Natural infection of trematodes in Lymnaea (Radix) auricularia rubiginosa in water reservoirs in Amphoe Muang, Khon Kaen Province

Lymnaea (Radix) auricularia rubiginosa (Michelin, 1831) was surveyed in 54 reservoirs of 18 districts in Amphoe Muang, Khon Kaen Province during February to May 1994. Lymnaeid snails were found in the water of 20 reservoirs, of which 16 reservoirs contained clear water and 4 turbid water. Two of the four turbid water reservoirs received drainage water from Khon Kaen Town. Two thousand four hundred and eight L. auricularia rubiginosa were collected and examined by shedding and crushing. Trematode infection occurred in 163 (6.77%) of 2,408 L. auricularia rubiginosa and some snails were infected with more than one cercarial species. Ninety-nine snails (4.11%) were infected with echinostomes, while mixed infection of echinostomes with Fasciola gigantica and with schistosomes was found in 5 snails (0.21%) and 2 snails (0.08%), respectively. Only 1 snail (0.04%), 19 snails (0.79%) and 37 snails (1.54%) were infected with F. gigantica, schistosomes and unidentified species, respectively. The mean size of infected snails was 6.89 +/- 2.02 mm (6.20-22.36) while the mean of sampled snails was 13.46 +/- 3.64 mm (4.00-26.55). The water plants which were found in reservoirs and presented with snails, were creeping water primose (Jusstaea repens), water lily (Nymphaea sp), water hyacinths (Eichornia crassipes) and grass.

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.

Field trials in the control of Opisthorchis viverrini with an integrated programme in endemic areas of northeast Thailand

A control programme of opisthorchiasis was carried out for three years in three villages of northeast Thailand in order to compare the effectiveness of two intervention measures. The intervention measures employed were to give praziquantel treatment to all infected people either once (village I) or twice (village II) per year with the integration of regular health education and sanitation improvement. A control village (village III) received no intervention during the study. Sampling of the population in these villages to estimate prevalence, intensity, reinfection and incidence of infection as well as knowledge of opisthorchiasis and number of latrines was performed at 6 monthly intervals throughout the duration of the study. At the initial assessment, there were no significant differences in the prevalence and intensity of infection of villages I and II. Both values were greatly reduced when assessed 6 months after the initiation of treatment, and the decrease in prevalence and intensity of infection did not differ between village I and II. The control village (village III), during the first 2 years, exhibited slight variation in the prevalence and intensity, and these decreased considerably in the third year of the study. The reinfection rate per 6 months in villages I and II was nearly equal. The incidence rate per 6 months in the two treated villages was lower than that of the control village. Marked improvement in knowledge of opisthorchiasis, behavioural changes of eating raw fish and increased numbers of latrines was evident in all of the villages during this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal variation in the prevalence and intensity of canine Gnathostoma spinigerum infection in northeastern Thailand

Gnathostoma spinigerum was found in gastric nodules in 4.1% of 2940 dogs surveyed in northeastern Thailand. The prevalence and worm burden of G. spinigerum exhibited a seasonal fluctuation. The parasites were more abundant in the rainy season and the early winter (August-December) than in the summer (April-March). Most parasites were sexually mature between August and December while immature worms were observed during March and April. The distribution of gnathostomes within the sampled dogs was highly dispersed and few animals were found to harbour more than five worms.

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.

Quantitative post-mortem study of Opisthorchis viverrini in man in north-east Thailand

The results of an autopsy study of Opisthorchis viverrini infection in 181 accident subjects in northeast Thailand are presented. The age-prevalence profiles were similar whether determined by faecal examination for parasite eggs or by recovery of worms from the liver. The prevalence increased rapidly with age and reached a plateau at 70-80% in adults. The overall prevalence estimated by faecal examination was 69.2%, while that measured by worm recovery was 79.2%. The average intensity of infection, as indicated by eggs per gram of faeces, rose with age and became relatively stable in groups over 20 years of age. Worm burden also increased rapidly with age, reaching a peak in the 31-40 year groups and slightly declining in the 2 oldest age groups. Fluke distribution between individual subjects was highly dispersed; most people harboured no or low worm burdens (0-200 worms) while a small group of subjects (16.5%) carried 66% of the total worms recovered. The distribution of flukes within the liver appeared to be homogeneous. The results of the present study were similar to those from field studies, and possible mechanisms that generate these observed patterns of infection are discussed.

Relationship between faecal egg count and worm burden of Opisthorchis viverrini in human autopsy cases

The relationship between faecal examination for egg output and worm burden of Opisthorchis viverrini in man of 181 autopsy cases from Northeast Thailand is described. Diagnosis of the parasite infection by stool examination for the presence of eggs was less sensitive than the worm recovery technique. Using Stoll's dilution and formalin-ether technique, no eggs were detected in the faeces of 20 cases harbouring low worm burdens (less than 20 worms). The quantitative faecal egg count by Stoll's dilution technique showed a strikingly close positive correlation with the number of worms recovered (r = 0.96, P less than 0.001) indicating a strong linear association between eggs per gram of faeces (epg) and worm burden. The number of epg per worm was inversely correlated to the worm burden (P less than 0.001), suggesting that density-dependent constraints on fecundity could operate to restrict egg output in heavy infections. The accuracy of egg counts for estimating worm burden and its relevance to parasite epidemiological research are discussed.

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.

Acute cholecystitis and Fasciola sp. infection in Thailand: report of two cases

Two cases of fascioliasis gigantica from Northeast Thailand presenting with cholecystitis and gall stones were reported. Both cases complained of abdominal pain. On laparotomy the worms were found. In one case five worms were recovered during bile duct exploration and bile drainage; eggs were also revealed in the bile. In the other case of ectopic fascioliasis one young adult worm was found in a nodule which adhered to liver and diaphragm. The parasites were identified as Fasciola gigantica.

Scanning electron microscopy of the tegumental surface of adult Haplorchis pumilio (Looss)

The surface structure of adult Haplorchis pumilio from experimentally infected hamsters was studied in detail using scanning electron microscopy. Almost the entire surface of the worm was covered with scale-like spines regularly arranged in transverse rows. Most spines were pectinate. The size of the spines and the number of the teeth in each individual were largest in the spines around the middle region of the worm. The area surrounding the excretory pore was free of spines displaying a slightly wrinkled appearance. Many ciliated papillae were present on the anterior two-thirds of the body. The papillae on the oral sucker were more abundant than those elsewhere. The body papillae were distributed in a bilaterally symmetrical arrangement, appearing in groups, pairs or singly between the spines.

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.

Ocular sparganosis: a cause of subconjunctival tumor and deafness

We report a patient with a subconjunctival mass lesion caused by a larva of Spirometra sp. The parasite, 44 cm long and 1.0 mm wide, was removed intact and alive with complete preservation of the patient's vision. The mode of infection was probably through consumption of contaminated drinking water.

Serodiagnosis of human gnathostomiasis

An enzyme-linked immunosorbent assay (ELISA) was evaluated for serodiagnosis of human ocular and visceral gnathostomiasis in comparison to an indirect haemagglutination (IHA) and precipitin (PPT) tests. The ELISA antibody titers were found to range from 1:400 to 1:51,200 against somatic and 1:200 to 1:25,600 against excretory-secretory (ES) antigens. When sera were tested at single dilutions, the ELISA was positive in 7 of 8 gnathostomiasis cases while only 5 and 3 were positive by IHA and PPT respectively. The overall specificity of the ELISA was 96.7% and 97.4% with somatic and ES antigens respectively. Since somatic and ES antigens produced similar ELISA results, either can be used for diagnostic purpose. It was suggested that the ELISA was a reliable serodiagnostic test for human gnathostomiasis.

Scanning electron microscopy of adult Echinostoma malayanum

Scanning electron microscopy observations of E. malayanum adult obtained from small intestines of infected rats was made. The number of collar spines were 41. The features observed were a pair of corner spines (3 oral and 2 aboral) total 10; a pair of lateral collar spines (10 spines each side); total 20; dorsal collar spines (5 oral and 6 aboral) total 11. Sensory papillae were found more densely situated on the circumoral disc around the oral sucker and on the ventral sucker. Other sensory organs, dome shaped, found only on the circumoral disc. The scales appear mainly on the ventral surface. The microvilli are present on the tegument where the scales occur, while the other part of dorsal side had pitted tegument.