Subramanian Swaminathan, Jambulingam Purushothaman, Chu Brian K, Sadanandane Candasamy, Vasuki Venkatesan, Srividya Adinarayanan, Mohideen AbdulKader Mohamed S, Krishnamoorthy Kaliannagounder, Raju Harikishan K, Laney Sandra J, Williams Steven A, Henderson Ralph H
Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Puducherry, India.
Neglected Tropical Diseases Support Center, Task Force for Global Health, Decatur, Georgia, United States of America.
PLoS Negl Trop Dis. 2017 Apr 13;11(4):e0005519. doi: 10.1371/journal.pntd.0005519. eCollection 2017 Apr.
The monitoring and evaluation of lymphatic filariasis (LF) has largely relied on the detection of antigenemia and antibodies in human populations. Molecular xenomonitoring (MX), the detection of parasite DNA/RNA in mosquitoes, may be an effective complementary method, particularly for detecting signals in low-level prevalence areas where Culex is the primary mosquito vector. This paper investigated the application of a household-based sampling method for MX in Tamil Nadu, India.
MX surveys were conducted in 2010 in two evaluation units (EUs): 1) a hotspot area, defined as sites with community microfilaria prevalence ≥1%, and 2) a larger area that also encompassed the hotspots. Households were systematically selected using a sampling interval proportional to the number of households in the EU. Mosquito pools were collected and analyzed by real-time polymerase chain reaction (qPCR). Two independent samples were taken in each EU to assess reproducibility of results. Follow-up surveys were conducted in 2012.
In 2010, the proportion of positive pools in the hotspot EU was 49.3% compared to 23.4% in the overall EU. In 2012, pool positivity was significantly reduced to 24.3% and 6.5%, respectively (p<0.0001). Pool positivity based on independent samples taken from each EU in 2010 and 2012 were not significantly different except for the hotspot EU in 2012 (p = 0.009). The estimated prevalence of infection in mosquitoes, measured by PoolScreen, declined from 2.2-2.7% in 2010 to 0.6-1.2% in 2012 in the hotspot area and from 0.9-1.1% to 0.2-0.3% in the larger area.
The household-based sampling strategy for MX led to mostly reproducible results and supported the observed LF infection trends found in humans. MX has the potential to be a cost-effective, non-invasive monitoring and evaluation tool with sensitive detection of infection signals in low prevalence settings. Further investigation and application of this sampling strategy for MX are recommended to support its adoption as a standardized method for global LF elimination programs.
淋巴丝虫病（LF）的监测与评估很大程度上依赖于在人群中检测抗原血症和抗体。分子异体监测（MX），即检测蚊子体内的寄生虫DNA/RNA，可能是一种有效的补充方法，尤其适用于在库蚊为主要蚊媒的低流行地区检测信号。本文研究了基于家庭抽样方法在印度泰米尔纳德邦的分子异体监测中的应用。
2010年在两个评估单元（EUs）开展分子异体监测调查：1）一个热点地区，定义为社区微丝蚴患病率≥1%的地点；2）一个更大的区域，其中也包括这些热点地区。使用与评估单元内家庭数量成比例的抽样间隔系统地选取家庭。收集蚊群并通过实时聚合酶链反应（qPCR）进行分析。在每个评估单元采集两个独立样本以评估结果的可重复性。2012年进行了随访调查。
2010年，热点评估单元中阳性蚊群的比例为49.3%，而整个评估单元为23.4%。2012年，蚊群阳性率分别显著降至24.3%和6.5%（p<0.0001）。2010年和2012年从每个评估单元采集的独立样本的蚊群阳性率除2012年的热点评估单元外无显著差异（p = 0.009）。通过PoolScreen测量的蚊子感染估计患病率在热点地区从2010年的2.2 - 2.7%降至2012年的0.6 - 1.2%，在更大区域从0.9 - 1.1%降至0.2 - 0.3%。
基于家庭的分子异体监测抽样策略产生了大多可重复的结果，并支持了在人类中观察到的淋巴丝虫病感染趋势。分子异体监测有潜力成为一种具有成本效益的、非侵入性的监测与评估工具，能够在低流行环境中灵敏地检测感染信号。建议进一步研究和应用这种分子异体监测抽样策略，以支持其作为全球淋巴丝虫病消除计划的标准化方法被采用。
