Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
Ministry of Health and Sanitation, Freetown, Sierra Leone.
PLoS Negl Trop Dis. 2014 Feb 6;8(2):e2700. doi: 10.1371/journal.pntd.0002700. eCollection 2014 Feb.
In West Africa, the principal vectors of lymphatic filariasis (LF) are Anopheles species with Culex species playing only a minor role in transmission, if any. Being a predominantly rural disease, the question remains whether conflict-related migration of rural populations into urban areas would be sufficient for active transmission of the parasite.
METHODOLOGY/PRINCIPAL FINDINGS: We examined LF transmission in urban areas in post-conflict Sierra Leone and Liberia that experienced significant rural-urban migration. Mosquitoes from Freetown and Monrovia, were analyzed for infection with Wuchereria bancrofti. We also undertook a transmission assessment survey (TAS) in Bo and Pujehun districts in Sierra Leone. The majority of the mosquitoes collected were Culex species, while Anopheles species were present in low numbers. The mosquitoes were analyzed in pools, with a maximum of 20 mosquitoes per pool. In both countries, a total of 1731 An. gambiae and 14342 Culex were analyzed for W. bancrofti, using the PCR. Two pools of Culex mosquitoes and 1 pool of An. gambiae were found infected from one community in Freetown. Pool screening analysis indicated a maximum likelihood of infection of 0.004 (95% CI of 0.00012-0.021) and 0.015 (95% CI of 0.0018-0.052) for the An. gambiae and Culex respectively. The results indicate that An. gambiae is present in low numbers, with a microfilaria prevalence breaking threshold value not sufficient to maintain transmission. The results of the TAS in Bo and Pujehun also indicated an antigen prevalence of 0.19% and 0.67% in children, respectively. This is well below the recommended 2% level for stopping MDA in Anopheles transmission areas, according to WHO guidelines.
We found no evidence for active transmission of LF in cities, where internally displaced persons from rural areas lived for many years during the more than 10 years conflict in Sierra Leone and Liberia.
在西非，淋巴丝虫病（LF）的主要传播媒介是按蚊属物种，库蚊属物种在传播中仅起次要作用，如果有作用的话。LF 是一种主要发生在农村地区的疾病，因此仍然存在一个问题，即农村人口因冲突而向城市迁移是否足以使寄生虫进行有效传播。
方法/主要发现：我们研究了塞拉利昂和利比里亚冲突后城市地区的 LF 传播情况，这些城市地区经历了大量农村向城市的人口迁移。对弗里敦和蒙罗维亚的蚊子进行了感染班氏丝虫的检测。我们还在塞拉利昂的博城和普杰洪区进行了传播评估调查（TAS）。收集的蚊子主要是库蚊属物种，而按蚊属物种数量较少。这些蚊子按蚊群进行分析，每个蚊群最多 20 只蚊子。在这两个国家，共对 1731 只冈比亚按蚊和 14342 只库蚊进行了 W. bancrofti 的 PCR 分析。在弗里敦的一个社区，发现有两个库蚊蚊群和一个冈比亚按蚊蚊群受到感染。池筛查分析表明，冈比亚按蚊的最大感染可能性为 0.004（95%CI 为 0.00012-0.021），库蚊为 0.015（95%CI 为 0.0018-0.052）。结果表明，冈比亚按蚊的数量较少，微丝蚴患病率低于维持传播所需的阈值。博城和普杰洪 TAS 的结果也分别表明，儿童的抗原患病率分别为 0.19%和 0.67%。这远低于世卫组织指南建议的 2%水平，即在按蚊传播地区停止 MDA。
我们在城市中没有发现 LF 传播的证据，而在塞拉利昂和利比里亚冲突的 10 多年中，来自农村地区的国内流离失所者在城市中生活了多年。
