A systematic survey of environmental DNA in Palau's lakes and waterfalls reveals an increase in levels after flooding.

OBJECTIVE

Leptospirosis is an important bacterial zoonosis which is widespread in tropical and subtropical islands and influences human and animal health which has secondary economic effects. Although leptospirosis is endemic in Palau, an Oceanian Pacific Island country, few systematic surveys of potential risk factors for infection, such as weather and host animals, have been conducted in the natural environment. We used environmental DNA metabarcoding to assess the distribution, species diversity, and abundance of pathogenic in this endemic region to investigate the potential environmental risks.

METHODS

Forty-two paired water samples, representing fine and rainy weather conditions, were collected from four representative waterfalls and lakes on Babeldaob Island, the largest island in Palau. High-throughput sequencing analysis was conducted for polymerase chain reaction products of leptospiral 16S rRNA and vertebrate animal mitochondrial 12S rRNA genes.

RESULTS

We revealed greater diversity and abundance in samples collected after continuous rain, particularly in the presence of flooding, compared with samples collected under typhoon, monsoon, or fine weather conditions. From same samples, six mammalian species including cats (), mice (), Yap flying fox (), rats (), and pigs () were repeatedly detected. These may be candidates of host animals of in Palau; however, their detection was not clearly correlated with that of .

CONCLUSION

We repeatedly detected several species of pathogenic from water samples of a wide region of Babeldaob Island. We confirmed that contamination in freshwater environments increased under rainy conditions, particularly in the presence of flooding. This information could be used to improve public health control measures in this region.