Egg-hatching mechanism of human liver fluke, Opisthorchis viverrini: a role for leucine aminopeptidases from the snail host, Bithynia siamensis goniomphalos

The human liver fluke Opisthorchis viverrini (Platyhelminthes, Trematoda, Digenea) uses snails of the genus Bithynia as first intermediate host. Peculiarly among trematodes, the eggs of O. viverrini hatch within the digestive tract of its snail host. It remains uncertain whether hatching in this species is mediated through mechanical fracture of the eggshell or by digestion with specific digestive enzymes. This study aimed to characterize enzymes with specific inhibitors and factors involved in the hatching activity of O. viverrini eggs. For measuring egg hatching in vivo, 50 O. viverrini mature eggs were fed to individual Bithynia siamensis goniomphalos snails at various temperature conditions for 24 hr. Ex vivo, mature eggs were incubated with crude snail extract and commercial leucine aminopeptidase (LAP). Egg-hatching of O. viverrini was temperature dependent, with optimal hatching occurring at 24-28 C, with a peak of hatching of 93.54% in vivo and 30.55% ex vivo occurring at these temperatures. Ex vivo hatching rates increased to 45.87% under anaerobic conditions at 28 C. Some 22.70% and 16.21% of heat-killed eggs also hatched within the snail digestive tract and snail extract, respectively, indicating that host molecules are involved in the hatching response. Most eggs hatch in the anterior regions of the digestive tract. Hatching was completely inhibited in the presence of bestatin, an inhibitor of LAP, but not in the presence of phosphatase inhibitors. Bestatin inhibition of hatching was reversible. Finally, egg hatching could be induced by addition of a porcine LAP. The results indicate that this digenean utilizes both LAP of the snail host and movement of miracidia for hatching

Melanoides tuberculata (Mollusca: Thiaridae) as an intermediate host of Centrocestus formosanus (Trematoda: Heterophyidae) in Brazil Melanoides tuberculata (Mollusca: Thiaridae) como hospedeiro intermediário de Centrocestus formosanus (Trematoda: Heterophyidae) no Brasil

Pleurolophocercous cercariae emerged from naturally infected Melanoides tuberculata from Minas Gerais State, Brazil, were used to perform experimental infection of laboratory-reared Poecilia reticulata. Mature metacercariae were obtained from the gills of fishes and force-fed to Mus musculus. The adult parasites which recovered from small intestines of mice were identified as Centrocestus formosanus. This is the first report of M. tuberculata as intermediate host of this heterophyid in Brazil.<br>Cercárias do tipo pleurolofocerca emergidas de Melanoides tuberculata naturalmente infectados coletados na represa da Pampulha, Belo Horizonte, Minas Gerais, Brasil, foram utilizadas para a infecção experimental de Poecilia reticulata criados em laboratório. Metacercárias maduras foram obtidas nas brânquias dos peixes e administradas por via oral a Mus musculus. Parasitos adultos recuperados no intestino delgado dos camundongos foram identificados como Centrocestus formosanus. Este é o primeiro relato de M. tuberculata como hospedeiro intermediário deste parasito no Brasil

Examining landscape determinants of Opisthorchis viverrini transmission

10.1007/s10393-012-0789-zEcoHealth93328-34