HTLV-1 is rare in Far North Queensland despite a significant burden of classically associated diseases

Human T-cell leukaemia virus type 1 and Adult T-cell leukaemia/lymphoma in Queensland, Australia: a retrospective cross-sectional study

OBJECTIVES

Human T-cell leukaemia virus type 1 (HTLV-1), an STI, is reported to be highly prevalent in Indigenous communities in Central Australia. HTLV-1 is an incurable, chronic infection which can cause Adult T-cell leukaemia/lymphoma (ATL). ATL is associated with high morbidity and mortality, with limited treatment options. We studied the prevalence of HTLV-1 and ATL in the state of Queensland, Australia.

METHODS

Serum samples stored at healthcare services in Brisbane, Townsville and Cairns and at haemodialysis units in Brisbane (2018-2019) were screened for HTLV-1/2 antibodies using the Abbott ARCHITECT chemiluminescent microparticle immunoassay (CMIA) for antibodies against gp46-I, gp46-II and GD21 (Abbott CMIA, ARCHITECT). Reactive samples were confirmed through Western blot. Pooled Australian National Cancer Registry surveillance data reporting on cases coded for ATL (2004-2015) were analysed.

RESULTS

Two out of 2000 hospital and health services samples were confirmed HTLV-1-positive (0.1%, 95% CI 0.02% to 0.4%), both in older women, one Indigenous and one non-Indigenous. All 540 haemodialysis samples tested negative for HTLV. All samples were HTLV-2-negative. Ten out of 42 (24.8%) reported cases of ATL in Australia were from Queensland (crude incidence rate 0.025/100 000; 95% CI 0.011 to 0.045); most cases were seen in adult men of non-Indigenous origin. Nineteen deaths due to ATL were recorded in Australia.

CONCLUSION

We confirm that HTLV-1 and ATL were detected in Queensland in Indigenous and non-Indigenous people. These results highlight the need for HTLV-1 prevalence studies in populations at risk of STIs to allow the implementation of focused public health sexual and mother-to-child transmission prevention strategies.

Melioidosis-a disease of socioeconomic disadvantage

BACKGROUND

There is growing recognition of the contribution of the social determinants of health to the burden of many infectious diseases. However, the relationship between socioeconomic status and the incidence and outcome of melioidosis is incompletely defined.

METHODS

All residents of Far North Queensland, tropical Australia with culture-proven melioidosis between January 1998 and December 2020 were eligible for the study. Their demographics, comorbidities and socioeconomic status were correlated with their clinical course. Socioeconomic status was determined using the Socio-Economic Indexes for Areas (SEIFA) Index of Relative Socio-economic Disadvantage score, a measure of socioeconomic disadvantage developed by the Australian Bureau of Statistics. Socioeconomic disadvantage was defined as residence in a region with a SEIFA score in the lowest decile in Australia.

RESULTS

321 eligible individuals were diagnosed with melioidosis during the study period, 174 (54.2%) identified as Indigenous Australians; 223/321 (69.5%) were bacteraemic, 85/321 (26.5%) required Intensive Care Unit (ICU) admission and 37/321 (11.5%) died. 156/321 (48.6%) were socioeconomically disadvantaged, compared with 56603/269002 (21.0%) of the local general population (p<0.001). Socioeconomically disadvantaged patients were younger, more likely to be female, Indigenous, diabetic or have renal disease. They were also more likely to die prior to hospital discharge (26/156 (16.7%) versus 11/165 (6.7%), p = 0.002) and to die at a younger age (median (IQR) age: 50 (38-68) versus 65 (59-81) years, p = 0.02). In multivariate analysis that included age, Indigenous status, the presence of bacteraemia, ICU admission and the year of hospitalisation, only socioeconomic disadvantage (odds ratio (OR) (95% confidence interval (CI)): 2.49 (1.16-5.35), p = 0.02) and ICU admission (OR (95% CI): 4.79 (2.33-9.86), p<0.001) were independently associated with death.

CONCLUSION

Melioidosis is disease of socioeconomic disadvantage. A more holistic approach to the delivery of healthcare which addresses the social determinants of health is necessary to reduce the burden of this life-threatening disease.

The temporospatial epidemiology of rheumatic heart disease in Far North Queensland, tropical Australia 1997-2017; impact of socioeconomic status on disease burden, severity and access to care

Background

The incidence of rheumatic heart disease (RHD) among Indigenous Australians remains one of the highest in the world. Many studies have highlighted the relationship between the social determinants of health and RHD, but few have used registry data to link socioeconomic disadvantage to the delivery of patient care and long-term outcomes.

Methods

A retrospective study of individuals living with RHD in Far North Queensland (FNQ), Australia between 1997 and 2017. Patients were identified using the Queensland state RHD register. The Socio-Economic Indexes for Areas (SEIFA) Score–a measure of socioeconomic disadvantage–was correlated with RHD prevalence, disease severity and measures of RHD care.

Results

Of the 686 individuals, 622 (90.7%) were Indigenous Australians. RHD incidence increased in the region from 4.7/100,000/year in 1997 to 49.4/100,000/year in 2017 (p<0.001). In 2017, the prevalence of RHD was 12/1000 in the Indigenous population and 2/1000 in the non-Indigenous population (p<0.001). There was an inverse correlation between an area’s SEIFA score and its RHD prevalence (rho = -0.77, p = 0.005).

249 (36.2%) individuals in the cohort had 593 RHD-related hospitalisations; the number of RHD-related hospitalisations increased during the study period (p<0.001). In 2017, 293 (42.7%) patients met criteria for secondary prophylaxis, but only 73 (24.9%) had good adherence. Overall, 119/686 (17.3%) required valve surgery; the number of individuals having surgery increased over the study period (p = 0.02).

During the study 39/686 (5.7%) died. Non-Indigenous patients were more likely to die than Indigenous patients (9/64 (14%) versus 30/622 (5%), p = 0.002), but Indigenous patients died at a younger age (median (IQR): 52 (35–67) versus 73 (62–77) p = 0.013). RHD-related deaths occurred at a younger age in Indigenous individuals than non-Indigenous individuals (median (IQR) age: 29 (12–58) versus 77 (64–78), p = 0.007).

Conclusions

The incidence of RHD, RHD-related hospitalisations and RHD-related surgery continues to rise in FNQ. Whilst this is partly explained by increased disease recognition and improved delivery of care, the burden of RHD remains unacceptably high and is disproportionately borne by the socioeconomically disadvantaged Indigenous population.

Rheumatic heart disease (RHD), a disease of poverty and disadvantage, is almost completely preventable. It is now extremely rare in wealthy countries, but in Far North Queensland in tropical Australia, the incidence of RHD, RHD-related hospitalisations and RHD-related surgery is continuing to rise, with the burden of disease borne almost entirely by the region’s Indigenous population. While the increasing incidence of RHD and its complications may be partly explained by improvements in local service delivery, the disease remains inextricably linked to socioeconomic disadvantage. In this study, not only were patients living in socioeconomically disadvantaged areas more likely to have RHD, but they were also paradoxically less likely to receive valve surgery. The current local model of care—which is centralised, medical and emphasises disease monitoring and secondary prophylaxis—appears to be having a limited impact on morbidity. Strategies must evolve—in partnership with Indigenous communities—to have a greater focus on disease prevention by addressing the personal, community and environmental factors that increase the risk of the disease. This is likely to not only reduce the incidence of RHD, but will also tend to reduce the burden of the many other diseases that result from socioeconomic disadvantage and that disproportionately affect Indigenous Australians.

Echocardiographic Screening Detects Rheumatic Heart Disease and Missed Opportunities in the Treatment of Group A Streptococcal Infections in Australian Torres Strait Islander Children

Rheumatic heart disease (RHD) is almost entirely preventable, but the incidence in indigenous Australians remains one of the highest in the world. A community-based echocardiogram screening program of 862 Torres Strait Islander children identified 25 (2.9%) new cases of RHD. Among these 25 children, 5/7 (71%) prior acute rheumatic fever presentations had not been recognized. There was a history of microbiologically confirmed group A Streptococcus infection in 17/25 (68%) children with RHD compared with 9/25 (36%) controls (odds ratio [OR] [95% CI]: 3.78 [1.17-12.19], P = 0.03). This was more likely to be a skin swab (16/25 [64%] cases versus 6/25 [24%] controls) than a throat swab (1/25 [4%] cases versus 3/25 [12%] controls) (OR [95% CI]: 5.33 [1.51-18.90] [P = 0.01]), supporting a role for skin infection in RHD pathogenesis. Household crowding and unemployment were common in the cohort, emphasizing the need for prioritizing strategies that address the social determinants of health. This study explores the burden of rheumatic heart disease diagnosed during an echocardiogram screening program in the Torres Strait Islands in tropical Australia and highlights the importance of primordial and primary prevention.

HTLV-I and Strongyloides in Australia: The worm lurking beneath

Strongyloidiasis and HTLV-I (human T-lymphotropic virus-1) are important infections that are endemic in many countries around the world with an estimated 370 million infected with Strongyloides stercoralis alone, and 5-10 million with HTVL-I. Co-infections with these pathogens are associated with significant morbidity and can be fatal. HTLV-I infects T-cells thus causing dysregulation of the immune system which has been linked to dissemination and hyperinfection of S. stercoralis leading to bacterial sepsis which can result in death. Both of these pathogens are endemic in Australia primarily in remote communities in Queensland, the Northern Territory, and Western Australia. Other cases in Australia have occurred in immigrants and refugees, returned travellers, and Australian Defence Force personnel. HTLV-I infection is lifelong with no known cure. Strongyloidiasis is a long-term chronic disease that can remain latent for decades, as shown by infections diagnosed in prisoners of war from World War II and the Vietnam War testing positive decades after they returned from these conflicts. This review aims to shed light on concomitant infections of HTLV-I with S. stercoralis primarily in Australia but in the global context as well.

Human T-cell lymphotropic virus type-1: a lifelong persistent infection, yet never truly silent

Human T-cell lymphotropic virus type-1 (HTLV-1) has a large global burden and in some key communities, such as Indigenous Australians living in remote areas, greater than 45% of people are infected. Despite HTLV-1 causing serious malignancy and myelopathic paraparesis, and a significant association with a range of inflammatory comorbidities and secondary infections that shorten lifespan, few biomedical interventions are available. HTLV-1 starkly contrasts with other blood-borne sexually transmitted viral infections, such as, HIV, hepatitis B virus, and hepatitis C virus, with no antiviral treatments that reduce virus-infected cells, no rapid diagnostics or biomarker assays suitable for use in remote settings, and no effective vaccine. We review how the replication strategies and molecular properties of HTLV-1 establish a long-term stealthy viral pathogenesis through a fine-tuned balance of persistence, immune cell dysfunction, and proliferation of proviral infected cells that collectively present robust barriers to treatment and prevention. An understanding of the nature of the HTLV-1 provirus and opposing actions of viral-coded negative-sense HBZ and positive-sense regulatory proteins Tax, p12 and its cleaved product p8, and p30, is needed to improve the biomedical tools for preventing transmission and improving the long-term health of people with this lifelong infection.

Rapid Progress toward Elimination of Strongyloidiasis in North Queensland, Tropical Australia, 2000-2018

Infection with Strongyloides stercoralis can cause life-threatening disease in immunocompromised patients. Strongyloidiasis is thought to be hyper-endemic in tropical Australia, but there are limited contemporary seroprevalence data to inform local elimination strategies. To define the temporospatial epidemiology of strongyloidiasis in Far North Queensland, tropical Australia, the serology results of 2,429 individuals tested for the infection between 2000 and 2018 were examined. The proportion of positive tests fell from 36/69 (52.2%) in 2000 to 18/222 (8.1%) in 2018 (P < 0.001). Indigenous patients were more likely to have a positive result (Odds Ratio [OR]: 3.9, 95% CI: 3.0-5.0); however, by the end of the study period, residence in a rural or remote location (OR 3.9 (95% CI: 1.2-13.0), P = 0.03) was a more important risk factor for seropositivity than Indigenous status (OR 1.1 (95% CI: 0.4-3.1) P = 0.91). Ivermectin prescription data were available for the period 2004-2018, with annual prescriptions increasing from 100 to 185 boxes (P = 0.01). The volume of ivermectin dispensed correlated negatively with seropositivity (Spearman's rho = -0.62, P = 0.02). An expanded environmental health program was implemented during the study period and likely contributed to the declining seroprevalence; however, the relative contributions of the individual components of this program are difficult to quantify. The seroprevalence of strongyloidiasis has declined markedly in this region of tropical Australia despite there being no targeted campaign to address the disease. Expanded prescription of ivermectin and public health interventions targeting the few remaining high-prevalence communities would be expected to expedite disease elimination.