Human T-lymphotropic virus type 1 (HTLV-1)

The human T-cell lymphotropic virus type 1 (HTLV-1) is a human retrovirus that causes an asymptomatic infection but is associated at a frequency of 1 to 10% ^{(Leal 2015, Carneiro 2014)} with a series of degenerative or immunological diseases such as tropical spastic paraparesis (TSP), T-cell leukemia or lymphoma, Sjögren's syndrome, arthritis and uveitis, Norwegian scabies, strongyloides stercoralis infestation and increased susceptibility to the development of tuberculosis infection and others ^{(Garcia 2019, Gotuzzo 2010 and 2004)}. Infection is very prevalent in countries of western and central Africa, Peru, the Caribbean, Colombia, Brazil and Japan. ^{(Rosadas 2019, Tagaya 2019)}

HTLV-1 is transmitted mainly through breastfeeding ^{(Millen 2022, Garcia 2019, Rosadas 2018, Boostani 2018, Carneiro 2014)}, especially if breastfeeding lasts more than 12 months (Paiva 2018). Transmission is more frequent if there is a higher viral load in the mother and there are siblings affected by HTLV-1 ^{(Paiva 2018)}. In addition to HTLV-1/2 proviral DNA, anti-HTLV 1 and 2 IgG antibodies are detected in breast milk. ^{(Rosadas 2021)}

Other means of transmission are sexual contact and transfusions. Transplacental transmission and transmission during delivery are very rare.

The prevention of transmission adopted in some highly endemic countries is prenatal screening and formula feeding. ^{(Ribeiro 2012)}

Breastfeeding durations of up to 6 months are not associated with greater transmission of HTLV-1 than feeding with artificial formula: 4-6% ^{(Boostani 2018)}, while breastfeeding for longer than 7 months is associated with transmissions from 14% to 32% ^{(Boostani 2018, Rosadas 2019)}, which is why some authors suggest breastfeeding for a maximum of 6 months when socioeconomic conditions do not allow formula feeding in safe and sustainable conditions ^{(Rosadas 2019, Mylonas 2010)}; in these situations, recommendations to not breastfeed or suspend it should be carefully made on a case-by-case basis. ^{Gotuzzo 2004)}

Feeding with expressed breastmilk frozen at -12º overnight has been used to nullify transmission ^{(Ando 2004)}. Pasteurization also prevents transmission ^{(Carneiro 2014)}. Although there is no known treatment for HTLV-1, antiretroviral therapy could be tried to prevent transmission through breastfeeding. ^{(Leal 2015)}

See below the information of this related product:

• Human T-lymphotropic virus type 2 (HTLV-2) (Unsafe. Moderate/severe adverse effects. Compatible under certain circumstances. Follow-up recommended. Use safer alternative or discontinue breastfeeding from 5 to 7 T ½ . Read Commentary.)