Risk factors for Cryptosporidium infection in low and middle income countries: A systematic review and meta-analysis

BackgroundCryptosporidium infection causes gastrointestinal disease and has a worldwide distribution. The highest burden is in developing countries.ObjectivesWe sought to conduct a systematic review and meta-analysis to identify Cryptosporidium risk factors in Low and Middle Income countries (LMICs).MethodsMedline Ovid and Scopus databases were searched with no restriction on year or language of publication. All references were screened independently in duplicate and were included if they presented data on at least 3 risk factors. Meta-analyses using random effects models were used to calculate overall estimates for each exposure.ResultsThe most frequently reported risk factors in the 15 included studies were overcrowding, household diarrhoea, poor quality drinking water, animal contact, open defecation/ lack of toilet and breastfeeding. The combined odds ratio for animal contact was 1.98 (95%CI: 1.11–3.54) based on 11 studies and for diarrhoea in the household 1.98 (95%CI: 1.13–3.49) based on 4 studies. Open defecation was associated with a pooled odds ratio of 1.82 (95%CI: 1.19–2.8) based on 5 studies. Poor drinking water quality was not associated with a significant Cryptosporidium risk, odds ratio 1.06 (95%CI: 0.77–1.47). Breastfeeding was protective with pooled odds ratio 0.4 (95%CI: 0.13–1.22), which was not statistically significant.ConclusionsBased on the included studies, crowded living conditions, animal contact and open defecation are responsible for the majority of Cryptosporidium cases in LMICs. Future studies investigating Cryptosporidium risk factors should have a good study design and duration, include appropriate number of cases, select suitable controls, investigate multiple relevant risk factors, fully report data and perform multivariate analysis.背景 隐孢子虫（Cryptosporidium）感染可引发胃肠道疾病，且呈全球流行态势，其疾病负担在发展中国家最为沉重。 目的 本研究旨在针对中低收入国家（Low and Middle Income Countries，LMICs）开展隐孢子虫感染危险因素的系统综述与荟萃分析（meta-analysis）。 方法 检索Medline Ovid与Scopus数据库，未对发表年份及语言设置任何限制。所有参考文献均由两名研究者独立重复筛查，仅纳入至少报告3种危险因素数据的研究。采用随机效应模型开展荟萃分析，以计算各暴露因素的合并效应量。 结果 纳入的15项研究中，最常被报告的危险因素包括居住拥挤、家庭内腹泻事件、饮用水质量不佳、动物接触、露天排便/缺乏卫生厕所，以及母乳喂养。基于11项研究的合并比值比（odds ratio, OR）显示，动物接触的合并OR为1.98（95%置信区间：1.11~3.54）；基于4项研究的家庭内腹泻合并OR为1.98（95%CI：1.13~3.49）。基于5项研究的露天排便合并OR为1.82（95%CI：1.19~2.80）。饮用水质量不佳与隐孢子虫感染风险无显著关联，合并OR为1.06（95%CI：0.77~1.47）。母乳喂养具有保护作用，合并OR为0.40（95%CI：0.13~1.22），但未达到统计学显著性。 结论 基于纳入的研究，居住拥挤、动物接触与露天排便是中低收入国家隐孢子虫感染病例的主要致病因素。未来开展隐孢子虫感染危险因素相关研究时，应采用严谨的研究设计与足够的研究周期，纳入足够数量的病例，选取合适的对照，调查多种相关危险因素，完整报告研究数据，并开展多变量分析。