly distribution, cytotaxonomic study, and intraborder cross transmission monitoring are recommended

Review of Ethiopian onchocerciasis elimination programme

Onchocerciasis is a severe parasitic infection which causes disabling skin and subcutaneous tissue changes. The disease is endemic in many African countries including Ethiopia. In 2013, Ethiopia launched Onchocerciasis elimination program with the goal of attaining interruption of onchocerciasis transmission nationwide by 2020. The country has successfully scaled up interventions and achieved 100% geographic coverage in all known endemic districts. The main strategy for interrupting the disease is mass drug administration (MDA) delivered two times per year. The treatment coverage for the last five years has been maintained at more than 80%. Despite many years of ivermectin MDA the transmission of onchocerciasis in many districts remained unabated. To achieve the 2020 goal, sustained high geographic and therapeutic coverage is required which is validated by coverage surveys. The programme should aim to improve the knowledge and attitude of the community towards the programme in order to improve drug compliance. The partnership between the relevant stakeholders should be strengthened to facilitate open discussions regarding the programme implementation and any challenges that may arise in the control and elimination of the disease. It is also important to consider intensified vector control

Cytotaxonomic characterization and estimation of migration patterns of onchocerciasis vectors (Simulium damnosum sensu lato) in northwestern Ethiopia based on RADSeq data.

BackgroundWhile much progress has been made in the control and elimination of onchocerciasis across Africa, the extent to which vector migration might confound progress towards elimination or result in re-establishment of endemism in areas where transmission has been eliminated remains unclear. In Northern Ethiopia, Metema and Metekel-two foci located near the Sudan border-exhibit continuing transmission. While progress towards elimination has been faster in Metema, there remains a problematic hotspot of transmission. Whether migration from Metekel contributes to this is currently unknown.Methodology/principle findingsTo assess the role of vector migration from Metekel into Metema, we present a population genomics study of 151 adult female vectors using 47,638 RADseq markers and mtDNA CoI sequencing. From additional cytotaxonomy data we identified a new cytoform in Metema, closely related to S. damnosum s.str, here called the Gondar form. RADseq data strongly indicate the existence of two distinctly differentiated clusters within S. damnosum s.l.: one genotypic cluster found only in Metema, and the second found predominantly in Metekel. Because blackflies from both clusters were found in sympatry (in all four collection sites in Metema), but hybrid genotypes were not detected, there may be reproductive barriers preventing interbreeding. The dominant genotype in Metema was not found in Metekel while the dominant genotype in Metekel was found in Metema, indicating that (at the time of sampling) migration is primarily unidirectional, with flies moving from Metekel to Metema. There was strong differentiation between clusters but little genetic differentiation within clusters, suggesting migration and gene flow of flies within the same genetic cluster are sufficient to prevent genetic divergence between sites.Conclusions/significanceOur results confirm that Metekel and Metema represent different transmission foci, but also indicate a northward movement of vectors between foci that may have epidemiological importance, although its significance requires further study