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.

Treatment of Opisthorchis viverrini and intestinal fluke infections with Praziquantel.

The study was carried out from September to November 1997 in Phrae Province of northern Thailand. A total of 95 adult patients with Opisthorchis-like ova in their stools were randomly treated with two different manufactured Praziquantels. Group 1, consisting of 49 patients, received a single dose of 40 mg per kg Praziquantel manufactured by the Thai Government Pharmaceutical Organization. Group 2 (46 patients) received Biltricide at the same dosage. Haplorchis taichui, H. yokogawai, Echinostome spp., O. viverrini, Taenia saginata and Enterobius vermicularis were expelled in the stools after treatment. Minute intestinal flukes were detected in 64% of patients. O. viverrini was found in lower proportion of 17%. By formalin-ether concentration examination one stool specimen from each patient, the cure rate in both groups on the 30th day of treatment was 100%. The side effects of the two different Praziquantel treatments were mild with no significant difference. Praziquantel, regardless of its manufacture, proved effective against O. viverrini and other minute intestinal flukes (H. taichui, H. yokogawai and Echinostome spp).

Opisthorchiasis and intestinal fluke infections in northern Thailand.

Four hundred and thirty-one residents from 16 provinces in northern Thailand who had previously been found positive for Opisthorchis viverrini or Opisthorchis viverrini-like eggs were given praziquantel 40 mg/kg. The stool was collected for 4 to 6 times and examined for adult worms. The prevalence of Opisthorchis viverrini in this group was 11.6%. Intestinal flukes, Haplorchis taichui and Haplorchis yokogawai, were predominantly found in 63.11% and 10.44% respectively. Other intestinal flukes (Centrocestus caninus, Echinostoma malayanum, Haplorchis pumilio, Phaneropsolus bonnei, Plagiorchid flukes, Prosthodendrium molenkampi and Stellantchasmus falcatus) were also found in small numbers.

Intestinal sarcocystosis in Thai laborers.

To determine the prevalence of Sarcocystis and other intestinal parasites in Thai laborers who were going abroad for work, stool examinations of 362 asymptomatic laborers were studied. The four most frequently parasites found in stool were Sarcocystis sp (23.2%), Opisthorchis viverini (40.3%), hookworm (21.5%), and Strongyloides stercoralis (14.1%). Giardia intestinalis (5.2%), Entamoeba coli (1.7%), Endolimax nana (2.5%), Blastocystis hominis (4.1%), Echinostoma sp (3.6%), Trichuris trichiura (0.3%), Taenia sp (1.7%), Hymenolepis nana (0.6%), and Enterobius vermicularis (0.3%) were present at low rates. Sarcocystis were frequently found in male laborers (83.3%) (p < .01). The laborers from northeastern Thailand (n = 278) had a higher prevalence (26.6%) of Sarcocystis infection (p < .01). This study shows that Thai laborers, particularly from northeastern Thailand, are commonly infected with intestinal parasites. The high prevalence rates of Sarcocystis and other intestinal parasites in this study were indicative of the local habit of eating raw beef and pork, poor living conditions, and low levels of hygiene in Thai laborers. Sarcocystosis could be a significant food-borne zoonotic infection in Thailand.

Pharmacokinetics of praziquantel in patients with opisthorchiasis.

The pharmacokinetics of praziquantel was investigated in 9 Thai male patients with asymptomatic opisthorchiasis (stool positive) and 9 patients (6 males, 3 females) with moderately advanced infection (hepatomegaly). The geometric means of the pretreatment Opisthorchis viverrini egg count in these patients were 2,950 vs 4,468 eggs per gram of stool. The results indicate the impairment of metabolism of praziquantel in the moderately advanced stage opisthorchiasis. The pharmacokinetics of the drug in these patients during the acute infection was markedly altered when compared with that after recovery and in patients with early stage of the infection. The clearance rate (Cl/f) was significantly reduced [medians and ranges of 106 (43-242) vs 192 (112-692) and 171 (133-427) ml/min/kg] and the t1/2z and MRT were prolonged [t1/2z: 3.8 (2.0-6.2) vs 2.7 (1.7-4.3) and 2.3 (1.7-2.8) hours; MRT: 6.2 (3.2-11.0) vs 4.6 (2.7-6.2) and 4.5 (2.9-5.1) hours]. In addition, AUCo-alpha was significantly greater [6.0 (2.5-15.6) vs 3.5 (0.6-6.0) and 3.9 (1.6-5.0) micrograms hour/ml].