Division of Malaria and Parasitic diseases, Korea Centers for Disease Control and Prevention, Seoul 122-701, Republic of Korea.
Malar J. 2010 Jul 9;9:195. doi: 10.1186/1475-2875-9-195.
Plasmodium vivax is divided into two subtypes, a dominant form, VK210 and a variant form, VK247. This division is dependent on the amino acid composition of the circumsporozoite (CS) protein. In this study, the prevalence of the VK247 variant form of P. vivax was investigated in Myanmar.
The existence of malaria parasites in blood samples was determined by microscopic examination, polymerase chain reaction (PCR) and DNA hybridization assays. To test for antibodies against P. vivax and Plasmodium falciparum in blood samples, an indirect immunofluorescence antibody test (IFAT) was performed using asexual blood antigens. An enzyme-linked immunosorbent assay with synthetic VK210 and VK247 antigens was carried out to discriminate between the P. vivax subtypes.
By thick smear examination, 73 (n=100) patients were single infected with P. vivax, one with P. falciparum and 13 with both species. By thin smear, 53 patients were single infected with P. vivax, eight with only P. falciparum and 16 with both. Most of the collected blood samples were shown to be P. vivax positive (n=95) by PCR. All cases that were positive for P. falciparum by PCR (n=43) were also positive for P. vivax. However, 52 cases were single infected with P. vivax. IFAT showed antibody titres from 1:32 to 1:4,096. Additionally, using specific antibodies for VK210 and VK247, ELISA showed that 12 patients had antibodies for only the VK210 subtype, 4 patients had only VK247 subtype antibodies and 21 patients had antibodies for both subtypes. Using a DNA hybridization test, 47 patients were infected with the VK210 type, one patient was infected with VK247 and 23 patients were infected with both subtypes.
The proportion of the VK247 subtype in Myanmar was 43.1% (n=25) among 58 positive cases by serodiagnosis and 25.6% (n=24) among 94 positive cases by genetic diagnosis. In both diagnostic methods, the infection status of malaria patients is highly diverse with respect to malaria species, and multiple clonal infections are prevalent in Myanmar. Therefore, the complexity of the infection should be considered carefully when diagnosing malaria in Myanmar.
间日疟原虫分为两种亚型，一种是主要形式 VK210，另一种是变异形式 VK247。这种划分取决于环子孢子蛋白的氨基酸组成。在这项研究中，调查了缅甸间日疟原虫 VK247 变异型的流行情况。
通过显微镜检查、聚合酶链反应（PCR）和 DNA 杂交试验来确定血液样本中疟原虫的存在。为了检测血液样本中对间日疟原虫和恶性疟原虫的抗体，采用间接免疫荧光抗体试验（IFAT），使用无性血抗原。通过酶联免疫吸附试验，用合成的 VK210 和 VK247 抗原来区分间日疟原虫的亚型。
通过厚涂片检查，100 例患者中有 73 例（n=100）单独感染间日疟原虫，1 例感染恶性疟原虫，13 例同时感染两种疟原虫。通过薄涂片，53 例患者单独感染间日疟原虫，8 例仅感染恶性疟原虫，16 例同时感染两种疟原虫。PCR 显示大多数采集的血液样本均为间日疟原虫阳性（n=95）。所有通过 PCR 检测为恶性疟原虫阳性的病例（n=43）也均为间日疟原虫阳性。然而，52 例为单独感染间日疟原虫。IFAT 显示抗体滴度为 1:32 至 1:4,096。此外，使用针对 VK210 和 VK247 的特异性抗体，ELISA 显示 12 例患者只有 VK210 型抗体，4 例患者只有 VK247 型抗体，21 例患者同时具有两种亚型的抗体。通过 DNA 杂交试验，47 例患者感染 VK210 型，1 例患者感染 VK247 型，23 例患者同时感染两种亚型。
在血清学诊断的 58 例阳性病例中，间日疟原虫 VK247 亚型的比例为 43.1%（n=25），在基因诊断的 94 例阳性病例中，间日疟原虫 VK247 亚型的比例为 25.6%（n=24）。在这两种诊断方法中，疟疾病例的疟疾物种感染状况高度多样化，并且多重克隆感染在缅甸很普遍。因此，在诊断缅甸的疟疾时，应仔细考虑感染的复杂性。
