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Tularemia
Last reviewed: 23.04.2024
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Tularemia (Latin tularemia, plague disease, rabbit fever, small plague, mouse disease, fever fever, epidemic lymphadenitis) is an acute zoonotic bacterial natural focal infectious disease with various mechanisms of transmission of the pathogen.
Tularemia is a febrile illness caused by Francisella tularensis, which resembles in its manifestations typhoid fever. Symptoms of tularemia include primary ulcerative lesions, regional lymphadenopathy, progressive symptoms of systemic disease and in some cases atypical pneumonia. Diagnosis of tularemia is primarily based on epidemiological data and the clinical picture of the disease. Treatment of tularemia is carried out by streptomycin, gentamycin, chloramphenicol and doxycycline.
ICD-10 code
- A21.0. Ulceroglandular tularemia.
- A21.1. Oculoglandular tularemia.
- A21.2. Pulmonary tularemia.
- A21.3. Gastrointestinal tularemia.
- A21.8. Other forms of tularemia.
- A21.9. Tularemia, unspecified.
What causes tularemia?
Tularemia is caused by Francisella tularensis, which is a small, pleomorphic, immobile, non-spore-forming aerobic bacillus that can enter the body by ingestion, inoculation, inhalation or contamination. Francisella tularensis can penetrate into visually undamaged skin, but actually penetrates through microdamages. Type A of the pathogen, which has a large virulence against humans, is found in rabbits and rodents. Type B of the pathogen usually leads to the development of a moderate oculoglandular infection. This type is found in water and in aquatic animals. Distribution among animals is usually carried out through bloodsucking ticks and cannibalism. Hunters, butchers, farmers and persons working with wool are most often infected. In the winter months, most infections are due to contact with infected wild rabbits (especially during their freshness). In the summer months, infections usually precede the cutting of infected animals or birds or contact with infected mites. Rarely, this disease can occur when eating poorly cooked infected meat, contaminated water, or mowing fields in endemic regions. In the western states, bites of horse or moose fleas and direct contact with the hosts of these parasites can be alternative sources of infection. The possibility of transmission of infection from man to man is not established. Laboratory workers are at high risk for infection, as this infection can be transmitted during normal work with infected specimens. Tularemia is considered as a possible agent of bioterrorism.
In cases of disseminated infection, characteristic necrotic lesions scattered throughout the body at different stages of evolution are found. These lesions can be from 1 mm to 8 cm in size, have a pale yellow color and are determined visually as primary lesions on the fingers, eyes and in the mouth area. Often they can be found in the lymph nodes, spleen, liver, kidneys and lungs. With the development of pneumonia, necrotic foci are found in the lungs. Despite the fact that acute systemic intoxication can develop, no toxins are detected in this disease.
What are the symptoms of tularemia?
Tularemia begins suddenly. It develops within 1-10 days (usually 2-4 days) after contact. This causes nonspecific symptoms of tularemia headache, chills, nausea, vomiting, fever 39.5-40 C and acute prostration. Appears extremely pronounced weakness, repeated chills with profuse sweats. Within 24-48 hours there is an inflammatory papula at the site of infection (finger, hand, eye, mouth of the oral cavity). Inflammatory papula does not appear in the case of glandular and typhoid tularemia. The papule quickly becomes pustular and ulcerated, resulting in the formation of a clean ulcer crater with a thin, colorless exudate. Ulcers are usually single on the hands and multiple on the eyes and in the mouth. Usually only one eye is damaged. Regional lymph nodes are enlarged and can be suppurated with abundant drainage. A condition resembling typhoid fever develops to the 5th day of the disease, and the patient may experience atypical pneumonia, which is sometimes accompanied by delirium. Despite the fact that signs of consolidation are usually present, weakened respiratory noises and rare rales can be the only physical findings in tularemic pneumonia. There is a dry, unproductive cough associated with chest pain. Nonspecific such rose-oleic rash may appear at any stage of the disease. There may be splenomegaly and perisplenitis. In the absence of treatment, body temperature remains elevated for 3-4 weeks and decreases gradually. Mediastinitis, lung abscess and meningitis are rare complications of tularemia.
In the treatment, the mortality rate is almost 0. In the absence of treatment, the mortality rate is 6%. Death with tularemia is usually the result of a stratified infection, pneumonia, meningitis or peritonitis. In cases of inadequate treatment, recurrences of the disease may occur.
Types of tularemia
- Ulcerative-glandular (87%) - Primary lesions are located on the hands and fingers.
- Typhoid (8%) - Systemic disease, accompanied by abdominal pain and fever.
- Oculoglandular (3%) - Inflammation of lymph nodes on one side, most likely due to inoculation of the pathogen in the eye, infected with fingers or hand.
- Glandular (2%) - Regional lymphadenitis in the absence of a primary lesion. Often cervical adenopathy, which suggests the oral infection.
Diagnosis of tularemia
The diagnosis of tularemia should be suspected if there is evidence of contact with rabbits or wild rodents or a tick bite. This takes into account the acute onset of symptoms and the characteristic primary damage. Patients should undergo a culture examination of blood and a diagnostic clinically important material (for example, sputum, detachable lesions) and antibody titers in acute and convalescent periods taken at intervals of 2 weeks. A 4-fold increase or appearance of a titer of more than 1/128 is considered diagnostic. The serum of patients with brucellosis can cross-react with antigens to Francisella tularensis, but titres are usually much lower. Fluorescent staining of antibodies is used in some laboratories. Often there is leukocytosis, but the number of leukocytes can be normal, with an increase in the proportion of polymorphonuclear neutrophils.
In view of the fact that Francisella tularensis is highly infectious, samples and culture medium should be investigated with suspicion of tularemia with special precautions and, if possible, these studies should be carried out in B or C class laboratories.
[How is tularemia treated?
Tularemia is treated with streptomycin 0.5 g intramuscularly every 12 hours (in the case of bioterrorism - 1 g every 12 hours) until the temperature normalizes. After this, 0.5 g once a day for 5 days. In children, the dose is 10-15 mg / kg intramuscularly after 12 hours for 10 days. Also effective drug is the appointment of gentamycin in a dose of 1-2 mg / kg intramuscularly or intravenously 3 times a day. Chloramphenicol (no oral form in the US) or doxycycline 100 mg orally after 12 hours may be prescribed until the temperature normalizes, but with the use of these drugs, recurrences of the disease may occur, and these drugs do not always prevent suppuration of the lymph nodes.
For the treatment of primary skin lesions, it is good to use moist salt dressings, which can also relieve the acuity of lymphangitis and lymphadenitis. Surgical drainage of large abscesses is rarely used, in cases when treatment of tularemia with antibiotics is delayed. With ocular tularemia, the imposition of warm salt compresses and the use of dark glasses allows some relief. In acute cases, 2% gomatropin 1-2 drops every 4 hours can relieve the symptoms of tularemia. Intensive headache is usually treatable with oral opioids (for example, oxycodone or hydroxycodone with acetaminophen).
How is tularemia prevented?
Tularemia is prevented by the use of clothing, which protects against ticks, and means that repels insects. A thorough examination to identify ticks should be carried out after returning from endemic regions. Ticks must be removed immediately. When working with rabbits and rodents, especially in endemic areas, it is necessary to use protective clothing such as rubber gloves and face protection masks, since Francisella tularensis can be present in faeces of animals and mites and in animal wool. A wild bird should be carefully prepared before use. Water, which is possibly contaminated, must be disinfected before use. Used vaccine against tularemia.
What is the prognosis of tularemia?
Tularemia has a favorable prognosis for frequently occurring forms of the disease, with pulmonary and generalized forms - serious. The lethality does not exceed 0.5-1% (according to American authors, 5-10%).
In the period of convalescence, long subfebrile condition, asthenic syndrome are typical, residual phenomena (enlarged lymph nodes, changes in the lungs) can be preserved. In a number of patients, work capacity is restored slowly, which requires a medical and labor expertise.