Blocking vertical transmission of human T cell lymphotropic virus type 1 and 2 through breastfeeding interruption

Human T cell lymphotropic virus type 1 and 2 (HTLV-1/2) causes serious diseases and is endemic in many parts of the world. It is transmitted from mother to child in 15-25% of the cases, primarily through breastfeeding. Proviral load and duration of breastfeeding are thought to play a role in transmission. This study aimed to detect HTLV-seropositive mothers through testing of neonates, to evaluate maternal HTLV proviral load and to measure the rates of transmission blocking when interruption of breastfeeding was implemented.

Neonates were screened for HTLV-1/2 IgG by enzyme immunoassay using the neonatal screening program of Minas Gerais State, Brazil. Breastfeeding interruption was recommended to those whose mothers were confirmed HTLV-positive. Children were tested by polymerase chain reaction at birth and at 12 months of age.

Of 55,293 neonates tested, 42 (0.076%) were positive for HTLV-1 or HTLV-2 IgG. All 42 were polymerase chain reaction-negative at birth and 1 of 37 (2.7%) became antibody-positive after 12 months. His mother had delivered him vaginally and was informed of the positive HTLV-1 polymerase chain reaction after 7 days of breastfeeding. The mother's proviral load was 271 copies/10,000 cells, whereas the average is 109.2 copies/10,000 cells (95% confidence interval: 70.56-147.83).

Maternal HTLV-1 proviral load and the route of delivery may have played a role in the transmission observed. Avoidance of breastfeeding was an effective measure to reduce HTLV transmission. In endemic countries, routine prenatal or neonatal screening combined with formula feeding for mothers confirmed HTLV-positive may be an important strategy to prevent future development of illnesses related to HTLV.