Scanning electron microscopic observations were made on the early third stage (eL3) larvae of Gnathostoma spinigerum (Sakolnakhon, northeast Thailand) from 3-week-old infected cyclops (Mesocyclops leuckarti). The morphological surfaces of the anterior end, head spine, body cuticle, amphid, papillae, posterior end of larvae were described and compared with the advance third-stage (aL3) larvae.
This study aims to develop an alternative field-based approach to interrupt the life cycle of O. viverrini. The effects of temperature, salinity, acidity, ultraviolet A, B, C radiation, and combinations of these physicochemical factors on the loss of infectivity of Opisthorchis viverrini cercariae were analyzed to determine values required for 50 and 95 % lethal concentrations (LC50 and LC95) and period of loss infection success (LI50 and LI95). Newly shed cercariae of O. viverrini were used. LC50 and LC95 values for temperature, salinity, and acidity on cercariae were 33.19 and 37.70 ºC, 7.29 and 8.40 ppt, 4.62 and 4.80 M H2CO3, respectively. The values of LI50 and LI95 on cercariae by exposure to UVA, UVB, and UVC were 19.54 and 20.11 h, 5.03 and 5.12 h, 3.37 and 6.02 min, respectively. Combinations of these factors in the presence of UVC proved damaging to cercariae most rapidly. The shortest loss infection time of LI50 and LI95 were 1.09 and 2.83 min. Cercariae were deemed to have lost the ability to infect cyprinid fish when they had shed their tails, even though they were still capable of some movement. In nature, temperature, salinity, acidity, ultraviolet radiation, and combinations of these factors, affect the ability of O. viverrini cercariae to infect cyprinid fish.
To explore larvicidal effects of anthelmintic drugs on Opisthorchis viverrini (O. viverrini) for alternative approach to interrupting its cycle for developing a field-based control program.The larvicidal activities of albendazole (Al), artesunate (Ar), praziquantel (Pzq) and miltefosine (Mf) on O. viverrini cercariae and mature metacercariae were investigated. Lethal concentrations (LC50 and LC95) of these drugs were determined. Mature metacercariae previously exposed to various concentrations of the drugs were administered to hamsters. Worms were harvested 30 d post infection and worm recovery rates calculated. Al, Ar, Pzq and Mf produced morphological degeneration and induced shedding tails of cercariae after 24 h exposure.The LC50 and LC95 of Al, Ar, Pzq and Mf on cercariae were 0.720 and 1.139, 0.350 and 0.861, 0.017 and 0.693, and 0.530 and 1.134 ppm, respectively. LC50 and LC95 of Ar on mature metacercariae were 303.643 and 446.237 ppm and of Mf were 289.711 and 631.781 ppm, respectively but no lethal effect in Pzq- and Al-treated groups (up to 1 ppt). No worms were found in hamsters administered Pzq-treated metacercariae. The adult worms from Al-treated metacercariae were significantly bigger in size compared to the control group (P < 0.05). Fecundity and body width were greater in adults from Mf-treated metacercariae compared to the control group (P < 0.05).The larvicidal effects of these drugs were high efficacy to O. viverrini cercariae but lesser efficacy to metacercariae. It should be further studied with the eventual aim of developing a field-based control program.
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. 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.
Background: Food-born trematode infections such as opisthochiasis are major causes of morbidity in Asia. Fish-borne trematode infections are commonly found in the northern and northeastern regions of Thailand. Several species of cyprinoid freshwater fish have been reported as secondary intermediate hosts. Objectives: To determine the prevalence of infections with Opisthorchis viverrini and other intestinal parasites in Chiang Mai Province, Thailand, which is an endemic area for minute intestinal fluke infections in Northern Thailand due to environmental characteristics and the traditional consumption of raw fish. Results: Stool samples were collected from 327 subjects from Cho Lae sub-district, Ban Pao sub-district, Mae Taeng district, Luang Nuea sub-district, Doi Saket district, and Nong Yaeng sub-district San Sai district, Chiang Mai. The subject ages were between 10 and 60 years. Of these, 144 were males and 183 were females (male to female ratio 1:1.27). Conclusion: Parasites were found in 36 stool samples (11.0%). The majority of detected parasites (17 cases, 5.2 percent) were Opisthorchis viverrini. Other intestinal parasites included hook-worms, Trichuris trichiura, and minute intestinal flukes. The highest prevalence (31.2%) was found in Cho Lae sub-district, Mae Taeng district. The prevalence of infection was significantly associated with the health behaviour of the subjects. There was no significant association with sex-distribution.
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. Key words: Opisthorchis viverrini, Bithynia siamensis goniomphalos, molluscicidal effect, Camellia oleifera, Garcinia mangostana, niclosamide, Thailand
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