The challenge of describing the epidemiology of HTLV in the Amazon region of Brazil

Abstract

HTLV-1 was the first described human retrovirus and was soon found to be associated with severe clinical diseases, including a devastating lymphoma/leukemia and other inflammatory diseases. Although HTLV-2 is not usually pathogenic, it is widely distributed among native Indian populations in Brazil, particularly in the Amazon region of the country. Presently, HTLV spreads mainly by the sexual route and from mother to child, and virus persistence is an active biological factor aiding its transmission. Recently, the use of illicit drugs has been shown to be an additional risk factor, showing the influence of new habits on the epidemiology of HTLV in the region. Despite the detection of the virus in several different populations in the Amazon region of Brazil for almost 30 years, the exact prevalence of HTLV-1/2 is not well defined. The original biases in sampling and the selection of epidemiologically unsuitable populations were commonly repeated in most prevalence studies, generating unreliable and conflicting figures that do not represent the actual prevalence of HTLV. The improvements in clinical and laboratory facilities have resulted in the description of several clinical manifestations that were previously unknown in the region. The extent of the spread of the virus must be defined in this region, which is the largest geographical area of the country. As prophylaxis advances toward the use of vaccines against HTLV-1, it is important to determine who is at risk of being infected and developing a disease to successfully implement preventive measures, particularly as proposals are made to eradicate the virus among humans.

Molecular Epidemiology of HIV-1 and HTLV-1/2 Among Female Sex Workers in Four Cities in the State of Para, Northern Brazil

“…It is possible that such a figure is a consequence of the higher level of risky behavior, such as injecting drug use and multiple sexual partners. Co-infections with the two viruses were not observed, unlike previous investigations with HIV-1-infected persons in the states of Para and Amapa, in which HTLV-1 and HTLV-2 co-infections were detected ( Vallinoto et al, 1998 ; Laurentino et al, 2005 ; Ishak et al, 2020 ). This indicates a low prevalence of co-infections among FSWs in the North region of Brazil.…”

“…The investigation of HTLV-1/2 infections among FSWs is the first approach in Amazon Region of Brazil, particularly in a highly endemic area of HTLV infection ( Ishak et al, 2020 ). The present study observed a higher general seroprevalence of HTLV-1 than those reported in the population of men who have sex with men (0.7%) ( Malta et al, 2010 ); candidates for blood donation in the Northeast of Brazil (1.2%) ( Ribeiro et al, 2018 ), the Brazilian state of Amazonas (0.13%) ( Morais et al, 2017 ) and in non-FSW women who had a similar socioeconomic profile, such as pregnant teenagers (0.6%) ( Guerra et al, 2018 ) and women from Belém, Pará (1.4%) ( Silva et al, 2018 ) and parturients (0.4%) of Salvador, Bahia ( Vargas et al, 2020 ).…”

“…HIV-1 subtypes B and F1 and BF1 recombinant were detected, as well as a high prevalence of transmitted drug resistant mutations (47.6%) ( da Costa et al, 2020 ). Although HTLV-1/2 infections are endemic in the State of Para and associated with risky sexual behavior ( Oliveira-Filho et al, 2019a ; Ishak et al, 2020 ), to date, there have been no epidemiological investigations of the virus among FSWs.…”

Prevalence and evolutionary analyses of human T-cell lymphotropic virus in Guangdong province, China: Transcontinental and Japanese subtype lineages dominate the prevalence

“…HTLV-1 is mainly prevalent in the Caribbean, South and Central America, Central and Western Africa, Southwestern Japan, Australia and Melanesia[ 4 ]. HTLV-2 has a more restricted distribution than HTLV-1, and is predominately prevalence among some Native Americans and Central African tribes.…”

HTLV in South America: Origins of a silent ancient human infection

“…Understanding the epidemiology of HTLV-1 and HTLV-2 is a key factor in explaining the origin of the viruses worldwide, particularly in South America and Brazil. Unfortunately, epidemiological information is sometimes old, with conflicting results, and consequently, it is not useful for defining appropriate measures for prevention and control and thus needs to be improved ( Ishak, Guimarães Ishak, and Vallinoto 2020 ). This information is useful for detecting the occurrence and frequency of the viruses in order to determine the pathways through which the virus moves and the possible routes for future spread.…”