Leptospirosis

Leptospirosis (Weil's disease, infectious jaundice, Japanese 7-day fever, nanukayami, water fever, icterohemorrhagic fever, etc.) is a general term for all infections caused by bacteria of the genus Leptospira, regardless of serotype; includes infectious, or leptospirotic, jaundice and dog fever. Symptoms of leptospirosis are biphasic. Both phases include episodes of fever, the second phase may sometimes include hepatitis, meningitis, and kidney damage. Diagnosis is based on the detection of leptospira in a dark field bacteriologically and serologically. Treatment of leptospirosis is carried out with doxycycline and penicillin.

ICD-10 codes

• A27.0. Icteric hemorrhagic leptospirosis.
• A27.8. Other forms of leptospirosis.
• A27.9. Leptospirosis, unspecified.

The first description of the disease under the name fievre jaune ("yellow fever") was given in 1812 by the military doctor Larrey, who observed patients from Napoleon's troops during the siege of Cairo. For a long time, the disease was called Weil-Vasiliev disease, since the first clinical descriptions of leptospirosis as an independent nosological form were given by A. Weil in Heidelberg (1886) and N.P. Vasiliev in Russia (1888). In 1907, the causative agents of the disease - spiral-shaped microorganisms - were first discovered using special staining methods during a postmortem examination of a human kidney (Stimson, USA). In 1915, a group of German doctors (Uhlenhut N.R. et al.) and Japanese researchers (Inada R., Do V. et al.) simultaneously isolated pathogens from sick people - German soldiers who fought in northeastern France ("French disease") and Japanese miners. The term "leptospira" (soft, delicate spiral) belongs to the microbiologist Nogushi (Japan, 1917). Later it became known that the pathogens have many serovars that cause lesions in humans. In the 1920s, the epidemiological role of animals as sources of human infection was revealed - rats, dogs, livestock.

What causes leptospirosis?

Leptospirosis is a zoonosis; the infection occurs in many domestic and wild animals in both a severe lethal form and as a carrier. In the latter case, the pathogens are excreted in the animal's urine for many months. A person becomes infected through direct contact with the urine or tissues of a sick animal or indirectly - through contaminated water and soil. Usually, the portal of infection are lesions of the skin and mucous membranes (oral cavity and nose, conjunctiva). Leptospirosis can be an occupational disease (in farmers, workers in slaughterhouses and other agricultural enterprises), but in the United States most cases of the disease are associated with recreation (in particular, with swimming in contaminated water). Dogs and cats are often the source of infection. Of the 40-100 cases registered annually in the United States, the majority occur in late summer - early fall. Due to the vagueness of clinical symptoms, it is possible that many more cases of the disease remain undiagnosed and unreported.

What are the symptoms of leptospirosis?

Leptospirosis has an incubation period that lasts from 2 to 20 days (usually 7-13). There are two phases of the disease. The septicemic phase begins with sudden chills, fever, headache, and severe muscle pain. After 2-3 days, conjunctival hyperemia appears. The liver and spleen rarely enlarge. This phase lasts 4-9 days; the temperature sometimes rises to 39 C or more, and chills recur. After the temperature drops, on the 6th-12th day of the disease, the second, or immune, phase begins, coinciding with the appearance of specific antibodies in the blood. The symptoms and fever described above resume, and signs of meningitis may develop. Iridocyclitis, optic neuritis, and peripheral neuropathy are rare. If infection occurs during pregnancy, leptospirosis can cause abortion, even during the recovery stage.

Weil's disease (leptospirosis jaundice) is a severe form of leptospirosis with jaundice associated with intravascular hemolysis, azotemia, anemia, hemorrhages, impaired consciousness, and continuous fever. Hemorrhagic phenomena are associated with damage to the capillary walls and include nosebleeds, petechiae, purpura, ecchymosis, then the development and rare progression to subarachnoid hemorrhages, hemorrhages in the adrenal glands and gastrointestinal bleeding. Signs of hepatocellular and renal dysfunction appear after 3-6 days. Kidney pathology includes proteinuria, pyuria, hematuria and azotemia. Thrombocytopenia is possible. Liver damage is minor and its functions are completely restored upon recovery.

In the anicteric form of the disease, the mortality rate is zero. If jaundice develops, the mortality rate reaches 5-10%, and in people over 60 years of age it can be even higher.

How is leptospirosis diagnosed?

Symptoms of leptospirosis may resemble those of viral meningoencephalitis, other spirochete infections, influenza, and hepatitis. A history of biphasic fever helps in the differential diagnosis of leptospirosis. Leptospirosis should be considered in all cases of fever of unknown origin (FUO) in individuals exposed to epidemiological conditions with a risk of leptospirosis.

Patients suspected of having leptospirosis should have blood cultures, acute and convalescent (3-4 weeks) antibody titers, complete blood counts, biochemical profiles, and liver function tests. If meningeal signs are present, a lumbar puncture should be performed; the CSF cell count is 10-1000/μL (usually <500/μL with mononuclear cells predominating). Glucose levels remain normal, and protein levels are <100 mg/dL.

The white blood cell count remains normal or slightly elevated, but can reach 50,000/μl in severe cases. The predominance of neutrophils (more than 70%) helps differentiate leptospirosis from viral infections. The bilirubin level in the blood is usually less than 20 mg/dl (less than 342 μmol/l), but can reach 40 mg/dl (684 μmol/l) in severe cases; jaundice may cause intravascular hemolysis, leading to severe anemia.

How is leptospirosis treated?

Antibacterial treatment of leptospirosis is quite effective, even if it is started late. In severe cases, penicillin G is recommended intravenously from 5 to 6 million units/day every 6 hours or ampicillin intravenously at 500-1000 mg every 6 hours. In mild cases, antibiotics can be prescribed orally - doxycycline 100 mg 2 times a day, ampicillin 500-750 mg every 6 hours or amoxicillin 500 mg every 6 hours for 5-7 days. In severe cases, it is also important to maintain water and electrolyte balance. Isolation of the patient is not necessary, but appropriate measures to control diuresis must be taken.

Doxycycline 200 mg once a week is used for prophylaxis in endemic areas.

How to prevent leptospirosis?

Leptospirosis can be prevented by identifying and treating leptospirosis in valuable animals, regularly deratizing populated areas, protecting water bodies from contamination by animal excrement, prohibiting swimming in stagnant water bodies, disinfecting water and open water sources, and fighting stray dogs.

Vaccination of farm animals and dogs is carried out, as well as routine vaccination of persons whose work is associated with the risk of leptospirosis infection: workers of livestock farms, zoos, pet stores, dog kennels. fur farms, enterprises for processing livestock raw materials, employees of laboratories working with leptospira cultures. The vaccine against leptospirosis is administered for the prevention of leptospirosis from the age of 7 in a dose of 0.5 ml subcutaneously once, revaccination after a year.