Leptospira

GENERAL CONCEPTS:

As the name implies, Leptospira are spiral shape organisms.
The diseases produced by Leptospira are termed "leptospirosis" and can vary from subclinical to fatal.
Leptospirosis is a zoonosis; man is an accidental host via contaminated animal urine.
The leptospirosis known as "Weil's disease" was first described in 1886.

DISTINCTIVE PROPERTIES:

Leptospira are thin, tightly coiled obligate aerobes that are highly motile.
Their structure is similar to other spirochetes; a multilayered outer membrane, helical shaped peptidoglycan and flagella located in the periplasmic space.
Their nutritional requirements include long-chain fatty acids and vitamins B1 and B12.
There are more than 180 serotypes of Leptospira described.

PATHOGENESIS:

Mucosa and broken skin provide the entry for leptospires.
The organisms produce a generalized infection with bacteremia (leptospiremic phase). Antibody is produced and the organisms then become localized primarily in the kidneys. Multiplication in the kidneys leads to shedding in the urine (leptospiruric phase). This may persist for weeks, months or years.
Leptospira produce no known exo- or endotoxins.
Damage to the endothelial lining of capillaries and renal failure are the most common reasons for death. Occasionally the central nervous system may become involved.
The host immune response is probably responsible for lesions associated with late phase of disease. This is suggested because antibiotics are ineffective after symptoms have persisted for more than 4 days.

HOST DEFENSES:

Antibody plus complement is leptospiricidal. Immunity against Leptospira is primarily humoral.
The cell-mediated response may be responsible for late manifestations.

EPIDEMIOLOGY:

Leptospirosis is a worldwide zoonosis.
The primary reservoir is rodents because, once infected, they shed the organisms for life. Dogs are a major source for human infections.
Direct or indirect contact with infected urine is the mode of transmission.

DIAGNOSIS:

Clinical: Leptosirosis is a general febrile disease that is often misdiagnosed as meningitis or hepatitis. Following a 7-14 day incubation period, patients experience fever, severe headache, pain and occasional jaundice. Symptoms last about 7 days then subside. The leptospiruric phase then lasts for several days before complete recovery.
Laboratory: Darkfield microscopic examination of the blood or urine combined with serologic tests is confirmatory.

CONTROL:

Sanitary: Reducing the prevalence in domestic animals via vaccine reduces human infection.
Immunological: A vaccine is available for animals, but not humans.
Chemotherapeutic: Penicillin or tetracycline is effective if given early.