School of Life Sciences, University of Nottingham, Nottingham, United Kingdom.
National Public Health Laboratories, Ministry of Health and Social Welfare, Banjul, The Gambia.
PLoS Negl Trop Dis. 2021 Oct 4;15(10):e0009823. doi: 10.1371/journal.pntd.0009823. eCollection 2021 Oct.
There is a need for recent information on intermediate snail hosts of schistosomes in The Gambia; the previous studies were conducted over three decades ago. This study assessed the incidence, species diversity, distribution and infection status of schistosome intermediate snail hosts in the country. Malacological surveys were conducted in all 5 regions of The Gambia: Central River Region (CRR), Upper River Region (URR), Western Region (WR), Lower River Region (LRR) and North Bank Region (NBR). Sampling of snails was undertaken at 114 sites that included permanent water bodies such as streams (bolongs), rice fields, irrigation canals and swamps; and temporal (seasonal) laterite pools. Ecological and physicochemical factors of sites were recorded. Snails were identified morphologically and screened for schistosome infections using molecular techniques. Freshwater snails were found at more than 50% (60/114) of sites sampled. While three species of Bulinus were collected, no Biomphalaria snails were found in any of the sites sampled. Of the total 2877 Bulinus snails collected, 75.9% were identified as Bulinus senegalensis, 20.9% as Bulinus forskalii and 3.2% as Bulinus truncatus. Seasonal pools produced the largest number of snails, and CRR was the region with the largest number of snails. Bulinus senegalensis was found more in seasonal pools as opposed to permanent sites, where B. forskalii and B. truncatus were observed to thrive. Bulinus snails were more common in seasonal sites where aquatic vegetation was present. In permanent sites, the abundance of snails increased with increase in water temperature and decrease in water pH. Bulinus senegalensis was found infected with both S. haematobium and S. bovis, while B. forskalii and B. truncatus had only S. bovis infection. While the human parasite S. haematobium was restricted to just four sites, the livestock parasite S. bovis had a much more widespread geographical distribution across both CRR and URR. This new information on the distribution of intermediate snail hosts of schistosomes in The Gambia will be vital for the national schistosomiasis control initiative.
冈比亚有必要了解当前的血吸虫中间宿主蜗牛信息；此前的研究是在三十多年前进行的。本研究评估了该国血吸虫中间宿主蜗牛的发病率、物种多样性、分布和感染状况。在冈比亚的 5 个地区（上河区、下河区、中河区、西河区和北岸区）进行了贝类学调查。在包括溪流（bolongs）、稻田、灌溉渠和沼泽等永久性水体以及临时（季节性）红土池在内的 114 个地点进行了蜗牛采样。记录了地点的生态和物理化学因素。通过分子技术对蜗牛进行形态学鉴定和血吸虫感染筛查。在超过 50%（60/114）的采样点发现了淡水蜗牛。虽然采集到了三种 Bulinus 蜗牛，但在任何采样点都没有发现 Biomphalaria 蜗牛。在总共采集的 2877 只 Bulinus 蜗牛中，75.9%鉴定为 Bulinus senegalensis，20.9%鉴定为 Bulinus forskalii，3.2%鉴定为 Bulinus truncatus。季节性池塘产生了最多的蜗牛，而中河区是蜗牛数量最多的地区。与永久性地点相比，季节性池塘中发现了更多的 Bulinus senegalensis，而 B. forskalii 和 B. truncatus 在永久性地点生长良好。在季节性地点，存在水生植被时，Bulinus 蜗牛更为常见。在永久性地点，随着水温升高和 pH 值降低，蜗牛的丰度增加。Bulinus senegalensis 被发现感染了 S. haematobium 和 S. bovis，而 B. forskalii 和 B. truncatus 仅感染了 S. bovis。虽然人类寄生虫 S. haematobium 仅局限于四个地点，但牲畜寄生虫 S. bovis 在中河区和上河区的分布更为广泛。冈比亚中间宿主蜗牛分布的新信息对国家血吸虫病控制计划至关重要。
