Background: The perpetuation of schistosomiasis japonica in the Philippines depends to a major extent on the persistence of its intermediate host Oncomelania hupensis quadrasi, an amphibious snail. While the malacological survey remains the method of choice in determining the contamination of the environment as evidenced by snails infected with schistosome larval stages, an emerging technology known as environmental DNA (eDNA) detection provides an alternative method. Previous reports showed that O. hupensis quadrasi eDNA could be detected in water, but no reports have been made on its detection in soil. Methods: This study, thus focused on the detection of O. hupensis quadrasi eDNA from soil samples collected from two selected schistosomiasis-endemic barangays in Gonzaga, Cagayan Valley using conventional and TaqMan-quantitative (qPCR) PCRs. Results: The results show that qPCR could better detect O. hupensis quadrasi eDNA in soil than the conventional method. In determining the possible distribution range of the snail, basic edaphic factors were measured and correlated with the presence of eDNA. The eDNA detection probability increases as the pH, phosphorous, zinc, copper, and potassium content increases, possibly indicating the conditions in the environment that favor the presence of the snails. A map was generated to show the probable extent of the distribution of the snails away from the body of the freshwater. Conclusion: The information generated from this study could be used to determine snail habitats that could be possible hotspots of transmission and should, therefore, be targeted for snail control or be fenced off from human and animal contact or from the contamination of feces by being a dumping site for domestic wastes.

The degree of land use and land cover (LULC) conversion of Mt. Pulag National Park (MPNP), Benguet Province, Philippines, from 1990–2020 was assessed to provide valuable information for land resource management strategies. The increasing demand for vegetable farming threatens the park with further degradation. The magnitude of changes in the LULC of MPNP was determined using Landsat 5 for 1990–2010 and Sentinel-2 for 2020. The FLAASH (Fast Line-ofsight Atmospheric Analysis of Hypercubes) algorithm was performed to enhance the reflectance of the satellite images before data analysis. The maximum likelihood classification (MLC) was used to classify the MPNP into five LULC changes: agricultural lands, barren lands, built-up areas, forest lands, and grasslands with areal percentage cover of 15.88, 0.26, 1.34, 80.51, and 2.01%, respectively, in 2020, and overall accuracy of 90.58%. The LULC percentage of change from 1990–2020 showed that agricultural areas increased by 8.96%, barren lands decreased by 2.14%, built-up areas increased by 1.02%, forest lands decreased by 8.35%, and grasslands increased by 0.51%. The results showed that the increasing area of human-induced LULC class such as the agriculture lands and built-up areas is the primary cause of forest land loss. However, the barren lands undergoing natural regeneration contribute to the gain of the forest area. Therefore, the LULC conversion pattern serves as a warning that the park will continue to lose a significant portion of the forest due to land conversion if no intervention is done.

χ-Conotoxins are known for their ability to selectively inhibit norepinephrine transporters, an ability that makes them potential leads for treating various neurological disorders, including neuropathic pain. PnID, a peptide isolated from the venom of Conus pennaceus, shares high sequence homology with previously characterized χ-conotoxins. Whereas previously reported χ-conotoxins seem to only have a single native disulfide bonding pattern, PnID has three native isomers due to the formation of different disulfide bond patterns during its maturation in the venom duct. In this study, the disulfide connectivity and three-dimensional structure of these disulfide isomers were explored using regioselective synthesis, chromatographic coelution, and solution-state nuclear magnetic resonance spectroscopy. Of the native isomers, only the isomer with a ribbon disulfide configuration showed pharmacological activity similar to other χ-conotoxins. This isomer inhibited the rat norepinephrine transporter (IC50 = 10 ± 2 µM) and has the most structural similarity to previously characterized χ-conotoxins. In contrast, the globular isoform of PnID showed more than ten times less activity against this transporter and the beaded isoform did not display any measurable biological activity. This study is the first report of the pharmacological and structural characterization of an χ-conotoxin from a species other than Conus marmoreus and is the first report of the existence of natively-formed conotoxin isomers.

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