Incidence of HTLV-I-Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) in Jamaica and Trinidad

Abstract

HTLV-I is sexually transmitted more efficiently from men to women than vice versa, and the majority of HTLV-I endemic areas report a female preponderance of HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) cases. The objective of this study was to estimate the gender- and age-specific incidence rates of HAM/TSP in the general population as well as in the HTLV-I-infected population in Jamaica and in Trinidad and Tobago. Incidence rates for HAM/TSP were computed based on all reported incident cases in both countries between 1990 and 1994. Population census reports for 1990 were used to calculate the population at risk. The age-standardized HAM/TSP incidence rate (mean +/- standard error of the mean) in Jamaica was 1.8 +/- 0.2/100,000 person years (PY). Among individuals of African descent in Trinidad and Tobago, the rate was 1.7 +/- 0.4/100,000 PY. As in HTLV-I seroprevalence, the incidence rate of HAM/TSP increased with age through the fifth decade of life and was three times as high in women than in men. The HAM/TSP incidence rate, calculated as a function of the number of HTLV-I-infected persons in each age stratum, is higher in women (24.7/100,000 PY) than in men (17.3/100,000 PY). With HTLV-I infection, the lifetime risk of developing HAM/TSP was estimated to be 1.9% overall and is slightly higher in women (1.8%) than in men (1.3%). Thus, the higher prevalence of HTLV-I in women in endemic areas does not fully explain the preponderance of female HAM/TSP, suggesting that other cofactors must be present. The higher incidence rate in women between the ages of 40 and 59 years, as well as the increase in HAM/TSP incidence rates with age, are indicative of the importance of adult-acquired HTLV-I infection, presumably through sexual transmission.

Global epidemiology of HTLV-I infection and associated diseases

“…Epidemiologic evidence suggests that sexual transmission of HTLV-I is the predominant mode of transmission leading to the later development of HAM/TSP. This contention is supported by the female predominance of HAM/TSP (Maloney et al, 1998) and by sexual activity at an earlier age and in higher frequency in HAM/TSP patients compared to matched HTLV-I carriers without HAM/TSP (Kramer et al, 1995). Rare cases, often with a short incubation period, have been reported after HTLV-I infection by blood transfusion (Osame et al, 1986a;Gout et al, 1990).…”

Evidence of Brain Inflammation in Patients with Human T-Lymphotropic Virus Type 1–Associated Myelopathy (HAM): A Pilot, Multimodal Imaging Study Using 11C-PBR28 PET, MR T1-Weighted, and Diffusion-Weighted Imaging

“…HTLV-1 is the etiologic agent of a progressive neurologic disease, HTLV-1-associated myelopathy (HAM) (2). HAM overtly affects 2%-4% of HTLV-1-infected persons at some point during this life-long infection (3,4), while subclinical disease is also reported (5). HAM is characterized clinically by several or all of the following: progressive spastic paraparesis, lumbar pain frequently radiating to legs, urinary symptoms, constipation, and impotence (6).…”

Human T-Cell Leukemia/Lymphoma Virus Type 1 p30, but Not p12/p8, Counteracts Toll-Like Receptor 3 (TLR3) and TLR4 Signaling in Human Monocytes and Dendritic Cells

“…It is currently estimated that 20 million people worldwide are HTLV-1 infected, but only a small percentage of them progress to disease, usually after long clinical latency. In fact, 3 to 5% of HTLV-1-infected individuals develop ATL and 0.3 to 2% develop TSP/ HAM, whereas the majority remain asymptomatic (3)(4)(5)(6)(7)(8)(9)(10). T cells have been considered the key target cells for HTLV-1 infection, as the virus is almost always present in the ATL cells and is found in the T cells of TSP/HAM patients.…”

“…PU.1 plays a critical role in cell activation and differentiation (24). Interestingly, PU.1 can interact with a variety of factors, including IRF4, ICSBP/IRF8, JUN, and NF-B, and promotes transcription of type 1 interferons (7,14,15,17,(23)(24)(25)(26). Therefore, PU.1 is involved in the signal transduction upon activation of different TLRs.…”