Five cases of Diphyllobothrium nihonkaiense infection with discovery of plerocercoids from an infective source, Oncorhynchus masou ishikawae.

Five persons from 2 families residing at Miyama Town, Mie Prefecture, Japan, ingested fresh raw fish Oncorhynchus sp. on 9 May 1999 that was caught at Owase district in Mie. They all expelled diphyllobothriid cestodes 11-37 days after ingesting the fish. The parasites were morphologically identical to Diphyllobothrium nihonkaiense Yamane et al., 1986. Five plerocercoids were detected from a portion of the fish. Nucleotide sequence of a region of the cytochrome c oxidase subunit I gene of mitochondrial DNA from an adult worm was identical with that from the plerocercoid. The fish was identified as Oncorhynchus masou ishikawae according to the nucleotide sequence of the nuclear ribosomal second internal transcribed spacer region II gene. This is the first record of D. nihonkaiense plerocercoids from O. m. ishikawae.

Studies on biting density and biting cycle of Culex quinquefasciatus, say in Khon Kaen City, Thailand.

Biting density and biting cycle of Culex quinquefasciatus in Khon Kaen City were examined during November 1994 to October 1995. Biting activity of the mosquito was assessed by using the indoor human bait method. Trapped mosquitos were identified and carefully dissected to determine their parities. Climatory data ie temperature, relative humidity and rainfall were also recorded during the study. The densities of mosquito ranged from 1.6/man/hour in December to 9.2/man/hours in March with the average of 5.0/man/hours. The lowest biting density was observed in winter and higher densities were in summer and rainy seasons. The temperature was the most important variable that influenced the biting density in each month of the year (p<0.05). The biting cycle showed that the mosquito active throughout the night, with peak activity at 22.00-23.00 hours. Parous rate of the mosquito ranged from 33.3% in February to 71.9% in November with the average of 47.3%. The biting proportion of parous mosquitos was high during the early hours of the night and gradually decreased until 06.00 hours, whereas that of the nulliparous mosquitos showed an increasing trend from 18.00 to 06.00 hours. The biting cycle of the parous mosquito reached the peak activity at 21.00-22.00 hours, 1 hour ahead of the peak for nulliparous mosquito. These findings suggested that Cx. quinquefasciatus in Khon Kaen City may be able to transmit bancroftian filariasis if they were exposed to microfilaria carrier individuals.

Nucleotide sequence of mitochondrial CO I and ribosomal ITS II genes of Opisthorchis viverrini in northeast Thailand.

The mitochondrial cytochrome c oxidase subunit I (CO I) gene and the second internal transcribed spacer region (ITS II) gene of Opisthorchis viverrini were compared among O. viverrini from various areas in northeast Thailand. The nucleotide sequences of partial CO I gene (417 bp) of O. viverrini differed among O. viverrini originated from Ubon Ratana, Leongpleuy, Ban Phai, Maha Sarakham, and Chatturat. These intraspecific variations were classified into 5 patterns but no area-specific pattem was observed. Amino acid sequence deduced from the nucleotide sequences of these genes was identical. Nucleotide sequences of a region of the O. viverrini ITS II gene (296 bp) from different areas were identical. However, they were different from those of Clonorchis sinensis, Haplorchis taichui, H. pumilio, Fasciola gigantica, Echinostoma malayanum and Centrocestus sp..

Expression of tenascin in bile duct cancer of hamster liver by combined treatment of dimethylnitrosamine with Opisthorchis viverrini infections.

Tenascin is an extracellular matrix glycoprotein known to be an essential factor for the modulation of reciprocal interactions between the epithelium and mesenchyme during embryogenesis and tumourigenesis. The interactions between the expression of tenascin in the liver of Syrian golden hamster and the development of bile duct cancer in an Opisthorchis viverrini-associated cholangiocarcinoma model were investigated. The tenascin was expressed in connective tissues surrounding the dilated ducts, ductal rims and the stroma of cancers, and strongly in the stroma flame of necrotic cancer nodules. The mRNA signal for tenascin was also recognized in the stroma cells. The potential roles of tenascin as prognostic tumour markers are discussed.