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. 2023 Sep 28;17(9):e0011005.
doi: 10.1371/journal.pntd.0011005. eCollection 2023 Sep.

Epidemiological and molecular evidence of intrafamilial transmission through sexual and vertical routes in Bahia, the state with the highest prevalence of HTLV-1 in Brazil

Aidê Nunes da Silva  1 , Thessika Hialla Almeida Araújo  1 , Ney Boa-Sorte  1 , Giovanne Farias  1 , Ana Karina Galvão-Barroso  1 , Antônio de Carvalho  1 , Ana Carolina Vicente  2 , Bernardo Galvão-Castro  1   3 , Maria Fernanda Rios Grassi  1   3
Affiliations

Epidemiological and molecular evidence of intrafamilial transmission through sexual and vertical routes in Bahia, the state with the highest prevalence of HTLV-1 in Brazil

Aidê Nunes da Silva et al. PLoS Negl Trop Dis. .

Abstract

Introduction: Familial clustering of HTLV-1 and related diseases has been reported in Brazil. However, intrafamilial transmission of HTLV-1 based on molecular analysis has been studied only in a few communities of Japanese immigrants and African-Brazilians.

Objective: To investigate the familial clustering of HTLV-1 infection and to determine the likely routes of transmission through epidemiological and genetic analyzes.

Methods: Medical records of 1,759 HTLV-1+ patients from de the Center for HTLV in Salvador, Brazil, were evaluated to identify first-degree relatives previously tested for HTLV-1. Familial clustering was assumed if more than one member of the same family was HTLV-1+. LTR regions of HTLV-1 sequences were analyzed for the presence of intrafamilial polymorphisms. Family pedigrees were constructed and analyzed to infer the likely transmission routes of HTLV-1.

Results: In 154 patients at least one other family member had tested positive for HTLV-1 (a total of 182 first-degree relatives). Of the 91 couples (182 individuals), 51.6% were breastfed, and 67.4% reported never using a condom. Of the 42 mother-child pairs, 23.8% had a child aged 13 years or younger; all mothers reported breastfeeding their babies. Pedigrees of families with 4 or more members suggests that vertical transmission is a likely mode of transmission in three families. Three families may have had both vertical and sexual transmission routes for HTLV-1. The genetic signatures of the LTR region of 8 families revealed 3 families with evidence of vertical transmission, another 3 families (spouses) with sexual transmission, and one family with both transmission routes. HTLV-1 sequences belonged to Cosmopolitan subtype HTLV-1a Transcontinental subgroup A.

Conclusion: Sexual and vertical transmission routes contribute to the intrafamilial spread of HTLV-1 in the state of Bahia.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Fig 1
Fig 1. Study design flowchart.
Created with BioRender.com.
Fig 2
Fig 2. Pedigrees of 20 families with likely routes of HTLV-1 transmission based on epidemiological data and sexual behavior.
Fig 3
Fig 3. Pedigrees of 8 families with likely routes of HTLV-1 transmission based on epidemiological data, sexual behavior and genetic sequencing of the HTLV-1 LTR region.
Family members highlighted in red represent, partners, children, or grandchildren of the index case who provided secondary information about sexual behavior and other risk factors.
See this image and copyright information in PMC

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