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Treponematosis (Endemic Syphilis) Workup

  • Author: Steven Fine, MD, PhD; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
Updated: Sep 25, 2015

Laboratory Studies

Treponematosis should be suspected in persons with appropriate clinical findings (eg, chronic skin or bone lesions) who live in or are from endemic areas. As with other treponeme diseases, confirmation of the diagnosis depends on dark-field examination, if available, or serologic testing. The epidemiologic setting is vital because the nonvenereal treponemes cannot be distinguished from T pallidum pallidum (the cause of venereal syphilis) with laboratory studies.

Tests for endemic treponematosis are the same as for syphilis. Because treponemes cannot be easily and readily cultured, use other laboratory methods of identifying infection. The current tests for syphilis fall into the following 3 categories: direct microscopic identification when lesions are present, nontreponemal tests used for screening, and treponemal tests used for confirmation.

Direct microscopy

Direct microscopic identification of treponemes from lesion fluids by either dark-field microscopy or direct fluorescent antibody should be the initial step in diagnosing a treponemal infection. This is most helpful during the primary stage of infection because treponemal antibodies do not usually appear until 1-4 weeks after the lesion has formed. See the image below.

Photomicrograph (540X) of Treponema carateum obtai Photomicrograph (540X) of Treponema carateum obtained from an early pinta lesion. Courtesy of the CDC.

A negative dark-field finding does not exclude the diagnosis of treponematosis because the organisms may be too few if the lesion is in the healing stage or if the infection has been altered by treatment.

Nontreponemal tests

These include the nontreponemal rapid plasma reagin (RPR) test and the Venereal Disease Research Laboratory (VDRL) test. These tests usually become positive within 2-4 weeks of the appearance of the primary lesion. They can be used as tests of cure because they usually become negative after treatment.

RPR is inexpensive and rapid and is convenient for screening large numbers of sera specimens.

The standard nontreponemal test is the VDRL slide test, in which serum is tested for its ability to flocculate a suspension of cardiolipin-cholesterol-lecithin antigen. This test is based on the observation that antibodies elicited against treponemal surface antigens cross-react with cardiolipin.

Treponemal tests

The confirmatory treponemal tests are the fluorescent treponemal antibody absorption (FTA-ABS) test, T pallidum hemagglutination assay (TPHA), and T pallidum particle agglutination assay (TPPA). These tests use T pallidum organisms as the antigen. The patient's serum is first absorbed to remove any naturally occurring cross-reacting antibody; it is then reacted with the organism.

Because of the nonstandardized, qualitative, and subjective nature of this test, its principal use is to confirm any positive VDRL or RPR test result.

Other tests

New rapid point-of-care tests are currently being evaluated.


Imaging Studies

Imaging studies are generally not used in the diagnosis or treatment of endemic treponematosis, although changes to bone periosteum and cartilage may be observed on radiography in late-stage yaws or endemic syphilis.


Histologic Findings

Dark-field microscopy of material from cutaneous lesions often yields treponemes. However, this technique may not be available in endemic areas, and pathologic diagnosis is not considered necessary. In yaws and pinta, granulomatous inflammation resembles that of syphilis. Endarteritis is a feature of late yaws lesions.

Contributor Information and Disclosures

Steven Fine, MD, PhD Associate Professor, Department of Internal Medicine, Division of Infectious Diseases, University of Rochester School of Medicine

Steven Fine, MD, PhD is a member of the following medical societies: American College of Physicians, Infectious Diseases Society of America, Phi Beta Kappa

Disclosure: Nothing to disclose.


Lynn S Fine, PhD, MPH Manager of Clinical Microbiology Laboratory, ACM Medical Laboratories; Adjunct Professor, Department of Biology, St John Fisher College and Nazareth College

Lynn S Fine, PhD, MPH is a member of the following medical societies: American Public Health Association, Phi Beta Kappa

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John L Brusch, MD, FACP Assistant Professor of Medicine, Harvard Medical School; Consulting Staff, Department of Medicine and Infectious Disease Service, Cambridge Health Alliance

John L Brusch, MD, FACP is a member of the following medical societies: American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Mark R Wallace, MD, FACP, FIDSA Clinical Professor of Medicine, Florida State University College of Medicine; Clinical Professor of Medicine, University of Central Florida College of Medicine

Mark R Wallace, MD, FACP, FIDSA is a member of the following medical societies: American College of Physicians, American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, International AIDS Society, Florida Infectious Diseases Society

Disclosure: Nothing to disclose.

Additional Contributors

Jeffrey M Zaks, MD Clinical Associate Professor of Medicine, Wayne State University School of Medicine; Vice President, Medical Affairs, Chief Medical Officer, Department of Internal Medicine, Providence Hospital

Jeffrey M Zaks, MD is a member of the following medical societies: American College of Cardiology, American College of Healthcare Executives, American Association for Physician Leadership, American Medical Association

Disclosure: Nothing to disclose.

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Nigerian boy with ulcerative skin lesions characteristic of yaws. Courtesy of the CDC/Dr. Lyle Conrad.
Photomicrograph (540X) of Treponema carateum obtained from an early pinta lesion. Courtesy of the CDC.
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