Daphne Ma, PhD
Nominated From: University of Washington
Research Site: Peru
Project: A Peru Unit for Neurosyphilis Diagnosis
Primary Mentor: Joseph Zunt, M.D., M.P.H (University of Washington)
Research Project Background
Syphilis, caused by the bacterium Treponema pallidum, is a re-emerging sexually transmitted disease (STD), with >45,000 new cases in the U.S. (Centers for Disease Control, 2010) and an estimated 12 million new adult cases annually (World Health Organization, 2012). This surge predominantly occurs among high-risk groups such as men-who-have-sex-with-men, low income populations in urban/underdeveloped areas and those infected with Human Immunodeficiency Virus (HIV) worldwide. In the resource-poor and developing nation of Peru where HIV and other STDs are endemic, ~20-30% of high-risk populations display seropositivity for syphilis (1,2). This trend is disturbing as penicillin has been used for >50 years in successfully treating and preventing transmission. This significant seroprevalence may reflect inadequate resources available in Peru for effective surveillance, prevention and treatment. Thus, syphilis presents a major public health concern for Peru and other developing countries globally. Neurological complications of syphilis manifest as asymptomatic neurosyphilis, meningitis, meningovasculitis, general paresis, tabes dorsalis, otologic syphilis or ocular syphilis (3-5). Neurosyphilis can occur early or late after infection because treponemes can enter the central nervous system (CNS) within days or weeks after initial contact. T. pallidum is estimated to be neuroinvasive in at least 70% of infected individuals (4). Immunocompromised individuals such as HIV seropositive patients have increased risk of developing neurosyphilis (6,7) and diminished likelihood of resolving symptoms (8). As T. pallidum cannot be cultured in vitro (7), diagnosing neurosyphilis involves detecting non-treponemal antibodies in the cerebrospinal fluid (CSF) using the Venereal Disease Research Laboratory (VDRL) test and characterizing CNS abnormalities (e.g. elevated white blood cells and protein levels). There are currently no specialized clinics/laboratories established for the diagnosis or study of neurosyphilis using CSF from Peruvian patients. This presents a challenge for timely diagnosis and therapy for symptomatic or asymptomatic neurosyphilis, as patients with neurosyphilis are less responsive to standard treatment compared to patients without CNS involvement (3). In addition, HIV seropositive patients respond slower to therapy (9); thus early detection and intervention would be especially critical for effectively treating neurosyphilis in these patients. As rates of HIV and syphilis co-infection have risen in the last decade worldwide (9), adequate infrastructure needs to be established to allow proper diagnosis and treatment of patients at risk for neurosyphilis, which could limit transmission and improve quality of life for patients living with syphilis.
Meet Dr. Ma:
Fogarty Fellows: Segundo Leon and Daphne Ma from NPGH Fogarty Fellows on Vimeo.