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There are two main species: Leptospira interrogans
, which contains
all of the pathogenic strains, and L. biflexa
, a non-pathogen. L.
has more than 200 serovariants that may be written as
if they are separate species.
have different preferred mammalian hosts,
for example the rat is the reservoir of L. interrogans
Leptospires colonize the renal tubules of their natural
hosts and are excreted in urine. Humans may be infected by
contact with animal urine or contaminated water or soil. Watersports
enthusiasts, sewer workers and agricultural workers are at
increased risk of infection.
Pathogenesis and Clinical features
The central nervous system, liver and kidneys are most affected by
the human disease. The severity varies between serovars.
There are two phases:
- bacteraemia, with fever, headache, myalgia, conjunctivitis and
- fever, uveitis and aseptic meningitis, which predominate after the
organisms disappear from the blood.
In addition, jaundice, haemorrhage, renal failure and myocarditis
occur in severe cases. A poor outcome is associated with
hypotension, renal failure and clinical evidence of pulmonary
involvement. Diagnosis is made by enzyme immunoassay (EIA),
microagglutination or nucleic acid amplification test (NAAT).
Penicillin or doxycycline must be commenced early in the
disease. Doxycycline is an effective prophylactic agent if exposure
to infection is likely to have occurred.
Borrelia are transmitted to humans via arthropods (lice or ticks)
throughout the world, with a well-defined geographical territory
and host specificity. For example, humans are the only host of
louse-borne relapsing fever (B. recurrentis
). Epidemics arise during
war or mass migration when humans invade the Borrelia-tick-
- Borrelia cause bacteraemia and fever. Antibodies clear the
organism from the blood, but antigenic variation allows relapse.
The disease resolves when the repertoire of antigenic variation is
- Presentation is with headache, myalgia, tachycardia, rigors,
hepatosplenomegaly and a petechial rash.
- Episodes last for 3-6 days; relapses occur a week apart.
- Louse-borne relapsing fever has a high mortality (up to 40%);
mortality in tick-borne disease rarely exceeds 5%.
- Myocarditis, cerebral haemorrhage and/or hepatic failure are
the usual causes of death.
- Postexposure doxycycline is effective in preventing disease.
- Doxycycline is treatment of choice.
, B. afzelii
and B. garinii
are transmitted by
Ixodes ticks and cause Lyme disease, which is endemic in the
eastern USA and Europe. Humans are accidental hosts. The early
symptoms are caused by the acute infective process; later manifestations
are thought to be related to the host immune response.
Typical features include:
- an initial expanding red macule or papule (erythema chronicum
- later headache, conjunctivitis, fever and regional
- complications including new skin lesions, myocarditis, arthritis,
aseptic meningitis, cranial nerve palsies and radiculitis;
- acrodermatitis chronica atrophicans, a red skin lesion, which
may also occur.
Diagnosis is made by EIA followed by Western blot. Doxycycline
or amoxicillin is used for treatment of early Lyme disease;
ceftriaxone for late or recurrent disease.
This is a painful, oral, ulcerative, destructive infection with Borrelia
vincentii and fusobacteria or other anaerobes. Clinical diagnosis
is confirmed by Gram stain. Treatment is with penicillin and
causes syphilis, which may be transmitted
sexually or congenitally. The incidence is now increasing worldwide,
having been falling for many years. The related organisms
and T. carateum
cause yaws and pinta respectively.
They are spread by contact, usually in childhood. Once common
in the tropics, they are now rare as the result of an eradication
penetrate intact skin or mucosa disseminating
throughout the body to cause disease in four stages:
- Primary chancre (painless ulcer with a rubbery edge and regional
- Secondary (an acute febrile illness with a generalized non-itchy
scaling rash that typically involves the palms, associated with
- Latent phase, which may last for many years.
- Tertiary (systemic lesions become symptomatic, e.g. aortitis,
posterior cord degeneration and dementia).
The characteristic syphilitic lesions (gummas), which consist of
necrosis and obliterative endarteritis with fibroblastic proliferation
and lymphocyte infiltration, are found throughout the body.
- Primary: dark-ground microscopy or NAAT.
- Later stages: EIA for specific IgG and IgM as well as cardiolipin
agglutination (measures disease activity) and tests based on cultivated
treponemes such as the treponemal haemagglutination test
- CSF testing should be performed to detect early central nervous
- Neonatal: detection of IgM by Western blotting.
- Penicillin (or either azithromycin or tetracyclines if the patient
- An acute febrile response (the Jarisch-Herxheimer reaction)
may develop in some patients after the first dose of antibiotics.
- Careful serological follow-up is essential to confirm cure and/or
detect early central nervous system involvement.