Clustering of Human T Lymphotropic Virus Type I Seropositivity in Montserrat, West Indies: Evidence for an Environmental Factor in Transmission of the Virus

Abstract

A community survey of human T cell lymphotropic virus type I (HTLV-I) in Montserrat, West Indies, identified 22 instances in which 2 HTLV-I-seropositive adults lived within 60 m of each other (close pairs), compared with 7.8 expected (P < .001). Five of these close pairs were mother-offspring or husband-wife. The remaining 17 pairs were of unrelated members in separate households. The percentages of male-female (41%), female-female (41%), and male-male (18%) types in these 17 pairs were very similar to those among the 1377 similarly defined pairs in which neither or only 1 member was seropositive, affording no support for extramarital heterosexual activity as an explanation for the clustering observed. Thus, the demography of HTLV-I was not accounted for completely by sexual and mother-to-offspring transmission. The predominance of clustering of unrelated HTLV-I-seropositive individuals in locations with high mosquito infestation raised the possibility of sporadic transmission of HTLV-I by hematophagous insects.

Unusual space-time patterning of the Fallon, Nevada leukemia cluster: Evidence of an infectious etiology

“…Horse flies have been shown to transmit BLV in 10% of bites, through mechanical transmission [53]. Evidence also suggests that insect vector modes of transmission of HTLV1, a virus associated with T-cell leukemia, may occur in humans [54]. …”

Global epidemiology of HTLV-I infection and associated diseases

“…Although the biological mechanism of transmission still needs to be clarified, infected cells seem to be essential for transmission, whether the exposure to the virus is through blood, sexual contact or breastfeeding. HTLV-I endemic areas are in the tropics, infection trends to cluster among families and neighbors and a decline in seroprevalence are observed in subsequent generations of people migrating from endemic to nonendemic areas (Miller et al, 1994). These observations strongly suggest the presence of biological or social cofactors influencing HTLV-I transmission (Maloney et al, 1991).…”

Detection of a Major Gene Predisposing to Human T Lymphotropic Virus Type I Infection in Children among an Endemic Population of African Origin

“…Familial aggregation of HTLV-I-seropositive individuals in high endemic areas (Japan, Caribbean and South America) have been reported in many studies [5,9,[16][17][18], raising the problem of the distinction between shared familial exposure factors and genetic factors. Furthermore, mother-to-child transmission of HTLV-I occurs in only 10%-20% of the children born from infected mothers, despite a frequently similar exposure to HTLV-I infection [19,20].…”