Genetic Comparison of <em>Oncomelania hupensis quadrasi</em> (Möllendorf, 1895) (Gastropoda: Pomatiopsidae), the Intermediate Host of <em>Schistosoma japonicum</em> in the Philippines, Based on 16S Ribosomal RNA Sequence

  • James Christopher C. Chua University of the Philippines Manila
  • Ian Kim B. Tabios University of the Philippines Manila
  • Pebbles Grayle P. Tamayo University of the Philippines Manila
  • Lydia R. Leonardo University of the Philippines Manila
  • Ian Kendrich C. Fontanilla University of the Philippines Diliman
  • Raffy Jay C. Fornillos University of the Philippines Diliman
  • Emmanuel Ryan C. De Chavez University of the Philippines Los Baños
  • Takeshi Agatsuma Kochi Medical School
  • Mihoko Kikuchi Nagasaki University
  • Naoko Kato-Hayashi Dokkyo Medical University
  • Yuichi Chigusa Dokkyo Medical University


Schistosomiasis japonica is a water-borne trematode infection transmitted by different subspecies of Oncomelania hupensis. As parasites may either co-evolve or locally adapt with their hosts, snail diversity, as revealed by morphometric and genetic studies, may reflect parasite diversity and elucidate snail susceptibility and transmission patterns. This study aimed to compare isolates of O. h. quadrasi based on a 342-bp fragment of the 16S ribosomal RNA gene. O. h. quadrasi isolates were collected from nine provinces known to have S. japonicum in the Philippines, namely Cagayan Valley, Bohol, Negros Occidental, Leyte, Davao, Davao del Sur, Mindoro Oriental, Northern Samar, and Sorsogon. O. h. hupensis and O. h. nosophora isolates were also collected from China and Japan, respectively. The 16S ribosomal RNA gene of each specimen was amplified and sequenced. Phylogenetic and network analyses based on the 221 16S rRNA gene sequences revealed that O. h. quadrasi clustered as a distinct clade from the two other subspecies. Of the four identified haplotypes for O. h. quadrasi, two haplotypes were from Negros Oriental (Ohq2 and Ohq3), and one haplotype was from Bohol (Ohq4). The isolates from the remaining seven provinces shared a common haplotype (Ohq1). The current study was able to show the relationship among O. hupensis subspecies and demonstrate the limited ability of mitochondrial 16S ribosomal molecular marker in differentiating O. h. quadrasi geographic strains in the Philippines.

Keywords: Oncomelania hupensis quadrasi, Schistosoma japonicum, Schistosomiasis japonica, Snail Intermediate Host, Haplotype, 16S Ribosomal RNA Gene