Vonghachack Youthanavanh, Sayasone Somphou, Khieu Virak, Bergquist Robert, van Dam Govert J, Hoekstra Pytsje T, Corstjens Paul L A M, Nickel Beatrice, Marti Hanspeter, Utzinger Jürg, Muth Sinuon, Odermatt Peter
Faculty of Basic Sciences, University of Health Sciences, Ministry of Health, Vientiane, Lao People's Democratic Republic.
Swiss Tropical and Public Health Institute, P.O. Box, CH-4002, Basel, Switzerland.
Infect Dis Poverty. 2017 Aug 10;6(1):127. doi: 10.1186/s40249-017-0335-x.
Given the restricted distribution of Schistosoma mekongi in one province in Lao People's Democratic Republic (Lao PDR) and two provinces in Cambodia, together with progress of the national control programmes aimed at reducing morbidity and infection prevalence, the elimination of schistosomiasis mekongi seems feasible. However, sensitive diagnostic tools will be required to determine whether elimination has been achieved. We compared several standard and novel diagnostic tools in S. mekongi-endemic areas.
The prevalence and infection intensity of S. mekongi were evaluated in 377 study participants from four villages in the endemic areas in Lao PDR and Cambodia using Kato-Katz stool examination, antibody detection based on an enzyme-linked immunosorbent assay (ELISA) and schistosome circulating antigen detection by lateral-flow tests. Two highly sensitive test systems for the detection of cathodic and anodic circulating antigens (CCA, CAA) in urine and serum were utilized.
Stool microscopy revealed an overall prevalence of S. mekongi of 6.4% (one case in Cambodia and 23 cases in Lao PDR), while that of Opisthorchis viverrini, hookworm, Trichuris trichiura, Ascaris lumbricoides and Taenia spp. were 50.4%, 28.1%, 3.5%, 0.3% and 1.9%, respectively. In the urine samples, the tests for CCA and CAA detected S. mekongi infections in 21.0% and 38.7% of the study participants, respectively. In the serum samples, the CAA assay revealed a prevalence of 32.4%, while a combination of the CAA assay in serum and in urine revealed a prevalence of 43.2%. There was a difference between the two study locations with a higher prevalence reached in the samples from Lao PDR.
The CCA, CAA and ELISA results showed substantially higher prevalence estimates for S. mekongi compared to Kato-Katz thick smears. Active schistosomiasis mekongi in Lao PDR and Cambodia might thus have been considerably underestimated previously. Hence, sustained control efforts are still needed to break transmission of S. mekongi. The pivotal role of highly sensitive diagnostic assays in areas targeting elimination cannot be overemphasised.
鉴于湄公血吸虫仅在老挝人民民主共和国（老挝）的一个省以及柬埔寨的两个省有分布，并且旨在降低发病率和感染率的国家控制项目取得了进展，消除湄公血吸虫病似乎是可行的。然而，需要灵敏的诊断工具来确定是否已实现消除目标。我们在湄公血吸虫病流行地区比较了几种标准和新型诊断工具。
采用改良加藤厚涂片法、基于酶联免疫吸附测定（ELISA）的抗体检测以及侧向流动试验检测血吸虫循环抗原，对来自老挝和柬埔寨流行地区四个村庄的377名研究参与者进行了湄公血吸虫的感染率和感染强度评估。使用了两种用于检测尿液和血清中阴极和阳极循环抗原（CCA、CAA）的高灵敏度检测系统。
粪便显微镜检查显示湄公血吸虫的总体感染率为6.4%（柬埔寨1例，老挝23例），而华支睾吸虫、钩虫、鞭虫、蛔虫和绦虫的感染率分别为50.4%、28.1%、3.5%、0.3%和1.9%。在尿液样本中，CCA和CAA检测分别在21.0%和38.7%的研究参与者中检测到湄公血吸虫感染。在血清样本中，CAA检测显示感染率为32.4%，而血清和尿液中CAA检测相结合显示感染率为43.2%。两个研究地点之间存在差异，老挝样本的感染率更高。
与改良加藤厚涂片法相比，CCA、CAA和ELISA结果显示湄公血吸虫的感染率估计值要高得多。因此，老挝和柬埔寨的活动性湄公血吸虫病此前可能被大大低估了。因此，仍需要持续的控制措施来阻断湄公血吸虫的传播。在以消除为目标的地区，高灵敏度诊断检测的关键作用再怎么强调也不为过。
