From regional and global perspectives, Thailand has progressed toward lymphatic filariasis transmission-free zone in almost entire endemic provinces, being verified by WHO by the end of 2012 after the 5-year implementation of mass drug administration (MDA) with diethylcarbamazine and albendazole as part of the National Program to Eliminate Lymphatic Filariasis (PELF) (2002–2006) and a 4-year expansion of post-MDA surveillance (2007–2010). However, Thai PELF has been challenging sensitive situations of not only border crossings of local people on Thailand-Myanmar border where focal distribution of forest- and forest fringe-related border bancroftian filariasis (BBF) is caused by nocturnally subperiodic Wuchereria bancrofti in local people living in pockets of endemic villages, but also intense cross-border migrations of Mon and Tanintharyi workers from Myanmar to Thailand who harbor nocturnally periodic W. bancrofti microfilaremic infection causing the emergence of imported bancroftian filariasis (IBF). Thus, this paper discusses the apparent issues and problems pertaining to epidemiological surveillance and postgenomic MDA evaluation for 2010–2020 convalescent BBF and IBF. In particular, the population migration linked to fitness of benzimidazole-resistant W. bancrofti population is a topic of interest in this region whether the resistance is associated with pressure of the MDA 2 drugs and the vulnerabilities epidemiologically observed in complex BBF or IBF settings. 1. Global and Regional Perspectives on Lymphatic Filariasis Elimination Life-threatening lymphatic filariasis (LF) is a mosquito-borne parasitic disease caused by two main filarial nematodes: Wuchereria bancrofti and Brugia malayi, and to a very lesser extent by Brugia timori. The disease affects about 1.3 billion people in 81 countries and territories in Asia-Pacific, Africa, and Americas; of these, estimated 120 million people are infected (Figure 1) [1]. It is estimated that about 600 million people live in endemic countries in South and East Asia (SEA) region accounting for 60% of global figure. Approximately, 60 million SEA people harboring microfilaremic infections account for a half of globally active LF burden [2]. The infection with either of these parasites in an endemic population can be eliminated as the result of large-scale control, that is, reducing the infection prevalence to the level below transmission threshold or to be considered as no longer public health problem. Thus, this potentially eradicable disease has been addressed as public health problem worldwide as the
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