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There are relatively few studies on parasite fauna of marine fishes in Philippine waters. This study aimed to determine the prevalence of marine ascaridoid infection in Decapterus species in Balayan Bay and Tayabas Bay. A total of 371 fishes belonging to three different species of Decapterus (D. tabl [n = 130], D. macrosoma [n = 121], and D. maruadsi [n = 120]) were collected. Ascaridoid parasite larvae were found in all fish host species, with an overall fish infection rate of 22%. The highest infection rate was observed in D. tabl (27.69%), followed by D. macrosoma (19%), and then D. maruadsi (17.50%). Moreover, a higher prevalence of infection was detected in Tayabas Bay (27.57%) than in Balayan Bay (15.59%). Molecular analyses based on the ITS2 and 18S rRNA gene supported the identification of the larvae into two species: Anisakis typica and Raphidascaris (Ichthyascaris) lophii. This is the first report of the genetic identification of these two helminth parasites in Decapterus fish species in the Philippines. Paucity in the database of Philippine marine fish parasites warrants more research efforts, especially concerning economically important fish species with implications to food safety and food security.

The Chinese pond mussel Sinanodonta woodiana (Lea, 1834) is a large freshwater bivalve species of the family Unionidae and a known invasive alien species. Proper verification of its identity as well as its source population is crucial for the control of its spread. However, its high plastic shell morphology that resembles other non-invasive species of unionids can be an obstacle. The distribution and ecological impact of this invasive unionid is not fully understood and should be further investigated to prevent further spread in the Philippines. In this study, we used the cytochrome oxidase I (cox1) gene to verify the identity of putative S. woodiana samples collected from Bato Creek in Oriental Mindoro and Lake Danao in Leyte, Philippines and elucidate their source populations. Eighteen cytochrome oxidase subunit 1 (cox1) barcodes were generated from samples collected from Lake Danao, Leyte (n=13) and Bato Creek, Oriental Mindoro (n=5). These barcodes were subjected to Basic Local Alignment Search Tool (BLAST) analysis, which showed that the cox1 sequences from the Philippine samples matched with those of S. woodiana (>94%) found in GenBank. The sequences were then aligned with cox1 sequences of S. woodiana and other unionid representatives from GenBank. Phylogenetic and haplotype network analyses also showed three haplotypes (Hap 1, 2, and 4) of S. woodiana samples from Lake Danao and Bato Creek. Hap 1 and 2 are distinct haplotypes observed in Lake Danao samples while Hap 4 is shared between Lake Danao and Bato Creek samples and have clustered with conspecific specimens from Malaysia and Indonesia, suggesting their potential Island Southeast Asian origin. [ABSTRACT FROM AUTHOR]

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 amplif ied 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 identif ied 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. [ABSTRACT FROM AUTHOR]

Snail control to complement mass drug administration is being promoted by the World Health Organization for schistosomiasis control. Oncomelania hupensis quadrasi , the snail intermediate host of Schistosoma japonicum in the Philippines, has a very focal distribution; thus, scrutinizing baseline data and parameters affecting this distribution is very crucial. In this study in Gonzaga, Cagayan, Philippines, snail habitats were surveyed, and the various factors affecting the existence of the snails were determined. Malacological surveys and the mapping of sites of perpetual wetness in five endemic and five neighboring non-endemic barangays were conducted. Environmental and physicochemical factors were also examined. Maps of both snail and non-snail sites were generated. Of the fifty sites surveyed, O. h. quadrasi were found in twelve sites, and two sites yielded snails that were infected with S. japonicum cercariae. Factors such as silty loam soil, proximity to a snail site, water ammonia, and soil attributes (organic matter, iron, and pH) are all significantly associated with the presence of snails. In contrast, types of habitats, temperatures, and soil aggregation have no established association with the existence of snails. Mapping snail sites and determining factors favoring snail presence are vital to eliminating snails. These approaches will significantly maximize control impact and minimize wasted efforts and resources, especially in resource-limited schistosomiasis endemic areas.

The time is passing, and the worms are still a major struggle for local people in Asian countries, especially the less empowered and in a situation of social vulnerability. We are working in the field in Laos, Thailand, and the Philippines where the usual control programs based only on human treatment are partially effective. Areas with mass drug administration could diminish, but not eliminate STHs of endemic areas. The persistence of helminthic NTDs in the environment and animal hosts makes the eradication a very difficult task. Great changes in the landscapes of endemic areas, such as construction of dams, can change the fauna and the lifestyle of local people. Those changes can improve infrastructure, but it can also lead to social vulnerability. The challenge, then, is to conceive new and directed control programs for helminthiasis based on multi- and transdisciplinary approaches diminishing the health gap in a globalized world. In this short review, we summarize the actual scenario concerning the main helminths in Southeast Asia and how an environmental DNA approach and the use of GIS could contribute to surveillance and control programs.