Leyva Jessica L, Pereira-Leitao Paola A, García-Meléndez Gabriel E, De Amicis Samuel, Celis Rodrigo, Hidalgo Mariana, Hernández Antonio, Carrión-Nessi Fhabián S, Forero-Peña David A
"Luis Razetti" School of Medicine, Universidad Central de Venezuela, Caracas, Venezuela.
Biomedical Research and Therapeutic Vaccines Institute, Ciudad Bolívar, Venezuela.
Malar J. 2025 Apr 13;24(1):120. doi: 10.1186/s12936-025-05356-z.
Despite a significant reduction in malaria cases in America, Venezuela has experienced a substantial increase between 2000 and 2019. Asymptomatic malaria, prevalent in both low- and high-endemic regions, poses a challenge due to the absence of clinical manifestations and often low parasitaemia. This study aims to determine the current prevalence of asymptomatic malaria in four rural communities of Sucre, the third most endemic state in the country.
A community-based cross-sectional study was conducted from October to December 2022 (high seasonality period). Individuals were interviewed in their households and assessed for malaria using rapid diagnostic tests (RDTs), thick and thin blood smear microscopy, and polymerase chain reaction (PCR). Asymptomatic individuals with PCR positive (PCR+) for Plasmodium were classified as cases, while PCR negative individuals were classified as controls. Descriptive statistics were used to analyse the data. The normality of numerical variables was assessed with the Kolmogorov-Smirnov test. Based on this assessment, Student's t-test was applied to normally distributed variables and Mann-Whitney U-test to non-normally distributed ones. For categorical variables, Pearson's chi-square test was used when less than 25.0% of cells had an expected frequency below five; otherwise, Fisher's exact test was employed.
The study involved 351 individuals, mostly women (54.7%), of mixed (non-indigenous) race (61.3%), with primary (6 years) education (40.7%). The most common occupations were students (30.5%), housekeepers (27.6%), and farmers (16.5%). Over half (54.4%) had lived at their current address for over 10 years. The prevalence of asymptomatic malaria by RDTs and microscopy was 0.3% (n = 1/351) as determined. However, PCR detected a higher prevalence of 24.8% (87 positive cases, 95.0% CI = 20.5-29.5), primarily caused by P. vivax (73.6%). The highest prevalences were observed in individuals aged over 15 years (27.1%, 95.0% CI = 21.6-33.1), males (28.3%, 95.0% CI = 21.7-35.6), those with a college (14 years) education (33.3%, 95.0% CI = 17.2-53.2), and educators (41.7%, 95.0% CI = 18-68.8). The rural community with the highest prevalence was Chacopata (30.6%, 95.0% CI = 17.4-46.7), followed by El Paujil (28.6%, 95.0% CI = 21.9-36.1), Yaguaraparo (23.2%, 95.0% CI = 15.1-33.1), and Cristóbal Colón (16.5%, 95.0% CI = 9.6-25.8). Two-thirds (66.7%) reported a malaria history, predominantly caused by P. vivax (70.5%), with a median of 3 previous episodes. At least one-third (35.5%) had non-adherence to treatment during their most recent malarial episode. No statistically significant differences were observed between sociodemographic characteristics and malaria history of individuals with asymptomatic malaria (PCR+) and controls.
RDTs and microscopy only managed to diagnose less than 1.0% of asymptomatic malaria cases. Active surveillance systems with high sensitivity such as PCR may provide accurate estimates of asymptomatic malaria prevalence needed for opportune diagnosis and treatment.
尽管美洲的疟疾病例显著减少，但委内瑞拉在2000年至2019年间疟疾病例大幅增加。无症状疟疾在低流行区和高流行区均普遍存在，由于缺乏临床表现且寄生虫血症往往较低，这构成了一项挑战。本研究旨在确定该国疟疾第三高流行州苏克雷四个农村社区无症状疟疾的当前流行情况。
于2022年10月至12月（高季节性时期）开展了一项基于社区的横断面研究。在个体家中对其进行访谈，并使用快速诊断检测（RDT）、厚薄血涂片显微镜检查和聚合酶链反应（PCR）对疟疾进行评估。疟原虫PCR检测呈阳性（PCR+）的无症状个体被分类为病例，而PCR检测呈阴性的个体被分类为对照。使用描述性统计分析数据。数值变量的正态性通过Kolmogorov-Smirnov检验进行评估。基于该评估，对正态分布变量应用学生t检验，对非正态分布变量应用Mann-Whitney U检验。对于分类变量，当少于25.0%的单元格预期频数低于5时，使用Pearson卡方检验；否则，采用Fisher精确检验。
该研究纳入了351名个体，其中大多数为女性（54.7%），种族为混合（非土著）（61.3%），接受小学（6年）教育（40.7%）。最常见的职业是学生（30.5%）、家庭主妇（27.6%）和农民（16.5%）。超过一半（54.4%）的个体在其当前住址居住超过10年。经RDT和显微镜检查确定的无症状疟疾患病率为0.3%（n = 1/351）。然而，PCR检测到的患病率更高，为24.8%（87例阳性病例，95.0% CI = 20.5 - 29.5），主要由间日疟原虫引起（73.6%）。在15岁以上个体（27.1%，95.0% CI = 21.6 - 33.1）、男性（28.3%，95.0% CI = 21.7 - 35.6）、接受大学（14年）教育的个体（33.3%，95.0% CI = 17.2 - 53.2）和教育工作者（41.7%，95.0% CI = 18 - 68.8）中观察到最高患病率。患病率最高的农村社区是查科帕塔（30.6%，95.0% CI = 17.4 - 46.7），其次是埃尔保希尔（28.6%，95.0% CI = 21.9 - 36.1）、亚瓜拉帕罗（23.2%，95.0% CI = 15.1 - 33.1）和克里斯托瓦尔·科隆（16.5%，95.0% CI = 9.6 - 25.8）。三分之二（66.7%）的个体报告有疟疾病史，主要由间日疟原虫引起（70.5%），既往发作次数中位数为3次。至少三分之一（35.5%）的个体在其最近一次疟疾发作期间未坚持治疗。无症状疟疾（PCR+）个体与对照的社会人口学特征和疟疾病史之间未观察到统计学显著差异。
RDT和显微镜检查仅能诊断不到1.0%的无症状疟疾病例。像PCR这样具有高灵敏度的主动监测系统可能为适时诊断和治疗所需的无症状疟疾患病率提供准确估计。
