Environmental Intervention Unit, Infectious Disease Division, icddr,b, Dhaka, Bangladesh.
Gangarosa Department of Environmental Health Sciences, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America.
PLoS Negl Trop Dis. 2022 Jun 23;16(6):e0010495. doi: 10.1371/journal.pntd.0010495. eCollection 2022 Jun.
Pit latrines are the most common latrine technology in rural Bangladesh, and untreated effluent from pits can directly contaminate surrounding aquifers. Sand barriers installed around the latrine pit can help reduce contamination but can also alter the decomposition of the fecal sludge and accelerate pit fill-up, which can counteract their benefits. We aimed to evaluate whether there was a difference in decomposition of fecal sludge and survival of soil-transmitted helminth (STH) ova among latrines where a 50-cm sand barrier was installed surrounding and at the bottom of the pit, compared to latrines without a sand barrier, in coastal Bangladesh. We assessed decomposition in latrine pits by measuring the carbon-nitrogen (C/N) ratio of fecal sludge. We enumerated Ascaris lumbricoides and Trichuris trichiura ova in the pit following 18 and 24 months of latrine use. We compared these outcomes between latrines with and without sand barriers using generalized linear models with robust standard errors to adjust for clustering at the village level. The C/N ratio in latrines with and without a sand barrier was 13.47 vs. 22.64 (mean difference: 9.16, 95% CI: 0.15, 18.18). Pits with sand barriers filled more quickly and were reportedly emptied three times more frequently than pits without; 27/34 latrines with sand barriers vs. 9/34 latrines without barriers were emptied in the previous six months. Most reported disposal methods were unsafe. Compared to latrines without sand barriers, latrines with sand barriers had significantly higher log10 mean counts of non-larvated A. lumbricoides ova (log10 mean difference: 0.35, 95% CI: 0.12, 0.58) and T. trichiura ova (log10 mean difference: 0.47, 95% CI: 0.20, 0.73). Larvated ova counts were similar for the two types of latrines for both A. lumbricoides and T. trichiura. Our findings suggest that sand barriers help contain helminth ova within the pits but pits with barriers fill up more quickly, leading to more frequent emptying of insufficiently decomposed fecal sludge. Further research is required on latrine technologies that can both isolate pathogens from the environment and achieve rapid decomposition.
坑式厕所是孟加拉国农村地区最常见的厕所技术，而未经处理的坑式厕所污水会直接污染周围的含水层。在厕所坑周围安装的沙障可以帮助减少污染，但也会改变粪便污泥的分解速度，并加速坑的填满，从而抵消其益处。我们旨在评估在沿海孟加拉国，与没有沙障的厕所相比，在坑的周围和底部安装 50 厘米高的沙障的厕所中，粪便污泥的分解和土壤传播性蠕虫（STH）卵的存活率是否存在差异。我们通过测量粪便污泥的碳氮（C/N）比来评估坑内的分解情况。我们在使用厕所 18 个月和 24 个月后，分别对坑内的蛔虫和鞭虫卵进行了计数。我们使用广义线性模型和稳健标准误差来调整村一级的聚类，比较了有沙障和无沙障的厕所之间的这些结果。有沙障和无沙障的厕所的 C/N 比分别为 13.47 和 22.64（平均差异：9.16，95%置信区间：0.15，18.18）。有沙障的坑填得更快，据报告，它们的清空频率是没有沙障的坑的三倍；在过去的六个月里，有沙障的 34 个厕所中有 27 个被清空，而没有沙障的 34 个厕所中只有 9 个被清空。大多数报告的处理方法是不安全的。与没有沙障的厕所相比，有沙障的厕所中未孵化的蛔虫卵的对数 10 平均计数显著更高（对数 10 平均差异：0.35，95%置信区间：0.12，0.58）和鞭虫卵（对数 10 平均差异：0.47，95%置信区间：0.20，0.73）。对于蛔虫和鞭虫，两种类型的厕所中未孵化的卵计数相似。我们的研究结果表明，沙障有助于将蠕虫卵限制在坑内，但有沙障的坑填得更快，导致未充分分解的粪便污泥更频繁地被清空。需要进一步研究既能将病原体与环境隔离又能实现快速分解的厕所技术。
