Usefulness of Seminested Multiplex PCR in Surveillance of Imported Malaria in Spain

The use of a new PCR-based method for the diagnosis of malaria in the Spanish Malaria Reference Laboratory has promoted an increase in confirmed cases of malaria. From August 1997 to July 1998, a total of 192 whole-blood samples and 71 serum samples from 168 patients were received from the hospitals of the Spanish National Health System. Most of the patients came from west-central African countries (85%). This molecular method showed more sensitivity and specificity than microscopy, detecting 12.4% more positive samples than microscopy and 13% of mixed infections undetectable by Giemsa stain. Plasmodium falciparum was the main species detected, with 68% of the total positive malaria cases, followed by Plasmodium malariae (29%), Plasmodium vivax (14%), and Plasmodium ovale (7%), including mixed infections in all cases. This report consists of the first wide, centralized survey of malaria surveillance in Spain. The reference laboratory conducted the analysis of all imported cases in order to detect trends in acquisition. The use of a seminested multiplex PCR permitted confirmation of the origins of the infections and the Plasmodium species involved and confirmation of the effectiveness of drug treatments. This PCR also allowed the detection of the presence in Spain of primaquine-tolerant P. vivax strains from west-central Africa, as well as the detection of a P. falciparum infection induced by transfusion.

西班牙疟疾参考实验室采用新型基于聚合酶链式反应（PCR）的疟疾诊断方法，推动了疟疾确诊病例数量的上升。
1997年8月至1998年7月期间，该实验室从西班牙国家医疗体系的各医院共收集168名患者的192份全血样本及71份血清样本。其中85%的患者来自中西非国家。
该分子检测方法的敏感性与特异性均优于显微镜镜检法：其阳性样本检出率较镜检高出12.4%，还可检出13%的吉姆萨染色法无法识别的混合感染病例。本次检出的疟原虫以恶性疟原虫（Plasmodium falciparum）为主，占疟疾确诊总病例的68%；其次依次为三日疟原虫（Plasmodium malariae，29%）、间日疟原虫（Plasmodium vivax，14%）与卵形疟原虫（Plasmodium ovale，7%），所有阳性病例均涵盖混合感染情形。
本报告为西班牙首次针对疟疾监测开展的大规模集中式调查。该参考实验室对所有输入性病例进行分析，以追踪感染来源的流行趋势。
半巢式多重PCR技术的应用，可确认感染来源、涉及的疟原虫种类，并验证药物治疗的有效性。该PCR技术还可检出在西班牙境内发现的、源自中西非的伯氨喹耐受型间日疟原虫毒株，同时也能检测到输血诱导的恶性疟原虫感染病例。