Update on Laboratory Diagnosis and Epidemiology of Trichomonas vaginalis: You Can Teach an “Old” Dog “New” Trichs

Abstract

Past viewpoints on Trichomonas vaginalis infection have characterized the associated clinical disease as a “nuisance” condition, with affected demographics largely being older African American females residing in urban centers. The advent of commercial molecular assays specific for T. vaginalis has offered a new outlook on trichomoniasis. Within high-prevalence sexually transmitted infection populations, parasite distribution is not localized to specific population centers, and T. vaginalis prevalence is elevated among both younger and older age groups. Adaptation of these molecular assays can additionally facilitate male screening and subsequent epidemiologic characterization. These findings, combined with associations between T. vaginalis infection and human immunodeficiency virus (HIV) acquisition/transmission and persistent human papillomavirus infection, support consideration of the expansion of T. vaginalis screening efforts in the realms of clinical practice and public health.

Introduction

The French microscopist, clinician, and researcher A. F. Donné discovered the protozoan T. vaginalis 180 years ago. Trichomoniasis, the clinical entity ascribed to the pathogen, has become the most prevalent non-viral sexually transmitted infection (STI) in the United States (Fig. 1). A surveillance study conducted by the U.S. Centers for Disease Control and Prevention (CDC) in 2008 estimated trichomoniasis prevalence in this country at 4 million cases, with approximately 1 million new cases of T. vaginalis infection being diagnosed annually [1]. As will be posited and further described throughout this review, several factors impact the true characterization of trichomoniasis. As an introductory example, T. vaginalis prevalence rates are rather disparate on a worldwide basis. In contrast to reports of >20% prevalence in some U.S., African, and indigenous Australian population centers [2, 3, 4, 5], a number of European, Asian-Pacific, and non-indigenous Australian studies have documented rates lower than 5% [6, 7, 8, 9, 10].

The advent of molecular-based laboratory detection of T. vaginalis has broadened our knowledge of trichomoniasis, allowing new perspectives on disease epidemiology and opportunities for prevention. In addition, advancements related to diagnostic algorithms have garnered much attention in the clinical research setting. A PubMed primary literature search (U.S. National Library of Medicine and the National Institutes of Health) conducted in February 2016 using the search parameter “Trichomonas vaginalis” filtered by the possibility of “antigen,” “molecular testing,” “nucleic acid hybridization,” “PCR,” “nucleic acid amplification testing,” “LAMP” (loop-mediated isothermal amplification), or “transcription-mediated amplification” selected 629 primary citations from the years 1964 to 2016, with over 25% published since the beginning of 2012. This brief commentary, with focus largely on literature published within the past 3 years, discusses updates on T. vaginalis epidemiology and laboratory testing.