Hanoi Medical University, Hanoi, Vietnam.
Vietnam People's Army Military Medical Department, Hanoi, Vietnam.
Malar J. 2022 Feb 8;21(1):40. doi: 10.1186/s12936-022-04060-6.
Malaria elimination by 2030 is an aim of many countries in the Greater Mekong Sub-region, including Vietnam. However, to achieve this goal and accelerate towards malaria elimination, countries need to determine the extent and prevalence of asymptomatic malaria as a potential reservoir for malaria transmission and the intensity of malaria transmission. The purpose of this study was to determine the prevalence of asymptomatic malaria and seropositivity rate in several districts of Gia Lai province in the Central Highlands of Vietnam.
A cross-sectional survey of asymptomatic malaria and serological testing was conducted in 3283 people living at 14 communes across seven districts in Gia Lai province in December 2016 to January 2017. Finger prick capillary blood samples were tested for malaria using rapid diagnostic testing and polymerase chain reaction (PCR), as well as detecting antibodies against 3 Plasmodium falciparum and 4 Plasmodium vivax antigens by indirect enzyme-linked immunosorbent assay (ELISA). Age-seroprevalence curves were fitted using reverse catalytic models with maximum likelihood.
The study population was predominantly male (65.9%, 2165/3283), adults (88.7%, 2911/3283) and of a minority ethnicity (72.2%, 2371/3283), with most participants being farmers and outdoor government workers (90.2%, 2960/3283). Using a small volume of blood (≈ 10 µL) the PCR assay revealed that 1.74% (57/3283) of the participants had asymptomatic malaria (P. falciparum 1.07%, P. vivax 0.40%, Plasmodium malariae 0.15% and mixed infections 0.12%). In contrast, the annual malaria prevalence rates for clinical malaria in the communities where the participants lived were 0.12% (108/90,395) in 2016 and 0.22% (201/93,184) in 2017. Seropositivity for at least one P. falciparum or one P. vivax antigen was 38.5% (1257/3262) and 31.1% (1022/3282), respectively. Age-dependent trends in the proportion of seropositive individuals in five of the districts discriminated the three districts with sustained low malaria prevalence from the two districts with higher transmission.
Asymptomatic Plasmodium carriers were found to be substantially more prevalent than clinical cases in seven districts of Gia Lai province, and a third of the population had serological evidence of previous malaria exposure. The findings add knowledge on the extent of asymptomatic malaria and transmission for developing malaria elimination strategies for Vietnam.
2030 年消除疟疾是大湄公河次区域包括越南在内的许多国家的目标。然而，要实现这一目标并加速消除疟疾，各国需要确定无症状疟疾的程度和流行率，因为无症状疟疾可能是疟疾传播的潜在储主，以及疟疾传播的强度。本研究旨在确定越南中部高地嘉莱省几个地区的无症状疟疾和血清阳性率。
2016 年 12 月至 2017 年 1 月，在嘉莱省 7 个区的 14 个公社对 3283 名无症状人群进行了横断面调查，包括血清学检测。使用快速诊断检测和聚合酶链反应（PCR）对指尖毛细血管血样进行疟疾检测，同时通过间接酶联免疫吸附试验（ELISA）检测针对 3 种恶性疟原虫和 4 种间日疟原虫抗原的抗体。使用最大似然反催化模型拟合年龄-血清阳性率曲线。
研究人群主要为男性（65.9%，2165/3283）、成年人（88.7%，2911/3283）和少数民族（72.2%，2371/3283），大多数参与者是农民和户外政府工作人员（90.2%，2960/3283）。使用小体积血液（≈10µL），PCR 检测显示 1.74%（57/3283）的参与者患有无症状疟疾（恶性疟原虫 1.07%，间日疟原虫 0.40%，卵形疟原虫 0.15%和混合感染 0.12%）。相比之下，参与者居住的社区的年度临床疟疾患病率分别为 2016 年 0.12%（108/90395）和 2017 年 0.22%（201/93184）。至少一种恶性疟原虫或一种间日疟原虫抗原的血清阳性率分别为 38.5%（1257/3262）和 31.1%（1022/3282）。五个区的年龄相关趋势可区分出三个疟疾持续低流行区和两个传播较高的区。
在嘉莱省的七个区发现，无症状疟原虫携带者的比例明显高于临床病例，三分之一的人口有疟疾既往感染的血清学证据。这些发现增加了关于无症状疟疾和传播程度的知识，为越南制定消除疟疾策略提供了依据。
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