Crimean-Congo haemorrhagic fever is an acute arbovirus infection with a characteristic natural foci, occurring with the phenomena of toxicosis and thrombohemorrhagic syndrome of varying severity. Disease is characterized by an acute onset with two waves of fever, headaches, muscle and joint pain, hemorrhagic rashes on the skin and mucous membranes, hemorrhages and bleeding. The diagnosis is based on clinical and epidemiological data, the results of ELISA, PCR. Treatment of Crimean-Congo haemorrhagic fever includes detoxification therapy, administration of specific immunoglobulin or immune serum, antiviral, hemostatic agents, blood preparations and blood substitutes.
Crimean-Congo haemorrhagic fever is a zoonotic natural focal disease, the viral pathogen of which is transmitted to humans by blood–sucking ticks. Crimean hemorrhagic fever belongs to the group of tick-borne hemorrhagic fevers; it is a dangerous infectious disease with a mortality rate of 10-40%. It is characteristic of the warm climate of steppe, forest-steppe and semi-desert zones; it is found in the Crimea, Central Caucasus and adjacent territories, in China, some countries of Europe and Africa. The incidence of CCHF is higher in people engaged in agricultural production – animal care, hay harvesting, and slaughtering. Crimean hemorrhagic fever is more often detected in men from 20 to 40 years old. Disease is characterized by spring-summer seasonality associated with tick activity.
The causative agent of Crimean-Congo haemorrhagic fever is an RNA genomic virus of the genus Nairovirus, family Bunyaviridae, capable of reproducing at two temperature ranges – 36-40 ° and 22-25 °C. This allows the virus to multiply both in humans and vertebrates, and in the body of blood-sucking insects. The Crimean hemorrhagic fever virus is sensitive to heating (instantly inactivated during boiling), the action of detergents, disinfectants. The source of the Crimean hemorrhagic fever virus in nature are rodents (hedgehogs, hares, mice), small and large cattle (sheep, goats, cows), as well as pigs, horses, dogs and birds. Specific vectors are mammalian parasites – more than 20 species of ixodes mites, mainly grazing mites of the genus Hyalomme.
The main mechanism of transmission of Crimean hemorrhagic fever is transmissible, with suction and bites of infected ixodic ticks. Contact (when the tick is crushed, infected material of sick animals and humans gets on the damaged skin) and aerogenic transmission routes (when the virus is in the air) are also possible. There is an nosocomial infection that occurs with insufficient processing and sterilization of medical instruments and equipment, reusable use of needles. The natural susceptibility of people to the CCHF virus is high.
The viral pathogen causes damage to the endothelium of small blood vessels, increased permeability of the vascular wall, impaired blood clotting, inhibition of hematopoiesis, the development of DIC syndrome. This is manifested by numerous hemorrhages in the internal organs (kidneys, liver), central nervous system, skin and mucous membranes. The disease is characterized by a morphological picture of infectious vasculitis with the development of dystrophic changes and foci of necrosis.
The duration of the incubation period, depending on the method of infection, is from 2 to 14 days (after a tick bite – 1-3 days, with contact transmission – 5-9 days). The symptoms of Crimean hemorrhagic fever can vary from erased to extremely severe. The initial period of infection (the first 3-5 days) is characterized by an acute condition with a sudden jump in temperature to 39-40 ° C, chills, weakness, dizziness. Patients complain of severe headache, myalgia and arthralgia, pain in the abdomen and lower back. Dry mouth, nausea and vomiting, hyperemia of the face, neck, conjunctiva and pharyngeal mucosa often appear. There is photophobia, excitement, sometimes even aggressiveness, which are then replaced by drowsiness, fatigue, depression. Before the manifestation of hemorrhagic syndrome, there is a short-term decrease in temperature to subfebrile, then a second wave of fever occurs.
During the height of the Crimean hemorrhagic fever (from 3-6 days of the disease), hemorrhagic manifestations of various severity occur – petechial rashes on the skin (exanthema) and oral mucosa (enanthema), purpura or large ecchymoses, hemorrhages at injection sites, nosebleeds, hemoptysis, in severe cases – copious abdominal bleeding (gastrointestinal, pulmonary, uterine). The condition of patients deteriorates sharply: lethargy, depression, pallor, acrocyanosis, tachycardia, arterial hypotension are noted. Lymphadenopathy, hepatomegaly are detected, meningeal syndrome, convulsions, confusion, coma may occur. The outcome of Crimean hemorrhagic fever is determined by the severity of thrombohemorrhagic syndrome.
With a favorable course of Crimean hemorrhagic fever, hemorrhages disappear after 5-7 days without relapses. Convalescence begins on the 9th-10th day of the disease and takes a long time (1-2 months or more); asthenic syndrome persists for another 1-2 years. Postinfectious immunity persists for 1-2 years after the infection. Complications of Crimean hemorrhagic fever can be pneumonia, pulmonary edema, liver and kidney failure, thrombophlebitis, infectious and toxic shock. Lethality ranges from 4 to 30%; the fatal outcome usually occurs in the second week of the disease.
Diagnosis of Crimean hemorrhagic fever is carried out taking into account epidemiological data (possible stay in endemic areas, seasonality), typical clinical signs (acute onset, two-wave fever, early thrombohemorrhagic syndrome), laboratory results (general blood and urine analysis, ELISA, RNIT, RNGA, PCR). Examination of patients should be carried out in compliance with the maximum degree of infectious safety.
In the hemogram for Crimean hemorrhagic fever, pronounced leukopenia, thrombocytopenia, increased ESR and hematocrit are noted; in the general analysis of urine – oliguria, hypostenuria, microhematuria. In the first few days of the disease and in the terminal stage, the diagnosis can be confirmed by detecting the virus RNA in blood and tissue samples by PCR. ELISA helps to determine the titer of specific IgM antibodies to the Crimean hemorrhagic fever virus for 4 months after the infection, IgG – for 5 years. Differential diagnosis of Crimean hemorrhagic fever is carried out with influenza, meningococcal infection, typhus, leptospirosis, thrombocytopenic purpura and Schenlein-Henoch disease, other types of hemorrhagic fevers.
If Crimean hemorrhagic fever is suspected, hospitalization and isolation of patients are mandatory. Treatment should be carried out in accordance with the principles of therapy of viral hemorrhagic fevers. Bed rest, diet, vitamin therapy are indicated. It is possible to introduce immune serum of convalescents or hyperimmune equine gamma globulin. The use of antiviral drugs (ribavirin, alpha interferon) has an effective therapeutic effect. In the initial period, detoxification and hemostatic therapy is carried out; transfusion of blood, erythrocyte and platelet mass is carried out in replacement doses. With the development of infectious and toxic shock, glucocorticosteroids are prescribed.
Prognosis and prevention
The prognosis for the rapid and severe course of Crimean hemorrhagic fever is serious: there is an early development of complications, a fatal outcome is possible. With timely treatment, the prognosis of the disease is favorable in most cases. The main prevention of Crimean hemorrhagic fever is to protect a person from attacks and bites of ticks carrying the virus, the use of personal protective equipment (wearing protective clothing, using protective nets, repellents), regular self-examinations. In medical institutions, it is mandatory to comply with the requirements for the prevention of nosocomial infections: caution when performing invasive procedures, working with the blood and secretions of patients; sterilization of instruments, the use of disposable syringes and needles. The destruction of the source and vectors of the Crimean hemorrhagic fever virus in nature is ineffective.