Transmission of STLV in a closed colony of macaques

A 3.3% seroprevalence of simian T-lymphotropic virus (STLV) was found in a closed breeding and research colony of rhesus and cynomolgus macaques in Thailand. Epidemiology of STLV within the colony was assessed by means of a retrospective analysis of banked and freshly collected serum samples, and a review of the animals' medical records. Evidence was found that the virus had been imported into the colony by some of the original animals, and was subsequently transmitted both vertically and horizontally. The cell-associated nature of STLV was demonstrated by iatrogenic transmission of the virus following a whole blood transfusion, but there was no transmission to animals that received only serum from the same infected donor. Transmission by all routes was infrequent, as indicated by the overall seroprevalence of 3.3% (14 of 420 samples) after the colony had been closed for 11 years. Maternal-infant transmission appeared to be < 12%.