INFECTIOUS DISEASES

MÁRCIO DE FIGUEIREDO FERNANDES, MD



Leptospirosis

Acute generalized infectious disease, caused by any 180-serotypes of Leptospira interrogans. Leptospirosis is a zoonosis of worldwide distribution, affecting a great number of wild and domestic mammals, which may behave like assymptomatic hosts and shed L. interrogans in the urine. Worldwide, rats are the most common source of human infection. The human is usually a dead-end-host; person-to-person transmission is rare.

Human infection commonly occurs after indirected contact with infected animals, via water, food, or soil contaminated with infected urine. Occupational exposure ( farmers, veterinarians, abattoir workers etc. ) is also frequent.

Clinical Manifestation

  • Incubation period: 2 - 20 days ( range 10 days).

  • Leptospirosis may follow a biphasic course:

    a) Septicemic phase ( duration: 4 - 7 dyas ): L. interrogans dissemination in blood, cerebrospinal fluid ( CSF ) and most tissues. Clinically it's characterized by extensive vasculitis.

    b) Immune phase ( duration: 10 - 30 days: leptospiroses disapper from blood and CSF, remaining intermittently inthe urine and aqueous humor. Clinically it's characterized by multissystemic manifestations.

    Anicteric Leptospirosis ( 90% of cases )

    a) Septic phase ( 3 - 7 days)
  • Abrupt onset with high fever and chills;
  • muscles aches, commonly involving muscles of the calf;
  • headache ( associated with retrobulbar pain ) and prostration;
  • abdominla pain, nausea, vomiting, diarrhea;
  • conjuctival suffusion.
    b) Immune phase ( 0 - 30 days ) may or may not occur:
  • Asseptic meningitis;
  • conjunctival hemorrhage;
  • rash;
  • cough, blood-stained sputum, pulmonary infiltrates;
  • acalculous cholecystitis ( common in children ).

    • Icteric Leptospiroses ( 5 - 10% of cases)

    a) Septic phase ( 3 - 7 days )
  • Symptoms similar to anicteric form.
    b) Immune phase ( 7 - 30 )
  • "Reddish" jaudice ( jaudice + conjunctival + cutaneous vasculites):
  • renal failure: oliguria or anuria ( rare ); increase BUN and serum creatine, with normal or decreased levels of serum potassium;
  • hemorrhagic manifestations: epistaxis, petechials rash, gastrointestinal and pulmonary hemorrhage;
  • myocarditis and pulmonary involment ( infiltrates );
  • hepatomegaly ( splenomegaly is rare ).

    • Weil syndrome

  • Characterized by jaundice, renal failure and hemorrhagic manifestations

    Diagnosis

    The definitive diagnosis of leptospirosis depends on seroconversion or greater rise in antibody titer, or isolation of leptospires from any clinical specimen. However, the etiological confirmation is absolutelly unnecessary for the start of therapeutics; the exclusion of other important diseases ( meningococcemia, malaria, yellow fever, septicemia etc.) is essential.

    Etiological dianosis

  • Darkfield examination from blood or CSF ( first week of disease );
  • Cultures
    -first wek of diseaese: from blood or CSF ( Fletcher or Stuart media ).
    -second week of disease and then: from urine

    Serologic diagnosis

  • Microscopic agglutination
    -Two blood specimem must be serologically compared in an interval of two weeks; initial titer of 1:100 or at least fourfold rise in antibody titer confirm the diagnosis
  • Macroscopic slide agglutination
  • ELISA, Dot-ELISA ( detection of leptospiral IgM antibodies )

    Laboratory findings

  • Total WBC count slightly elevated with neutrophilia
  • increased erythrocyte sedimentation rate ( about 60 mm );
  • thrombocytopenia;
  • increased BUN and serum creatinine;
  • normo/hypokalemia
  • urinalysis with proteinuria, hematuria and casts;
  • increase in serum bilirubin ( predominantly direct ) levels;
  • alkaline phosphatase level moderately elevated, as well as SGOT and SGPT levels;
  • marked elevation in serum creatinine phosphokinase ( CK ) and MB variant, this second one in case of myocarditis.

    Treatment

    Most cases, even those regarded as severe, tend to complete recuperation. despite of specifc management. General suportive therapy is essential in the management of severe leptospirosis to detect and to deal with life-threatening complications ( renal failure, hypotension and hemorrage ).

    In relation to antimicrobial therapy, there is an agreement that either penicillin G ( 2,4 - 3,6 million units/day i.v ) or tetracycline ( 2g/ day in divided doses p.o. ) may shorten the course of the illness, but only if therapy is started by the fourth day of the illness. Other beta-lactam agents are also useful.

    Prevention

    Antimicrobial prevention is only indicated for those people who are under risk of exposure - except on epidemics - to leptospires ( doxycilcine 200mg/week ) and for those ones with known exposure ( doxycycline 100mg for 7 days ).

    Vaccination of domestic mammals prevents the disease, but cannot avoid the infection and the shedding of L. interrogans in the urine and the consequent human infection.

    Effective rat control, appropriated occupational wear ( boots, gloves, etc ) and desinfection of contaminated work areas are important measures in order to reduce the incidence of disease.

    If you have suggestions or comments send an e-mail to Márcio de Figueiredo Fernandes

    Back to INFECTIOUS DISEASES

    Back to SPECIALTIES

    Back to MEDSTUDENTS HOMEPAGE