A prospective study of diet, lifestyle, and genetic factors and the risk of cancer in Khon Kaen Province, northeast Thailand: description of the cohort.

Cohort studies are the preferred design in observational epidemiology, but few involving the general population have been performed in Asia, and most concern affluent urban populations.The Khon Kaen study has recruited about 25,000 subjects, aged mainly 35-64, from villages in the relatively underdeveloped north-east of Thailand. All subjects underwent simple physical examination, completed an interviewer-administered questionnaire (including sections on lifestyle, habits, and diet) and donated specimens of blood, which were processed and stored in a biological bank at -20 degrees C. Female subjects (about 16,500) were offered screening by Pap smear, and specimens of cells from the cervix were stored at -20 degrees C. This paper describes the methodology of the study, and the characteristics of the participants. Almost all subjects are peasant farmers, with low annual income and body mass, although 14.6% of women had a BMI in the obese range (>30 kg/m(2)). Smoking was common among men (78% regular smokers, most of whom used home-produced cigarettes), but rare among women. Fertility levels were relatively high, with a more than half the women having four or more live births. 23.4% of subjects were infected with the liver fluke Opisthorchis viverrini, known to be highly endemic in this region. Follow-up of the cohort is by record-linkage to the provincial cancer registry. By 2003, 762 cancer cases had occurred, the most common being cancers of the liver (363 cases) and cervix uteri (44 cases). The antecedents of these cancers are being investigated using a nested case-control approach. The cohort will yield increasing numbers of cancers for study in the next decade, giving important information on the relative importance of dietary and lifestyle factors in a rural population, undergoing gradual transition to a more westernised lifestyle.

The present situation of paragonimiasis in endemic area in Phitsanulok Province.

A cross-sectional survey and evaluation of paragonimiasis situation from endemic area in Phitsanulok Province was studied. Studies on the species and prevalence of parasites which infected people in Noen Maprang, Phitsanulok Province were also conducted during October 1999-March 2000. The sputum specimens were collected and examined to identify Paragonimus heterotremus eggs. In addition fecal samples were collected and examined for parasites by the formalin-ethyl acetate concentration technique. P. heterotremus eggs were detected in 2 out of 391 sputum specimens; a prevalence of 0.51%. A total of 584 stool specimens were obtained and examined. It was found that the prevalence of parasitic infection was 36.30%. Opisthorchis viverrini infection was the most prevalent (10.78%), followed by Strongyloides stercoralis (9.59%), hookworm (8.22%), Echinostoma spp (2.23%), minute intestinal flukes (1.54%), Taenia species (1.37%), Enterobius vermicularis (0.68%), Entamoeba coli (1.03%) and Giardia lamblia (0.86%). The prevalent rate of paragonimiasis in this endemic area in Phitsanulok Province has decreased during the past decade. However, there were other important parasite infections, especially opisthorchiasis and strongylodiasis and these should be studied further.

Seroprevalence of specific total immunoglobulin (Ig), IgG and IgM antibodies to Toxoplasma gondii in blood donors from Loei Province, Northeast Thailand.

A total samples from 345 healthy blood donors from Loei Province, Northeast Thailand were examined for anti-Toxoplasma gondii antibodies by ELISA. The seroprevalence of the anti-Toxoplasma gondii total Ig, IgG and IgM antibodies was 4.9%, 4.1% and 4.3%, respectively. Overall seropositive rate was 33 out of 345 individuals (9.6%). Among the seropositve cases, 5 (15.2%), 2 (6.1%) and 13 (39.4%) of the samples were determined by using each type of anti-T. gondii total Ig, IgG and IgM antibodies, respectively. The seropositive sera was also determined by combining of anti-T. gondii antibodies (anti-T. gondii total Ig with IgG and anti-T. gondii total Ig with IgM antibodies). These results were 10 (30.3%) and 2 (6.1%) cases, respectively. Only one (3%) sample had all types of anti-T. gondii antibodies. In addition, the frequency distribution curves of ELISA optical densities of anti-T. gondii total Ig, IgG and IgM antibodies in blood donor presented "unimodal" curves. The negative results were found in the age group that less than 20 years old and more than 51. The highest seropositive results were found in two age groups (21-30 and 31-40 years old), and males were significantly higher than female (p < 0.05). These results demonstrated that when using anti-T. gondii total Ig, IgG and IgM antibodies for determining the seroprevalence, the sensitivity was twice that with the anti-T. gondii, total Ig antibody alone.

Excretory-secretory antigenic components of adult Fasciola gigantica recognized by infected human sera.

The immunogenic components of Fasciola gigantica excretory-secretory (ES) products were revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting technic using sera from patients with F. gigantica infection, from patients with clinical suspected fascioliasis, from patients with other illness and from healthy adults. By SDS-PAGE, it was found that the ES products comprised more than 6 polypeptides. Immunoblotting analysis revealed 12 components which were strongly recognized by fascioliasis antisera. These antigenic components had a molecular mass ranging from less than 14.4 to 38 kDa. One antigenic band of 27 kDa was found to give a consistent reaction with fascioliasis antisera (100% sensitivity and 98% specificity). The present findings suggest that the 27 kDa components are sensitive and specific for the diagnosis of human F. gigantica infection.

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.

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.

Quetelet index, hemoglobin and parasitic infection of rural women in northeast Thailand.

The Quetelet index, hemoglobin and parasitic infection rates of adolescent and young women from 21 villages in Northeast Thailand were assessed. Data were collected in the hot, rainy and cold seasons of the year. The proportion of undernourished females varied between 10 and 15% when a cut-off point of 18.7 of the Quetelet index was chosen. 23 to 33% of the women had hemoglobin levels below 12 g%. Parasitic infection rates with various intestinal helminths were high but not related to the nutritional status or anemia.

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.

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.

Prevalence and intensity of Opisthorchis viverrini in rural community near the Mekong River on the Thai-Laos border in northeast Thailand.

The prevalence and intensity of Opisthorchis viverrini in fourteen villages in Nakhon-Phanom province, Northeast, Thailand have been investigated. Overall prevalence of O. viverrini infection was 66.4 per cent in a total population of 2,412 individuals. The prevalence was 18.5 per cent in children under 5 years, 38.9 per cent in those aged 5-9 years, and ranged from 64.9 per cent to 82.2 per cent in the age group above 10 years. The intensity of O. viverrini infection increased with age. The mean faecal egg output was highest in the 30-34 year age group and remained relatively constant through older ages. In all age groups the prevalence and intensity of infection in both men and women were similar. The population was divided according to the presence and intensity of infection as follow, 33 per cent were uninfected, 59 per cent had light infections (less than 1,000 eggs per g of faeces; EPG), 7 per cent had moderate infections (1,000-10,000 EPG), and 1 per cent had heavy (greater than 10,000 EPG). Other important intestinal infections found in this community are hookworm, Taenia spp. and Trichuris trichiura with the prevalence of 17.9 per cent, 1.1 per cent and 1.1 per cent respectively.

Laboratory evaluation of Bacillus thuringiensis H-14 against Aedes aegypti larvae in the northeast region of Thailand.

Laboratory bioassays using a preparation of Bacillus thuringiensis H-14 (Bt.H-14), namely Skeetal were conducted to determine their effectiveness against late 3rd/early 4th instar larvae of Aedes aegypti. The larvae were collected from municipal areas in 7 provinces, namely Burirum, Roi-Et, Khon Kaen, Ubol Ratchatani, Nakorn Phanom, Surin and Nakorn Ratchasima, in the Northeast of Thailand. It was found that for Skeetal, LC50 ranged from 128 to 151 nl/l (average 143) and LC90 ranged from 254 to 289 nl/l (average 275). The mortality rate of Ae. aegypti larvae in the 7 provinces did not differ significantly (p greater than 0.05) at a concentration of 300 nl/l. The result of the bioassays show that the preparation of Bt.H-14 is very effective against Ae. aegypti larvae in Northeast of Thailand and the mosquito larvae in the various areas were nearly equal in susceptibility to Bt.H-14.

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.

A high incidence of liver cancer in Khon Kaen Province, Thailand.

Based on a population-based cancer registry in Khon Kaen Province, Thailand, data were collected actively and passively from all hospitals, health centers and the office of the Chief Medical Officer of Khon Kaen. The data were collected prospectively for the year 1988 and retrospectively for the years 1985-1987. Liver cancer, especially cholangiocarcinoma, was the leading cancer in both sexes. The age-standardized incidence rates for the year 1988 were 89.2/10(5) in males and 35.5/10(5) in females respectively, which are among the highest rates recorded in the world. The number of reported liver cancer cases increased each year. The observed geographical clusters of liver cancer appear to be associated with the prevalence and intensity of Opisthorchis viverrini infection, as reported in previous studies in this area.

Serodiagnosis of human paragonimiasis caused by Paragonimus heterotremus.

Enzyme-linked immunosorbent assay (ELISA) and indirect hemagglutination tests (IHA) were evaluated for serodiagnosis of human paragonimiasis caused by Paragonimus heterotremus using homologous adult worm extract as antigen. IgG-ELISA was the most sensitive, being positive in all paragonimiasis sera tested while IHA and IgA-ELISA gave 88% and 59% positive rates respectively. Cross reactivity in IgG-ELISA was detected with fascioliasis sera, producing overall assay specificity of 97%. It is suggested that IgG-ELISA is a reliable serodiagnostic test for human paragonimiasis caused by Paragonimus heterotremus.

Prevalence of toxoplasma antibodies in blood donors and pregnant women in Khon Kaen Province.

Serum samples from blood donors and pregnant women in Khon Kaen were examined for antibodies to Toxoplasma by an indirect hemagglutination and indirect fluorescent antibody techniques. It was found that 6.4 per cent of the blood donors were positive by the indirect hemagglutination and 6.2 per cent by indirect fluorescent antibody tests. The seroprevalence in pregnant women were 12.0 per cent by indirect hemagglutination and 4.7 per cent by indirect fluorescent antibody tests. The frequency distribution curves of indirect hemagglutination titers were unimodal in both the groups studied. From the basis of these findings, it was concluded that toxoplasmosis is not endemic in Khon Kaen and the transmission occurs at a very low level.

Scanning electron microscopic study of nocturnally subperiodic Brugia malayi (Filarioidea: Onchocercidae), Narathiwat, Southern Thailand.

Scanning Electron Microscopic (SEM) observations were made on the adult females and males of nocturnally subperiodic Brugia malayi (Narathiwat, Southern Thailand) from 8-month-old intra-peritoneally infected jirds (Meriones unguiculatus). Descriptions of the morphological surfaces of anterior end, vulva, body cuticle, anus, posterior end of females and anterior end, body cuticle, cloaca, caudal papillae, spicules, sheath, posterior end of males were demonstrated. The comparison among these and other filarial parasites were also investigated.