LEPTOSPIROSIS

Leptospirosis (Weil's disease) is an important public health problem in urban India, with localized outbreaks during monsoons. While most cases are asymptomatic, clinical spectrum may range from non-specific febrile illness to severe disease with meningitis or hepato-renal dysfunction.

Epidemiology: Leptospira interrogans—the only patho­genic leptospires in humans, is primarily a zoonotic infection, with accidental human infection. Rat is the main source of human infection, though other animal reservoirs include dogs, cats and cattle. Infected animals excrete spirochetes in urine, which may be transmitted to humans via exposure to contaminated water or soil.

While sporadic cases are seen in animal-handlers, e.g. agricultural/veterinary workers, localized outbreaks are common in urban slums after heavy rains/floods, due to contact of rat-excreta-contaminated water with human skin.

Pathogenesis: Leptospira enter the body through moist and abraded skin/mucus membrane and spread to all organs via blood stream. Initial spirochetemia is pathologically characterized by vascular endothelial damage and resultant ischemia in liver, kidneys, meningitides and muscles, leading to early manifestations (septicemic phase). With appearance of circulating antibodies after 2-7 days, leptospires disappear from circulation but immunological damage may lead to further complications (immune phase).

Clinical spectrum: Most cases of human leptospirosis are asymptomatic. In symptomatic cases, the incubation period is 7-12 days and clinical presentation may be biphasic, divided into:

• Septicemic phase (3-7 days), characterized by abrupt onset of high fever with chills, severe headache, conjunctival suffusion, myalgia and nausea/vomiting. On examination, these children have: (a) dehydration with hypotension, (b) extreme muscular tenderness, (c) generalized lymphadenitis and hepatosplenomegaly, and (d) uncommon manifestations, e.g.

• Asymptomatic or silent phase for few hours or days, though it may be absent in icteric leptospirosis.

• Immune phase presenting as either aseptic meningitis (anicteric leptospirosis) or hepatorenal dysfunction (icteric leptospirosis).

Anicteric leptospirosis is characterized by aseptic meningitis with headache, neurological signs and CSF abnormalities, which resolve spontaneously within a week.

Icteric leptospirosis (Weil's syndrome) is less common in children (lt;10%) and characterized by—(a) hepatic abnormalities, e.g. progressive jaundice, hepatomegaly and hepatic failure, (b) renal abnormalities, e.g. hema­turia or renal failure (c) hypotension/shock and (d) hemorrhagic manifestations, e.g. epistaxis or gut bleeding. Immune phase is relative long (10-30 days) in icteric leptospirosis.

Diagnosis must be suspected in any acute febrile illness with severe myalgia/headache, icterus or renal failure, during rainy season, which may be confirmed by:

• Elevated IgM antibody titers from 5^th day of illness, gt;1:100 in at least two specimens or gt;2-4-fold rise over 2 weeks, by standard slide agglutination test or ELISA, with sensitivity of 80-90%,

• Positive microscopic agglutination test (MAT) is considered as the gold standard for serodiagnosis, though diagnostic titers vary with endemicity of disease. In regions where leptospirosis is common, there may be a substantial proportion of the population with elevated titers of MAT.

• Direct identification of Ieptospires in urine or infected tissues, by dark-field microscopy, fluorescent antibody staining or phase-contrast microscopy, though sensitivity declines after first week of illness.

• Molecular tests, i.e. PCR-DNA in blood, urine or spinal fluid are as diagnostic as direct identification, but cannot identify serovars.

In addition, most cases have thrombocytopenia and must be assessed for liver function tests, renal profile and CSF examination, if clinically indicated.

Modified Paine's criteria may be useful for presumptive diagnosis of leptospirosis awaiting confirmatory reports, based on clinical, epidemiological and laboratory criteria with assigned individual scores.

Treatment is supportive and specific (antibiotics).

• Antimicrobial therapy is most effective if started within 7 days of onset and drugs of choice include:

- IV Crystalline Penicillin (50,000 100,000 U/kg/d for 5-7 days) in severe cases with Ceftriaxone (IV 75-100 mg/kg/d for 5-7 days) or Cefotaxime as alternatives, or

- PO Doxycycline (5-10 mg/kg/d for 7 days) in milder cases. PO Azithromycin (10 mg/kg/d for 3 days) or Amoxycillin (50-100 mg/kg/d for 76 days) are alternatives in younger children.

• Supportive therapy includes antipyretics, cold com­presses for muscle pain, correction of fluid and electrolyte abnormalities, continuous monitoring and management of hepatorenal dysfunction, including dialysis.

Prevention of leptospirosis includes: (a) Rodent­control measures, (b) avoidance of contact with contami­nated water during floods, (c) prophylactic Doxycycline (200 mg/week) in travelers to outbreak area, and

(d) immunization of live-stocks.

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