The declining pattern of seroepidemiology of hepatitis A virus infection among adolescents in Bangkok, Thailand.

Hepatitis A virus (HAV) is a health problem in countries where seroepidemiology shows changes from hyperendemicity to intermediate endemicity. Throughout the last decade, we studied, in Bangkok, the seroprevalence of hepatitis A virus antibody (anti-HAV) among adolescents of different age groups. In 1996, 245 serum specimens from children aged between 10 and 19 were tested for anti-HAV by ELISA method. The results were compared to those obtained in 1987 and 1993 from students of the same age and attending the same school. Anti-HAV was detected in 31.4%, 14.6% and 12.7% of school children in the years 1987, 1993 and 1996, respectively. Each year, it was found that an increasing prevalence of anti-HAV was related to an increasing age. From 1987 to 1996, the age specific prevalence of anti-HAV was markedly decreased in younger children. The surveillance of the epidemiological trend of HAV infection is important for implementing preventive measures and for controlling the disease.

An outbreak of hepatitis A in school children at Nakhon Si Thammarat, southern Thailand.

Hepatitis A antibody prevalence in Southeast Asia has markedly declined among children and adolescents. Therefore increasing a number of susceptible populations could result in an outbreak or epidemic. This paper reports an intensive study of an outbreak of hepatitis A in a primary school children during an endemic at Nakhon Si Thammarat, Southern Thailand. Eighty-nine children were inspected randomly from the total of 269 students, age ranged from 7-12 years old. The school children and parents were interviewed for their illness. Serological tests for antiHAV IgM and antiHAV (total antibody) were performed by ELISA. There were 36 cases of clinical acute hepatitis were positive for antiHAV IgM because of serological tests were performed nearly 4 months later. Seventy of 89 children tested were positive for antiHAV and 16 of them were positive for IgM class. Seven of 16 children with antiHAV IgM positive were asymptomatic. The significant risk factors for children with positive antiHAV were occurrence of hepatitis patients in the family and no latrine (p < 0.01). Endemic transmission in this outbreak occurred rapidly. Therefore preventive measures are essential in reducing the infection rate. In addition to personal hygiene, immunoprophylaxis with either immunoglobulin or HAV vaccine is recommended.

Comparative results in detection of HCV antibodies by using a rapid HCV test, ELISA and immunoblot.

Viral hepatitis C is a major problem of post-transfusion hepatitis. The best measure for preventing hepatitis C infection in transfusion is blood donor screening. There are many methods for detecting hepatitis C virus antibodies. ELISA is one of the sensitive screening methods. However it needs equipment, technical skills and it is time consuming. The Genelabs Diagnostics HCV-SPOT is a simple, rapid test for the detection of anti-HCV. This paper reports comparative results in detection of HCV antibodies by using GLD HCV-SPOT, ELISA and GLD/DBL HCV BLOT. One hundred and ninety-two specimens from blood donors patients with chronic hepatitis, cirrhosis, hepatoma and miscellaneous chronic liver diseases were tested by HCV-spot assay and HCV ELISA. The positive specimens were confirmed by the immunoblot assay. Only one of 140 samples negative by HCV-SPOT was positive by ELISA. The sensitivity and specificity of HCV-SPOT assays were 97.6% and 92.6% respectively. The positive predictive value was 78.8%, negative predictive value was 99.3%, accuracy was 93.6%. The rapid HCV-SPOT assay can be used in the management of transplantation graft procedures or emergency blood screening for transfusion. In addition, it can be used in small, local hospitals without any expensive equipment.

Risk factors of streptococcal colonization in school age children.

We studied the factors influencing the colonization of Streptococcus in school age children aged 6-11 years from 2 low socioeconomic schools of the Bangkok Metropolitan area. 4,055 throat swab cultures were performed. Beta hemolytic Streptococcus (BHS) and beta hemolytic Streptococcus group A (BHSA) were isolated in 1,747 (43%) and 744 (18%) respectively. 1,547 questionnaires were returned from the children. Of these, 750 and 570 were found to have BHS and BHSA in the throat, respectively. Among the risk factors, considered, teeth brushing of one time or none per day was significant for BHS positive in the throat as compared with the BHS negative group, while personal hygiene such as sharing glass with other, playing in dirty water, poor housing sanitation and low family income was significantly associated with the BHSA positive group. With the combination of certain clinical manifestations, these factors may increase the accuracy of predicting streptococcal infection.

Randomized, single-blind comparison of the immunogenicity and reactogenicity of 20 micrograms and 10 micrograms doses of hepatitis B vaccine in adolescents.

The study compares the effect of two different doses of a recombinant DNA hepatitis B vaccine (Engerix-B) administered to 320 healthy adolescents divided randomly into two equal groups, using the 0, 1 and 6 month's vaccination schedule. Initially the larger dose elicited protective levels of antibody in a greater proportion of subjects. The seroprotection rates were significantly higher at both months 1 (17.6% v/s 9.2%) and 2 (68.8% v/s 56.7%). The difference was especially relevant 6 months after the start of the vaccination schedule when a 92.4% seroprotection rate was obtained in the 20 micrograms dose group, whereas only 78.3% of subjects in the 10 micrograms dose group had protective antibody levels. Furthermore there were significant differences in anti-HBs geometric mean titers for seroconverters at months 6 (109 v/s 56mlU/ml) and 7 (4774 v/s 2705mlU/ml). However one month after the third vaccine administration, both doses produced similar high seroprotection rates (97.9% and 97.1%, respectively). The difference in the generally mild overall reactogenicity for the 2 dose levels was not remarkable although the higher dose produced more local symptoms. The conclusion from the study was that the 10 micrograms dose produces a very good antibody response in adolescents, provided the full vaccination course of three doses, according to a 0, 1 and 6 month's schedule, is administered. However, the 20 micrograms dose should be used if compliance to the full course is in doubt since a 92.4% seroprotection rate can be obtained with 2 injections compared to only 78.3% with the 10 micrograms dose.

Changing seroepidemiology of hepatitis A virus infection in Thailand.

Hepatitis A is an infectious disease commonly found in many developing countries. The infection usually is asymptomatic in children and only a small percentage has clinical hepatitis of varying severity. Hepatitis A infection becomes more symptomatic with increasing age. We studied hepatitis A antibody prevalence in many population groups of Thailand and investigated the changing patterns of hepatitis A antibody in comparison with previous seroepidemiological surveys in the past decade. The antibody prevalence in Bangkok and in the rural areas of Thailand had markedly declined among the children and adolescents studied. Only one-fifth to one-fourth of children and adolescents had antibody to hepatitis A. The prevalence differed from that of a decade ago. These data probably reflect the marked improvement of hygienic conditions and effective health education, which have reduced exposure to HAV infection among young children. When an effective hepatitis A vaccine with long lasting immunity becomes available, subgroups of the populations at risk of infection will be the targets for immunization.

Group A beta-hemolytic streptococcal type M11 sepsis and empyema: a case report.

A case of serious suppurative disease caused by GABHS in a previously well 2-month-old Thai female presenting with clinical features of sepsis and right pleural effusion was reported. Treatment was initially with cloxacillin and a right side intercostal drainage. When subsequent cultures of blood and pleural fluid grew GABHS; intravenous penicillin was substituted. She made an uneventful recovery. Typing of the GABHS revealed non typable T-antigen and M-protein 11 GABHS, although very sensitive to penicillin, can cause severe and rapidly progressive disease in a very young infant. This is the first case of GABHS type M11 causing pleural effusion and sepsis in an infant ever reported in Thailand. Epidemiologic study might be indicated if an epidemic should occur.

Seroepidemiology of antibody to hepatitis A in the rural eastern part of Thailand.

Hepatitis A is a disease commonly found in Thai children. However, there are very few reports on the age specific prevalence in Thailand. We studied the hapatitis A virus (HAV) antibody titer in a population in the rural eastern part of Thailand, using an antiHAV ELISA test (Abbott Laboratories, North Chicago Ill). Three hundred and sixty four subjects from Pong Nam Ron, Chanthaburi Province and 236 of children and adults from Bo Thong, Chon Buri Province were studied for age specific prevalence of antiHAV. The immunity against HAV increased with age. Fifty percent of Pong Nam Ron children had antiHAV antibodies at the age of 8-9 years and at the age of 12-13 years of Bo Thong children. The overall antibody prevalence rate was 67.9% in Pong Nam Ron and 59.3% in Bo Thong Districts. According to our data, less than 30 percent of children under 10 years old in the eastern part of Thailand were seropositive for HAV. This finding indicated a much lower incidence than previously reported which may reflect better personal and food hygiene.

Occurrence of beta-hemolytic streptococcus group G in school children and sick children.

We studied the occurrence of Streptococcus group G in throat cultures obtained from school children of poor socioeconomic status and in sick children brought to our hospital. The results revealed a high occurrence of group G Streptococci (44% and 91.5% respectively) in cases positive for beta-hemolytic Streptococci.

Hepatitis A antibody in secondary school children in Bangkok.

There are very few published reports on the prevalence of hepatitis A virus in Thailand. This paper is to report the prevalence of the antibody to hepatitis A virus (anti HAV) in secondary school children of different age groups in Bangkok. One hundred seventy two serum specimens from students (age 10-19 years, from M1-M6) were tested for anti HAV by ELISA. The antibodies were detected in 25, 27.3, 31, 30 and 50 percent of children who were in the age groups of 10-11, 12-13, 14-15, 16-17 and 18-19 years respectively. Children with positive anti HAV had histories of jaundice or liver disease more than children without anti HAV. (p < 0.05) The members of the families in both groups (with and without anti HAV) were not significantly different (6.8 + 3.2 vs 7.0 + 2.9) According to our data, two-thirds of secondary school children had no immunity to hepatitis A virus. When hepatitis A vaccine is available, these subjects may be considered a target population for vaccination for disease control.