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Human herpesvirus 8 in Brazilian Amerindians: does vertical transmission play a role?

To the Editor—Biggar et al. [1] presented an attractive study of human herpesvirus 8 (HHV-8) epidemiology in Brazilian Amerindian populations. Use of the immunofluorescence assay for the detection of latent antibodies showed a high prevalence of HHV-8 (53%) in 781 natives of different tribes with no differences by sex, language, ethnicity, or geography. In children !10 years of age, the prevalence was 41%, with a steady increase to 65% in persons 130 years old. The authors hypothesized that such an HHV-8 hyperendemic condition, with a high prevalence among young children, suggests an oral rather than a sexual route of HHV-8 transmission. The role of HHV-8 vertical transmission, however, does not appear to have been fully investigated. The existence of different modes of HHV-8 transmission through horizontal (either oral or sexual) and vertical routes has been suggested [2, 3], but the data of Biggar et al. [1] should be evaluated either in the context of the seroprevalence of other ubiquitous infections (e.g., cytomegalovirus and Epstein-Barr virus) or in that of sexually transmitted infections (e.g., herpes simplex virus 2 and hepatitis B virus [HBV]). A similar high prevalence of HBV serologic markers (range, 62.8%–95.7%) has been found in different Amerindian populations: in Tupi Monde, Xavante [4], Karitinana [5], and other Amazon populations [6] and in Yaomami in the upper Orinoco River in Venezuela [7]. It is argued that the high rates of HBV seroprevalence in Amerindian populations and in other Amazonian groups could be related to a complex of cultural practices with an enhanced likelihood of bloodborne transmission (e.g., bloodletting, scarification, and tattooing). On the basis of this hyperendemic HHV-8 prevalence, age-stratified data could suggest both horizontal and vertical routes of transmission, but perinatal acquisition could probably play a pivotal role among causes of infection in infants and children. In fact, Biggar et al. [1] showed that the prevalence of HHV-8 antibodies among children 0–4 years of age, particularly in boys, is higher than that in older children. Mother-to-child transmission has been demonstrated for HHV-8 infection [8], and in endemic areas, such as the Brazilian Amazon, it could represent a noteworthy route of transmission, as already shown for HBV infection. Further longitudinal surveys are needed to confirm the major role played by vertical transmission in determining a high HHV8 seroprevalence.