Familial transmission of Human T-cell lymphotrophic virus : silent dissemination of an emerging but neglected infection

Abstract

Background: HTLV-1 is a retrovirus that causes lymphoproliferative disorders and inflammatory and degenerative diseases of the central nervous system in humans. The prevalence of this infection is high in parts of Brazil and there is a general lack of public health care programs. As a consequence, official data on the transmission routes of this virus are scarce. Objective: To demonstrate familial aggregation of HTLV infections in the metropolitan region of Belém, Pará , Brazil. Method: A cross-sectional study involving 85 HTLV carriers treated at an outpatient clinic and other family members. The subjects were tested by ELISA and molecular methods between February 2007 and December 2010. Results: The prevalence of HTLV was 43.5 per cent (37/85) for families and 25.6 per cent (58/227) for the family members tested (95 per cent CI:1.33 to 3.79, P = 0.0033). Sexual and vertical transmission was likely in 38.3 per cent (23/60) and 20.4 per cent (29/142) of pairs, respectively (95 per cent CI: 1.25 to 4.69, P = 0.0130). Positivity was 51.3 per cent (20/39) and 14.3 per cent (3/21) in wives and husbands, respectively (95 per cent CI:0.04 to 0.63, P = 0.0057). By age group, seropositivity was 8.0 per cent (7/88) in subjects ,30 years of age and 36.7 per cent (51/139) in those of over 30 years (95 per cent CI: 0.06 to 0.34, P,0.0001). Positivity was 24.1 per cent (7/29) in the children of patients infected with HTLV-2, as against only 5.8 per cent (4/69) of those infected with HTLV-1 (95 per cent CI: 0.05 to 0.72, P = 0.0143). Conclusion: The results of this study indicate the existence of familial aggregations of HTLV characterized by a higher prevalence of infection among wives and subjects older than 30 years. Horizontal transmission between spouses was more frequent than vertical transmission. The higher rate of infection in children of HTLV-2 carriers suggests an increase in the prevalence of this virus type in the metropolitan region of Belém.