Ku fever

Qu fever is an acute or chronic disease that is caused by a bacterium similar to the rickettsia Coxiella burnetii. Symptoms of acute illness include sudden onset of fever, headache, weakness and interstitial pneumonitis. Manifestations of a chronic disease depend on the affected organ. The diagnosis is confirmed by several serological tests, sowing MO or PCR. Treatment of fever is performed by Ku doxycycline and chloramphenicol.

Coxiella burnetii is a small intracellular pleomorphic bacillus that is no longer classified as rickettsia. Molecular studies have made it possible to classify it as Proteobacteria of the same group as Legionella.

ICD Code 10

A78. Ku-fever.

Epidemiology of ku-fever

Ku-fever is a natural focal zoonotic infection. There are two types of foci of disease: primary natural and secondary agricultural (anthropurgic). In natural foci the pathogen circulates between the carriers (ticks) and their warm-blooded feeders: mites → warm-blooded animals → ticks.

The reservoir of the pathogen in natural foci is ixodids, partially gamasaceous and argasid mites (more than seventy species), in which transfacial and transovarial rickettsia transfer are observed, as well as wild birds (47 species) and wild mammals - rickettsia carriers (more than eighty species). The existence of a persistent natural foci of infection contributes to the infection of various types of domestic animals (large and small cattle, horses, camels, dogs, donkeys, mules, poultry, etc.).

[1], [2], [3], [4]

What causes ku-fever?

Ki fever around the world is considered as an asymptomatic infection of domestic and farm animals. Sheep and cattle are the main reservoirs of human infection. C. Burnetii is found in feces, urine, milk and tissues (especially in the placenta). This microorganism is also preserved in nature, in the cycle the animal is a tick.

Cases of this disease occur among people whose work is associated with close contact with farm animals or their products. Transmission of the infection usually occurs by inhalation of infected aerosols, but the disease can also occur when eating contaminated raw milk. Coxiella burnetii is very virulent, resistant to inactivation and retains viability in dust and feces for months. Even 1 this microorganism can cause disease.

Q fever may be acute or chronic. Acute illness is a febrile infection, in which the respiratory system is often affected, but in some cases, liver damage is possible. Chronic fever Ky usually manifests with endocarditis or hepatitis. It is also possible to develop osteomyelitis.

Pathogenesis of ku-fever

Ku-fever is a cyclic benign rickettsial reticuloendotheliosis. In connection with the absence of tropism of the causative agent to the vascular endothelium, panvasculitis does not develop, therefore the rash and other symptoms of vascular lesions are not characteristic of the disease. Unlike other rickettsiosis, coxiella reproduce mainly in histiocytes and macrophages.

What are the symptoms of ku-fever?

Fever Ku has an incubation period that varies from 18 to 21 days (the deadlines are 9-28 days). Some infections are accompanied by minimal symptoms, but in most cases, patients develop influenza-like symptoms. The onset of the disease is sudden, with fever, acute headache, chills, acute weakness, myalgia, anorexia and profuse sweats. The fever can reach 40 C, and the duration of the febrile period can be from 1 week to 3 or more. Respiratory symptoms, dry non-productive cough and pleural pain appear on the 4-5th day after the onset of the disease. Pulmonary symptoms can be particularly acute in elderly and weakened patients. In physical examination, wheezing is often detected, and symptoms of pulmonary consolidation can be identified. In contrast to diseases caused by rickettsia, the infection does not appear with this infection.

Acute liver damage, which develops in some patients, resembles viral hepatitis. At the same time, fever, weakness, hepatomegaly, accompanied by pain in the right upper quadrant, and, possibly, jaundice appear. Headache and symptoms of the respiratory tract are often absent. Chronic form of fever may be manifested by fever of unknown origin. This disease must be differentiated with other causes of hepatic granulomas (for example, in tuberculosis, sarcoidosis, histoplasmosis, brucellosis, tularemia, syphilis) by performing laboratory tests.

Endocarditis in this disease resembles subacute infective endocarditis caused by the bacteria of the viridans group; more often, the aortic valve is affected, but vegetation can be detected on any valve. There may appear thickening of the fingers, arterial emboli, hepato- and splenomegaly, and purple rash.

Fever Ku is a fatal disease in only 1% of untreated patients. In some patients with lesions of the nervous system, residual events are formed.

The most severe forms of the disease occur with aerogenic infection, nevertheless it is a cyclic infection, during which the following periods are distinguished: incubation, initial (3-5 days), high (4-8 days) and convalescence. Allocate the following forms of the disease:

• acute (duration of the disease 2-4 weeks) - in 75-80% of patients;
• subacute or prolonged (1-3 months) - in 15-20% of patients:
• chronic (from several months to one year and more) - in 2-30% of patients;
• erased.

How is ku-fever diagnosed?

Laboratory diagnostics of ku-fever consists in the formulation of serological reactions: RA, RSK, RNIF, the results of which are analyzed taking into account the phase variations of the coxial cells, which makes it possible to differentiate patients and recover from illness (diagnostic standard).

At the beginning of its course, fever Ku reminds many infections (eg, influenza, other viral infections, salmonellosis, malaria, hepatitis, brucellosis). At later stages, it resembles many forms of bacterial, viral and mycoplasma pneumonia. Important diagnostic information is contact with animals or their products.

The immunofluorescence method is the diagnostic method of choice. It is also possible to apply ELISA. Also for diagnosis, serological tests (usually paired sera in the complement fixation reaction) can be used. PCR-study allows to determine the microorganism in the biopsy material. C. Burnetii can be sown from clinical specimens, but this is only feasible in special laboratories. Routine cultures of blood and sputum are negative.

Patients with respiratory signs and symptoms of the disease are shown chest X-ray. At the same time, x-ray signs of the disease may include pleural blackouts, pleural effusion, and fractional consolidation. The general appearance of the lungs may resemble bacterial pneumonia, but is histologically more similar to psittacosis and some viral pneumonia.

In acute Ku fever, a general blood test may be normal, but approximately 30% of patients have leukocyte counts. In typical cases, the level of alkaline phosphatase, ACT and ALT is moderately elevated (2-3 times). When conducting a liver biopsy, histological examination reveals diffuse granulomatous changes.

How is ku-fever treated?

Primary treatment of fever Ku includes the appointment of doxycycline at a dose of 200 mg orally 1 time, after which the drug is prescribed at a dose of 100 mg 2 times a day until clinical improvement and no fever within 5 days. Treatment with doxycycline continues for at least 7 days. The second line of treatment is the administration of chloramphenicol in a dose of 500 mg orally or intravenously 4 times a day for 7 days. Fluoroquinolones and macrolides are also effective.

In the case of endocarditis treatment should be at least 4 weeks. In this case, the most preferred drugs are tetracyclines. In cases where antibiotic treatment is only partially effective, damaged valves should be replaced surgically, but sometimes recovery occurs without surgical intervention. Clear treatment for chronic hepatitis is not defined.

The patient must be isolated. There is an effective vaccination against ku-fever. These vaccines should be used to protect workers in slaughterhouses, dairies, raw material processors, shepherds, wool sorter, farmers and others at high risk. These vaccines are not available on the commercial market, but can be obtained in special laboratories, for example, at the Army Medical Research Institute of Infectious Diseases in Fort Detrick, Maryland.

What is the prognosis of ku-fever?

Ku-fever has a favorable prognosis with timely full-fledged treatment, although the recovery period in some patients is longer than with other rickettsiosis, and is accompanied by asthenoapatoabulic syndrome, vegetative and vestibular disorders.

Lethal outcomes are rare and are usually caused by the development of endocarditis, the main syndrome of chronic form of fever.