Social and behavioral factors associated with Clonorchis infection in one commune located in the Red River Delta of Vietnam.

Social behavioral factors associated with Clonorchis infection are needed for control measures. The population in Nga Tan commune were randomly sampled and questioned to determine knowledge, perception, and health behavioral factors associated with Clonorchis infection among heads of households. The cellophane thick smear method was applied to examine their stool samples. Seven hundred and seventy-one cases were examined, the positive rates were 17.2%, 66.9%, 78.7%, 15.9%, and 0.14% for Clonorchis sinensis, Ascaris lumbricoides, Trichuris trichiura, hookworm, and Dicrocoelium dendriticum respectively. There was no significant difference between the infection rate of clonorchiasis, education level, and family income groups (p > 0.05). But there was significance difference between the infection rate of clonorchiasis and people living in different family sizes (p < 0.01). Thirty-four clonorchiasis patients treated with praziquantel 25 mg/kg/day for three days showed a cure rate in 30 days of 97.1%.

Mapping soil-transmitted helminths in Southeast Asia and implications for parasite control.

Establishing the current status and distribution of soil-transmitted helminths is essential for developing and implementing parasite control. Although Southeast Asia is known to have a high prevalence of infection, a precise estimate of the total disease burden has not been fully described. Here, we use Geographical Information Systems (GIS) to collate and map recent published surveys on soil-transmitted helminth epidemiology and distribution for this region. Distinct geographical variation was observed, which is suggested to reflect climatic variation, as well as behavioral differences. However, for much of the region few data are available, and therefore it proved necessary to generate predictions of the distribution of soil-transmitted helminths using remotely sensed (RS) satellite sensor environmental variables. A significant finding was the importance of land surface temperature in influencing the distribution of Ascaris lumbricoides and Trichuris trichiura. Spatial analyses using RS satellite sensor data were then used to generate predictive maps of infection risk. This information provided the basis for an estimate of the population at risk of infection and the numbers requiring treatment. These applications of GIS and remote sensing provide a good basis for developing control of soil-transmitted helminths in the region.

A cross-sectional study of intestinal parasitic infections among schoolchildren in Nan Province, Northern Thailand.

A cross-sectional study of the prevalence of intestinal parasitic infections at eight schools in Bo Klau district and four schools in Chalerm Prakiet district, Nan Province, in January and February, 2001. A total of 1,010 fecal samples were examined using the formalin-ether sedimentation technique. Results revealed that the rate of helminthic infection was 60.0%, while protozoa accounted for 36.2% of infections; mixed infections were common, resulting in a total prevalence of both parasites of 68.1%. Helminthic parasites, listed by frequency of infections, were Ascaris lumbricoides (21.7%), hookworm (18.5%), Trichuris trichiura (16.3%), Opisthorchis viverrini (1.7%), Strongyloides stercoralis (0.9%) and Enterobius vermicularis (0.9%). The protozoal infections were Entamoeba coli (25.8%), Giardia lamblia (5.3%), Endolimax nana (2.5%), Entamoeba histolytica (1.4%), Blastocystis hominis (0.8%), Chilomastix mesnili (0.3%) and Iodamoeba bütschlii (0.1%). This study emphasizes the need for improved environmental hygiene ie clean water supplies and enhanced sanitation, in affected communities. Health promotion, by means of a school-based educational approach is recommended; regular check-ups should be implemented, and a continuos program of treatment should be considered.

Efficacy of multiple dose mebendazole against trichuriasis in Thai and Karen patients.

Treatment of trichuriasis with mebendazole 500 mg for three days, and 100 mg twice daily for three days, yielded cure rates of 93.9 and 88.9% in Thai patients, while the cure rates in Karen patients were 96.2 and 95.5% respectively. The total number of Thai and Karen trichuriasis patients were 60 and 48, when tested by modified cellophane thick smear Kato-Katz technique. There were no significant differences among the two groups of patients and doses of treatment (p > 0.05).

IgG- and IgG4-detected antigens of Dirofilaria immitis adult worms for bancroftian filariasis by enzyme-linked immunoelectrotransfer blot.

In Thailand, Wuchereria bancrofti filariasis has persisted along the border between Thailand and Myanmar, its dynamic distribution caused by the infected transmigrants between neighboring countries, and the availability of susceptible mosquito vectors. Dirofilaria immitis adult worm was used as a source of antigens, excretory-secretory (ES) and partial surface extracts, to detect human filariasis. ES products showed several stained bands with Coomassie brilliant blue ranging from 14.5-93 kDa and mostly being glycoproteins as shown by concurrent reaction with Concanavalin A, except those at 18, 16 and 14.5 kDa which stained only with Coomassie brilliant blue. Surface proteins of 33.5-91.5 kDa were stained with Coomassie brilliant blue and showed smear bands with Concanavalin A. By enzyme-linked immunoelectrotransfer blot, Bancroftian filariasis sera gave specific reactions with glycoprotein ES antigens at MW 20.5 kDa against anti-human IgG. A prominent band of 18 kDa appeared consistently with the IgG4-ES antigen system. Surface extracts reacting with IgG and IgG4 were considered to be unsuitable as antibodies from all cases of filariasis could not detect any bands.

Comparative studies on protein, isoenzyme and DNA restriction endonuclease profiles of Thai Paragonimus metacercariae.

General proteins and 14 enzymes from metacercariae of Paragonimus heterotremus, P. siamensis and P. westermani were determined by vertical polyacrylamide gel electrophoresis. The isoenzyme profiles showed considerable interspecific polymorphism for general protein (PT), malate dehydrogenase (MDH), malic enzyme (ME) and tetrazolium oxidase (TO) while those of glucose phosphate isomerase (GPI) and phosphoglucomutase (PGM) showed similarity. The Pt-6 and To-I loci can be used as identification markers for these three species. The preliminary study of the molecular biology of Paragonimus heterotremus P. siamensis and P. westermani was based on analysis of metacercarial genomic DNA with restriction endonuclease Pst I. Agarose gel electrophoresis revealed restriction fragment length differences among the three species studied. The DNA restriction fragments were approximately 4-6 fragments, ranging from 5.35 to 14.67 kb. Among these. P westermani shared two homologous fragments with P. siamensis, ie, 5.35 and 7.22 kh, none with P. heterotremus, while P. heterotremus shared only one with P. siamensis, ie, 8.16 kb. Thus, the DNA restriction fragment length differences can be used to differentiate among these three species.

Clinostomum trematode from human eye.

The first human case of Clinostomum lacramalitis in Thailand is reported. A 38-year-old man visited an ophthalmology clinic after having itchy pain in the right eye for two days. Ophthalmological examination revealed a living worm adhered to the lacramal opening and after removal, it was identified as Clinostomum sp. The patient admitted that he used to eat raw freshwater fish, he caught in Prachin Buri Province where he lives.

Use of delipidized antigens of Taenia solium metacestodes in IgG-ELISA for detection of neurocysticercosis.

The development of IgG-ELISA for detecting neurocysticercosis is aimed at the routine laboratory, and requires a particular antigen preparation, an acceptable number of serum samples to be tested (both homologous and heterologous) and patients with a diversity of helminthic infections to rule out cross-reactions. This study characterizes IgG-antibodies from cases of neurocysticercosis by assaying the sera against ether-delipidized antigens (5 microg/ml) prepared from metacestodes of Taenia solium. The test had a sensitivity of 90% and a specificity of 83%. IgG-antibodies from heterologous serum samples elicited a number of false positives (25/147) from six different helminthic infections, ie paragonimiasis, echinococcosis, opisthorchiasis, ascariasis, taeniasis and fascioliasis. In additional tests to detect antibody levels to these stage-related antigens, one of three serum samples from T. solium-infected cases gave negative at OD value of 0.187 while the others yielded 0.472 and 0.576. Conversely, assays of all serum samples from neurocysticercosis cases reacted against antigens from Echinococcus granulosus cystic fluid, Paragonimus heterotremus and Opisthorchis viverrini adult worms. In comparison, the antigens from these three species yielded higher mean OD values when assayed against the corresponding infected serum samples. Furthermore, neurocysticercosis cases yielded OD values that are separate and distinct from those of paragonimiasis cases.

Opisthorchis viverrini metacercaria in Thai freshwater fish.

Examination for metacercaria in freshwater fish, the common intermediate hosts of Opisthorchis viverrini was carried out during 1992-1996. The 4-year survey of fish from markets in 14 provinces revealed that metacercariae of O. viverrini were found in fish from Udon Thani, Sa Kaeo and Prachin Buri Provinces; fish from Aranyaprathet district had the highest positive rates (25-28%). Fish from 12 provinces were found to be positive with heterophyid metacercariae, namely: Haplorchis pumilio, H. taichui, H. yokogawai, Stellantchasmus falcatus, Centrocestus formosanus and Haplorchoides cahirinus. It was also observed that the prevalence of O. viverrini metacercaria in fish decreased markedly during the last 10 years.

Gnathostome infection in swamp eels, Fluta alba, in central Thailand.

To investigate the distribution of gnathostome worms in central Thailand, the infective larvae of Gnathostoma spp were examined from the flesh and liver of swamp eels, Fluta alba. Seven hundred and eighty-eight eels were purchased from markets in 11 provinces; Ang Thong (30), Ayutthaya (36), Chachoengsao (30), Lop Buri (30), Nakhon Nayok (437), Pathum Thani (30), Prachin Buri (48), Ratchaburi (53), Saraburi (30), Samut Prakan (30) and Suphan Buri (34). The highest rate of gnathostome infection was observed in swamp eels from Nakhon Nayok (68.7%). The infection rates in Ayutthaya, Ang Thong, Prachin Buri, Ratchaburi, Saraburi and Lop Buri were 33.3%, 26.7%, 25.0%, 18.9%, 13.3% and 10.0% respectively. Gnathostome larvae were not found in swamp eels from Chachoengsao, Pathum Thani, Samut Prakan and Suphan Buri. Among the 9,573 larvae recovered, almost all were the advanced third stage larvae of G. spinigerum, except one larva from Nakhon Nayok and two larvae from Ratchaburi which were identified as the advanced third stage larvae of G. vietnamicum and G. hispidum respectively. This study is the first report of swamp eels as natural intermediate hosts of G. vietnamicum and G. hispidum.

Seasonal variation in the intensity of Gnathostoma larvae in swamp eels (Fluta alba) sold in a local market in Bangkok.

The viscera of swamp eels were obtained from a local market in Bangkok twice a month from June 1996 to May 1997. The livers were separated, weighed and counted. Gnathostome larvae were recovered from the livers by the digestion technic, examined, identified, and counted. A total of 12,278 Gnathostoma larvae were obtained from 18,561.1 g (15,264 pieces) of eel livers. The overall average number of larvae/g liver and the overall average number of larvae/liver are 0.91 and 0.94, respectively. The greatest number of larvae/g liver (on average) was in December (high levels of infection during the months of October to December) whereas the lowest was in April (lowest levels of infection during the months of March to April). Thus there was a marked decrease in the average number of larvae/g liver during January to April, which then started to rise in May. This finding suggests that the level of infection abruptly decreases soon after the completion of the rainy season, starts to rise when the rain has come, and reaches its peak when the amount of rainfall is highest. More than 99% of the total gnathostome larvae recovered were identified to be G. spinigerum, and 25.4% of the entire larvae recovered bore variant or abnormal cephalic hooklets. The most common unusual feature was that there were extra rudimentary hooklets above row one, below row four and in between the four rows of hooklets which comprised 21.4%. In addition, the body size and the number of cephalic hooklets of G. spinigerum are also discussed.

The impact of primary health care intervention on reinfection of soil-transmitted helminths in the community.

A study to evaluate the impact of primary healthy (PCH)care practices on the prevention of reinfection of soil-transmitted helminths (STH) was carried out in Nakhon Si Thammarat Province, southern Thailand. Fecal samples from the inhabitants of Ban Paruhas, the implementing village, and Ban Pungsing, the control village, were examined following mass treatment with a three-day regimen of albendazole (400 mg). Training of health volunteers, implementation of a health education program through village broadcasting system and improvements in sanitation including increasing the number of latrines were carried out at Ban Paruhas village. After one year of implementation, prevalence and intensity of STH in both villages were determined using Kato-Katz's method. Pre- and post intervention stool examination results were compared. The overall prevalence of STH at post-intervention decreased significantly in both villages, with a greater degree of reduction appearing in ascariosis and hookworm infections in the village where PHC was implemented.

Human infection of Centrocestus caninus in Thailand.

Examination of fecal samples, collected after treatment with praziquantel, of the persons positive with opisthorchioid eggs residing in the northern provinces of Thailand, was carried out. Five adults Centrocestus were recovered in one sample from Doi Saket, Chiang Mai and one adult was found in another fecal sample from Wiang Pa Pao, Chiang Rai. The worms had 26-30 spines arranging in two rows around the oral sucker which agreed with the character of C. caninus. This is the first record of natural human infection with Centrocestus in Thailand.

Evaluation of Bithynia funiculata snail antigens by ELISA-serodiagnosis of human opisthorchiasis.

Four batches of crude somatic antigens from: (1) Opisthorchis viverrini adult worms, (2) Bithynia funiculata-whole body, (3) B. funiculata-head-foot, and (4) B. funiculata-visceral mass were assayed against sera from 81 opisthorchiasis patients, 30 parasite-free healthy individuals, and 50 individuals infected with other helminthic infections, and their antibody levels determined. By IgG-ELISA, the antigenic reactive proteins were found in both the head-foot and the visceral mass of B. funiculata snails, but the whole snail antigens gave the best results. Furthermore, it was as good as when O. viverini antigens were used. Antibody levels of sera from patients with opisthorchiasis assayed against antigens from whole B. funiculata snails were significantly higher than those of the other two groups. The cut-off value for positivity at 0.228 gave 80.2% sensitivity and 81.2% specificity. Cross reactions were observed with sera from patients with paragonimiasis and strongyloidiasis. No cross reactions were found to occur with sera from healthy individuals.

Effect of albendazole and mebendazole on soil-transmitted helminth eggs.

Primary school children from Nakhon Si Thammarat Province, Thailand, on endemic area of soil-transmitted helminths, were selected for study. The infected children were divided into two groups and pair-matched according to intensity of infections: group I were given albendazole (400mg) single dose and group II were given mebendazole (100mg) twice daily for 3 days. On the day following treatment, the number of Trichuris eggs in the stool markedly increased and the egg shape was also altered. These phenomena did not occur in Ascaris infections since 100% cure rate were obtained using both drugs. Incomplete ovicidal effect of the drugs to Trichuris and Ascaris eggs were demonstrated, embryos were observed to develop within the treated eggs and they hatched after feeding them to experimental animals. In hookworm infection, albendazole stimulated the females to release more eggs after medication, but both drugs showed complete ovicidal effect upon examining the eggs from the second bowel movement.

Minimum effective doses of mebendazole in treatment of soil-transmitted helminths.

Three hundred and fifteen primary school children infected with soil-transmitted helminths were divided into 5 groups. Three groups were treated with 25, 50 and 75 mg mebendazole (MBZ) single dose. One group was given MBZ conventional dose of 100 mg twice daily for 3 days and another group was given albendazole (ABZ) standard dose of 400 mg single dose. Every trial lower MBZ dose 75 mg, 50 mg and 25 mg regimen were highly effective against Ascaris lumbricoides but only moderately effective against Trichuris trichiura and Necator americanus.

Efficacy of single-dose mebendazole, polymorphic forms A and C, in the treatment of hookworm and Trichuris infections.

A therapeutic trial of single mebendazole, 300 mg polymorph A, 300 mg polymorph C and 500 mg polymorph C, in the treatment of hookworm and Trichuris infections was carried out at primary schools in Southern Thailand. The total of 958 children were randomly allocated in seven treatment groups including the placebo control and the standard dose control (100 mg polymorph C bid for 3 days). The egg reduction rates and the cure rates of 300 mg and 500 mg polymorph C were similar, but inferior to those of the standard dose in both hookworm and Trichuris infections. The efficacy of single dose 300 mg polymorph A was not different from that of the placebo control (alpha = 0.05) in both infections.

Intestinal fluke infections in Southeast Asia.

Twenty-three species of intestinal flukes reported in man in Southeast Asia are assigned to seven families: Echinostomatidae, Fasciolidae, Heterophyidae, Lecithodriidae, Microphallidae, Paramphistomatidae and Plagiorchiidae. The majority of species belongs to the Heterophyidae and Echinostomatidae families. Common species are Fasciolopsis buski, Echinostoma ilocanum, E. malayanum, E. revolutum and Haplorchis yokogawai. The countries where large number of species were reported are Thailand (14 species), Philippines (12 species), Indonesia (8 species) and Malaysia (4 species). Only one species was recognized in Laos, and Vietnam. Several species reported in man in the other regions, were reported in animals in Southeast Asia. It is possible that these are present in humans but have not yet been reported.

Practicable IFAT slide antigen preparations for detection of Gnathostoma spinigerum antibodies in rabbits.

This study was designed to determine which stage of Gnathostoma spinigerum and which method of the preparation of test antigens are the most suitable for the detection of antibodies in serum of rabbits infected with advanced third stage larvae (AL3) of G. spinigerum by the indirect fluorescent antibody test (IFAT). Antigens from parasite ova and first stage larvae (L1) were obtained from freshly preserved specimens and affixed to glass slides with egg albumin. AL3 antigens consisted of paraffin sections, cryostat sections and pellets of crude worm soluble extract. Slides of adult male and female worms were prepared in cryostat sections. Pellets of crude worm soluble extract (AL3) smeared onto slides gave the best positive reaction followed by AL3 cryostat sections and L1.