Re-emergence of human T-lymphotropic viruses in West Africa

Abstract

Human T-lymphotropic viruses (HTLV) are Deltaretroviruses that infect millions of individuals worldwide via the same transmission routes as HIV. With the aim of exposing the possible re-emergence of HTLV in West Africa since discovery, a systematic review was carried out, focusing on the distribution of the virus types and significance of frequent indeterminate reports, while highlighting the need for mandatory routine blood screening. Capturing relevant data from discovery till date, sources searched were Google Scholar, CrossRef, NCBI (PubMed), MEDLINE, Research Gate, Mendeley, abstracts of Conferences and Proceedings, organization websites and reference lists of selected papers. A total of 2626 references were initially retrieved using search terms: Worldwide prevalence of HTLV, HTLV in Africa, HTLV in West Africa, HTLV subtypes, HTLV 3 and 4 in Africa, HTLV of African origin, HTLV seroindeterminate results, Spread of HTLV. These references were rigorously trimmed down to 76. Although evidence shows that HTLV is still endemic in the region, West Africa lacks recent epidemiological prevalence data. Thorough investigations are needed to ascertain the true cause of indeterminate Western Blot results. It is imperative that routine screening for HTLVs be mandated in West African health care facilities.

Prevalence of human T-lymphotropic virus 1/2 in Nigeria’s capital territory and meta-analysis of Nigerian studies

“…8 HTLV-1 subtypes are associated with specific regions of the globe, while HTLV-2 subtypes are related to highly specific subpopulations and behaviour like injection drug use. 8 This study seems to be the first report of HTLV-1/2 prevalence in both healthy and diseased study groups in FCT, Nigeria. A previous study 7 was limited to HIV-positive individuals.…”

“…Abuja is a cosmopolitan city and the capital of Nigeria, characterized by high level of ethno-cultural diversity; this could therefore be the reason for the zero prevalence obtained from the study as ethno-cultural diversity and environmental differences have been found to be linked to the geographical variation in HTLV prevalence. 2,8 The limited number of study participants analysed could be the cause of zero prevalence obtained. The study participants also may not have been exposed to the viruses.…”

“…7 Olaleye et al 4 reported prevalence rates ranging from 0.5% to 5.50% in different South-Western studies in the 90s. 8 In 2011, Terry Alli et al 9 found 3.6% seroprevalence of HTLV among blood donors in South-Western Nigeria. Durojaiye et al 5 found 0.5% prevalence among blood donors in 2014, while Yuguda et al 10 reported 3.2% in 2017 without confirmatory assays.…”

“…8 Out of the four neighbouring countries of Nigeria, Cameroon seems to be the only country with relatively recent reports of HTLV incidence. 2,8 Niger and Benin 8 Republics have reports from 80s and 90s, while no reports of the virus has been found in Chad. The modes of transmission of HTLV-1/2, like human immunodeficiency virus (HIV), include vertical (prolonged breastfeeding, complications during delivery and transplacental (intrauterine) route), parenteral (blood transfusion–transmission, intravenous drug use, sharing of razor blades and/or other sharp objects, organs donation and transplantation from infected persons, iatrogenic and/or occupational hazards or accidents) and sexual transmission patterns.…”

“…8 Furthermore, screening of blood and/or blood components prior to donation has hitherto not been mandated, as is the practice in the Western world. 8 The country’s policy on blood transfusion is still restricted to other transfusion-transmitted infections such as hepatitis B virus (HBV), hepatitis C virus (HCV), HIV and Syphilis. 1 Despite being the capital of Nigeria and a cosmopolitan city constantly visited en masse by individuals from all over the country, only one study 7 (HTLV-1/HIV co-infection) has been carried out in Abuja, which found a prevalence of 6.5% among HIV-positive individuals.…”