S48 Gut 1996; 38 (suppl 2): S48-S55 Hepatitis B and hepatitis delta virus infection in South America J R Torres R Abstract among other factors, by a deteriorating public About 100 000 cases of acute hepatitis B health and educational infrastructure, over- virus (HBV) infection occur annually in crowding of populations crammed into a few South America. The overall prevalence of large cities, resulting from uncontrolled inter- HBV infection in low risk populations nal and external influxes of population, as well ranges from 6.7% to 41%, while hepatitis B as persistent and extreme poverty.4 5 7 10 14-16 surface antigen (HBsAg) rates range from While it is certain that both HBV and HDV 0.4% to 13%. In high endemicity aboriginal infections are highly prevalent in South or rural populations, perinatal transmis- America, pronounced regional differences in sion may play a major part in the spread infection and carrier rates do exist, not only of HBV. In urban populations, however, among different nations within the area but also horizontal transmission, probably by - because of racial, geographical, socio- sexual contact, is the predominant mode of economic, and other related factors - within spread, with higher rates ofHBV positivity individual countries. Thus, in terms of mor- in lower socioeconomic groups. High risk bidity and mortality, a complex regional mosaic populations such as health care workers of epidemiological patterns and pathologies and haemodialysis patients show higher emerges. rates of HBV infection than comparable populations elsewhere. The risk of post- transfusion hepatitis B remains high in Data limitations some areas. Concomitant HBV infection Information on HBV prevalence in different may accelerate the chronic liver disease areas of South America remains partial and seen in decompensated hepatosplenic scarce, at best. Most available data are inher- schistosomiasis. In the north, the preva- ently biased as they originate from blood bank lence of hepatitis delta virus (HDV) infec- reports, and blood donors are often selected tion ranks among the highest in the world. from healthy adult populations. Furthermore, In the south, the problem appears negli- blood banks that perform routine HBV sero- gible although it is increasing within high logical screening are mostly located in urban risk urban communities. HDV superinfec- settings, and important differences in testing tion has been the cause of large outbreaks methodology exist. offulminant hepatitis. The cost ofcompre- Although National Hepatitis Committees hensive or mass vaccination programmes have been established to facilitate the accumu- remains unaffordable for most South lation of valuable local data, only limited infor- American countries. Less expensive alter- mation exists from any single country with natives such as low dose intradermal regard to HBV prevalence according to race, schedules ofimmunisation have been used age, socioeconomic level or urban/rural status. with success in selected adult subjects. As most cases of HDV infection occur (Gut 1996; 38 (suppl 2): S48-S55) precisely in rather remote locations, such as the Amazon Basin, where the prevalence of HBV Keywords: hepatitis B, hepatitis delta, South America, infection is highest, epidemiological informa- epidemiology, control. tion is especially hard to collect. Moreover, the true prevalence of HDV can be difficult to estimate because it increases the severity of Viral hepatitis remains an important cause of chronic liver disease and is also found more morbidity and mortality in many Latin frequently in people with chronic HBV liver American countries, where hepatitis A virus disease than in asymptomatic HBV carriers. (HAV), hepatitis B virus (HBV), hepatitis C Therefore, to clarify the level of endemicity virus (HCV), hepatitis delta virus (HDV) and, and the predominant regional patterns ofHDV to a lesser degree, hepatitis E virus, have all spread, more reliable figures are required on been reported as aetiological agents of both HDV prevalence, both in known HBV Infectious Diseases major regional outbreaks and isolated cases. 1-14 carriers and in those people with chronic liver Section, Tropical 13 17 18 Medicine Institute of Among these, HBV, HCV, and HDV are the disease.7 Caracas, Universidad key agents responsible for chronic infection and The shortcomings of analysing limited Central de Venezuela, liver disease. epidemiological data are illustrated by two Venezuela Caracas, In common with other developing regions of recent surveys of different Peruvian towns.4 10 J R Torres R the world with high rates ofviral hepatitis, most One such survey showed that the prevalence of Correspondence to: American countries socio- antibodies to hepatitis B surface antigen (anti- Dr J R Torres R, Sociedad South display Medica Clinica Santa Sofia, economic conditions that favour the occur- HBs) in coastal towns was very similar to that PO Box 14-9073, Coral rence of B and other related reported in the main cities, reaching a high of Gables, Fl 33 114-907, hepatitis Venezuela. infections. Such conditions are characterised, 16%.410 In contrast, towns located closest to HBV and HDV in South America S49 jungle areas showed the highest prevalence of HBV continues to spread throughout South anti-HBs of approximately 86%.4 10 The America with very variable frequencies authors suggested two possible factors to between one region and another.7 13 Available explain these findings: firstly, the proximity of surveillance data on partially classified hepati- the latter two towns to the Amazonic region; tis cases have shown morbidity rates that range secondly, the probability that, in those areas, from 25 to 150 cases per 100 000 population HBV infection is acquired at an early age.10 per year.920 A significant proportion of such In Huanta (Ayacucho), an Andean city cases - mostly those seen in the adult popula- located 2400 metres above sea level, 36 healthy tion - can be attributed to HBV infection. native residents and 100 acute hepatitis Accumulated data also suggest that HBV is the patients were evaluated as part of the same cause of 25-67% of all cases of chronic hepati- study.4 The prevalences of hepatitis B surface tis in Latin America and is also probably antigen (HBsAg) and antibodies to hepatitis B responsible for 10-70% of all cases of primary core antigen (anti-HBc) were found to be liver carcinoma.9 13 20 5.5% and 30.5%, respectively, among resi- dents, and 2l1% and 53% among patients. Not a single case ofHDV infection was reported. In Acute hepatitis B contrast, a similar study carried out among 143 HBV as a cause of acute hepatitis has only been healthy students selected randomly from four investigated in a few countries, where it has schools in the same city only two years later been shown to be the causative agent in up to showed a much higher prevalence of HBsAg 50% of patients screened.2 7 9 12 13 21 In (16%), and anti-HBc (84.8%), as well as general, it has been estimated that 140 000 to markers of previous HDV infection (17.9% 400 000 new cases of acute hepatitis B may be with anti-HDV antibodies).19 occurring annually in the entire Latin American region - two thirds of them in South America alone - including 440 to 1000 cases of SEROLOGICAL ASSAYS fulminant hepatitis.6 9 13 16 20 22-26 Higher rates Some South American countries currently of fulminant hepatitis are seen in areas where manufacture their own diagnostic kits for concurrent HBV and HDV infections are either HBV or HDV. As a result, the serologi- common.13 16 22-26 cal assays used in each study may vary, further complicating the interpretation of available data. The high cost of diagnostic tests prevents Chronic hepatitis B precise identification of the specific virus Currently available information on the epi- involved in each reported case, which also demiology of chronic hepatitis B infection in affects the quality of surveillance records. the region is largely derived from seropreva- Newly developed serological assays remain lence studies in blood donors. According to out ofreach for most South American countries, such studies, the seroprevalence of HBsAg and are not expected to be routinely intro- ranges from 0.4% in some areas of Chile up to duced in the near future. They include the 13% in northern Brazil, demonstrating a wide new micro ELISA techniques for detection of spectrum of HBsAg prevalence, not only HBV pre-S1 protein and anti-pre-S2, HBV- within the region, but also between different DNA hybridisation techniques, polymerase populations of a particular geographical area chain reaction (PCR) with oligonucleotides (Table I).2 6 7 9-11 13 20 21 27-29 However, it specific for certain regions of the HBV should be emphasised that calculations of genome, HDV antigen (HDAg) determination HBV seroprevalence based only on HBsAg by immunoblotting, and HDV-RNA detection determination in blood donors probably by spot hybridisation. underestimate the actual level of HBV infec- The many shortcomings in available data tion in a particular country. Larger population further hamper the assessment of the actual screening studies incorporating additional impact of HBV and HDV infections on the HBV serological markers, such as anti-HBc occurrence of chronic hepatitis and primary and anti-HBs, will provide a more accurate liver carcinoma, as well as their interaction picture.7 9 10 17 18 20 21 29 Data such as these are with alcoholic and post-transfusion hepatitis in available for only half of all South American the region. nations,