Sample characteristics per health district.

BackgroundLymphatic filariasis (LF) is a parasitic disease-causing severe pain, disfiguring, and disabling clinical conditions such as lymphoedema and hydrocoele that are associated with morbidity and stigma. The disease has been targeted for global elimination with the annual mass drug administration (MDA) strategy. We have evaluated the need to implement mass drug administration against W. bancrofti infection in urban zones of Monrovia using both serology and molecular Xenomonitoring (XM).MethodologyConfirmatory mapping protocols recommended by WHO were carried out in the four health districts of Monrovia. Schools were selected using probability proportionate to size (PPS) and eligible children aged 9–14 years were tested for circulating filarial antigen (CFA) using an Alere Filariasis Test Strip (FTS). Health Districts were assessed as requiring MDA if they exceeded the critical cut off of 3 positive tests corresponding to CFA ≥ 2%. Two health districts were selected for entomological investigations based on pre-disposing risk factors for mosquitoes. Mosquito collection was carried out using exit traps (ETs) and gravid trap (GTs) for 6 months. Mosquitos were tested for W. bancrofti DNA using qPCR.Principal findingsNinety-six children in the sample had a positive serology test result, with a mean CFA prevalence of 5.3% (95% CI: 4.4 - 6.5%). All four health districts exceeded the critical cut off of 3 cases and in Somalia Drive there were 59 positive tests. In Central Monrovia which had 4 cases, 2 of them are likely locally imported from Somalia Drive where the children reported living. A total of 19,355 potential vector mosquitoes were collected, of which 84.4% (16,335) were Culex and 16.6% (3,020) An. gambiae. All mosquitoes were analyzed, and none were found to be infected with W. bancrofti.ConclusionMDA is required in three health districts of Monrovia. Confirmatory mapping protocols require adaptation for urban settings. The sampling strategy for the XM was unable to identify transmission in this case and requires further research to optimise it for informing MDA implementation decisions.背景 淋巴丝虫病（Lymphatic filariasis, LF）是一种寄生虫病，可引发剧烈疼痛、毁形性与致残性临床病症，例如淋巴水肿与鞘膜积液，这类病症会导致患者罹患疾病并承受污名化压力。该疾病已被纳入全球消除目标，采用年度集体服药（mass drug administration, MDA）策略开展防控。本研究评估了在蒙罗维亚城区针对班氏吴策线虫（Wuchereria bancrofti, W. bancrofti）感染实施集体服药的必要性，采用血清学与分子媒介昆虫监测（Xenomonitoring, XM）两种方法。 方法学 本研究遵循世界卫生组织（World Health Organization, WHO）推荐的确证绘图方案，在蒙罗维亚的四个卫生行政区开展研究。采用按规模比例抽样（probability proportionate to size, PPS）方法选取学校，对年龄9~14岁的符合入组条件的儿童，使用雅培丝虫病检测试纸（Alere Filariasis Test Strip, FTS）检测其循环丝虫抗原（circulating filarial antigen, CFA）。若某卫生行政区的阳性检测数超过临界阈值（对应CFA阳性率≥2%，即阳性样本数≥3例），则判定该行政区需实施集体服药。根据蚊虫传播的潜在危险因素，选取两个卫生行政区开展昆虫学调查。采用出屋诱捕器（exit traps, ETs）与孕蚊诱捕器（gravid traps, GTs）进行为期6个月的蚊虫采集。采用实时定量聚合酶链式反应（quantitative polymerase chain reaction, qPCR）检测蚊虫体内的班氏吴策线虫DNA。 主要研究结果 本研究样本中共96名儿童的血清学检测结果呈阳性，平均CFA阳性率为5.3%（95%置信区间：4.4~6.5%）。四个卫生行政区的阳性检测数均超过临界阈值，其中索马里大道（Somalia Drive）辖区共检出59例阳性样本。蒙罗维亚中部辖区检出4例阳性样本，其中2例极有可能为本地输入性病例，据患儿自述，其居住地位于索马里大道辖区。本研究共采集到19355只潜在媒介蚊虫，其中84.4%（16335只）为库蚊属蚊虫，16.6%（3020只）为冈比亚按蚊（Anopheles gambiae, An. gambiae）。对所有蚊虫进行检测后，未发现任何样本携带班氏吴策线虫DNA。 结论 蒙罗维亚的三个卫生行政区需实施集体服药。确证绘图方案需针对城市环境进行适配优化。本研究采用的媒介监测抽样策略未能成功检测到本地区的传播情况，需开展进一步研究以优化该策略，为集体服药实施决策提供依据。