Leptospirosis is a naturally focal zoonotic infectious disease characterized by damage to the liver, as well as to the kidneys and nervous system against the background of general intoxication. It is often accompanied by hemorrhagic symptoms and jaundice. The causative agent of leptospirosis can enter the body through mucous membranes or injured skin. From infection to the first clinical manifestations of leptospirosis, it can take from several days to a month. Microscopic detection of leptospira in the blood preparation plays an important role in the early diagnosis of leptospirosis, the results of bakposev are often of retrospective significance.
Leptospirosis causes Leptospira interrogans. It is a gram-negative aerobic mobile spiral rod resembling a spirochete. Currently, more than 230 leptospira serovars have been isolated. Bacteria have moderate resistance in the environment, pathogenic leptospira die when exposed to sunlight, high temperatures. In water, different strains can exist from several hours to a month. In dry soil, the viability of leptospira persists for 2 hours, in swampy soil – up to 10 months. They can tolerate freezing, are able to survive the winter in moist soil and reservoirs. Leptospira is stored on food products for 1-2 days. They die within 20 minutes when exposed to one percent hydrochloric acid and a half-percent solution of phenol.
The main reservoir of leptospirosis in nature are rodents (mice, rats, gray voles) and insectivorous mammals (hedgehogs, shrews). The reservoir and source of infection are also farm animals (pigs, sheep, cows, goats, horses), fur-bearing animals on animal farms, dogs. The animal is contagious throughout the entire period of the disease. Rodents suffer from chronic leptospirosis, secreting the pathogen in the urine. Transmission of leptospirosis from humans is extremely unlikely.
Leptospirosis is spread by the fecal-oral mechanism mainly by water. In addition, it is possible to note the probability of transmission by contact and food (feed). A person becomes infected with leptospirosis through mucous membranes or microtrauma of the skin. Infection can occur when bathing in bacteria-contaminated reservoirs (and swallowing water), working with farm animals.
A person has a high natural susceptibility to this infection. After leptospirosis, immunity is stable and long-lasting, but specific for this serovar of bacteria and re-infection with leptospira with a different antigenic structure is possible.
The gates of infection for leptospira are the mucous membranes of the digestive tract, nasopharynx, sometimes the genitals and urinary tract, as well as damage to the skin. In the field of the introduction of the pathogen, no pathological changes are noted. Leptospira spreads with the flow of lymph, settling in the lymph nodes, multiplying there, and dispersing through the circulatory system to organs and systems. Leptospira are tropic to macrocytic phagocytes, tend to accumulate in the tissues of the liver, spleen and kidneys (sometimes in the lungs) causing local inflammation.
The incubation period of leptospirosis ranges from a few days to a month, averaging 1-2 weeks. The disease begins acutely, with a sharp rise in temperature to high numbers, with tremendous chills and pronounced symptoms of intoxication (intense headache, myalgia, especially in the calf and abdominal muscles, weakness, insomnia, anorexia). On examination, hyperemia and swelling of the face are noted, herpetiform rash may appear on the lips and wings of the nose, the contents of the vesicles are hemorrhagic in nature. Irritated conjunctiva, injected sclera, moderate hyperemia of the mucous membrane of the pharynx, oropharynx, hemorrhages in the submucosal layer may occur.
Measles-like or petechial rashes on the trunk, limbs appear after 2-4 days. The rash can persist from several hours to several days. Hemorrhagic syndrome (petechiae and hemorrhages) can complement the leptospirosis clinic from the very first days of the disease. Severe course may be accompanied by hemorrhagic rash in the armpits and elbow bends, hematuria (up to a visible admixture of blood in the urine), nasal, uterine, gastrointestinal bleeding, hemoptysis (up to hemorrhagic pulmonary edema).
Disorders of the respiratory system in the first days are usually not noted, occur with the progression of infection and in the midst of the disease with moderate and severe course most often have a pathogenetic relationship with hemorrhagic syndrome. Cardiac disorders (rhythm changes, muffled heart tones, a drop in peripheral blood pressure) are associated with intoxication syndrome.
In addition, patients may notice disorders of the digestive system: abdominal pain, nausea and vomiting, hepatomegaly and splenomegaly, severity and soreness during palpation in the right hypochondrium. Sometimes jaundice of a hepatic nature develops: the sclera turn yellow, the skin turns an intense saffron color, feces discolor, urine acquires a beer shade. Patients may be disturbed by skin itching.
With kidney damage, patients complain of pain in the lumbar region, oliguria is noted (up to anuria), urine acquires a dark color, often with an admixture of blood. Pasternatsky’s symptom is positive. On the part of the nervous system, sleep disorders, headache, increased anxiety, excitement are noted. Meningeal symptoms may occur (in 10-15% of cases, at the height of the disease, patients demonstrate a serous meningitis clinic).
Fever with leptospirosis persists for up to a week, after which a critical decrease in temperature occurs. Sometimes there is a second wave of fever. This is followed by a period of convalescence, during which there is a gradual subsiding of symptoms and restoration of organ functions. In case of timely medical care and moderate severity of the disease, recovery usually occurs after 3-4 weeks. In 20-30% of cases, relapses of infection may occur, in which there is less severity of fever and multiple organ disorders, the duration of attacks is usually several days. In general, a recurrent infection can last up to 2-3 months.
The most common complication of the disease is kidney failure. In severe cases, it can develop in the first week, providing a high mortality rate of more than 60%. Other complications may be liver failure, hemorrhages in lung tissue, adrenal glands, muscles, internal bleeding.
Among other things, complications from the nervous system are possible: meningitis, meningoencephalitis. Complications from the organs of vision: iritis and iridocyclitis. Leptospirosis can contribute to the attachment of secondary bacterial infection: secondary pneumonia, abscesses, bedsores.
The general blood test for leptospirosis is characterized by a picture of bacterial infection – leukocytosis with neutrophil predominance, increased ESR. The peak period may decrease the content of red blood cells and the concentration of eosinophils and platelets.
As an analysis of the state of organs and systems, a biochemical blood test is used (signs of functional disorders in the liver are noted), a urine test (microhematuria, signs of jaundice may be detected). With hemorrhagic syndrome, a coagulation study is performed – a coagulogram. In case of kidney damage, a patient with leptospirosis is consulted by a nephrologist, an ultrasound of the kidneys is performed. Meningial symptoms are an indication for lumbar puncture.
The specific diagnosis consists in the back-seeding of blood (leptospira can be detected in a drop of blood by microscopy), in some cases, the pathogen is isolated and the back-seeding is carried out on nutrient media. Due to the long-term growth of leptospira culture, sowing is important for retrospective confirmation of the diagnosis. Serological diagnostics is performed using HCR in paired sera. The antibody titer begins to increase at the height of the disease, the second analysis is taken during the convalescence period. A highly specific and sensitive technique for the diagnosis of leptospirosis is the detection of bacterial DNA using PCR. Diagnosis can be carried out from the first days of the disease.
Patients with leptospirosis are subject to hospitalization if severe complications are likely to develop and for the purpose of clinical and laboratory monitoring of the state of the body in dynamics. Patients are shown bed rest for the entire period of fever and 1-2 days after normalization of temperature. In case of symptoms of kidney failure, patients also stay in bed. Dietary restrictions are prescribed in accordance with the existing functional disorders of the liver and kidneys.
Etiotropic therapy involves the use of antibiotics. With leptospirosis, benzylpenicillin, prescribed intramuscularly, has proven itself well. Alternatively, it is possible to use ampicillin intravenously. Severe leptospirosis is treated with doxycycline. The complex of therapeutic measures includes the use of a specific anti-leptospirosis heterologous immunoglobulin.
Measures of nonspecific therapy include detoxification, symptomatic agents, monitoring of the respiratory and cardiovascular system and rheological properties of blood. In case of acute liver failure, renal or heart failure, pulmonary edema, resort to the usual measures of intensive therapy.
Prognosis and prevention of leptospirosis
Usually leptospirosis has a favorable prognosis, fatal cases are mainly associated with insufficient or untimely medical care and a weakened state of the body. Currently, mortality from leptospirosis does not exceed 1-2%. An increase of this indicator to 15-20% is possible during periods of mass epidemics.
Prevention of leptospirosis implies, first of all, control over the morbidity of farm animals, as well as restriction of rodent reproduction (deratization of urban facilities, rural farms). Sanitary and hygienic measures include monitoring the condition of water sources (both places of water intake for the needs of the population and public beaches), agricultural land. Specific vaccination measures imply the introduction of the killed leptospirosis vaccine to persons working with animals, or to citizens who are in an epidemic focus during outbreaks of leptospirosis.