School of Pharmacy, Walailak University, Nakhon Si Thammarat, Thailand.
Drug and Cosmetics Excellence Center, Walailak University, Nakhon Si Thammarat, Thailand.
PLoS Negl Trop Dis. 2024 Jul 12;18(7):e0012331. doi: 10.1371/journal.pntd.0012331. eCollection 2024 Jul.
Soil-transmitted helminthiases (STHs) are common in tropical and subtropical regions. Southern Thailand experiences an extended rainy season, leading to persistently moist soil. This condition supports the life cycle of STHs, hindering effective control due to reinfection and low drug efficacy. We implemented a novel STH control strategy during the dry season aimed at decreasing reinfection rates without enhancing sanitation or hygiene practices. However, there were unexpected, prolonged droughts linked to El Niño events from 2014 to 2016. Additionally, we assessed the effects of these drought conditions on further control measures without the use of anthelmintics.
METHODOLOGY/PRINCIPAL FINDINGS: A longitudinal study was conducted from 2012 to 2016. Stool samples collected from 299 participants were analyzed using the Kato-Katz and agar plate culture methods. Participants who tested positive for STHs received a single 400 mg dose of albendazole. The efficacy of the treatment was evaluated three weeks later. To confirm the control measures were implemented during the dry season, we monitored the number of rainy days following albendazole treatment for 52 days, of which 38 were without rain. Follow-up stool examinations were carried out in 2013 and 2016, with no additional doses of albendazole administered. Rainfall and rainy day data, which served as indicators of unexpected droughts due to El Niño, were collected from the nearest local meteorological stations. Before the drought, there was a decrease in STH prevalence in 2013-except for trichuriasis-attributable to the dry season control efforts. Despite these efforts, STH prevalence remained high. Remarkably, in 2016, following the drought period, the prevalence of trichuriasis, which had not changed previously, spontaneously declined without further albendazole treatment compared to 2013. Furthermore, the prevalence of strongyloidiasis remained unchanged likely due to its low susceptibility to drought conditions, as it can reproduce within hosts. Conversely, the prevalence of other STHs consistently declined. The drought and possible improvements in sanitation and hygiene practices contributed to this decrease by reducing rates of reinfection and new infection and by increasing the natural cure rate. Additionally, some participants infected with hookworms or Trichuris who were not cured by albendazole experienced natural remission.
CONCLUSIONS/SIGNIFICANCE: Control measures implemented during the dry season, combined with a 14-month-long drought induced by the El Niño event of 2014-2016, and some improvements in sanitation and hygiene practices, contributed to a decrease in both the prevalence and intensity of STHs, except for S. stercoralis. Over time, S. stercoralis is likely to become the predominant species among the STHs.
土壤传播性蠕虫病（STHs）在热带和亚热带地区很常见。泰国南部雨季时间长，导致土壤持续湿润。这种情况支持了 STHs 的生命周期，由于再感染和低药效，阻碍了有效的控制。我们在旱季实施了一种新的 STH 控制策略，旨在降低再感染率，而不加强卫生或卫生习惯。然而，2014 年至 2016 年期间，厄尔尼诺事件导致了出乎意料的、长时间的干旱。此外，我们评估了这些干旱条件对进一步控制措施的影响，而没有使用驱虫药。
方法/主要发现：这项研究从 2012 年到 2016 年进行了纵向研究。从 299 名参与者中采集的粪便样本使用加藤厚涂片和琼脂平板培养法进行了分析。检测到 STHs 阳性的参与者接受了单次 400 毫克剂量的阿苯达唑。三周后评估治疗效果。为了确认控制措施是在旱季实施的，我们监测了阿苯达唑治疗后 52 天内的雨天数量，其中 38 天没有下雨。2013 年和 2016 年进行了后续粪便检查，没有给予额外剂量的阿苯达唑。由于厄尔尼诺现象导致的意外干旱，我们从最近的当地气象站收集了降雨和雨天数据。在干旱之前，2013 年，除了与旱季控制措施有关的鞭虫病外，STHs 的流行率有所下降。尽管采取了这些措施，STHs 的流行率仍然很高。值得注意的是，2016 年，在干旱期之后，与 2013 年相比，以前没有变化的鞭虫病流行率在没有进一步的阿苯达唑治疗的情况下自发下降。此外，由于其对干旱条件的低敏感性，钩虫和类圆线虫的流行率保持不变，因为它可以在宿主体内繁殖。相反，其他 STHs 的流行率持续下降。干旱和可能改善的卫生和卫生习惯通过降低再感染和新感染率以及提高自然治愈率，有助于减少 STHs 的流行率和严重程度，除了 S. stercoralis 外。此外，一些感染钩虫或鞭虫但未被阿苯达唑治愈的参与者经历了自然缓解。
结论/意义：旱季实施的控制措施，加上 2014-2016 年厄尔尼诺事件导致的 14 个月干旱期，以及一些卫生和卫生习惯的改善，除了 S. stercoralis 外，还降低了 STHs 的流行率和严重程度。随着时间的推移，S. stercoralis 可能成为 STHs 中的主要物种。
