34-10: Leptospirosis

ESSENTIALS OF DIAGNOSIS

GENERAL CONSIDERATIONS

Leptospirosis is an acute and sometimes severe treponemal infection that is caused by several species within the genus Leptospira. The disease is distributed worldwide, and it is among the most common zoonotic infections. The leptospires enter through minor skin lesions and probably via the conjunctiva. Cases have occurred in international travelers after swimming or rafting in contaminated water, and occupational cases occur among sewer workers, rice planters, abattoir workers, and farmers. Sporadic urban cases have been seen in homeless persons exposed to rat urine. Infection may also be transmitted to humans by the ingestion of food and drink contaminated by the urine of an infected animal.

CLINICAL FINDINGS

A. Symptoms and Signs

Anicteric leptospirosis, the more common and milder form of the disease, is often biphasic. After an incubation period of 2–20 days, the initial or “septicemic” phase begins with abrupt fever to 39–40°C, chills, abdominal pain, severe headache, and myalgias, especially of the calf muscles. There may be marked conjunctival suffusion. Leptospires can be isolated from blood, CSF, and tissues. Following a 1- to 3-day period of improvement in symptoms and absence of fever, the second or “immune” phase begins; however, in severe disease the phases may appear indistinct. Leptospires are absent from blood and CSF but are still present in the kidney, and specific antibodies appear. A recurrence of symptoms is seen as in the first phase of disease with the onset of meningitis. Uveitis (which can be unilateral or bilateral and usually involves the entire uveal tract), rash, nausea, vomiting, diarrhea, and adenopathy may occur. A rare but severe manifestation is hemorrhagic pneumonia. The illness is usually self-limited, lasting 4–30 days, and complete recovery is the rule.

Icteric leptospirosis (Weil syndrome) is the more severe form of the disease, characterized by impaired kidney and liver function, abnormal mental status, hemorrhagic pneumonia, hypotension, and a 5–40% mortality rate. Symptoms and signs often are continuous and not biphasic.

Pretibial fever, a mild form of leptospirosis caused by Leptospira autumnalis, occurred during World War II at Fort Bragg. In pretibial fever, there is patchy erythema on the skin of the lower legs or generalized rash occurring with fever.

Leptospirosis with jaundice must be distinguished from hepatitis, yellow fever, rickettsial disease, and relapsing fever.

B. Laboratory Findings

The leukocyte count may be normal or as high as 50,000/mcL (50 × 10⁹/L), with neutrophils predominating. The urine may contain bile, protein, casts, and red cells. Oliguria ...