Leptospirosis

Leptospirosis is a globally important zoonotic disease caused by spirochetes of the genus Leptospira. Leptospires are tightly and regularly coiled, with characteristic hooked ends (hence the species name interrogans), and are highly motile, spinning around their longitudinal axis and darting back and forth.

Cause/Mode of Transmission:

Human-to-human transmission does not occur. The most important sources of transmission to humans are rats, dogs, cattle, and pigs. Factors that facilitate human infection are those that bring susceptible persons into indirect contact with contaminated animal urine through surface waters, moist soil, or other wet environments or into direct contact with urine and other excreta (e.g., products of parturition, placenta) of infected animals. Leptospires infect humans through the mucosa (usually conjunctival and possibly oral or tonsillar) or through macerated, punctured, or abraded skin.

Signs/Symptoms:
Leptospirosis is classically described as biphasic. Acute fever in the initial leptospiremic phase lasts for 3–10 days, during which period the organism may be cultured from blood. In a later immune phase, fever is not responsive to antibiotic therapy but leptospires can be isolated from urine. Physical examination may include any of the following findings, none of which is pathognomonic for leptospirosis: conjunctival suffusion (dilated conjunctival blood vessels in the absence of discharge); pharyngeal erythema without exudate; muscle tenderness; rales on lung auscultation or dullness on chest percussion over areas of pleural hemorrhage; rash (which may be macular, maculopapular, erythematous, petechial, or ecchymotic); jaundice; meningismus; and hypo- or areflexia, particularly in the legs.

conjunctival suffusion

Weil's disease is characterized by variable combinations of jaundice, acute kidney injury, hypotension, and hemorrhage—mostcommonly involving the lungs but also potentially affecting the gastrointestinal tract, retroperitoneum, pericardium, and brain. Other syndromes include aseptic meningitis, uveitis, cholecystitis, acute abdomen, and pancreatitis (with hypo- or hyperglycemia).

Diagnostics:
The organisms cannot be seen by direct light microscopy. To visualize the spirochetes directly in culture or in clinical specimens, dark-field or phase-contrast microscopy must be used.

Treatment:
Mild leptospirosis often is not specifically identified and typically resolves without antibiotic treatment. Mild disease should be treated with oral antibiotics—in particular, doxycycline, especially where rickettsial infections (including scrub typhus) are coendemic. severe leptospirosis frequently requires empirical initiation of broad-spectrum parenteral therapy before the diagnosis can be confirmed.

Prevention

No vaccine is available for human leptospirosis. Preventive strategies, including prophylaxis with doxycycline, have been variably effective in different settings. General sanitation approaches (e.g., rodent control) and avoidance of swimming in potentially contaminated places (e.g., for recreational use) are recommended, but these measures are difficult to apply consistently.

Leptospirosis guidelines from PCP and PSMID

Resources:

Harrison's Principle of Internal Medicine 18th ed
Philippinr College of Physician