Department of Environmental Health Sciences and Technology, Jimma University, P.O. Box 378, Jimma, Ethiopia.
Department of Medical Laboratory Sciences & Pathology, Jimma University, P.O. Box 378, Jimma, Ethiopia.
Infect Dis Poverty. 2019 Nov 20;8(1):93. doi: 10.1186/s40249-019-0604-y.
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.
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.
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.
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.
确定蜗牛种群的感染率是蜗牛传播疾病的流行病学研究的基本工具之一。在这项研究中，我们选择确定埃塞俄比亚西南部奥莫-吉贝河流域淡水蜗牛的吸虫感染情况。
我们于 2016 年旱季（3 月至 5 月）从湖泊、湿地、河流、水库和灌溉渠的 130 个观测点采集蜗牛样本。采集后立即通过尾蚴脱落来检查蜗牛样本中的吸虫感染情况。在每个调查点评估栖息地条件、水质、人类与水的接触习惯和其他人类活动。使用冗余分析（RDA）检查尾蚴感染与环境变量之间的关系。通过蒙特卡罗置换法在 499 次置换中检验 RDA 生成的特征值和尾蚴-环境相关性的统计显著性。
共采集到 3107 只属于五个物种的蜗牛。最丰富的物种是比氏巴蜗牛，占总采集量的 66%。总体而言，有 109 只（3.6%）蜗牛被发现感染了吸虫（尾蚴）。比氏巴蜗牛的感染率最高，占所有感染蜗牛的 85%。共记录了 8 种形态不同的尾蚴，包括：后尾蚴、短分叉无咽distome 尾蚴、双吸盘尾蚴、短分叉无咽单吸盘尾蚴、剑尾尾蚴、长分叉有咽 distome 尾蚴、Strigea 尾蚴和未识别的尾蚴。短分叉无咽 distome 尾蚴和后尾蚴是最丰富的尾蚴，分别占所有感染的 36%和 34%。灌溉渠和湖泊采样点的水电导率和 5 天生物需氧量平均值较高。居民的粪便、尿液、牲畜放牧、耕作和游泳等人类活动与吸虫感染高度相关。
蜗牛种类的丰度、发生和感染率在很大程度上受到水理化质量、居民卫生和与水接触行为的影响。粪便和尿液的正确处置以及减少人类和动物与地表水的接触，以减少蜗牛传播疾病的传播。
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