Refining benthic macroinvertebrate kick sampling protocol for wadeable rivers and streams in Ethiopia.

Streams and rivers cover a larger proportion of the Earth's surface but are highly affected by human pressures. Conversely, bioassessment methods are in their infancy in developing countries such as Ethiopia. In this study, we compared 2- and 3-min macroinvertebrate kick samples at multiple locations for both riffle habitat (RH) and multihabitat (MH) approaches. The performance of each method was evaluated statistically using benthic macroinvertebrate metrics and diversity indices. Results of the Kruskal-Wallis analysis in this study showed no significant differences among methods tested in minimally impacted streams in Ethiopia and generally performed equally irrespective of the methods employed except for total abundances and Ephemeroptera abundances. Furthermore, multivariate analysis of the relative abundances of macroinvertebrate communities using analysis of similarity (ANOSIM), RELATE, non-metric multidimensional scaling (MDS), and classification strength-sampling method comparability (CS-SMC) indicated a high similarity in the macroinvertebrate communities recorded among all methods employed in this study area. However, the index of multivariate dispersion (IMD) test showed variations in relative abundances of macroinvertebrate communities among the methods. In summary, if the focus is not on rare taxa and the required information is not dependent on additional evidence provided by the use of lower taxonomic levels of identification (genus and species), the results of the present study support the use of the shorter 2-min RH kick sampling method for the bioassessment of wadeable rivers and streams in Ethiopia.

Environmental determinants of distribution of freshwater snails and trematode infection in the Omo Gibe River Basin, southwest Ethiopia.

BACKGROUND: Determination of infection rates of snail populations is one of the basic tools for epidemiological studies of snail borne diseases. In this study, we opted to determine the trematode infection of freshwater snails in the Omo-Gibe River Basin, southwest Ethiopia. METHODS: We collected snail samples from 130 observation sites in lakes, wetlands, rivers, reservoirs and irrigation canals surveyed during the dry season (March to May) in 2016. The snail samples were examined for trematode infections by cercarial shedding immediately after collection. Habitat conditions, water quality, human water contact practices and other human activities were assessed at each survey site. A redundancy analysis (RDA) was used to examine the relationship between cercarial infection and environmental variables. The statistical significance of eigenvalues and cercariae-environment correlations generated by the RDA were tested using Monte Carlo permutations at 499 permutations. RESULTS: A total of 3107 snails belonging to five species were collected. The most abundant species was Biomphalaria pfeifferi, representing 66% of the total collection. Overall, 109 (3.6%) of the snails were found infected with trematodes (cercariae). Biomphalaria pfeifferi was found to be the most highly infected, accounting 85% of all infected snails. A total of eight morphologically different types of cercariae were recorded, which included: Echinostoma cercariae, brevifurcate apharyngeate distome cercariae, amphistome cercariae, brevifurcate apharyngeate monostome cercariae, xiphidiocercariae, longifurcate pharyngeate distome cercariae, strigea cercariae and unidentified cercariae. Brevifurcate apharyngeate distome cercariae, and Echinostoma cercariae were the most abundant cercariae, accounting for 36 and 34% of all infection, respectively. The mean concentration of water conductivity and 5 days biological oxygen demand were higher in irrigation canals and lake sampling points. Human activities such as open field defecation, urination, livestock grazing, farming, and swimming were highly correlated with trematode infection. CONCLUSIONS: The abundance, occurrence and infection rates of snail species were largely influenced by water physicochemical quality, sanitation and water contact behaviour of the inhabitants. Human activities, such as open field defecation and urination, livestock grazing, farming, and swimming were important predictors of the abundance of cercariae. Therefore, awareness creation should be implemented for proper containment of excreta (urine and faeces) and reducing human and animal contacts with surface waters to reduce snail-borne disease transmission.