Omsk hemorrhagic fever

Omsk hemorrhagic fever (OGL) is an acute viral zoonotic natural focal disease with a transmissible mechanism of transmission of the pathogen, characterized by wave-like fever, general intoxication, development of hemorrhagic syndrome and vegetative-vascular dystonia, as well as CNS, lung, kidney damage and relatively benign course.

ICD-10 code

A98.1. Omsk hemorrhagic fever.

Epidemiology of Omsk haemorrhagic fever

The main source and reservoir of the virus are the ticks Dermacentorpictus and Dermacentor marginatus (the virus is transmitted transovarially and during metamorphosis). In addition, natural foci detect rodents infected with Omsk hemorrhagic fever virus (vole, mouse, rat, shrew, muskrat, chipmunks, water rats and other rodents). Infection of people occurs mainly through the bite of mites, as well as airborne dust from rodents, contact - when cutting carcasses of animals and alimentary - when using raw lake water. The natural susceptibility of people is high: the virus affects all age groups of the population, but mostly people aged 20-40 years (mainly commercial workers and people engaged in field work in forest-steppe areas) fall ill. Natural foci of Omsk hemorrhagic fever are known in Omsk, Tyumen. Orenburg, Kurgan. Novosibirsk regions, and also in the north of Kazakhstan. The seasonality of the morbidity is clearly expressed: the first ascent is observed in the spring-summer months (May-June) - the period of tick activity (the transmissive transmission route): the second one in the autumn months (September-October) during the catching period of the muskrat (non-transmissible transmission route).

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

What causes Omsk hemorrhagic fever?

Omsk hemorrhagic fever is caused by the arbovirus of the family Flariviridae, the genus Flavivirus. The genome is represented by single-stranded RNA; on the antigenic structure is close to the genome of tick-borne encephalitis virus. According to electron microscopy, the dimensions of the virion are up to 40 nm; it has a spherical shape, cubic symmetry; covered with a two-layered shell containing lipids and proteins having antigenic properties and determining group- and species-specific determinants. The Omsk haemorrhagic fever virus multiplies in the cytoplasm on the membranes of the Golgi complex. It is highly pathogenic for white mice, muskrat and narrow-crested voles: causes paralytic phenomena in some species of monkeys after intracerebral infection. It is well cultivated in cell cultures of embryonic tissue of mice, chickens, hamsters, monkeys and humans, but the pronounced cytopathogenic effect gives only in tissue cultures of pig embryo. The Omsk haemorrhagic fever virus becomes highly virulent in passage on white mice and muskrats; is a danger of intralaboratory infection of employees working with infected animals. The virus is inactivated by disinfecting solutions (3% solution of carbolic acid, 3% solution of lysol, 1% solution of chloramine); at a temperature of 70-80 ° C perished in 10 minutes. At boiling - instantly: at 4 ° C it is inactivated after 29 days; in 50% glycerol is stored up to 7 months; in the dried state - up to 4 years.

Pathogenesis of Omsk haemorrhagic fever

Omsk hemorrhagic fever has been studied insufficiently. Intruding into the human body through the damaged skin, mucous membranes of the respiratory tract and digestive organs, the virus with blood flow spreads throughout the body and affects mainly the endothelium of the vessels of the microcirculatory bed, the adrenal glands, the autonomic nervous system and the spleen. The defeat of small blood vessels in various organs and tissues causes the development of hemorrhagic syndrome.

Symptoms of Omsk hemorrhagic fever

The incubation period of Omsk hemorrhagic fever is 2-10 days (an average of 5-7).

Symptoms of Omsk haemorrhagic fever give grounds to distinguish:

• typical forms of the disease (hemorrhagic);
• atypical forms of the disease (without hemorrhagic manifestations).

The degree of severity of the disease is:

• light current;
• medium-heavy current;
• heavy current.

According to the nature of clinical manifestations, there are:

• acute course (no relapse):
• acute recurrent course (with repeated temperature wave).

Omsk hemorrhagic fever begins acutely, suddenly, with a high fever, chills, a sharp headache, dizziness, severe weakness, muscle pain in the limbs and back, nausea and nosebleeds. Body temperature from the first day of the disease reaches high values (39-40 ° C), lasts for 3-4 days, and then decreases by 7-15 days. Almost 50% of patients in the period of convalescence (at the second or third week of the course of the disease) reveal a repeated wave of fever, during which the symptoms of Omsk hemorrhagic fever resumed with worsening of the condition. The second wave of the disease lasts 4-14 days. But it proceeds more easily. Against the backdrop of fever, the patients are listless, lie motionless with their head thrown back, slowed down, reluctant to answer questions. There is a puffiness and hyperemia of the face, neck; injection of vessels of the sclera and conjunctiva; bright coloration of soft and hard palate, gums with the development of small and large hemorrhages on them. From 3-4 days of the course of the disease hemorrhagic symptoms of Omsk hemorrhagic fever develop, the earliest of which is the appearance of a hemorrhagic rash on the anterior and lateral surfaces of the chest, the extensor surfaces of the arms and legs; positive symptoms of tourniquet and pinch. Possible nasal, pulmonary, gastrointestinal and uterine bleeding, more often uninvolved, but repeated throughout the disease several times. In the period of exacerbation, sometimes the cerebral and meningeal symptoms of Omsk hemorrhagic fever, transient focal clinical manifestations are revealed. Often revealed lesions of the respiratory system in the form of bronchitis and small-focal pneumonia, which is a characteristic feature of the clinical picture of Omsk haemorrhagic fever (as opposed to other hemorrhagic fevers). Diuresis is reduced, but the development of renal failure does not reveal. Involving the organs of the digestive system is expressed by nausea, vomiting, bitterness and dry mouth, hepatomegaly, epigastric pain. Characteristic reversible changes in the cardiovascular system in the form of bradycardia, widening the boundaries of the heart to the left, the deafness of cardiac tones and arterial hypotension. The course of the convalescence period depends on the presence of a repeated febrile wave and complications.

Complications of Omsk haemorrhagic fever

Omsk hemorrhagic fever is complicated rarely. Complications include otitis or parotitis (often purulent), pyelitis, late focal pneumonia. The majority of patients with Omsk hemorrhagic fever ends in complete recovery. In uncomplicated cases, the outlook is favorable.

[5],

Mortality and causes of death

In severe course, death may occur in the early stages as a result of intoxication or bleeding and on the 30-45th day of the course of the disease from septic complications. Mortality does not exceed 1%.

Diagnosis of Omsk haemorrhagic fever

Clinical symptoms of Omsk haemorrhagic fever:

• An acute onset with a sharp rise in body temperature, myalgia; often there is bronchitis and pneumonia: the development of hemorrhagic (petechial rash, bleeding in the sclera, hemoptysis: nasal, gastrointestinal, pulmonary and uterine bleeding) and meningeal syndromes in the absence of pronounced manifestations of renal failure.
• A repeated increase in body temperature during convalescence.
• Epidemiological anamnesis (stay in endemic for Omsk hemorrhagic fever areas, tick bite, peculiarities of professional activity).
• Seasonality.

Specific and nonspecific laboratory diagnostics of Omsk haemorrhagic fever

Nonspecific laboratory diagnostics of Omsk haemorrhagic fever

• Clinical blood test. There is an increase in the hemoglobin and the number of red blood cells, leukopenia, moderate neutrophilia with a shift to the left. Thrombocytopenia. Decrease in ESR to 3-7 mm / h.
• General urine analysis. Characteristic: proteinuria. Microhematuria, cylindruria, the presence of urine in the sediment already from 2 days of the disease of granular cells of the renal epithelium and the epithelium of the urinary tract (up to 20-30 in the field of vision).

Specific laboratory diagnostics of Omsk haemorrhagic fever

• Method of fluorescent antibodies (in paired sera).
• PCR.

Instrumental diagnostics of Omsk haemorrhagic fever

When radiographing chest organs reveal a picture of interstitial pneumonia.

The electrocardiogram reveals reversible diffuse changes in the myocardium in the form of deformation and expansion of the QRS complex, as well as changes in the voltage of the teeth P and T.

Conduct ultrasound of the kidneys.

Differential diagnosis of Omsk haemorrhagic fever

Differential diagnosis of Omsk haemorrhagic fever is performed with other hemorrhagic fevers, tick-borne encephalitis, leptospirosis.

[6], [7], [8], [9]

Indications for hospitalization

Omsk haemorrhagic fever is a reason for mandatory hospitalization in an infectious hospital regardless of the severity and period of the disease. Outpatient monitoring and treatment of patients with suspected Omsk haemorrhagic fever is unacceptable. Transportation of the patient should be as gentle as possible, with the exception of shocks and shaking.

Treatment of Omsk haemorrhagic fever

Medicamentous treatment of Omsk hemorrhagic fever includes pathogenetic and symptomatic treatment.

Etiotropic treatment of Omsk haemorrhagic fever has not been developed.

Pathogenetic treatment of Omsk haemorrhagic fever

Detoxification treatment of Omsk haemorrhagic fever - intravenous injection of 5-10% glucose solutions, isotonic sodium chloride solution with ascorbic acid and cocarboxylase. Dezagreganty (pentoksifillin), xanthinal nicotinate, dipyridamole, angioprotectors (calcium gluconate, etamzilate, rutoside, calcium dobezilate) are used; freshly frozen plasma, protease inhibitors (aprotinin); antioxidants (vitamin E, ubiquinone compositum), enterosorbents (hydrolysis lignin, povidone).

With complications of inflammatory nature, antibiotics are prescribed: penicillins. Cephalosporins, chloramphenicol, ofloxacin, ciprofloxacin.

Diet and diet

It is necessary to comply with bed rest.

It is recommended that the food be gentle - fractional, in a warm state, with the transition to a common table (No. 15) during the reconvalescence period.

[10], [11], [12], [13]

Approximate terms of incapacity for work

The patients are discharged at a satisfactory state of the patient and normalization of laboratory parameters (clinical analyzes of blood and urine). The terms of incapacity for work are determined individually. The period of release from work after discharge is: for a mild form of the disease - 7-10 days, moderate - 10-14 days, heavy - 15-30 days.

[14], [15]

Clinical examination

All convalescents are subject to medical examination by Omsk hemorrhagic fever. The follow-up period for the Omsk haemorrhagic fever recovered with a mild form was 3 months, moderate and heavy - 12 months.

Supervision is conducted by an infectious disease specialist, and in his absence - a district therapist. The first follow-up examination is carried out 1 month after discharge from the hospital (urine and blood are examined), the next one at 3, 6, 9 and 12 months.

[16], [17], [18], [19],

What should the patient know?

Recommended full-fledged food with the exception of irritating spicy foods, alcoholic beverages; compliance with the physical regime (contraindicated: heavy physical work, hypothermia, bath, sauna, sports for 6-12 months). Prescribe the reception tonic and polyvitamins.

How is Omsk haemorrhagic fever prevented?

Specific prophylaxis of Omsk haemorrhagic fever

In the outbreaks, the vaccine against tick-borne encephalitis is used (due to the similarity of the antigenic characteristics of the pathogens, a stable immunity against both diseases develops), and dead moldo-vaccine is also used from the brain of white mice infected with the Omsk hemorrhagic fever virus. In case of emergency cases, passive immunoprophylaxis with serum of convalescents (30-50 ml intramuscularly) is performed in laboratories.

Nonspecific prophylaxis of Omsk haemorrhagic fever

Carry out the destruction of mites in nature, the fight against rodents; It is necessary to observe individual security measures (use of protective clothing, insecticides, when working in dusty areas - respirators).

What prognosis is Omsk haemorrhagic fever?

In comparison with HFRS and CHF, Omsk haemorrhagic fever has a rather favorable prognosis, which depends on adherence to the principles of hospitalization, patient care, timely and comprehensive drug treatment, and prevention of complications.