 |
Leptospirosis
includes all infections caused by the genus Leptospira, regardless of serotype, including
infectious (spirochetal) jaundice and canicola fever. Symptoms are
biphasic. Both phases involve acute febrile episodes; the 2nd phase
sometimes includes hepatic, renal, and meningeal involvement. Diagnosis
is by darkfield microscopy, culture, and serology. Treatment is
with doxycycline or penicillin.
Leptospirosis, a zoonosis occurring in many domestic and wild animals, may cause inapparent illness or serious, even fatal, disease. A carrier state exists in which animals shed leptospires in their urine for months. Human infections are acquired by direct contact with infected urine or tissue, or indirectly by contact with contaminated water or soil. Abraded skin and exposed mucous membranes (conjunctival, nasal, oral) are the usual entry portals. Leptospirosis can be an occupational disease (eg, of farmers or sewer and abattoir workers), but in the US, most patients are exposed incidentally during recreational activities (eg, swimming in contaminated water). Dogs and rats are other common probable sources. The 40 to 100 annual US cases occur mainly in late summer and early fall. Because distinctive clinical features are lacking, probably many more cases are not diagnosed and reported.
Symptoms and Signs
The incubation period ranges from 2 to 20 (usually 7 to 13) days. The disease is characteristically biphasic. The septicemic phase starts abruptly, with headache, severe muscular aches, chills, and fever. Conjunctival suffusion usually appears on the 3rd or 4th day. Splenomegaly and hepatomegaly are uncommon. This phase lasts 4 to 9 days, with recurrent chills and fever that often spikes to > 39° C. Defervescence follows. The 2nd, or immune, phase occurs between the 6th and 12th day of illness, correlating with appearance of antibodies in serum. Fever and earlier symptoms recur, and meningitis may develop. Iridocyclitis, optic neuritis, and peripheral neuropathy occur infrequently. If acquired during pregnancy, leptospirosis, even during the convalescent period, may cause abortion.
Weil's syndrome (icteric leptospirosis) is a severe form with jaundice from intravascular hemolysis, and usually azotemia, anemia, diminished consciousness, and continued fever. Onset is similar to that of less severe forms. However, hemorrhagic manifestations, which are due to capillary injury and include epistaxis, petechiae, purpura, and ecchymoses, then develop and rarely progress to subarachnoid, adrenal, or GI hemorrhage. Thrombocytopenia may occur. Signs of hepatocellular and renal dysfunction appear from the 3rd to 6th day. Renal abnormalities include proteinuria, pyuria, hematuria, and azotemia. Hepatic damage is minimal, and healing is complete.
Mortality is nil in anicteric patients. With jaundice, the mortality rate is 5 to 10%; it is higher in patients > 60 yr.
Diagnosis
Similar symptoms can result from viral meningoencephalitis, other spirochetal infections, influenza, and hepatitis. The history of biphasic illness may help differentiate leptospirosis. Leptospirosis should be considered in any patient with FUO who might have been exposed to leptospires.
Patients with suspected leptospirosis should have blood cultures, acute and convalescent (3 to 4 wk) antibody titers, CBC, serum chemistries, and liver function tests. Meningeal findings mandate lumbar puncture; the CSF cell count is between 10 and 1000/μL (usually < 500/μL), with predominantly mononuclear cells. CSF glucose is normal; protein is < 100 mg/dL.
The peripheral blood WBC count is normal or slightly elevated in most but may reach 50,000/μL in severely ill patients with jaundice. The presence of > 70% neutrophils helps differentiate leptospirosis from viral illnesses. In jaundiced patients, bilirubin levels are usually < 20 mg/dL (< 342 μmol/L) but may reach 40 mg/dL (684 μmol/L) in severe infection; marked intravascular hemolysis in such patients may cause significant anemia.
Treatment
Antibiotic therapy is effective even when begun relatively late. In severe illness, penicillin G 5 to 6 million units IV q 6 h or ampicillin 500 to 1000 mg IV q 6 h is recommended. In less severe cases, doxycycline 100 mg po q 12 h, ampicillin 500 to 750 mg po q 6 h, or amoxicillin 500 mg po q 6 h may be given for 5 to 7 days. In severe cases, supportive care, including fluid and electrolyte therapy, is also important. Patient isolation is not required, but urine must be handled and disposed of carefully.
Doxycycline 200 mg po given once/wk during a period of known geographic exposure prevents disease.
Last full review/revision November 2005
Content last modified November 2005
| |
