Epidemiological interactions between urogenital and intestinal human schistosomiasis in the context of praziquantel treatment across three West African countries

Background: In many parts of sub-Saharan Africa, urogenital and intestinal schistosomiasis co-occur, and mixed species infections containing both Schistosoma haematobium and S. mansoni can be common. During co-infection, interactions between these two species are possible, yet the extent to which such interactions influence disease dynamics or the outcome of control efforts remains poorly understood. Methodology/Principal Findings: Here we analyse epidemiological data from three West African countries co-endemic for urogenital and intestinal schistosomiasis (Senegal, Niger and Mali) to test whether the impact of praziquantel (PZQ) treatment, subsequent levels of re-infection or long-term infection dynamics are altered by co-infection. In all countries, positive associations between the two species prevailed at baseline: infection by one species tended to predict infection intensity for the other, with the strength of association varying across sites. Encouragingly, we found little evidence that co-infection influenced PZQ efficacy: species-specific egg reduction rates (ERR) and cure rates (CR) did not differ significantly with co-infection, and variation in treatment success was largely geographical. In Senegal, despite positive associations at baseline, children with S. mansoni co-infection at the time of treatment were less intensely re-infected by S. haematobium than those with single infections, suggesting competition between the species may occur post-treatment. Furthermore, the proportion of schistosome infections attributable to S. mansoni increased over time in all three countries examined. Conclusions/Significance: These findings suggest that while co-infection between urinary and intestinal schistosomes may not directly affect PZQ treatment efficacy, competitive interspecific interactions may influence epidemiological patterns of re-infection post-treatment. While re-infection patterns differed most strongly according to geographic location, interspecific interactions also seem to play a role, and could cause the community composition in mixed species settings to shift as disease control efforts intensify, a situation with implications for future disease management in this multi-species system.

研究背景：在撒哈拉以南非洲的诸多区域，泌尿生殖道血吸虫病与肠道血吸虫病常共同流行，同时感染埃及血吸虫（Schistosoma haematobium）与曼氏血吸虫（S. mansoni）的混合物种感染也较为常见。在合并感染状态下，这两种血吸虫之间存在相互作用的可能，但此类相互作用对疾病流行动态或防控工作成效的影响程度仍不甚明确。
研究方法与主要结果：本研究针对泌尿生殖道与肠道血吸虫病共同流行的3个西非国家（塞内加尔、尼日尔、马里）的流行病学数据展开分析，旨在检验吡喹酮（praziquantel, PZQ）治疗的效果、后续再感染水平或长期感染动态是否会因合并感染而发生改变。所有研究国家的基线数据均显示两种血吸虫感染呈正相关：感染其中一种血吸虫的个体，其另一种血吸虫的感染强度往往也更高，且关联强度随研究位点不同存在差异。令人欣慰的是，本研究未发现合并感染对吡喹酮治疗效果存在显著影响：按物种划分的虫卵减少率（egg reduction rates, ERR）与治愈率（cure rates, CR）在合并感染与单一感染群体间无显著差异，治疗成功率的差异主要源于地域因素。在塞内加尔，尽管基线水平呈正相关，但治疗时合并感染曼氏血吸虫的儿童，其埃及血吸虫的再感染强度低于仅感染单一物种的儿童，这提示治疗后两种血吸虫间可能存在竞争作用。此外，3个研究国家中由曼氏血吸虫引起的血吸虫感染占比均随时间推移有所上升。
结论与意义：本研究结果表明，尽管泌尿生殖道与肠道血吸虫的合并感染不会直接影响吡喹酮的治疗效果，但种间相互作用可能会改变治疗后的再感染流行病学特征。尽管再感染模式的地域差异最为显著，但种间相互作用同样发挥着一定作用，且随着疾病防控力度的加大，可能会导致混合感染场景下的群落组成发生改变，这一情况对该多物种感染体系未来的疾病管理具有重要参考价值。