Spirochetes and Related Infections: Syphilis, Lyme Disease, Relapsing Fever, Leptospirosis

A vocab-style set of flashcards covering the key concepts, agents, disease stages, diagnostics, treatments, and prevention related to spirochetes: Treponema (syphilis and non-syphilitic treponematoses), Borrelia (Lyme disease and relapsing fever), and Leptospira (leptospirosis).

Spirochetes

Thin, regular, coiled Gram-negative bacteria; helical; strict parasites with complex growth requirements; include Treponema, Leptospira, Borrelia.

Treponema

Genus that includes causative agents for syphilis and non-syphilitic treponematoses.

Syphilis

Disease caused by Treponema pallidum pallidum; transmitted sexually and transplacentally; stages include primary, secondary, latency, tertiary, congenital.

Treponema pallidum pallidum

Causative agent of syphilis; humans are natural hosts; extremely fastidious and sensitive; requires host for survival.

Chancre

Initial lesion of primary syphilis at the inoculation site; highly contagious fluid containing Treponema pallidum.

Primary syphilis

Stage with chancre; spirochete enters blood; lymph node inflammation.

Secondary syphilis

Stage with hematogenous spread; widespread rash (including palms/soles), fever, malaise; highly contagious.

Latency

Asymptomatic stage after secondary syphilis; can progress to tertiary; early latent (

Early latent syphilis

Less than one year; potentially infectious (except to fetus).

Late latent syphilis

More than one year; generally not infectious (except to fetus).

Tertiary syphilis

Late stage with damage to multiple tissues; gummas; neurosyphilis; cardiac syphilis; not contagious (except to fetus).

Gummas

Painful, swollen granulomatous lesions in skin, organs due to tertiary syphilis.

Neurosyphilis

CNS involvement in tertiary syphilis; can cause paralysis, dementia, meningitis, seizures.

Cardiac syphilis

Aortic aneurysm or other aortic root damage due to tertiary syphilis.

Congenital syphilis

Treponema pallidum crosses placenta; infection possible any trimester; ~40% infant death; classic stigmata include Hutchinson’s teeth and saber shin.

Hutchinson’s teeth

Notched, barrel-shaped incisors seen in congenital syphilis.

Saber shin

Sharp-edged, anteriorly convex tibia seen in congenital syphilis.

Dark-field microscopy

Direct visualization of T. pallidum in chancre exudate during early primary syphilis.

PCR

Polymerase chain reaction for detecting Treponema pallidum DNA in lesions.

Direct Fluorescent Antibody (DFA) testing

Immunofluorescent detection of T. pallidum in lesion material.

Non-treponemal serology tests

Screening tests detecting anti-cardiolipin antibodies (not specific for T. pallidum): VDRL and RPR.

VDRL

Venereal Disease Research Laboratory test; non-treponemal serology for syphilis.

RPR

Rapid Plasma Reagin; non-treponemal serology for syphilis.

Treponemal serology tests

Tests detecting antibodies specific to T. pallidum: FTA-ABS and TPHA.

FTA-ABS

Fluorescent treponemal antibody absorption test; confirms T. pallidum infection.

TPHA

Treponema pallidum hemagglutination assay; treponemal antibody test.

Penicillin G

Primary treatment for syphilis; alternative is doxycycline.

Doxycycline

Alternative antibiotic for syphilis when penicillin is unsuitable.

Non-syphilitic treponematoses

Yaws, Bejel, Pinta; non-STD infections transmitted by contact or shared utensils.

Yaws

Caused by T. pallidum ssp. pertenue; chronic, debilitating skin lesions; tropical regions; mainly children.

Bejel

T. pallidum ssp. endemicum; deforming infection of mouth, nasal cavity, body; Middle East/North Africa.

Pinta

T. carateum; superficial depigmented skin lesions; tropical Latin America.

Treponema pallidum pertenue

Subspecies causing Yaws.

Treponema pallidum endemicum

Subspecies causing Bejel.

Treponema carateum

Species causing Pinta.

Borrelia

Genus including agents of Lyme disease and relapsing fever.

Relapsing fever

Fever relapses caused by antigenic variation; due to Borrelia species.

Antigenic variation

DNA rearrangement (gene conversion) in Borrelia enabling immune evasion and recurring fevers.

Gene conversion

DNA rearrangement mechanism behind Borrelia antigenic variation.

Borrelia recurrentis

Agent of epidemic (louse-borne) relapsing fever.

Epidemic relapsing fever

Relapsing fever transmitted by body lice; higher mortality historically.

Borrelia hermsii

Agent of endemic (tick-borne) relapsing fever.

Endemic relapsing fever

Relapsing fever transmitted by soft-bodied ticks; more prolonged endemic cycles.

Borrelia turicatae

Endemic, tick-borne relapsing fever agent.

Borrelia parkeri

Endemic relapsing fever agent transmitted by ticks.

Lyme disease

Infection by Borrelia burgdorferi; transmitted by ticks; long attachment required.

Borrelia burgdorferi

Causative agent of Lyme disease.

Erythema migrans (ECM)

Bull’s-eye skin lesion seen weeks after tick bite in early Lyme disease.

Bull’s-eye rash

Classic description of erythema migrans in Lyme disease.

Early Lyme manifestations

Erythema migrans with flu-like symptoms; weeks after bite.

Late Lyme manifestations

Cardiac/neurologic involvement and arthritis months to years after infection.

Lyme diagnostics (PCR/serology)

PCR can detect Borrelia; serology includes ELISA and immunofluorescence for antibodies.

Doxycycline (Lyme)

First-line antibiotic for early Lyme disease; duration ~20-30 days.

Ceftriaxone

Antibiotic used for late or neuroborreliosis Lyme disease.

Black-legged tick

Vector for Lyme disease; Ixodes species; long attachment required for transmission.

Prevention of Lyme disease

Avoid tick exposure; use repellents; perform tick checks.

Leptospira

Genus causing leptospirosis; pathogenic L. interrogans; nonpathogenic L. biflexa.

Leptospira interrogans

Pathogenic species causing leptospirosis; target kidneys, liver, brain, eyes.

Leptospira biflexa

Harmless, free-living saprobe species.

Leptospirosis

Zoonotic spirochetal infection from animal urine; mainly affects kidneys and liver.

Weil’s disease

Severe leptospirosis with jaundice, hepatic/renal failure, hemorrhage; can cause meningitis.

Leptospiremia

Bloodstream phase of leptospira infection early in disease.

Transmission of leptospirosis

Zoonotic; humans acquire via contact with urine-contaminated water or food.

Diagnosis of leptospirosis

Dark-field/phase-contrast microscopy early; PCR; culture; serology (ELISA, MAT).

Treatment of leptospirosis

Penicillin or doxycycline; IV for mod/severe cases; doxycycline for prophylaxis.

Prevention of leptospirosis

Avoid exposure to contaminated water; control animal reservoirs.