Epidemiological aspects of retrovirus (HTLV) infection among Indian populations in the Amazon Region of Brazil

Abstract

HTLV was initially described in association with a form of leukemia in Japan and a neurological disease in the Caribbean. It was soon shown that HTLV-II was endemic among Amerindians and particularly among Brazilian Indians. The Amazon Region of Brazil is presently the largest endemic area for this virus and has allowed several studies concerning virus biology, the search for overt disease, epidemiological data including detailed demographic data on infected individuals, clear-cut geographic distribution, definition of modes of transmission and maintenance within small, epidemiologically-closed groups, and advances in laboratory diagnosis of the infection. A new molecular subtype named HTLV-IIc was further described on the basis of genome sequencing and phylogenetic analysis. This subtype is present in other areas of Brazil, indicating that the virus is additionally both a valuable marker for tracing past human migration routes in the Americas and a probable marker for social habits of the present human population. HIV, the other human retrovirus, is still not prevalent among indigenous communities in the Brazilian Amazon, but these groups are also easy targets for the virus.

Identification of human T-cell lymphotropic virus infection in a semi-isolated Afro-Brazilian quilombo located in the Marajó Island (Pará, Brazil)

“…Regarding our previous study that did not identified HTLV-1 infection in other Amazonian populations composed by descendents of African slaves (Ishak et al 2003), the current results represent the first report of HTLV-1 infection in a mocambo located in the Brazilian Amazon region. Furthermore, the presence of HTLV-1 in this geographical area is of paramount importance because of the previous description of a cluster of cases of TSP/HAM in two individuals residing in Cachoeira do Arari county, Marajó Island (Ishak et al 2002).…”

“…HTLV-1 is endemic worldwide and HTLV-2 infection has been shown to be endemic in native American Indian populations (Hall et al 1992, Ishak et al 1995. In Brazil, particularly in the Amazon region, HTLV-1 and HTLV-2 infections have been found among urban and rural populations with relevant endemicity (Ishak et al 1995, 2003, Vallinoto et al 1998). The molecular epidemiology has been well established concernig HTLV-2 infection and it has shown the occurrence of a new molecular subtype named HTLV-2c (Ishak et al 1995).…”

Sexual transmission of human T-cell lymphotropic virus type 1

“…HTLV-2 is prevalent in native populations, such as indigenous peoples in the Americas and Pygmy tribes in Africa, and in intravenous drug users [15][16][17][18][19] . Despite a 65% homology with HTLV-1, HTLV-2 has not been consistently associated with human disease; however, neurological disorders similar to HAM/TSP have been observed in patients with HTLV-2 infection 15,20 .…”

Confirming the presence of HTLV-1 infection and the absence of HTLV-2 in blood donors from Arequipa, Peru

“…Curiously, HTLV-1 is also endemic among Amerindians in Peru, a population thought to be infected with HTLV-2 in several countries of Latin America 7,13,19,22 . Nevertheless, HTLV-2 was only detected in two Peruvian Amazonian Indians and in several MSM from Peru 19,28 .…”