Department of Life Sciences, Natural History Museum, Wolfson Wellcome Biomedical Laboratories, Cromwell Road, London, SW7 5BD, UK.
London Centre for Neglected Tropical Disease Research, London, UK.
Parasit Vectors. 2017 Oct 10;10(1):460. doi: 10.1186/s13071-017-2395-y.
This study was designed to determine the distribution and identity of potential intermediate snail hosts of Schistosoma spp. in Bengo, Luanda, Kwanza Norte and Malanje Provinces in north-western Angola. This is an area where infection with Schistosoma haematobium, causing urogenital schistosomiasis, is common but little is yet known about transmission of the disease. Angola has had a varied past with regard to disease control and is revitalising efforts to combat neglected tropical diseases.
Snails were sampled from 60 water-contact points. Specimens of the genera Bulinus, Biomphalaria or Lymnaea were screened for trematode infections by inducing cercarial shedding. Snails were initially identified using shell morphology; subsequently a cytochrome c oxidase subunit 1 (cox1) gene fragment was amplified from a subset of snails from each site, for molecular identification. Cercariae were captured onto FTA cards for molecular analysis. Specimens of Bulinus angolensis collected from the original locality of the type specimen have been characterised and comparisons made with snails collected in 1957 held at the Natural History Museum, London, UK.
In total snails of nine genera were identified using morphological characteristics: Biomphalaria, Bulinus, Gyraulus, Lanistes, Lentorbis, Lymnaea, Melanoides, Physa and Succinea. Significant for schistosomiasis transmission, was the discovery of Bulinus globosus, B. canescens, B. angolensis, B. crystallinus and Biomphalaria salinarum in their type-localities and elsewhere. Bulinus globosus and B. angolensis occurred in two distinct geographical areas. The cox1 sequence for B. globosus differed markedly from those from specimens of this species collected from other countries. Bulinus angolensis is more closely related to B. globosus than originally documented and should be included in the B. africanus group. Schistosoma haematobium cercariae were recovered from B. globosus from two locations: Cabungo, Bengo (20 snails) and Calandula, Malanje (5 snails). Schistosoma haematobium cercariae were identified as group 1 cox1 corresponding to the type common throughout the African mainland.
Various freshwater bodies in north-western Angola harbour potential intermediate snail hosts for urogenital schistosomiasis, highlighting the need to map the rest of the country to identify areas where transmission can occur and where control efforts should be targeted. The molecular phylogeny generated from the samples confirmed that considerable variation exists in B. globosus, which is the primary snail host for S. haematobium in many regions of Africa.
本研究旨在确定本戈、罗安达、北宽扎和马兰热省西北部安哥拉的潜在中间螺宿主的分布和身份。该地区普遍存在引起尿路血吸虫病的曼氏血吸虫感染，但对该病的传播知之甚少。安哥拉在疾病控制方面经历了不同的过去，正在重振努力以防治被忽视的热带病。
从 60 个接触水的地点采集螺。通过诱导尾蚴脱落，对双脐螺属、片形肾螺属或椎实螺属的标本进行吸虫感染筛查。螺类最初根据壳形态进行鉴定;随后，从每个地点的一部分螺类中扩增出一段细胞色素 c 氧化酶亚基 1 (cox1) 基因片段，用于分子鉴定。尾蚴被捕获到 FTA 卡上进行分子分析。从原始模式标本采集的安哥拉圆扁螺的标本已被表征，并与 1957 年在英国伦敦自然历史博物馆保存的螺类进行比较。
总共使用形态特征鉴定了九个属的螺类：片形肾螺属、双脐螺属、圆扁螺属、兰蒂斯螺属、 Lentorbis 螺属、椎实螺属、黑螺属、泡螺属、Physa 螺属和 Succinea 螺属。对血吸虫病传播具有重要意义的是，在其模式产地和其他地方发现了 Bulinus globosus、B. canescens、B. angolensis、B. crystallinus 和 Biomphalaria salinarum。B. globosus 和 B. angolensis 出现在两个不同的地理区域。来自不同国家的 B. globosus 标本的 cox1 序列差异明显。B. angolensis 与最初记录的 B. globosus 更为密切相关，应归入 B. africanus 组。从两个地点的 B. globosus 中回收了 B. haematobium 尾蚴：本戈的卡邦古（Bengo）（20 只螺）和马兰热的坎兰杜拉（Calandula）（5 只螺）。B. haematobium 尾蚴被鉴定为第 1 组 cox1，与整个非洲大陆的典型类型相对应。
安哥拉西北部的各种淡水体都可能是尿路血吸虫病的潜在中间螺宿主，这突显了需要绘制该国其他地区的地图，以确定可能发生传播的地区和应针对的控制努力的目标。从样本中生成的分子系统发育证实，B. globosus 存在相当大的变异，它是非洲许多地区 B. haematobium 的主要螺类宿主。
