School of Nursing and Public Health, Department of Public Health Medicine, University of KwaZulu-Natal, Durban, South Africa.
Geography Department, Faculty of Science and Engineering, Bindura University of Science Education, Bag 1020, Bindura, Zimbabwe.
Parasit Vectors. 2021 Apr 23;14(1):222. doi: 10.1186/s13071-021-04720-7.
Schsistosomiasis is endemic in sub-Saharan Africa. It is transmitted by intermediate host snails such as Bulinus and Biomphalaria. An understanding of the abundance and distribution of snail vectors is important in designing control strategies. This study describes the spatial and seasonal variation of B. globosus and Bio. pfeifferi and their schistosome infection rates between May 2014 and May 2015 in Ingwavuma, uMkhanyakude district, KwaZulu-Natal province, South Africa.
Snail sampling was done on 16 sites once every month by two people for 30 min at each site using the scooping and handpicking methods. Snails collected from each site were screened for schistosome mammalian cercariae by the shedding method. The negative binomial generalised linear mixed model (glmm) was used to determine the relationship between abundances of the intermediate host snails and climatic factors [rainfall, land surface temperatures (LST), seasons, habitats, sampling sites and water physico-chemical parameters including pH and dissolved oxygen (DO)].
In total, 1846 schistosomiasis intermediate host snails were collected during the study period. Biompharia pfeifferi was more abundant (53.36%, n = 985) compared to B. globosus (46.64%, n = 861). Bulinus globosus was recorded at 12 sites (75%) and Bio. pfeifferi was present at 7 sites (43.8%). Biompharia pfeifferi cohabited with B. globosus at all the sites it was present. High numbers of Bio. pfeifferi (n = 872, 88.5%) and B. globosus (n = 705, 81.9%) were found between winter and mid-spring. Monthly rainfall showed a statistically significant negative relationship with the abundance of B. globosus (p < 0.05). Dissolved oxygen (DO) had a statistically significant positive relationship with the abundance of Bio. pfeifferi (p < 0.05) while (LST) had a statistically significant negative relationship (p < 0.05). More B. globosus (8.9%, n = 861) were shedding schistosome mammalian cercariae compared to Bio. pfeifferi (0.1%, n = 985) confirming the already documented high prevalence of S. haematobium in Ingwavuma compared to S. mansoni.
Results of this study provide updated information on the distribution of schistosomiasis intermediate host snails in the study area and contributes towards the understanding of the transmission dynamics of schistosomiasis at the micro-geographical scale in this area.
血吸虫病在撒哈拉以南非洲流行。它通过中间宿主蜗牛（如 Bulinus 和 Biomphalaria）传播。了解蜗牛媒介的丰度和分布情况对于设计控制策略非常重要。本研究描述了 2014 年 5 月至 2015 年 5 月期间南非夸祖鲁-纳塔尔省乌姆哈兰古区因格瓦努马的 B. globosus 和 Bio. pfeifferi 的空间和季节性变化及其血吸虫感染率。
每月在 16 个地点由两人进行两次蜗牛采样，每次 30 分钟，使用挖取和手工采集方法。从每个地点采集的蜗牛通过脱落法筛选哺乳动物尾蚴。使用负二项广义线性混合模型（glmm）确定中间宿主蜗牛丰度与气候因素[降雨量、地表温度（LST）、季节、栖息地、采样地点和水理化参数（包括 pH 值和溶解氧（DO）]之间的关系。
在研究期间共采集了 1846 只血吸虫病中间宿主蜗牛。与 B. globosus（46.64%，n=861）相比，Biompharia pfeifferi 更为丰富（53.36%，n=985）。Bulinus globosus 记录在 12 个地点（75%），Bio. pfeifferi 存在于 7 个地点（43.8%）。Bio. pfeifferi 与 B. globosus 同时存在于所有存在的地点。Bio. pfeifferi（n=872，88.5%）和 B. globosus（n=705，81.9%）数量较多的月份是冬末至早春。月降雨量与 B. globosus 的丰度呈统计学显著负相关（p<0.05）。溶解氧（DO）与 Bio. pfeifferi 的丰度呈统计学显著正相关（p<0.05），而地表温度（LST）与丰度呈统计学显著负相关（p<0.05）。与 Bio. pfeifferi（0.1%，n=985）相比，B. globosus （8.9%，n=861）释放血吸虫哺乳动物尾蚴的比例更高，证实了在因格瓦努马已经记录到比曼氏血吸虫更高的埃及血吸虫流行率。
本研究结果提供了该研究区域中血吸虫病中间宿主蜗牛分布的最新信息，并有助于了解该地区微地理尺度上血吸虫病的传播动态。
