I. General Characteristics
- Gram-negative, spiral-shaped spirochete with tightly coiled, thin, flexible body and hooked ends (resembling a question mark).
- Motile via two axial filaments (endoflagella) located between the outer membrane and peptidoglycan.
- Obligate aerobe — requires oxygen for survival.
- Slow-growing organism; best cultured in Fletcher's medium or Ellinghausen-McCullough-Johnson-Harris (EMJH) medium.
- Not stained well by Gram stain; better visualized with dark-field microscopy or silver stain.
- Natural reservoir: wild and domestic animals, especially rodents (e.g. rats).
IV. Epidemiology
- Reservoir: Primarily rodents (rats), but also livestock, dogs, and other mammals.
- Transmission:
- Contact with water, soil, or food contaminated with urine of infected animals.
- Entry via abrasions, mucous membranes, or conjunctiva.
- Occupational risk: Veterinarians, farmers, sewage workers.
- Geography: Worldwide, especially tropical and subtropical regions with poor sanitation.
V. Diseases Caused – Leptospira
Leptospira causes leptospirosis, a biphasic zoonotic illness that can range from mild flu-like symptoms to life-threatening systemic disease.
Leptospiremic Phase (1st Phase):
- Early, acute stage with sudden onset of symptoms.
- Presents as a flu-like illness: high fever, chills, severe headache, and myalgia (especially in the calf muscles).
- Conjunctival suffusion (reddening of the eyes without discharge) is a characteristic clinical clue.
- Leptospires circulate in the blood and CSF during this phase , allowing isolation through culture or detection by PCR.
Immune Phase (2nd Phase):
- Begins a few days after initial symptoms subside.
- IgM antibodies appear, and immune-mediated symptoms dominate.
- Clinical features include:
- Aseptic meningitis (very common),
- Uveitis,
- Skin rash, and
- In some cases, progression to multi-organ failure.
Weil’s Disease (Severe Leptospirosis):
- A life-threatening complication of leptospirosis.
- Marked by a classic triad:
- Jaundice (due to hepatic dysfunction),
- Renal failure (tubulointerstitial nephritis),
- Hemorrhagic signs (e.g., GI bleeding, petechiae).
- May be accompanied by myocarditis and pulmonary hemorrhage — often fatal if untreated.
Aseptic Meningitis:
- A frequent neurologic manifestation of the immune phase.
- Presents with headache, photophobia, neck stiffness, but CSF cultures are sterile (hence 'aseptic').