ASSESSING FILOPALUDINA MARTENSI AS A POSSIBLE BIOLOGICAL CONTROL AGENT TO LIMIT BITHYNIA SIAMENSIS GONIOMPHALOS SNAILS, THE FIRST INTERMEDIATE HOST OF O.VIVERRINI IN NORTHEAST THAILAND

Abstract

The liver fluke Opisthorchis viverrini persists as one of the most prevalent human parasitic disease in the Lower Mekong Region. In particular, Northeast Thailand has observed high Opisthorchis viverrini infection rates throughout its provinces. To complete the life cycle of Opisthorchis viverrini, freshwater snails of the Bithynia genus is required to serve as the first intermediate hosts. Despite the use of various parasitic control measures such as molluscicides, Opisthorchis viverrini infections have been persistent and have not been completely eradicated. As such, multiple research has highlighted the possibility of implementing biological control measures through the native competitor snail Filopaludina martensi martensi. Current knowledge of snail ecology and population dynamics between Filopaludina and Bithynia snails remains poorly understood. This study has revealed that environmental determinants such as water conductivity, salinity, pH and soil texture affects the physical and chemical characteristics of snails through utilizing statistical tests including independent t-tests, one-way ANOVA and bivariate correlations. Both snail species adapt to these variations in environmental conditions through phenotypic plasticity by altering shell characteristics and morphology. Results from laboratory experiments indicate that both snails do not merely engage in interspecific competition, but display antagonistic and aggressive behaviour. Using ecological indices, analyses into the population dynamics suggests that despite engaging in interspecific competition, both snail species are able to coexist in their natural environments due to the different ecological niches it occupies. Filopaludina snails indicate preferences for pond habitats while Bithynia snails prefer stream or paddy habitats. Therefore, this thesis highlights the importance of understanding snail ecology and snail population dynamics as a means to assess the possibility of Filopaludina snails as a potential biological control agent to manage Opisthorchis viverrini transmissions.