Sriwichai Patchara, Karl Stephan, Samung Yudthana, Kiattibutr Kirakorn, Sirichaisinthop Jeeraphat, Mueller Ivo, Cui Liwang, Sattabongkot Jetsumon
Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.
Malar J. 2017 Jun 21;16(1):258. doi: 10.1186/s12936-017-1900-2.
Cross-border malaria transmission is an important problem for national malaria control programmes. The epidemiology of cross-border malaria is further complicated in areas where Plasmodium falciparum and Plasmodium vivax are both endemic. By combining passive case detection data with entomological data, a transmission scenario on the northwestern Thai-Myanmar border where P. falciparum is likely driven by importation was described, whereas P. vivax is also locally transmitted. This study highlights the differences in the level of control required to eliminate P. falciparum and P. vivax from the same region.
Malaria case data were collected from malaria clinics in Suan Oi village, Tak Province, Thailand between 2011 and 2014. Infections were diagnosed by light microscopy. Demographic data, including migrant status, were correlated with concomitantly collected entomology data from 1330 mosquito trap nights using logistic regression. Malaria infection in the captured mosquitoes was detected by ELISA.
Recent migrants were almost four times more likely to be infected with P. falciparum compared with Thai patients (OR 3.84, p < 0.001) and cases were significantly associated with seasonal migration. However, P. falciparum infection was not associated with the Anopheles mosquito capture rates, suggesting predominantly imported infections. In contrast, recent migrants were equally likely to present with P. vivax as mid-term migrants. Both migrant groups were twice as likely to be infected with P. vivax in comparison to the resident Thai population (OR 1.96, p < 0.001 and OR 1.94, p < 0.001, respectively). Plasmodium vivax cases were strongly correlated with age and local capture rates of two major vector species Anopheles minimus and Anopheles maculatus (OR 1.23, p = 0.020 and OR 1.33, p = 0.046, respectively), suggesting that a high level of local transmission might be causing these infections.
On the Thai-Myanmar border, P. falciparum infections occur mostly in the recent migrant population with a seasonality reflecting that of agricultural activity, rather than that of the local mosquito population. This suggests that P. falciparum was mostly imported. In contrast, P. vivax cases were significantly associated with mosquito capture rates and less with migrant status, indicating local transmission. This highlights the different timelines and requirements for P. falciparum and P. vivax elimination in the same region and underlines the importance of multinational, cross-border malaria control.
跨境疟疾传播是国家疟疾防控项目面临的一个重要问题。在恶性疟原虫和间日疟原虫均为地方流行的地区，跨境疟疾的流行病学情况更为复杂。通过将被动病例检测数据与昆虫学数据相结合，描述了泰国-缅甸边境西北部的传播情况，其中恶性疟原虫感染可能由输入引起，而间日疟原虫也存在本地传播。本研究强调了在同一地区消除恶性疟原虫和间日疟原虫所需控制水平的差异。
收集了2011年至2014年期间泰国北碧府Suan Oi村疟疾诊所的疟疾病例数据。通过光学显微镜诊断感染情况。使用逻辑回归分析将包括移民身份在内的人口统计学数据与同时收集的1330个蚊虫诱捕夜的昆虫学数据进行关联。通过酶联免疫吸附测定法检测捕获蚊虫中的疟疾感染情况。
与泰国患者相比，近期移民感染恶性疟原虫的可能性几乎是其四倍（比值比3.84，p<0.001），病例与季节性移民显著相关。然而，恶性疟原虫感染与按蚊捕获率无关，表明主要是输入性感染。相比之下，近期移民出现间日疟原虫感染的可能性与中期移民相同。与泰国本地居民相比，这两个移民群体感染间日疟原虫的可能性均为其两倍（比值比分别为1.96，p<0.001和1.94，p<0.001）。间日疟原虫病例与年龄以及两种主要病媒按蚊微小按蚊和大劣按蚊的本地捕获率密切相关（比值比分别为1.23，p=0.020和1.33，p=0.046），表明高水平的本地传播可能导致了这些感染。
在泰国-缅甸边境，恶性疟原虫感染主要发生在近期移民人群中，其季节性反映了农业活动的季节性，而非当地蚊虫种群的季节性。这表明恶性疟原虫大多是输入性的。相比之下，间日疟原虫病例与蚊虫捕获率显著相关，与移民身份的相关性较小，表明存在本地传播。这突出了在同一地区消除恶性疟原虫和间日疟原虫的不同时间线和要求，并强调了跨国跨境疟疾控制的重要性。
