Submicroscopic and Asymptomatic Plasmodium Parasitaemia Associated with Significant Risk of Anaemia in Papua, Indonesia

Submicroscopic Plasmodium infections are an important parasite reservoir, but their clinical relevance is poorly defined. A cross-sectional household survey was conducted in southern Papua, Indonesia, using cluster random sampling. Data were recorded using a standardized questionnaire. Blood samples were collected for haemoglobin measurement. Plasmodium parasitaemia was determined by blood film microscopy and PCR. Between April and July 2013, 800 households and 2,830 individuals were surveyed. Peripheral parasitaemia was detected in 37.7% (968/2,567) of individuals, 36.8% (357) of whom were identified by blood film examination. Overall the prevalence of P. falciparum parasitaemia was 15.4% (396/2567) and that of P. vivax 18.3% (471/2567). In parasitaemic individuals, submicroscopic infection was significantly more likely in adults (adjusted odds ratio (AOR): 3.82 [95%CI: 2.49–5.86], pp = 0.013), individuals not sleeping under a bednet (AOR = 1.4 [1.0–1.8], p = 0.035), and being afebrile (AOR = 3.2 [1.49–6.93], p = 0.003). The risk of anaemia (according to WHO guidelines) was 32.8% and significantly increased in those with asymptomatic parasitaemia (AOR 2.9 [95% 2.1–4.0], p = 0.007), and submicroscopic P. falciparum infections (AOR 2.5 [95% 1.7–3.6], p = 0.002). Asymptomatic and submicroscopic infections in this area co-endemic for P. falciparum and P. vivax constitute two thirds of detectable parasitaemia and are associated with a high risk of anaemia. Novel public health strategies are needed to detect and eliminate these parasite reservoirs, for the benefit both of the patient and the community.

亚显微疟原虫感染是重要的寄生虫贮存宿主库，但其临床相关性尚未明确。本研究在印度尼西亚巴布亚南部采用整群随机抽样方法开展了一项横断面家庭调查，通过标准化问卷收集数据，并采集血液样本用于血红蛋白（haemoglobin）检测。采用血膜显微镜检查与聚合酶链式反应（PCR）检测疟原虫血症。2013年4月至7月期间，共完成800户家庭、2830名个体的调查。37.7%（968/2567）的个体中检出外周血疟原虫血症，其中36.8%（357例）经血膜检查确认。总体而言，恶性疟原虫（Plasmodium falciparum，P. falciparum）疟原虫血症患病率为15.4%（396/2567），间日疟原虫（Plasmodium vivax，P. vivax）为18.3%（471/2567）。在疟原虫血症感染者中，成人（校正比值比（adjusted odds ratio, AOR）：3.82，95%置信区间（confidence interval, CI）：2.49~5.86，p=0.013）、未使用蚊帐就寝者（AOR=1.4，95%CI：1.0~1.8，p=0.035）以及无发热者（AOR=3.2，95%CI：1.49~6.93，p=0.003）发生亚显微感染的风险显著更高。依据世界卫生组织（WHO）指南，该研究人群的贫血发生风险为32.8%，无症状疟原虫血症感染者（AOR=2.9，95%CI：2.1~4.0，p=0.007）与亚显微恶性疟原虫感染者（AOR=2.5，95%CI：1.7~3.6，p=0.002）的贫血风险显著升高。在恶性疟原虫与间日疟原虫共同流行的该区域，无症状及亚显微感染占可检测疟原虫血症病例的三分之二，且与较高的贫血风险密切相关。为惠及患者与社区福祉，亟需研发新型公共卫生策略以检测并消除此类寄生虫贮存宿主库。