Hav among Hill-tribe Youth in Northern Thailand

A cross-sectional analytic study of 190 hill-tribe youth in a community in the north of Thailand was conducted to investigate the sero-prevalence of HAV and factors related to positive anti-HAV antibody. The studied youth, whose ages ranged from 15 to 24 years, were interviewed about socio-economic status and personal hygiene. Blood specimens were collected to detect antiHAV by ELISA commercial kit. Household environmental sanitation conditions were observed and drinking water samples were screened for bacterial contamination using SI2 medium. Following the anti-HAV assay, the studied youth were divided into two groups: anti-HAV positive, and anti-HAV negative. The studied variables of the two groups were analyzed by χ test to find factors related to anti-HAV positivity. The results revealed that 87% of the studied youth were positive for anti-HAV. There was no statistically significant difference between age group/gender and anti-HAV positivity, p = 0.46 and 0.16, respectively. Approximately 35.79 to 45.79% washed their hands with soap before preparing food, before eating and after using the latrine. About 88% did not improve the potability of their drinking water. The results of screening for bacterial contamination in drinking water samples found that 73.53% were contaminated with coliform bacteria. Factors related to positive anti-HAV antibody included monthly income, number of household members, use of latrine, hand-washing with soap after using latrine, household refuse management and control of insects and rodents; p = 0.04, 0.007, 0.013, 0.008, <0.001 and <0.001, respectively. The findings suggested that appropriate household environmental management should be improved in this community to reduce HAV transmission. is transmitted from person to person by the fecaloral route or ingestion of contaminated food or water (Hadler, 1991; WHO, 1999). Improvements in public hygiene and higher socio-economic levels are associated with declining prevalence of infection. In communities that have intermediate rates of hepatitis A, the disease occurs among children, adolescents and young adults, in contrast to communities that have high rates of hepatitis A, in which the majority of cases occur among children less than 15 years of age (Poovorawan et al, 1997; Hadler, 1991). In Thailand, HAV infection caused 60-70% of acute hepatitis in children aged less than 15 years (Poovorawan et al, 1997). A previous study in 1981 reported that a large number of Thai children have become seropositive for anti-HAV (Burke et al, 1981). For the last ten years, the socio-economic situation and sanitary conditions have improved signifiSOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 570 Vol 34 No. 3 September 2003 cantly in a newly industrialized countries. Many countries in Southeast Asia have experienced changes in age-specific seroprevalence of anti-HAV antibodies; this infection has been shifting from childhood to adulthood (Jutavijittum et al, 2002). Increasingly susceptible adolescents and young adults contribute to sporadic symptomatic hepatitis A, particularly among high school children, communities and factory workers. In young children, HAV infection may be asymptomatic in about 75% of infected cases. Presumably, many more children have unrecognized infection and can be a source of infection for others (Hadler and McFarland, 1986; Rosenblum et al, 1991). The true incidence and prevalence of the infection are still unknown, especially among hill-tribe communities, low socioeconomic communities and communities with unsanitary environments. Most hill-tribes found in the northern part of Thailand, and their cultures, attract travelers to visit their communities. Travelers from lowendemic areas may be at risk of acquiring HAV (WHO, 1992). This study attempted to investigate the sero-prevalence of HAV among youth of the Akha hill-tribes. The household environmental sanitation conditions were observed and factors including socio-economic status, personal hygiene and household environmental sanitation related to positive anti-HAV antibody were assessed. The results are valuable for preventing and controlling HAV infection and for improving the personal hygiene and environmental sanitation conditions in this studied community, and may be extended to other hill-tribe communities in the north of Thailand. MATERIALS AND METHODS Study design and study samples This study was of cross-sectional analytic design, conducted between October 1999 and September 2000. The study involved 190 young people whose ages ranged from 15 to 24 years. The subjects of the study were of both genders, an Akha hill-tribe in Amphoe (district) Mae Suai, Chiang Rai Province, in the north of Thailand. The studied sample size was calculated by the formula n = Z∝/2 PQ N/[Z 2 ∝/2PQ + d (N-1)], where n = sample size, N = Akha hill-tribe persons whose ages ranged from 15 to 24 years in the studied community during the study = 375 persons, Z∝/2 = standard deviation at 95% confidence interval = 1.96, P = estimated proportion of anti-HAV in the low sanitary population from the previous study = 0.4 (Poovorawan et al, 1994), Q = 1-P = 0.6, d = the acceptable error set at 0.05. Therefore, the required studied sample size was about 190 persons. Data collection and laboratory assay The studied subjects were 190 young Akha hill-tribe individuals who voluntarily participated in the study. They received an explanation of the study and informed consents were signed for participation. All participants with no history of HAV vaccination were interviewed about socio-economic status and personal hygiene by using questionnaires. Blood specimens were collected for anti-HAV detection by an ELISA commercial kit (HEPAVASE A-96, General Biologicals Corp, Taiwan) with approximately 100% sensitivity and specificity. The household environmental sanitation conditions were observed. Studied households drinking water samples were collected to screen coliform bacteria using sanitation index 2 medium (SI2 medium) developed by the Thai Ministry of Public Health with 87.64% sensitivity and 88.31% specificity (Luksamijarulkul et al, 2001). Following the laboratory assay for HAV antibody, the studied subjects were divided into 2 groups: the first group was antiHAV-positive subjects and the second was subjects without anti-HAV. The studied variables included socio-economic status, personal hygiene and environmental sanitation conditions of the two groups. These were analyzed to determine some factors related to anti-HAV positivity.