Seroepidemiology of human T cell lymphotropic virus in the Republic of Panama.

The human T-lymphotropic virus (HTLV) and associated diseases, adult T cell leukemia and spastic paraparesis, appear to be endemic in southwestern Japan and the Caribbean. This cross-sectional population-based study was conducted to describe the seroepidemiology of HTLV in the Republic of Panama. HTLV antibody was measured by first generation and commercial ELISA tests and confirmed by competitive binding ELISA, a radioimmunoassay for anti-p 24, and Western blot. Of 3,231 subjects greater than or equal to 15 years of age, 135 (4.2%) had antibody detected in ELISA screening tests, but because only 20% were confirmed positive, HTLV seroprevalence varied from 0.2-2% throughout the Republic. Infection with HTLV clustered in Guaymi Indians living in Bocas del Toro province (9.9% prevalence rate). With the exception of Guaymi Indians, no major geographic, urban/rural, male/female or racial differences in antibody prevalence were observed; specifically, HTLV infection rates were not elevated in black Panamanians. Clustering of infection in an isolated Amerind population must be further investigated. The small proportion of screen-positive sera which confirmed positive illustrates the importance of strict uniform criteria for seropositivity.

Human T-cell leukemia virus-I and hematologic malignancies in Panama.

Serum samples were obtained in a 2-year period (November 1, 1984-December 31, 1986) from 136 Panamanian patients with hematologic malignancies identified by a population-based registry designed for studies investigating human T-cell lymphotropic virus (HTLV)-I. Only three patients had clinical and serologic findings of HTLV-I-associated adult T-cell leukemia/lymphoma (ATLL). The authors conclude that although classical HTLV-I-associated ATLL occurs in the Panamanian population, it is not as prevalent as in other Caribbean populations.

Geographic distribution of HTLV-I and identification of a new high-risk population.

Epidemiologic studies indicate that human T-cell lymphotropic virus type I (HTLV-I), the causative agent of most cases of adult T-cell leukemia/lymphoma (ATLL) in Southeast Japan and the Caribbean islands and the probable cause of a progressive neurological disorder often referred to as tropical spastic paraparesis, occurs with unusual geographic clustering. The current large-scale serosurvey was undertaken to improve our understanding of HTLV-I prevalence in different parts of the world. We analyzed 43,445 serum samples collected from various geographic locales worldwide; 76% of these sera came from clinically healthy donors. Samples were initially screened by an enzyme-linked immunosorbent assay (ELISA) and 4,353 were further evaluated by means of competition assays. In this study, which did not include sera from endemic areas of Japan, a high prevalence of infection was observed in several countries in the Caribbean basin. A significant age-sex difference was observed between populations in the Caribbean and non-endemic regions of Japan. The reason for the male excess in non-endemic areas of Japan will require further study, while the female excess in the Caribbean basin is compatible with the previously described pattern for other HTLV-I-endemic areas. A newly recognized area of possible endemicity was southern Florida, where evidence of infection with HTLV-I or a related virus was found in a group of native Americans whose sera were collected in 1968. In certain parts of the world, particularly sub-Saharan Africa, important problems in determining specificity of reactivity occurred, probably because of cross-reacting antibodies. No pattern was detected that could explain the cross-reactivity solely on the basis of geographic areas, specific patterns of non-viral parasitic infection, or methods of handling the specimens. It is possible that these cross-reactivities are antibodies to proteins from HTLV-I-related retroviruses yet to be discovered.

Transmission of HTLV-I and HIV among homosexual men in Trinidad.

Risk for human T-cell lymphotropic virus type (HTLV-I) and human immunodeficiency virus (HIV) infection was evaluated in 100 homosexual or bisexual men from Trinidad. High seropositivity for HTLV-I (15% vs 2.4% in the general population) was linked to duration of homosexuality and numbers of partners, suggesting that HTLV-I, like HIV, can be transmitted by homosexual sex. Forty percent of homosexuals compared with 0.19% of the general population were seropositive for HIV, and sexual contact with US homosexual men and prior history of gonorrhea were major risk factors. The seroprevalence of HIV was three times higher than that for HTLV-I, suggesting that HIV is more efficiently transmitted, especially since HIV appears to have been recently introduced into Trinidad. Altered immune status was prominent in individuals infected with HIV and coinfected with HIV and HTLV-I. Whether HIV/HTLV-I coinfection amplifies clinical effects is a hypothesis that will require further evaluation.