Control Methods for Snail-Borne Zoonoses

Histopathological changes in tissues of Bithynia siamensis goniomphalos incubated in crude extracts of camellia seed and mangosteen pericarp

The present study was performed to observe histopathological changes in tissues of Bithynia siamensis goniomphalos (Gastropoda, Bithyniidae) incubated in crude extract solutions of camellia (Camellia oleifera) seed and mangosteen (Garcinia mangostana) pericarp, and furthermore to estimate the molluscicidal effects of 2 plant substances. Substantial numbers of bithyniid snails were incubated in various concentrations of 2 plant solution for 24 hr. As the positive control, snails incubated in various concentrations of niclosamide, a chemical molluscicide, were used. The histopathological findings were observed in sectioned snail specimens of each experimental and control groups. The results showed that both camellia and mangosteen extracts had molluscicidal effects at 24 hr with 50% lethal concentration (LC50) at concentrations of 0.003 and 0.002 g/ml, respectively, while niclosamide had LC50 at concentrations 0.599 ppm. B. siamensis goniomphalos snail tissues (foot, gill, and digestive system) showed disruption of columnar muscle fibers of the foot, reduction of the length and number of gill cilia, numerous mucous vacuoles, and irregularly shaped of epithelial cells. Irregular apical and calciferous cells, dilatation of the digestive gland tubule, and large hemolymphatic spaces, and irregular apical surfaces, detachment of cilia, and enlargement of lysosomal vacuoles of epidermis were also shown in all groups. By the present study, it is confirmed that 2 plants, camellia and mangosteen, are keeping some substance having molluscicidal effects, and histopathological findings obtained in this study will provide some clues in further studies on their action mechanisms to use them as natural molluscicides.

Global status of fish-borne zoonotic trematodiasis in humans

Fishborne zoonotic trematodes (FZT), infecting humans and mammals worldwide, are reviewed and options for control discussed. Fifty nine species belonging to 4 families, i.e. Opisthorchiidae (12 species), Echinostomatidae (10 species), Heterophyidae (36 species) and Nanophyetidae (1 species) are listed. Some trematodes, which are highly pathogenic for humans such as Clonorchis sinensis, Opisthorchis viverrini, O. felineus are discussed in detail, i.e. infection status in humans in endemic areas, clinical aspects, symptoms and pathology of disease caused by these flukes. Other liver fluke species of the Opisthorchiidae are briefly mentioned with information about their infection rate and geographical distribution. Intestinal flukes are reviewed at the family level. We also present information on the first and second intermediate hosts as well as on reservoir hosts and on habits of human eating raw or undercooked fish.