U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA.
Henry M. Jackson Foundation for the Advancement of Military Medicine, 6720A Rockledge Drive, Suite 400, Bethesda, MD, 20817, USA.
BMC Infect Dis. 2021 Sep 9;21(1):937. doi: 10.1186/s12879-021-06626-2.
Malaria and schistosomiasis present considerable disease burden in tropical and sub-tropical areas and severity is worsened by co-infections in areas where both diseases are endemic. Although pathogenesis of these infections separately is well studied, there is limited information on the pathogenic disease mechanisms and clinical disease outcomes in co-infections. In this study, we investigated the prevalence of malaria and schistosomiasis co-infections, and the hematologic and blood chemistry abnormalities in asymptomatic adults in a rural fishing community in western Kenya.
This sub-study used samples and data collected at enrollment from a prospective observational cohort study (RV393) conducted in Kisumu County, Kenya. The presence of malaria parasites was determined using microscopy and real-time-PCR, and schistosomiasis infection by urine antigen analysis (CCA). Hematological analysis and blood chemistries were performed using standard methods. Statistical analyses were performed to compare demographic and infection data distribution, and hematologic and blood chemistry parameters based on different groups of infection categories. Clinically relevant hematologic conditions were analyzed using general linear and multivariable Poisson regression models.
From February 2017 to May 2018, we enrolled 671 participants. The prevalence of asymptomatic Plasmodium falciparum was 28.2% (157/556) and schistosomiasis 41.2% (229/562), with 18.0% (100/556) of participants co-infected. When we analyzed hematological parameters using Wilcoxon rank sum test to evaluate median (IQR) distribution based on malarial parasites and/or schistosomiasis infection status, there were significant differences in platelet counts (p = 0.0002), percent neutrophils, monocytes, eosinophils, and basophils (p < 0.0001 each). Amongst clinically relevant hematological abnormalities, eosinophilia was the most prevalent at 20.6% (116/562), whereas thrombocytopenia was the least prevalent at 4.3% (24/562). In univariate model, Chi-Square test performed for independence between participant distribution in different malaria parasitemia/schistosomiasis infection categories within each clinical hematological condition revealed significant differences for thrombocytopenia and eosinophilia (p = 0.006 and p < 0.0001, respectively), which was confirmed in multivariable models. Analysis of the pairwise mean differences of liver enzyme (ALT) and kidney function (Creatinine Clearance) indicated the presence of significant differences in ALT across the infection groups (parasite + /CCA + vs all other groups p < .003), but no differences in mean Creatinine Clearance across the infection groups.
Our study demonstrates the high burden of asymptomatic malaria parasitemia and schistosomiasis infection in this rural population in Western Kenya. Asymptomatic infection with malaria or schistosomiasis was associated with laboratory abnormalities including neutropenia, leukopenia and thrombocytopenia. These abnormalities could be erroneously attributed to other diseases processes during evaluation of diseases processes. Therefore, evaluating for co-infections is key when assessing individuals with laboratory abnormalities. Additionally, asymptomatic infection needs to be considered in control and elimination programs given high prevalence documented here.
疟疾和血吸虫病在热带和亚热带地区造成了相当大的疾病负担，在这两种疾病流行的地区，合并感染会使病情恶化。虽然这些感染的发病机制分别得到了很好的研究，但在合并感染中，关于致病疾病机制和临床疾病结果的信息有限。在这项研究中，我们调查了肯尼亚西部一个农村渔业社区中无症状成年人中疟疾和血吸虫病合并感染的流行情况，以及血液学和血液化学异常情况。
本研究使用了前瞻性观察队列研究（RV393）在肯尼亚基苏木县入组时收集的样本和数据。通过显微镜检查和实时-PCR 确定疟原虫的存在，通过尿抗原分析（CCA）确定血吸虫病感染。使用标准方法进行血液学分析和血液化学检查。基于不同的感染类别，比较了人口统计学和感染数据分布，以及血液学和血液化学参数。使用一般线性和多变量泊松回归模型分析临床相关的血液学情况。
从 2017 年 2 月至 2018 年 5 月，我们共招募了 671 名参与者。无症状恶性疟原虫的流行率为 28.2%（157/556），血吸虫病为 41.2%（229/562），其中 18.0%（100/556）的参与者合并感染。当我们使用 Wilcoxon 秩和检验分析血液学参数，以评估基于疟原虫和/或血吸虫病感染状态的中位数（IQR）分布时，血小板计数（p=0.0002）、中性粒细胞、单核细胞、嗜酸性粒细胞和嗜碱性粒细胞的百分比有显著差异（p<0.0001 各）。在临床相关的血液学异常中，嗜酸性粒细胞最常见（20.6%，116/562），而血小板减少症最不常见（4.3%，24/562）。在单变量模型中，卡方检验用于独立性分析，结果显示不同疟疾寄生虫血症/血吸虫病感染类别的参与者分布与每个临床血液学条件之间存在显著差异，血小板减少症和嗜酸性粒细胞存在显著差异（p=0.006 和 p<0.0001，分别），这在多变量模型中得到了证实。对肝酶（ALT）和肾功能（肌酐清除率）的平均差异进行分析，表明 ALT 在感染组之间存在显著差异（寄生虫+/CCA+与所有其他组 p<0.003），但感染组之间的平均肌酐清除率没有差异。
我们的研究表明，在肯尼亚西部的这个农村地区，无症状恶性疟原虫和血吸虫病感染的负担很高。疟疾或血吸虫病的无症状感染与实验室异常有关，包括中性粒细胞减少、白细胞减少和血小板减少。在评估疾病过程时，这些异常可能会被错误地归因于其他疾病过程。因此，在评估有实验室异常的个体时，评估合并感染是关键。此外，鉴于这里记录的高患病率，需要考虑无症状感染在控制和消除规划中的作用。
