Imported Plasmodium falciparum and locally transmitted Plasmodium vivax: cross-border malaria transmission scenario in northwestern Thailand

• Published in: Malaria Journal
• Main Authors: Patchara Sriwichai, Stephan Karl, Yudthana Samung, Kirakorn Kiattibutr, Jeeraphat Sirichaisinthop, Ivo Mueller, Liwang Cui, Jetsumon Sattabongkot
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2017
• Subjects: Malaria transmission; Border malaria; Migration; Mosquito infection; Thailand; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-017-1900-2; https://doaj.org/article/046291ba00a94c9ebf71834292802c01

Abstract Background 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. Methods 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. Results 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. Conclusions On the Thai–Myanmar border, P. falciparum infections occur mostly in ...