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Treponema pallidum ssp. pallidum:
Motile,
Gram-negative, microaerophilic spirochaete (with tapered end)
(see WebLinked
image)- Cause
of venereal syphilis
- Outer
sheath encloses axial fibrils wrapped around protoplasmic cylinder
- Axial
fibrils originate at both poles and may overlap at center of cell in Treponema
and Borrelia, but not in Leptospira
- Obligate
intracellular pathogen
(see WebLinked
image)
- Cannot
be grown in vitro
- Do
not survive well outside of host
- Transmitted
from direct sexual contact or from mother to fetus
- Not
highly contagious (about 1 chance in 10 of acquiring disease from infected
partner
- Long
incubation period during which time host is non-infectious
- Useful
epidemiologically for contact tracing and administration of preventative
therapy
- Prostitution
for drugs or for money to purchase drugs remains central epidemiologic aspect
of transmission
- Capacity
to invade intact mucus membranes or skin with abrasions
- Most
common sites of inoculation are the cervix or vagina in the female and the
penis in the male
- Syphilis
is a disease of blood vessels and of the perivascular areas
- Primary
disease process involves invasion of mucus membranes, rapid multiplication,
wide dissemination through perivascular lymphatics
and systemic circulation prior to development of the primary lesion
- 10-90
days (usually 3-4 weeks) after initial contact the host mounts an inflammatory
response at the site of inoculation resulting in the hallmark syphilitic
lesion, called the chancre (changes from hard to ulcerative), with profuse
shedding of spirochetes; swelling of capillary walls and regional lymph
nodes with draining
- Prmary
lesion is resolved by fibrotic walling-off
- Secondary
disease appears 2-10 weeks after primary lesion
- Secondary
lesions of the skin and mucus membranes are highly contagious
- Generalized
immunological response
- Following
secondary disease, host enters latent period (first 4 years = early latent;
subsequent period = late latent)
- About
40% of late latent patients progress to late tertiary syphilitic disease
- Tertiary
syphilis characterized by localized dermal lesions (gummas) in which few
organisms are present and reflects the immunologic reaction of the host
- Late
neurosyphilis develops in about 1/6 untreated cases, usually more than 5
years after initial infection
- Central
nervous system and spinal cord involvement (dementia, seizures, wasting,
etc.)
- Cardiovascular
involvement appears 10-40 years after intial infection with resulting myocardial
insufficiency and death
- Congenital
syphilis results from transplacental infection with T. pallidum
- Septicemia
in the developing fetus and widespread dissemination
- Abortion,
neonatal mortality, and late mental or physical problems resulting from
scars from the active disease and progression of the active disease state
- In
spite of a vigorous host immune response the organisms are capable of persisting
for decades
- Infection
is neither fully controlled nor eradicated
- In
early stages, there is an inhibition of cell-mediated immunity that abate
in late stages of disease, hence late lesions tend to be localized
- Penicillin
remains drug of choice but WHO monitors treatment recommendations
- 7-10
days continuous for early stage and at least 21 days continuous beyond the
early stage
- Prevention
with barrier methods and prophylactic treatment of contacts identified through
epidemiological tracing
- Other
nonvenereal treponemal diseases include yaws (T. pallidum ssp. pertenue),
pinta (T. carateum), and bejel (T. pallidum ssp. endemicum)
- Diagnostic
serological test = Wassermann test
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