Abstract
BackgroundThe Human T Lymphotropic Virus type 1 (HTLV-1) subtype C is endemic to central Australia where each of the major sequelae of HTLV-1 infection has been documented in the socially disadvantaged Indigenous population. Nevertheless, available epidemiological information relating to HTLV-1c infection is very limited, risk factors for transmission are unknown and no coordinated program has been implemented to reduce transmission among Indigenous Australians. Identifying risk factors for HTLV-1 infection is essential to direct strategies that could control HTLV-1 transmission.MethodsRisk factors for HTLV-1 infection were retrospectively determined for a cohort of Indigenous Australians who were tested for HTLV-1 at Alice Springs Hospital (ASH), 1st January 2000 to 30th June 2013. Demographic details were obtained from the ASH patient management database and the results of tests for sexually transmitted infections (STI) were obtained from the ASH pathology database.ResultsAmong 1889 Indigenous patients whose HTLV-1 serostatus was known, 635 (33.6 %) were HTLV-1 Western blot positive. Only one of 77 (1.3 %) children tested was HTLV-1 infected. Thereafter, rates progressively increased with age (15–29 years, 17.3 %; 30–49 years, 36.2 %; 50–64 years, 41.7 %) reaching 48.5 % among men aged 50–64 years. In a multivariable model, increasing age (OR, 1.04; 95 % CI, 1.03–1.04), male gender (OR, 1.41; 95 % CI, 1.08–1.85), residence in the south (OR, 10.7; 95 % CI, 7.4–15.6) or west (OR, 4.4; 95 % CI, 3.1–6.3) of central Australia and previous STI (OR, 1.42; 95 % CI, 1.04–1.95) were associated with HTLV-1 infection. Infection was acquired by three of 351 adults who were tested more than once during the study period (seroconversion rate, 0.24 (95 % CI = 0.18–2.48) per 100 person-years).ConclusionsThis study confirms that HTLV-1 is highly endemic to central Australia. Although childhood infection was documented, HTLV-1 infection in adults was closely associated with increasing age, male gender and STI history. Multiple modes of transmission are therefore likely to contribute to high rates of HTLV-1 infection in the Indigenous Australian population. Future strategies to control HTLV-1 transmission in this population require careful community engagement, cultural understanding and Indigenous leadership.
Highlights
The Human T Lymphotropic Virus type 1 (HTLV-1) subtype C is endemic to central Australia where each of the major sequelae of HTLV-1 infection has been documented in the socially disadvantaged Indigenous population
The HTLV-1 serostatus was known for a total of 1889 patients of whom 1254 were HTLV-1 seronegative and 635 were HTLV-1 infected (HTLV-1 Western blot positive, 629; HTLV-1 Western blot indeterminate/HTLV-1 polymerase chain reaction (PCR) positive, 6) (Fig. 2)
Complicated strongyloidiasis and was subsequently found to be HTLV-1 infected when he presented with respiratory failure complicating multi-lobar bronchiectasis
Summary
The Human T Lymphotropic Virus type 1 (HTLV-1) subtype C is endemic to central Australia where each of the major sequelae of HTLV-1 infection has been documented in the socially disadvantaged Indigenous population. The Human T Lymphotropic Virus type 1 (HTLV-1) is an oncogenic retrovirus that preferentially infects CD4+ T cells [1]. At least 5–10 million HTLV-1 infected people reside in clusters of high endemicity worldwide [2]. One such endemic focus is present in central Australia where infection with the Australo-Melanesian HTLV-1 subtype C is prevalent [3]. The virus is closely cell associated and transmission typically follows exposure to infected lymphocytes in blood, through breast-feeding or sexual intercourse [1]. Infection rates generally increase with age, among women who are thought to be at greatest risk of sexual transmission [1]
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