HTLV seroepidemiology in a central African population with high incidence of tropical spastic paraparesis

In Lisala (Equateur region, Zaire), where a cluster of tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM) was described, 28/200 (14%) out-patients and hospital personnel were HTLV antibody positive. No differences in prevalences were observed between out-patients and hospital personnel or between ethnic groups. The annual attack rate of TSP/HAM is estimated at 0.15-0.3 per 1000 infected. The ethnic and familial clustering of TSP/HAM together with the high attack rate suggests the presence of co-factors for the progression to disease. This high prevalence of HTLV antibodies contrasts with the low prevalence in another part of the Equateur region.