Silent dissemination of HTLV-1 in an endemic area of Argentina. Epidemiological and molecular evidence of intrafamilial transmission

BACKGROUND Molecular and epidemiological studies of transmission routes and risk factors for infection by HTLV-1 are extremely important in order to implement control measures, especially because of the high prevalence of HTLV-1 in several regions of the world. San Salvador de Jujuy, Northwest Argentina, is a highly endemic area for HTLV-1 and foci of tropical spastic paraparesis/HTLV-1-associated myelopathy. OBJECTIVE To gain further insight into the role of intrafamilial transmission of HTLV-1 in a highly endemic region in Argentina. METHOD Cross-sectional study in Northwest Argentina. Epidemiological data and blood samples were collected from 28 HTLV-1 infected subjects (index cases) and 92 close relatives/cohabitants. HTLV-1 infection was diagnosed by detection of antibodies and proviral DNA. The LTR region was sequenced and analyzed for genetic distances (VESPA software), in addition to determination and identification of polymorphisms to define HTLV-1 family signatures. RESULTS Fifty seven of the 120 subjects enrolled had antibodies against HTLV-1 and were typified as HTLV-1 by PCR. The prevalence rate of HTLV-1 infection in family members of infected index cases was 31.52% (29/92). The infection was significantly associated with gender, age and prolonged lactation. Identity of LTR sequences and presence of polymorphisms revealed high prevalence of mother-to-child and interspousal transmission of HTLV-1 among these families. CONCLUSION There is an ongoing and silent transmission of HTLV-1 through vertical and sexual routes within family clusters in Northwest Argentina. This evidence highlights that HTLV-1 infection should be considered as a matter of public health in Argentina, in order to introduce preventive measures as prenatal screening and breastfeeding control.