Parasites and Vector Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.
Research Foundation in Tropical Diseases and Environment (REFOTDE), Buea, Cameroon.
PLoS Negl Trop Dis. 2021 Jan 19;15(1):e0008926. doi: 10.1371/journal.pntd.0008926. eCollection 2021 Jan.
The impact of large scale Mass Drug Adminstration (MDA) of ivermectin on active onchocerciasis transmission by Simulium damnosum, which transmits the parasite O. volvulus is of great importance for onchocerciasis control programmes. We investigated in the Mbam river system area, the impact of MDA of ivermectin on entomological indices and also verify if there are river system factors that could have favoured the transmission of onchocerciasis in this area and contribute to the persistence of disease. We compared three independent techniques to detect Onchocerca larvae in blackflies and also analyzed the river system within 9 months post-MDA of ivermectin.
Simulium flies were captured before and after 1, 3, 6 and 9months of ivermectin-MDA. The biting rate was determined and 41% of the flies dissected while the rest were grouped into pools of 100 flies for DNA extraction. The extracted DNA was then subjected to O-150 LAMP and real-time PCR for the detection of infection by Onchocerca species using pool screening. The river system was analysed and the water discharge compared between rainy and dry seasons.
We used human landing collection method (previously called human bait) to collect 22,274 adult female Simulium flies from Mbam River System. Of this number, 9,134 were dissected while 129 pools constituted for molecular screening. Overall biting and parous rates of 1113 flies/man/day and 24.7%, respectively, were observed. All diagnostic techniques detected similar rates of O. volvulus infection (P = 0.9252) and infectivity (P = 0.4825) at all monitoring time points. Onchocerca ochengi larvae were only detected in 2 of the 129 pools. Analysis of the river drainage revealed two hydroelectric dams constructed on the tributaries of the Mbam river were the key contributing factor to the high-water discharge during both rainy and dry seasons.
Results from fly dissection (Microscopy), real-time PCR and LAMP revealed the same trends pre- and post-MDA. The infection rate with animal Onchocerca sp was exceptionally low. The dense river system generate important breeding sites that govern the abundance of Simulium during both dry and rainy seasons.
大规模使用伊维菌素进行大规模药物治疗（MDA）对传播寄生虫奥氏曼森线虫的致倦库蚊的有性传播有重大影响，奥氏曼森线虫传播寄生虫奥氏旋盘尾丝虫。我们在 Mbam 河流系统地区进行了研究，调查了 MDA 对昆虫学指标的影响，并验证了是否存在河流系统因素有利于该地区的旋盘尾丝虫传播，并导致疾病持续存在。我们比较了三种独立的技术来检测致倦库蚊中的奥氏旋盘尾丝虫幼虫，并在 MDA 后 9 个月内分析了河流系统。
在伊维菌素 MDA 前、后 1、3、6 和 9 个月采集致倦库蚊。测定叮咬率，并对 41%的苍蝇进行解剖，其余苍蝇分为 100 只苍蝇一组进行 DNA 提取。提取的 DNA 随后用于 O-150 LAMP 和实时 PCR，使用池筛选检测奥氏旋盘尾丝虫属物种的感染。分析了河流系统，并比较了雨季和旱季的水流量。
我们使用人类着陆采集方法（以前称为人类诱饵）从 Mbam 河流系统收集了 22274 只成年雌性致倦库蚊。其中，解剖了 9134 只，组成了 129 个分子筛选池。观察到 1113 只苍蝇/人/天的总体叮咬率和 24.7%的产卵率。所有诊断技术在所有监测时间点都检测到相似的奥氏旋盘尾丝虫感染率（P = 0.9252）和感染力（P = 0.4825）。在 129 个池中仅检测到奥氏奥氏线虫幼虫 2 个。河流排水系统的分析表明，在 Mbam 河支流上建造的两座水电站是雨季和旱季高水流量的关键因素。
蝇解剖（显微镜）、实时 PCR 和 LAMP 的结果显示 MDA 前后趋势相同。动物奥氏旋盘尾丝虫的感染率异常低。密集的河流系统产生了重要的繁殖地，在旱季和雨季都控制着致倦库蚊的丰度。
