Bagamoyo Research and Training Centre, Ifakara Health Institute, Bagamoyo, United Republic of Tanzania.
Department of Pediatrics and Child Health, Muhimbili University Health and Allied Sciences (MUHAS), Dar es Salaam, United Republic of Tanzania.
PLoS Negl Trop Dis. 2024 Aug 12;18(8):e0012412. doi: 10.1371/journal.pntd.0012412. eCollection 2024 Aug.
Parasitic infectious agents rarely occur in isolation. Epidemiological evidence is mostly lacking, and little is known on how the two common parasites Plasmodium and soil transmitted helminths (STH) interact. There are contradictory findings in different studies. Synergism, antagonism and neutral effect have been documented between Plasmodium and STH. This study investigated the impact of STH on clinical malaria presentation and treatment outcome.
A matched case control study with a semi longitudinal follow up according to World Health Organization (WHO) antimalarial surveillance guideline was done among children aged 2 months to 9 years inclusively living in western rural areas of Bagamoyo, coastal region of Tanzania. Cases were children with uncomplicated and severe malaria enrolled from the health facilities while controls were children with asymptomatic Plasmodium parasitemia enrolled from the same community.
In simple conditional regression analysis there was a tendency for a protective effect of STH on the development of clinical malaria [OR = 0.6, 95% CI of 0.3-1.3] which was more marked for Enterobius vermicularis species [OR = 0.2, 95% CI of 0.0-0.9]. On the contrary, hookworm species tended to be associated with increased risk of clinical malaria [OR = 3.0, 95% CI of 0.9-9.5]. In multiple conditional regression analysis, the overall protective effect was lower for all helminth infection [OR = 0.8, 95% CI of 0.3-1.9] but remained significantly protective for E. vermicularis species [OR = 0.1, 95% CI of 0.0-1.0] and borderline significant for hookworm species [OR = 3.6, 95% CI of 0.9-14.3]. Using ordinal logistic regression which better reflects the progression of asymptomatic Plasmodium parasitemia to severe malaria, there was a 50% significant protective effect with overall helminths [OR = 0.5, 95% CI of 0.3-0.9]. On the contrary, hookworm species was highly predictive of uncomplicated and severe malaria [OR = 7.8, 95% (CI of 1.8-33.9) and 49.7 (95% CI of 1.9-1298.9) respectively]. Generally, children infected with STH had higher geometric mean time to first clearance of parasitemia.
The findings of a protective effect of E. vermicularis and an enhancing effect of hookworms may explain the contradictory results found in the literature about impact of helminths on clinical malaria. More insight should be gained on possible mechanisms for these opposite effects. These results should not deter at this stage deworming programs but rather foster implementation of integrated control program for these two common parasites.
寄生虫感染很少单独发生。流行病学证据大多缺乏，人们对两种常见寄生虫疟原虫和土壤传播性蠕虫（STH）之间的相互作用知之甚少。不同的研究有相互矛盾的发现。疟原虫和 STH 之间存在协同作用、拮抗作用和中性作用。本研究调查了 STH 对临床疟疾表现和治疗结果的影响。
在坦桑尼亚沿海地区巴加莫约西部农村地区，对 2 个月至 9 岁的儿童进行了一项匹配的病例对照研究，采用世卫组织抗疟监测指南的半纵向随访。病例为从医疗机构招募的无并发症和严重疟疾儿童，对照为从同一社区招募的无症状疟原虫寄生虫血症儿童。
在简单条件回归分析中，STH 对临床疟疾发展有保护作用的趋势[OR=0.6，95%CI 为 0.3-1.3]，其中蛲虫物种[OR=0.2，95%CI 为 0.0-0.9]更为明显。相反，钩虫物种倾向于增加临床疟疾的风险[OR=3.0，95%CI 为 0.9-9.5]。在多条件回归分析中，所有寄生虫感染的总体保护作用较低[OR=0.8，95%CI 为 0.3-1.9]，但对蛲虫物种仍具有显著保护作用[OR=0.1，95%CI 为 0.0-1.0]，对钩虫物种具有边缘显著保护作用[OR=3.6，95%CI 为 0.9-14.3]。使用更能反映无症状疟原虫寄生虫血症向严重疟疾进展的有序逻辑回归，总寄生虫有 50%的显著保护作用[OR=0.5，95%CI 为 0.3-0.9]。相反，钩虫物种是无并发症和严重疟疾的高度预测因子[OR=7.8，95%CI（1.8-33.9）和 49.7（95%CI 为 1.9-1298.9）]。一般来说，感染 STH 的儿童寄生虫血症首次清除的几何平均时间更长。
蛲虫和钩虫的保护作用和增强作用的发现可以解释文献中关于寄生虫对临床疟疾影响的相互矛盾的结果。应该更深入地了解这些相反作用的可能机制。这些结果不应在现阶段阻止驱虫计划，而应促进这两种常见寄生虫的综合控制计划的实施。
