Malaria and Vector Research Group (MVRG), Biotechnology Research Center (BRC), Institut Pasteur Iran, Tehran, P,O, Box 1316943551, Iran.
Malar J. 2012 Apr 25;11:126. doi: 10.1186/1475-2875-11-126.
In malaria endemic areas, continuous exposure to Plasmodium parasites leads to asymptomatic carriers that provide a fundamental reservoir of parasites, contributing to the persistence of malaria transmission. Therefore, in the present investigation, the presence and prevalence of malaria asymptomatic cases were determined to evaluate the reservoir of infection in two malaria endemic areas with a previous history of malaria transmission in the south of Iran, Bashagard and Ghale-Ganj districts of Hormozgan and Kerman provinces, respectively, where malaria transmission has been drastically reduced in the recent years.
The population samples (n = 500 from each of the studied areas) were randomly collected from non-febrile, long-term residing, aged two to over 60 years, during 20092010. Three identical surveys were carried out in both study areas and in each phase all the consent participants were interviewed and clinically examined. In all, three surveys to detect hidden parasite reservoirs (both Plasmodium falciparum and Plasmodium vivax), thick and thin blood smears and a highly sensitive nested-PCR were applied. In addition, the sero-prevalence survey for detecting malaria exposure was done by using a serological marker.
In this study, P. vivax and P. falciparum parasites were not detected by light microscopy and nested-PCR assay in all three surveys of samples. Antibody responses against P. vivax and P. falciparum were detected in 1% and 0.2% of the total examined individuals, respectively, in Bashagard district. Regarding to Ghale-Ganj district, about 0.9% of the individuals had IgG -specific antibody to P. vivax at the first and second surveys, but at the third survey 0.45% of the participants had positive antibody to P. vivax parasite. IgG -specific antibody to P. falciparum was detected in 0.2% of the participants at the first and follow-up surveys. The overall regional differences were not statistically significant (P > 0.05).
Taken together, the lack of asymptomatic carrier with the evidence of extremely low sero-positive to both P. vivax and P. falciparum among examined individuals supported the limited recent transmission in the studied areas and, therefore, these parts of Iran have potential to eliminate the disease in the next few years. However, continued follow up and action are still needed in both studied areas and also in their neighbouring province, Sistan and Baluchistan, which has the highest reported cases of malaria in Iran and also, has the largest border line with Afghanistan and Pakistan, with no elimination activities. This data will provide useful information for managing elimination activities in Iran.
在疟疾流行地区，持续暴露于疟原虫会导致无症状感染者的出现，这些感染者是寄生虫的重要储存库，导致疟疾传播持续存在。因此，在本研究中，我们确定了疟疾无症状病例的存在和流行情况，以评估伊朗南部两个疟疾流行地区的感染储存库，这两个地区分别是霍尔木兹甘省的巴沙加德和盖勒甘杰区，以及克尔曼省，在这些地区，疟疾传播近年来已大幅减少。
在 2009 年至 2010 年期间，从每个研究地区随机抽取 500 名无发热、长期居住、年龄在 2 岁以上至 60 岁以上的非发热、长期居住的人群作为研究对象。在两个研究地区进行了三次相同的调查，在每个阶段，所有同意参与的人都接受了访谈和临床检查。在所有调查中，均采用厚血涂片、薄血涂片和高度敏感的巢式 PCR 检测来检测隐藏的寄生虫储存库（包括恶性疟原虫和间日疟原虫）。此外，还通过血清学标志物检测进行了疟疾暴露的血清阳性率调查。
在本研究中，在所有三次样本调查中，均未通过光学显微镜和巢式 PCR 检测到间日疟原虫和恶性疟原虫寄生虫。在巴沙加德区，1%的总检查个体中检测到针对间日疟原虫和恶性疟原虫的抗体反应，0.2%的个体中检测到针对恶性疟原虫的抗体反应。关于盖勒甘杰区，大约 0.9%的个体在第一和第二次调查中对间日疟原虫 IgG 具有特异性抗体，但在第三次调查中，0.45%的参与者对间日疟原虫寄生虫具有阳性抗体。在第一次和随访调查中，0.2%的参与者中检测到针对恶性疟原虫的 IgG 特异性抗体。区域间的总体差异无统计学意义（P>0.05）。
综上所述，在所检查的个体中，没有无症状感染者，且针对间日疟原虫和恶性疟原虫的血清阳性率极低，这支持了研究地区最近传播的局限性，因此，伊朗的这些地区有望在未来几年内消除这种疾病。然而，仍需要在两个研究地区以及伊朗疟疾病例报告率最高的与阿富汗和巴基斯坦接壤的锡斯坦和俾路支省继续开展后续工作和行动，这些地区目前没有消除活动。这些数据将为伊朗的消除活动管理提供有用的信息。
