Genetic Diversity of An. cAntonensis UsinG Pcr-rAPD MArkers Vol 43 No. 3 May 2012 567 Correspondence: Chalit Komalamisra, Depart- ment of Helminthology, Faculty of Tropical Medicine, 420/6 Ratchawithi Road, Bangkok 10400, Thailand. Tel/Fax: +66 (0) 2643 5600 E-mail: tmckm@mahidol.ac.th POPULATION STRUCTURE OF ANGIOSTRONGYLUS CANTONENSIS (NEMATODA: METASTRONGYLIDAE) IN THAILAND BASED ON PCR-RAPD MARKERS Urusa Thaenkham, Wallop Pakdee, Supaporn Nuamtanong, Wanna Maipanich, Somchit Pubampen, Surapol Sa-nguankiat, and Chalit Komalamisra Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand Abstract. Angiostrongylus cantonensis is the causative agent of angiostrongyliasis, which is widely distributed throughout the world. It can specifcally infect many species of intermediate and defnitive hosts. This study examined the genetic dif- ferentiation and population structure using the RAPD-PCR method of parasites obtained from 8 different geographical areas of Thailand. Based on 8 primers, high levels of genetic diversity and low levels of gene fow among populations were found. Using genetic distance and neighbor-joining dendrogram methods, A. cantonensis in Thailand could be divided into two groups with statistically signif- cant genetic differentiation of the two populations. However, genotypic variations and haplotype relationships need to be further elucidated using other markers. Keywords: Angiostrongylus cantonensis , population structure, PCR-RAPD, Thailand INTRODUCTION Angiostrongylus cantonensis (rat lung- worm) is a nematode of rodents, and adult worms live inside the pulmonary arteries (Alto, 2001). Humans occasionally acquire infection by ingesting raw or undercooked snail, slug, prawn, tadpole, or contami- nated vegetables, containing infective A. cantonensis larvae (Bronstein et al, 1978; Oku et al, 1980; Wang et al, 2008). The parasitic worm is neurotropic in humans and can cause eosinophilic meningitis (Alto, 2001). A. cantonensis is distributed widely in 30 countries, and outbreaks are frequently reported in many countries in Asia and in the Pacifc and Caribbean Islands (Wang et al, 2008). Many kinds of freshwater snails (Pila spp, Pomacea canaliculata, Biomphal- aria alexandrina, Lymnaea natalensis, and Melanoides tuberculata) and land snails (Achatina fulica and Hemiplecta spp) are reportedly paratenic hosts (Tasana et al, 2009). In China, P. canaliculata and Ac. fulica are believed to be closely associated with angiostrongyliasis. In Thailand, the high rate of angiostrongyliasis is linked to the custom of eating raw Pila snails (Wang et al, 2008). However, the highest infection rate (44.3%) of A. cantonensis is from Ac. fulica, while the rate among Pila spp is around 0.9% (Pipitgool et al, 1997). Ac. fulica is also a major source of