A Ten Year Serological Survey of Hepatitis A , B and C Viruses Infections in Nepal

Background: In 1987, we reported that the prevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection in Nepal was low, as compared to hepatitis A virus (HAV) infection, and that no human T-lymphotropic type-1 (HTLV-1) infection was found in Nepal. Objectives: To determine changes in the prevalence of HAV, HBV, and HCV infections between 1987 and 1996 in inhabitants of Bhadrakali (suburban) and Kotyang (rural) villages in Nepal. Study design: We did a cross-sectional survey of 458 inhabitants of two Nepalese villages, to assess the prevalence of antibody to HAV (anti-HAV), antibody to hepatitis B core antigen (antiHBc), hepatitis B surface antigen (HBsAg), antibody to HCV (anti-HCV), and antibody to HTLV-I (anti-HTLV-I). Results: Anti-HAV was detected in 454 (99.1 %), HBsAg in 5(1.1 %), anti-HBc in 33 (7.2%) and anti-HCV in 8 (1.7%) of serum samples tested in 1996. Statistically significant differences by gender or age group were nil. The prevalence of HCV infection was significantly higher in 1996 than in 1987 after adjusting for age of subjects living in the two villages (p<0.01). The prevalence of HBsAg was significantly higher in 1996 than 1987 in Bhadrakali after adjusting for the factor of age (p<0.05). Between 1987 and 1996, evidence for HTLV-1 positive residents was nil. Conclusion: These results suggest that HAV has been endemic in Nepal for long time while not of HBV, and that HCV infection tends to be increased recently. J Epidemiol, 1999; 9 : 350-354


Study Population
The present study was a cross-sectional survey of inhabitants of two villages in Nepal.Between August and September 1996, 458 inhabitants (Mean age 43.1 years; range 15-90 years), including 222 from Bhadrakali (112 males, 110 females; mean age 46.3 years) and 236 from Kotyang (117 males, 119 females; mean age 39.8 years ) were available for study.We examined HAV, HBV, HCV and HTLV-1 markers in these areas between 1987 and 1996.The results of surveys carried out on the two villages of Nepal in 1987 were documented 14).Blood samples were screened for HAV, HBV, HCV and HTLV-1 infections.The two villages are about 1,200km above sea level and 75km apart.Kotyang, located on the eastern side of a mountain separating Kathmandu and Sun Chose Valleys, is an isolated rural village about 30km east of Kathmandu, and the inhabitants have to walk many hours to reach the nearest roads.Most residents are engaged in agriculture and the population is approximately 1500.In this village, no dwelling has treated municipal water; all the villagers drink spring water and there is no sewage system.Bhadrakali is located on terraces that extend downward from Burhanikanth to Kathmandu and is easily accessible by public transportation.The main occupation is agriculture, but some villagers are office workers.The population is approximately 3900.This village has both piped and tanked water and there exists a simple sewage system.The boiling of drinking water is not customary in either village 15).The study protocol, including blood sampling, was explained by Nepalese doctors to all subjects, the purpose was explained to leaders of the villages and their consent was obtained prior to start of the survey.A study had been done to assess health status of the residents and to determine the prevalence of hypertension and the possible factors influencing the pathogenesis of hypertension 16,17).
Approximately l0m1 of blood was with drawn from subjects in a supine position, following as after overnight fast.After centrifugation, the sera were frozen within a few hours, stored as in 1987 (99.3%).There were no significant differences in the overall anti-HBc and HBsAg prevalences between 1996 (1.1%,7.2%)and 1987 (0.3%,7.5%).
The overall anti-HCV prevalence was significantly higher in 1996 (1.7%) than in 1987 (0.1%)(p<0.01;Mantel-Haenszel test).Although there was no evidence of anti-HCV in the subjects under 55-64 years in 1987, there were a few cases of anti-HCV all age groups, except for the >_65 age group in 1996.Statistically significant differences for these infections by age group were nil.
TABLE 3 shows a comparison of the prevalence of the tested viral markers between in 1987 and 1996.There were no significant differences in the prevalence of HAV, HBV and HCV infections between the two village in 1987 or in 1996.Although anti-HCV did increase in both villages, there were no significant differences between age groups.
In Bhadrakali, the prevalence of HBsAg was significantly higher in 1996 (2.3%) than in 1987 (0.3%)(p<0.05;Mantel-Haenszel test).Moreover, the prevalence of HBsAg in 1987 and 1996 was 0.5% (1/188)) and 0% in residents under 34 years age and 3.0% (2/66) and 3.9% (3/77) in those over 55 years age, respectively, but the difference was not statistically significant.Thus, the prevalence of HBsAg tended to increase in the younger age groups (under 34 years age) and in the older age groups (over 55 years age) in 1996, as compared to findings in 1987.Moreover, there was no significant difference in the prevalence of anti-HBc between 1987 and 1996.In Kotyang, the prevalence of HBsAg and anti-HBc decreased from 0.4% and 7.8% in 1987 to 0% and 4.2% in 1996, but with no statistical significance.

DISCUSSION
This study revealed serological evidence of a high prevalence of HAV infection in contrast to a low prevalence of HBV infection between 1987 and 1996.Differences in anti-HAV prevalence among countries is probably related to differences in environmental and socioeconomic conditions.We reported that the prevalence of anti-HAV in Okinawa 30 years ago was significantly higher than in Kyushu, Japan 19).We also reported that fewer subjects had HAV infection as sanitary conditions had improved, a decision based on analysis using a the catalytic model 20, 21).Therefore, our results suggest that hygienic and sanitary conditions that may have facilitated the fecal-oral spread of HAV infection not seem to have been much improved in Nepal since 1987.
In developed nations, HBV infection is usually acquired through parenteral, sexual, or perinatal exposure.However, horizontal transmission is predominant in the less developed nations, though changes in customs, lifestyle, and socioeconomic conditions may influence the relative contributions of the different modes of HBV transmission.Although overall HBV infection did not change as did HAV infection from 1987 to 1996, the prevalence of HBV infection in Bhadrakali significantly increased compared to that in Kotyang, which a more isolated area.Bhadrakali is located in a suburban area near Kathmandu and is readily accessible by public transport.Thus, many people earn their living in Kathmandu.There are more opportunities for transmission by the percutaneous route as a result of medicine interventions, drug use or tattooing, and sexual intercourse than in Kotyang, which is a much more isolated area.We reported that HBV infection among nursery school children was markedly reduced in Okinawa, Japan 22).This is attributed to a combined administration of hepatitis B immunoglobulin and hepatitis B vaccine which protects against maternal transmission.This approach to immunization may be effectively in these villages in Nepal.Because our study was a cross-sectional survey and may have included bias, a cohort study will be necessary for evaluation of the prevalence of HBV infection.
Major routes of HCV transmission are percutaneous exposure to blood through blood transfusion or contaminated needles 23,24).We found the prevalence of HCV infection to be significantly increased from 1987 to 1996.Although the anti-HCV prevalences in each villages tended to increase in different age groups, this trend was not statistically significant, possibly because numbers were too few.We reported that medical interventions probably played a more important role in the spread of the HCV infection in a village in Japan than did familial transmission 25).Our results suggest that percutaneous medical treatment has increased in these villages in Nepal .However, the question of whether or not HCV is actually transmitted by the percutaneous route as a result of medical treatment or drug use or by tattooing in these villages is difficult to answer.Further study with a longer observation period is required to show the precise route of HCV infection.
The HTLV-1 virus has two major routes of transmission, percutaneous exposure via blood transfusion and familial transmission (mother-to-child transmission via breast feeding and male-to-female transmission through sexual contact) 1, 10, 16) We found no anti-HTLV-1 positive inhabitants and HTLV-1 has not been spread to the surveyed area in Nepal.
These villages in Nepal had a continuously high prevalence of HAV infection, in contrast to HBV infection, as seen in 1987 and 1996.Moreover, the results of this study showed that HCV infection significantly increased, indicating that there is a high risk of HCV infection.

Table 1 .
Age and sex-specific prevalences of anti-HAV, HBsAg, anti-HBc and anti-HCV in Nepal , 1996.

Table 2 .
Age and sex-specific prevalence of anti-HAV, HBsAg, anti-HBc and anti-HCV between 1987 and 1996 in Nepal.

Table 3 .
Aee and sex-specific prevalence of anti-HBc and anti-HCV between Bhadrakali and Kotyang between 1987 and 1996, in Nepal.