HTLV-1/2 in Indigenous Peoples of the Brazilian Amazon: Seroprevalence, Molecular Characterization and Sociobehavioral Factors Related to Risk of Infection

Abstract

HTLV-1/2 infection is endemic in Indigenous peoples of the Americas. Its origin is attributed to the migratory flow of Amerindian ancestral peoples. The present study aimed to investigate the seroprevalence of HTLV-1/2 infection in Indigenous peoples of the Brazilian Amazon. A total of 3350 Indigenous people belonging to 15 communities were investigated. The investigation was performed using serological (ELISA), molecular (qPCR) and confirmatory (Western blot and/or Inno-Lia) tests to detect and differentiate the infection. The seroprevalence was 8.3% for HTLV-1/2 infection, with 0.1% of individuals seropositive for HTLV-1 and 8.1% for HTLV-2. The prevalence of infection was statistically higher in women (10.1%) than in men (6.5%) (p = 0.0002). This female predominance was observed in all age groups; in females the prevalence was significant from 41 years old (p < 0.0001) and in males from 51 years old (p < 0.0001). Here, we present a prevalence of HTLV-1/2 among Indigenous peoples of the Brazilian Amazon. The endemic infection in these groups must reflect the different epidemiological profiles observed in these peoples, such as sexual transmission through rejection of condom use, breastfeeding, especially in cases of cross-breastfeeding, and the high rate of pregnancy in the villages.

Long-term prevalence follow-up (1967–2022) of HTLV-2 among vulnerable indigenous populations in the Amazon region of Brazil

“… (#1) Maloney et al, 1992 ; (#2) Ishak et al, 1995 ; (#3) Vallinoto et al, 2002 ; (#4) Braço et al, 2019 ; (#5) Abreu et al, 2023 . * Vallinoto et al, 2019 ; **Kayapó villages.…”

“…The general prevalence rates of HTLV-2 infection ranged from 5.7% ( Maloney et al, 1992 ) to 8.1% ( Abreu et al, 2023 ). There were nine villages that had a low (0.1–5%) prevalence of infection (Yanomami, Galibi, Waiãpi, Cinta Larga, Karitiana, Guajajara, Aikewara Surui, Wayana Apalai, and Gavião Parkateje), one with a medium (5.1–10%) prevalence of infection (Jamamadi), and nine with a high (>10.1%) prevalence of infection (Tiryio, Arara do Laranjal, and seven Kayapó villages: Aukre, Kubenkokre, Pykany, Kikretum, Kokraimoro, Xikrin, and Gorotire).…”

“…Seroreactivity to HTLV-1 was sporadically reported ( Ishak et al, 1995 ) and present in the Galibi (one person), Yanomami (three people), and Aukre Kayapó village (one person) in samples collected in the 1980s and 1990s. In the 2020s, HTLV-1 infections were present solely among four individuals of the Juruna people and Gorotire Kayapó village ( Abreu et al, 2023 ).…”

“…High prevalence rates were reported, but they were related to HTLV-2 ( Ishak et al, 1995 ; Vallinoto et al, 2002 ). Surveillance of HTLV-1/2 continued for the following 40 years, including visits to new villages and revisits to infected and noninfected villages ( Vallinoto et al, 2002 , 2019 ; Braço et al, 2019 ; Abreu et al, 2023 ). With the massive amount of information, it was possible to define clear patterns of HTLV-2 transmission within epidemiologically closed and semiclosed communities, mother-to-child transmission, intrafamiliar aggregation, possible clinical outcomes, and common pitfalls in the laboratory diagnosis of HTLV-2, possibly as a consequence of a new molecular subtype (HTLV-2c) inherent to the ARB ( Ishak et al, 1995 , 2001 , 2007 ; Lewis et al, 2000 ; Vallinoto et al, 2002 ; da Costa et al, 2013 ; Braço et al, 2019 ; Abreu et al, 2023 ).…”

“…Most reports have shown heterogeneous HTLV-2 infection among the distinct indigenous groups in the ARB, with seroprevalence rates ranging from 0 to 40% ( Maloney et al, 1992 ; Ishak et al, 1995 , 2020 ; Vallinoto et al, 2019 ; Abreu et al, 2023 ). In the present study, possible epidemiological changes were analyzed within the scenario of HTLV-2 infection as a result of more than 30 years of studies in indigenous villages in the ARB and spanning 56 years of retrospectively investigated samples in an attempt to answer important questions: Why have seroprevalence rates seemed to drop over the years?…”