ENDEMIC TRANSMISSION OF HTLV TYPE-II AMONG KAYAPO INDIANS OF BRAZIL

Serological studies on 926 blood samples from 703 Brazilian Kayapo (Ca yapo) Indians showed, by conventional definition of HTLV seropositivit y, a 28% prevalence of human T lymphotropic virus (HTLV) infection, th e highest yet reported. Immunoblot (WB) and SYNTH-EIA patterns indicat e that the predominant infecting agent is type II. Of children under 1 5 years old, 12% were positive, and of persons over 60; more than 60%. Perinatal and heterosexual modes of transmission offer an adequate ex planation of this incidence. Infection in infancy may include infectio n via breast milk from women other than the mother. Evidence of new in fection in adults is apparent at an earlier age in women than in men. This pattern of antibody prevalence was not determined by cohort effec ts, as demonstrated by tests of serial specimens. Enzyme immunosorbent assay (EIA) absorbencies were not stable in the paired specimens: fiv e serum pairs reverted and mean absorbencies declined over some age ra nges. Many specimens with relatively high, but less than positive, EIA results were positive by immunoblot (WB). This suggests that the stan dard EIA end point does not identify all infected persons. If the WB a lone indicates positivity, 47% of the whole population, and more than 80% of the older age groups, are infected with HTLV-II.