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..

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.

Metacercariae isolated from cyprinoid fishes in Khon Kaen District by digestion technic.

Several kinds of fresh-water fishes collected from natural water resources in Khon Kaen District were digested with 0.25% pepsin A to obtain the infective stage or metacercariae of fish-borne trematodes. Most of them harbored at least 3 species of trematodes. Two families of medical trematodes, i.e., Family heterophyidae and Family Opisthorchiidae, were isolated. The heterophyid flukes consisted of Haplorchis taichui, H. pumilio and Centrocestus formosanus. Opisthorchis viverrini was the only parasite of the Family Opisthorchiidae found in these fish. Among these four species, H. taichui was predominant and found in all kinds of fish examined, especially Hampala dispar.

Angiostrongylus infections in rats and snails in northeast Thailand.

A survey of Angiostrongylus infections in rats and snails was carried out in the provinces of Ubon Ratchathani, Udon Thani. Kalasin, Chaiyaphum and Khon Kaen in northeast Thailand. Only two Rattus norvegicus (3.8%) and one Bandicota indica (1.4%) out of 151 R. rattus, 52 R. norvegicus and 69 B. indica examined were infected with adult lung worms. All worms recovered were A. cantonensis. Prevalence of infection in 423 Pila polita was 0.9% while all of 77 P. ampullacea were negative for larvae. In contrast to this 36.4% of 500 Achatina fulica harbored L3 of Angiostrongylus (with variations of between 29% and 46% in the five provinces). The average infection intensity in A. fulica was 13.6 L3 (1 to 441). Experimental infection of Wistar rats with L3 (isolated from A. fulica resulted in a recovery rate of 48.3% of adult worms of which 91.7% and 8.3% were identified as A. cantonensis and A. malaysiensis, respectively. This is the first proven finding of A. malaysiensis in northeast Thailand.

Studies on lophocercous cercariae from Bithynia siamensis goniomphalus (Prosobranchia: Bithyniidae).

Cercariae from Bithynia siamensis goniomphalus were studied in an area endemic for opisthorchiasis. Snails emitted different types of cercariae when shedding was induced by illumination. In addition to two lophocercous cercariae, a monostome cercaria (probably Notocotylus sp), two different furcocercariae and a xiphidiocercaria were found. Two similar types of lophocercous cercariae were distinguishable and one could be identified as Opisthorchis viverrini. To date the cercaria of O. viverrini has been regarded as the only lophocercous cercaria in the endemic area of opisthorchiasis. Therefore, differences between these cercariae were further characterized by scanning electron microscopy to enable us to avoid misinterpretations of O. viverrini in Bithynia.

Studies on metacercariae from naiads in northeast Thailand.

One hundred and eleven naiads from six different dragonfly species were investigated for the presence of metacercariae. Sixty-nine animals (62.2%) were infected with intensities up to more than 150 cysts per animal. The metacercarial cysts were characterized by light and scanning electron microscopy. Two types of metacercariae could be differentiated by morphological features of cyst surface, cyst wall and size.

Intracerebral hematoma caused by sparganum: a case report.

Cerebral sparganosis is caused by migrating larvae of Spirometra mansonoides. This condition is rare. The presenting symptoms include headache, seizures and focal neurological deficit, which are due to a parasitic granulomatous space-occupying lesion. The authors report a case of intracerebral hematoma, which has never been reported as a presenting symptom of cerebral sparganosis. The surgical treatment of this complicated condition yielded poor results when compared to previous reports of the uncomplicated condition.

Comparative studies on the morphology of the eggs of Opisthorchis viverrini and lecithodendriid trematodes.

Iodine staining and scanning electron microscopy were used to determine the morphological features distinguishing Opisthorchis viverrini from lecithodendriid eggs in human feces. The embryonated eggs of lecithodendriid trematodes differ from O. viverrini by the presence of an iodophilic body, a large mass at the posterior end of miracidium that stains brown in 0.2% iodine solution and the curved miracidium of Phaneropsolus bonnei. All forms of lecithodendriid eggs can be differentiated from those of O. viverrini by a set of morphological features of the shell surface, the knob, the operculum, the shoulder, the shape and size. On the basis of these differences, it is possible to perform differential egg counts.

Transmission of Angiostrongylus cantonensis through the giant African snail Achatina fulica: an experimental study.

Observations on transmission of the rat lung worm, Angiostrongylus cantonensis, from rats to the snail intermediate host. Achatina fulica, in a vacant lot in Bangkok are described. The prevalence of A. cantonensis increased with snail age until 200 days of age when it attained a plateau of 50-60%. The overall prevalence was 53%. The worm burden slowly rose with age until 200 days of age beyond which it remained relatively constant. The highest mean worm burden of 5,478 was observed in the oldest age group. The parasite distribution in the snail population was highly aggregated both within each age class and in the overall population. Experiments on susceptibility of snails to laboratory infection revealed that worm recovery was dependent on dose of first stage larval infection but was independent of snail size in the range of 4-8 cm. The percent worm recovery of third stage larvae was negatively correlated with dose of infection, and no density-dependent effects of worm burden on worm size were observed.

Eggshell morphology of the small eggs of human trematodes in Thailand.

Light and scanning electron micrographs of Opisthorchis viverrini, Haplorchis taichui, H. pumilio, A Phaneropsolus bonnei, and Prosthodendrium molenkampi eggs were studied. Under light microscopy. O. viverrini eggs had rough eggshells and prominent shoulders. H. taichui, H. pumilio were similar in shape and had smooth eggshells and prominent shoulders. H. pumilio eggs were bigger than H. taichui eggs. P. bonnei and P. molenkampi eggs had smooth eggshells and indistinct shoulders. P. bonnei eggs were thinner and bigger than P. molenkampi eggs. Some deformed eggs of O. viverrini and Haplorchis sp. were found and they had no embryos and indistinct opercula. Under scanning electron microscopy, O. viverrini eggs looked like musk-melon skin; they had prominent shoulders and long knobs. H. taichui eggs had curly, thread-like ridges and prominent shoulders and knobs. H. pumilio eggs had streched ridges, like Chinese bitter mormodica, and prominent shoulders. P. bonnei and P. molenkampi eggs had smooth eggshells and small shoulders and knobs.

Influence of water current on the distribution of Opisthorchis viverrini infection in northeastern villages of Thailand.

The prevalences of Opisthorchis viverrini infection in the villages on the banks of rivers and those far from the rivers were studied in Loei and Nong Khai Provinces in Thailand. Most of the people examined in the present study were agriculturalists. The overall prevalence of O. viverrini infection was 41.3%. The prevalence of infection in males and in females in the villages far from the rivers were 52.6% and 51.7%, respectively, while the percent of people in the villages on the banks with infection were 27.9% and 21.7%, respectively. Prevalence of infection among the people residing far from the rivers was higher than those residing on the banks. This was observed despite the higher recording of raw fish consumption in villages on the banks. Infection level increased sharply in the age-group 6-10 years old among people residing far from the rivers. High prevalences of infection were observed in age groups from 11 to 50 years. Both types of villages had a similar proportion of houses with sanitary latrines.

Comparative in vitro sensitivity to metronidazole of Trichomonas vaginalis with isolates and clones.

Isolates of Trichomonas vaginalis from a group of Thai women in Khon Kaen, Thailand were studies for their in vitro sensitivity to metronidazole. Forty-five isolates of T. vaginalis and further 226 laboratory clones of these isolates were examined for drug sensitivity under anaerobic conditions using the CPLM (Cysteine-Peptone-Liver infusion Maltose) medium. The in vitro sensitivity of T. vaginalis to metronidazole, recorded as MLC values revealed highly variable sensitivity profiles Greater than 90% of the trichomonads studies were susceptible to relatively low concentrations of metronidazole in the range of 1-10 micrograms/ml. The remaining fraction of trichomonads, appeared to be less sensitive and required higher concentration of drug to attain the MLCs. The highest recorded MLC was 60 micrograms/ml. The geometric mean MLC of the 45 isolates was 7.99 micrograms/ml while that of The influence of the individual clones of subpopulations of T. vaginalis on the observed sensitivity of the isolate was also examined. A positive linear relationship was observed between the MLC of the isolated and the MLC of the least sensitive clone of the same isolate (p less than 0.05). This suggests that the most resistant clone present within an isolate of T. vaginalis plays an important role in determining the overall drug sensitivity of the isolate.

Scanning electron microscopy of the early third-stage larvae of Gnathostoma spinigerum.

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.