Lemin Morgan E, Cadavid Restrepo Angela, Mayfield Helen J, Lau Colleen L
School of Population Health, University of Queensland, Brisbane, QLD 4006, Australia.
Trop Med Infect Dis. 2022 Oct 12;7(10):295. doi: 10.3390/tropicalmed7100295.
Under the Global Program to Eliminate Lymphatic Filariasis (LF) American Samoa conducted seven rounds of mass drug administration (MDA) between 2000 and 2006. Subsequently, the territory passed the WHO recommended school-based transmission assessment survey (TAS) in 2011/2012 (TAS-1) and 2015 (TAS-2) but failed in 2016, when both TAS-3 and a community survey found LF antigen prevalence above what it had been in previous surveys. This study aimed to identify potential environmental drivers of LF to refine future surveillance efforts to detect re-emergence and recurrence. Data on five LF infection markers: antigen, Wb123, Bm14 and Bm33 antibodies and microfilaraemia, were obtained from a population-wide serosurvey conducted in American Samoa in 2016. Spatially explicit data on environmental factors were derived from freely available sources. Separate multivariable Poisson regression models were developed for each infection marker to assess and quantify the associations between LF infection markers and environmental variables. Rangeland, tree cover and urban cover were consistently associated with a higher seroprevalence of LF-infection markers, but to varying magnitudes between landcover classes. High slope gradient, population density and crop cover had a negative association with the seroprevalence of LF infection markers. No association between rainfall and LF infection markers was detected, potentially due to the limited variation in rainfall across the island. This study demonstrated that seroprevalence of LF infection markers were more consistently associated with topographical environmental variables, such as gradient of the slope, rather than climatic variables, such as rainfall. These results provide the initial groundwork to support the detection of areas where LF transmission is more likely to occur, and inform LF elimination efforts through better understanding of the environmental drivers.
在全球消除淋巴丝虫病计划（LF）下，美属萨摩亚在2000年至2006年期间进行了七轮大规模药物给药（MDA）。随后，该地区在2011/2012年（TAS-1）和2015年（TAS-2）通过了世界卫生组织推荐的基于学校的传播评估调查（TAS），但在2016年未通过，当时TAS-3和一项社区调查均发现淋巴丝虫病抗原流行率高于以往调查。本研究旨在确定淋巴丝虫病的潜在环境驱动因素，以完善未来的监测工作，以检测疾病的再次出现和复发。关于五个淋巴丝虫病感染标志物的数据：抗原、Wb123、Bm14和Bm33抗体以及微丝蚴血症，来自2016年在美属萨摩亚进行的全人群血清学调查。关于环境因素的空间明确数据来自免费可用的来源。针对每个感染标志物建立了单独的多变量泊松回归模型，以评估和量化淋巴丝虫病感染标志物与环境变量之间的关联。牧场、树木覆盖和城市覆盖始终与淋巴丝虫病感染标志物的较高血清阳性率相关，但不同土地覆盖类别之间的关联程度不同。高坡度、人口密度和作物覆盖与淋巴丝虫病感染标志物的血清阳性率呈负相关。未检测到降雨与淋巴丝虫病感染标志物之间的关联，这可能是由于全岛降雨变化有限。本研究表明，淋巴丝虫病感染标志物的血清阳性率与地形环境变量（如坡度）的关联更为一致，而不是与降雨等气候变量相关。这些结果为支持检测更可能发生淋巴丝虫病传播的地区提供了初步基础，并通过更好地了解环境驱动因素为消除淋巴丝虫病的努力提供信息。
