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The snail Bithynia siamensis goniomphalos acts as the first intermediate host for the human liver fluke Opisthorchis viverrini , the major cause of cholangiocarcinoma (CCA) in Northeast Thailand. The undisputed link between CCA and O. viverrini infection has precipitated efforts to understand the molecular basis of host–parasite interactions with a view to ultimately developing new control strategies to combat this carcinogenic infection. To date most effort has focused on the interactions between the parasite and its human host, and little is known about the molecular relationships between the liver fluke and its snail intermediate host. In the present study we analyse the protein expression changes in different tissues of B. siamensis goniomphalos induced by infection with larval O. viverrini using iTRAQ labelling technology. We show that O. viverrini infection downregulates the expression of oxidoreductases and catalytic enzymes, while stress-related and motor proteins are upregulated. The present work could serve as a basis for future studies on the proteins implicated in the susceptibility/resistance of B. siamensis goniomphalos to O. viverrini , as well as studies on other pulmonate snail intermediate hosts of various parasitic flukes that infect humans. Biological significance Despite the importance and high prevalence of opisthorchiasis in some regions of Southeast Asia and the direct relationship between infection by Opisthorchis viverrini and the incidence of cholangiocarcinoma, little is known of the modifications induced by this parasite in its snail intermediate hosts. This time-course study provides the first in-depth quantitative proteomic analysis of experimentally infected Bithynia siamensis goniomphalos . We show how motor and stress-related proteins are upregulated in infected snails, while O. viverrini infection downregulates the expression of oxidoreductases and catalytic enzymes. This work serves as a basis for the development of new strategies, focused on the invertebrate intermediate hosts, to control parasite transmission. [ABSTRACT FROM AUTHOR]

Determining of the success of a parasite's infectiveness in its snail host clearly depends on environmental conditions. Temperature, one of the most influential factors impinging on metabolism of cold-blooded animals, is believed to be an important factor in parasitic infection in snails. In order to elucidate the influence of temperature, sex and size of snails on infectivity of Opisthorchis viverrini to its first intermediate host, Bithynia siamensis goniomphalos , 960 snails were divided into 2 groups by sex. Each group was subdivided by their size into small and medium sub-groups. Each snail was fed with embryonated uterine-eggs of O. viverrini at different temperatures (16–37 °C, 3 °C intervals). Dissections were carried out 1, 7, 14, 28 and 56 days thereafter and detection of O. viverrini infection was undertaken by PCR using specific primers. Infection was strongly temperature-dependent, as temperature increases of 1 °C resulted in increased odds of infection 5.4% ( P < 0.01). A temperature of 34 °C gave the highest rate of infection of 44.14%. We also found that the odds of infection in small sized snails was 39.8% higher relative to medium sized snails ( P < 0.05). Relative to day 1, the decrease in the odds of infection was detected when the day post infection was longer ( P < 0.01). Proportion of infection in female was not different to male significantly. [ABSTRACT FROM AUTHOR]