Health economic implications of testing blood donors in South Africa for HTLV 1 & 2 infection

Geographic distribution, clinical epidemiology and genetic diversity of the human oncogenic retrovirus HTLV-1 in Africa, the world's largest endemic area

The African continent is considered the largest high endemic area for the oncogenic retrovirus HTLV-1 with an estimated two to five million infected individuals. However, data on epidemiological aspects, in particular prevalence, risk factors and geographical distribution, are still very limited for many regions: on the one hand, few large-scale and representative studies have been performed and, on the other hand, many studies do not include confirmatory tests, resulting in indeterminate serological results, and a likely overestimation of HTLV-1 seroprevalence. For this review, we included the most robust studies published since 1984 on the prevalence of HTLV-1 and the two major diseases associated with this infection in people living in Africa and the Indian Ocean islands: adult T-cell leukemia (ATL) and tropical spastic paraparesis or HTLV-1-associated myelopathy (HAM/TSP). We also considered most of the book chapters and abstracts published at the 20 international conferences on HTLV and related viruses held since 1985, as well as the results of recent meta-analyses regarding the status of HTLV-1 in West and sub-Saharan Africa. Based on this bibliography, it appears that HTLV-1 distribution is very heterogeneous in Africa: The highest prevalences of HTLV-1 are reported in western, central and southern Africa, while eastern and northern Africa show lower prevalences. In highly endemic areas, the HTLV-1 prevalence in the adult population ranges from 0.3 to 3%, increases with age, and is highest among women. In rural areas of Gabon and the Democratic Republic of the Congo (DRC), HTLV-1 prevalence can reach up to 10-25% in elder women. HTLV-1-associated diseases in African patients have rarely been reported in situ on hospital wards, by local physicians. With the exception of the Republic of South Africa, DRC and Senegal, most reports on ATL and HAM/TSP in African patients have been published by European and American clinicians and involve immigrants or medical returnees to Europe (France and the UK) and the United States. There is clearly a huge underreporting of these diseases on the African continent. The genetic diversity of HTLV-1 is greatest in Africa, where six distinct genotypes (a, b, d, e, f, g) have been identified. The most frequent genotype in central Africa is genotype b. The other genotypes found in central Africa (d, e, f and g) are very rare. The vast majority of HTLV-1 strains from West and North Africa belong to genotype a, the so-called 'Cosmopolitan' genotype. These strains form five clades roughly reflecting the geographic origin of the infected individuals. We have recently shown that some of these clades are the result of recombination between a-WA and a-NA strains. Almost all sequences from southern Africa belong to Transcontinental a-genotype subgroup.

Health state utility values in people living with HTLV-1 and in patients with HAM/TSP: The impact of a neglected disease on the quality of life

BACKGROUND

HTLV-1 is a neglected sexually transmitted infection despite being the cause of disabling neurological disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). There is no treatment for this infection and public health policies are essential to reduce its transmission. However, there are no data to support adequate cost-effective analysis in this field. The aim of this study was to obtain health state utility values for individuals with HAM/TSP and HTLV-1 asymptomatic carriers (AC). The impact of both states on quality of life (QoL) is described and compared to other diseases.

METHODS

A cross-sectional observational study of 141 individuals infected with HTLV-1 (79 with HAM/TSP and 62 AC) from three Brazilian states (Rio de Janeiro, São Paulo and Alagoas) and from the United Kingdom. Participants completed a validated general health questionnaire (EQ-5D, Euroqol) from which country specific health state utility values are generated. Clinical and epidemiological data were collated.

PRINCIPAL FINDINGS

Health state utility value for HAM/TSP was 0.2991. QoL for 130 reported clinical conditions ranges from 0.35 to 0.847. 12% reported their quality of life as worse as death. Low QoL was associated with severity rather than duration of disease with a moderate inverse correlation between QoL and Osame's Motor Disability Score (-0.4933) Patients who are wheelchair dependent had lowest QoL whilst those still walking unaided had the highest. AC also reported impaired QoL (0.7121) compared to general population.

CONCLUSION

HTLV-1 and its associated neurological disease has a marked impact on QoL. This study provides robust data to support the development of cost-utility analysis of interventions for HTLV-1.

High prevalence of human T-cell leukemia virus type-1b genotype among blood donors in Gabon, Central Africa

BACKGROUND

The African continent is considered to be the largest endemic area of HTLV‐1 infection, with at least several million infected individuals. Systematic screening of blood donors can prevent the transmission of HTLV‐1 in blood. Gabon is one of the countries with the highest prevalence of HTLV‐1 worldwide, and yet the routine testing of blood donors has still not been introduced.

METHODS

All blood donations collected between April and July 2017 at the Centre National de Transfusion Sanguine of Gabon were studied. Plasma samples were screened by ELISA for the presence of HTLV‐1/2 antibodies. Western blot (WB) and polymerase chain reaction (PCR) tests were used for confirmation.

RESULTS

In total, 3123 blood donors were tested, including 1740 repeat and 1378 first‐time blood donors (FTBDs). Of them, 132 samples tested positive for HTLV‐1/2 by ELISA (4.2%). WB and PCR confirmed HTLV‐1 infection for 23 individuals. The overall prevalence of HTLV‐1 was 0.74% [95% CI 0.47%‐1.10%], 1% in FTBD, and 0.5% in repeat donors. Age and sex‐adjusted prevalence was five‐fold lower in FTBD than in the general adult population of rural areas of Gabon. All detected HTLV‐1 strains belonged to the central African HTLV‐1b genotype but were highly diverse.

CONCLUSION

We report an overall prevalence of HTLV‐1 of 0.74%, one of the highest values reported for blood donors in Africa. Given the high risk of HTLV‐1 transmission in blood, it is necessary to conduct cost‐effectiveness studies to determine the need and feasibility of implementing screening of HTLV‐1 in blood donors in Gabon.