A case-control study of risk factors associated with human T-cell lymphotrophic virus type-I seropositivity in blood donors from Guadeloupe, French West Indies

How do socioeconomic determinants of health affect the likelihood of living with HTLV-1 globally? A systematic review with meta-analysis

Introduction

Human T Lymphotropic Virus type 1 (HTLV-1) is a neglected retrovirus associated with many clinical disorders, most notably Adult T-cell Leukemia/Lymphoma and HTLV-1-Associated Myelopathy (HAM). Found in endemic clusters across the world, high prevalence has been reported in minoritized groups who suffer from health inequities. This study investigates the association between HTLV-1 prevalence and the following socioeconomic determinants of health: education, income, and employment, which are markers of health inequity.

Methods

A systematic review was conducted by searching the following databases: Ovid/Medline, Embase, Global Health Database, Web of Science, LILACS and SciELO. Primary studies in English, Spanish and Portuguese mentioning HTLV-1 and one of education, income and/or employment were included. A random-effects meta-analysis was performed, and odds ratios (OR) were calculated to determine the association between these socioeconomic determinants of health and HTLV-1 prevalence.

Results

42 studies were included. The likelihood of having HTLV-1 was higher in individuals with less than completed primary education compared to those who completed primary education (OR 1.86 [95% CI 1.34-2.57]; p < 0.01). This may be because individuals with low education have reduced access to and understanding of health information, thus increasing the prevalence of risk factors associated with HTLV-1 infection. No other determinants were found to be statistically significant.

Conclusion

Fewer years of schooling are associated with increased likelihood of contracting HTLV-1. Therefore, health promotion materials and public health policies regarding HTLV-1 must consider those with lower educational levels to effectively reduce disease transmission.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=335004, identifier (CRD42022335004).

Clinical and Public Health Implications of Human T-Lymphotropic Virus Type 1 Infection

Human T-lymphotropic virus type 1 (HTLV-1) is estimated to affect 5 to 10 million people globally and can cause severe and potentially fatal disease, including adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The burden of HTLV-1 infection appears to be geographically concentrated, with high prevalence in discrete regions and populations. While most high-income countries have introduced HTLV-1 screening of blood donations, few other public health measures have been implemented to prevent infection or its consequences. Recent advocacy from concerned researchers, clinicians, and community members has emphasized the potential for improved prevention and management of HTLV-1 infection. Despite all that has been learned in the 4 decades following the discovery of HTLV-1, gaps in knowledge across clinical and public health aspects persist, impeding optimal control and prevention, as well as the development of policies and guidelines. Awareness of HTLV-1 among health care providers, communities, and affected individuals remains limited, even in countries of endemicity. This review provides a comprehensive overview on HTLV-1 epidemiology and on clinical and public health and highlights key areas for further research and collaboration to advance the health of people with and at risk of HTLV-1 infection.

HTLV-1 and Co-infections

Human T lymphotropic virus type 1 (HTLV-1) is a retrovirus that causes lifelong T-cell infection in humans, impacting the host immune response. This virus causes a range of clinical manifestations, from inflammatory conditions, including neuronal damage (HTLV-1 associated myelopathy, HAM) to life-threatening leukemia (adult T-cell leukemia, ATL). Human T lymphotropic virus type 1 is also associated with increased risk of all-cause mortality, but the mechanisms remain unclear. As a blood-borne and sexually transmitted infection (STI), HTLV-1 shares transmission routes to many other pathogens and although it has worldwide distribution, it affects mainly those in low- and middle-income tropical areas, where the prevalence of other infectious agents is high. These factors contribute to a high incidence of co-infections in people living with HTLV-1 (PLHTLV). This comprehensive review addresses the impact of HTLV-1 on several co-infections and vice-versa. There is evidence of higher rates of HTLV-1 infection in association with other blood borne (HCV, HBV) and sexually transmitted (Syphilis, Chlamydia, HPV, HSV) infections but whether this represents increased susceptibility or opportunity is unclear. Higher frequency of Mycobacterium tuberculosis (MTb) and Mycobacterium leprae (M. leprae) is observed in PLHTLV. Reports of opportunistic infections and high frequency of crusted scabies in patients with HTLV-1 points to immune impairment in those individuals. Human T lymphotropic virus type 1 may influence the persistence of pathogens, exemplified by the higher rates of Schistosoma mansoni and Strongyloides stercoralis (St. stercoralis) treatment failure observed in PLHTLV. This retrovirus is also associated with increased tuberculosis (TB) severity with some evidence pointing to a deleterious impact on leprosy outcome as well. These findings are supported by immune alterations observed in those co-infected individuals. Although the role of HTLV-1 in HCV outcome is debatable, most data indicate that HTLV may negatively impact the clinical course of hepatitis C. Co-infections may also influence the risk of developing HTLV-1 associated disease, but data are still limited. The impact of HTLV-1 on the response to more common infections, might contribute to the increased mortality rate of HTLV-1. Large scale prospective controlled studies on the prevalence and impact of HTLV-1 in co-infections and vice-versa are needed. Human T lymphotropic virus type 1 impact in public health is broad. Measures to increase awareness and to prevent new infections are needed.

Human T-Lymphotropic Virus Type I (HTLV-1) Infection among Iranian Blood Donors: First Case-Control Study on the Risk Factors

Human T-cell lymphotropic virus type 1 (HTLV-1) infection is an endemic condition in Northeast Iran and, as such, identification of risk factors associated with the infection in this region seems to be a necessity. All the possible risk factors for HTLV-1 seropositivity among first-time blood donors were evaluated in Mashhad, Iran, during the period of 2011–2012. Blood donation volunteers were interviewed for demographic data, medical history, and behavioral characteristics and the frequencies of risk factors were compared between HTLV-1 positive (case) and HTLV-1 negative (control) donors. The data was analyzed using Chi square and t-tests. Logistic regression analysis was performed to identify independent risk factors for the infection. Assessments were carried out on 246 cases aged 17–60 and 776 controls aged 17–59, who were matched based on their ages, gender, and date and center of donation. Logistic analysis showed low income (OR = 1.53, p = 0.035), low educational level (OR = 1.64, p = 0.049), being born in the cities of either Mashhad (OR = 2.47, p = 0.001) or Neyshabour (OR = 4.30, p < 0001), and a history of blood transfusion (OR = 3.17, p = 0.007) or non-IV drug abuse (OR = 3.77, p < 0.0001) were significant predictors for infection with HTLV-1. Lack of variability or small sample size could be reasons of failure to detect some well-known risk factors for HTLV-1 infection, such as prolonged breastfeeding and sexual promiscuity. Pre-donation screening of possible risk factors for transfusion-transmissible infections should also be considered as an important issue, however, a revision of the screening criteria such as a history of transfusion for more than one year prior to donation is strongly recommended.

High prevalence of HTLV-I infection in Mashhad, Northeast Iran: a population-based seroepidemiology survey

BACKGROUND

Mashhad, in the northeast of Iran has been suggested as an endemic area for human T cell lymphotropic virus type I (HTLV-I) infection since 1996.

OBJECTIVES

We performed a community-based seroepidemiology study to examine the prevalence and risk factors for HTLV-I infection in the city of Mashhad.

STUDY DESIGN

Between May and September 2009, overall 1678 subjects from all the 12 geographical area of Mashhad were selected randomly by multistage cluster sampling for HTLV antibody. The study population included 763 males and 915 females, with the mean age of 29.1 ± 18.5 years. 1654 serum samples were assessed for HTLV antibody using ELISA and reactive samples were confirmed by Western blot and PCR.

RESULTS

The overall prevalence of HTLV-I infection in whole population was 2.12% (95% CI, 1.48-2.93) with no significant difference between males and females (p = 0.093) and the prevalence of HTLV-II seropositivity was 0.12% (95% CI, 0.02-0.44). The HTLV-I Infection was associated with age (p<0.001), marital status (p<0.001), education (p = 0.047), and history of blood transfusion (p = 0.009), surgery (p<0.001), traditional cupping (p = 0.002), and hospitalization (p = 0.004). In logistic regression analysis, age was the only variable that had a significant relation with the infection (p = 0.006, OR = 4.33).

CONCLUSIONS

Our results demonstrated that Mashhad still remains an endemic area for HTLV-I infection despite routine blood screening. Thus, further strategies are needed for prevention of the virus transmission in whole population.

[Sociodemographic, epidemiological and behavioral profile of women infected with HTLV-1 in Salvador, Bahia, an endemic area for HTLV]

The objective was to describe the sociodemographic, epidemiological and behavioral characteristics of women infected with HTLV-1 (64) and uninfected women (66) in Salvador, Bahia. The serological diagnosis was obtained via Elisa, Western Blot and Immunofluorescence. Epidemiological and sociodemographic data were collected using a standardized questionnaire. The chi-squared or Fisher test was used for categorical data and ANOVA or Kruskal-Wallis (3 groups) and the T-test or Mann-Whitney (2 groups) were used for continuous data. Associated variables were adjusted using logistic regression. More than half (57.8%) of the seropositive women were asymptomatic. The symptomatic women (with HAM/TSP) had fewer years of education. Comparison between seronegative and seropositive women showed that blood transfusion, anal sex practices, first sexual intercourse before the age of 18 years and three or more sexual partners over women's lifetime were risk factors for HTLV-1 infection. The prevention of both sexual transmission and vertical transmission (breastfeeding) should be reinforced. Prenatal screening is of paramount importance.

HTLV-I in the general population of Salvador, Brazil: a city with African ethnic and sociodemographic characteristics

The city of Salvador has the highest prevalence of HTLV-I among blood donors in Brazil. To study the prevalence of HTLV-I among the general population of Salvador, 30 "sentinel surveillance areas" were selected for the investigation of various infectious diseases, and 1385 individuals within these areas were surveyed according to a simple random sample procedure. ELISA was used to screen plasma samples for antibodies to HTLV-I, and the positive samples were tested by a confirmatory assay (Western blotting). The overall prevalence of HTLV-I was 1.76% (23/1385). Infection rates were 1.2% for males and 2.0% for females. Specific prevalence demonstrated an increasing linear trend with age. No one younger than 13 years of age was infected. Multivariate analysis estimated adjusted odds ratios for the association of HTLV-I with age of 9.7 (3.3; 30.4) for females and 12.3 (1.47; 103.1) for males. Less education and income might be associated with HTLV-I infection in females. Phylogenetic analysis of the long terminal repeat fragments showed that most of the samples belonged to the Latin American cluster of the Transcontinental subgroup (Cosmopolitan subtype). For the entire city of Salvador, it is estimated that approximately 40000 individuals are infected with HTLV-I. Our results suggest multiple post-Colombian introductions of African HTLV-Ia strains in Salvador.