High prevalence of antibodies to hepatitis A and E viruses and viremia of hepatitis B, C, and D viruses among apparently healthy populations in Mongolia

Abstract

The prevalence of infection with hepatitis A virus (HAV), HBV, HCV, HDV, and HEV was evaluated in 249 apparently healthy individuals, including 122 inhabitants in Ulaanbaatar, the capital city of Mongolia, and 127 age- and sex-matched members of nomadic tribes who lived around the capital city. Overall, hepatitis B surface antigen (HBsAg) was detected in 24 subjects (10%), of whom 22 (92%) had detectable HBV DNA. Surprisingly, HDV RNA was detectable in 20 (83%) of the 24 HBsAg-positive subjects. HCV-associated antibodies were detected in 41 (16%) and HCV RNA was detected in 36 (14%) subjects, none of whom was coinfected with HBV, indicating that HBV/HCV carriers account for one-fourth of this population. Antibodies to HAV and HEV were detected in 249 (100%) and 28 (11%) subjects, respectively. Of 22 HBV DNA-positive subjects, genotype D was detected in 21 subjects and genotype F was detected in 1 subject. All 20 HDV isolates recovered from HDV RNA-positive subjects segregated into genotype I, but these differed by 2.1 to 11.4% from each other in the 522- to 526-nucleotide sequence. Of 36 HCV RNA-positive samples, 35 (97%) were genotype 1b and 1 was genotype 2a. Reflecting an extremely high prevalence of hepatitis virus infections, there were no appreciable differences in the prevalence of hepatitis virus markers between the two studied populations with distinct living place and lifestyle. A nationwide epidemiological survey of hepatitis viruses should be conducted in an effort to prevent de novo infection with hepatitis viruses in Mongolia.

FIG. 1.

Phylogenetic tree constructed by the neighbor-joining method based on the partial nucleotide sequence of the S gene (396 nt) of 74 HBV isolates, using a woolly HBV (AF046996) as an outgroup. In addition to the 22 Mongolian isolates found in the present study (which are indicated in boldface type for visual clarity), 52 reported HBV isolates of genotypes A to H whose entire sequence is known were included for comparison. Each reported isolate is indicated with the accession number followed by the name of the country where it was isolated. Asterisks denote Mongolian HBV strains that were isolated from serum samples that were also positive for HDV RNA. Bootstrap values are indicated for the major nodes as a percentage of the data obtained from 1,000 resamplings.

FIG. 2.

Phylogenetic tree constructed by the neighbor-joining method based on the partial nucleotide sequence (522 to 526 nt) of 51 HDV isolates. In addition to the 20 Mongolian isolates obtained in the present study, which are indicated in boldface type, 31 reported HDV isolates of genotypes I to III whose entire sequence is known were included for comparison. The reported isolates are indicated with the accession number followed by the name of the country of isolation, when available. Bootstrap values are indicated for the major nodes as a percentage of the data obtained from 1,000 resamplings.