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Crimean hemorrhagic fever - Causes and pathogenesis
Last reviewed: 04.07.2025
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Causes of Crimean hemorrhagic fever
The cause of Crimean hemorrhagic fever is an arbovirus of the Bunyaviridae family, genus Nairovirus: spherical or ellipsoidal shape, 90-105 nm in size; covered with a lipid-containing membrane with spikes. The virus genome contains 3 fragments (L-, M-, S-) of a single-stranded circular "minus" chain of RNA encoding transcriptase, nucleocapsid protein (N) and envelope glycoproteins (G1 and G2). The hemagglutinating ability of the causative agent of Crimean hemorrhagic fever is provided by one of the surface glycoproteins. The causative agent of Crimean hemorrhagic fever is able to multiply in the cells of the brain and abdominal cavity of newborn white mice, in newborn white rats and in a culture of transplanted piglet kidney cells. After passage through a living organism, the virus increases virulence. The causative agent of Crimean hemorrhagic fever can be inactivated by disinfectant solutions, fat solvents (ether, paraformaldehyde, alcohol). At 45 C the virus dies within 2 hours, when boiled - instantly. It is well preserved in a frozen state.
[ Pathogenesis of Crimean hemorrhagic fever
The pathogenesis has not been studied sufficiently. After penetrating the human body, the virus multiplies in the vascular endothelium, epithelial cells of the liver, kidneys and in the reticuloendothelial system, causing vasculitis with predominant damage to the vessels of the microcirculatory bed. Then viremia develops, which corresponds to the initial period of the disease. According to PCR, viremia lasts 5-9 days. Its intensity correlates with the severity of the disease. As a result of the direct vasotropic action of the virus, damage to the adrenal glands and hypothalamus, there is an increase in vascular permeability and an increase in disorders in the hemostasis system, which is clinically expressed by symptoms of hemorrhagic diathesis.
Epidemiology of Crimean hemorrhagic fever
The main natural reservoir of the Crimean hemorrhagic fever pathogen is ticks of the genus Hyalomma (H. pl. plumbeum, H. scupens, H. marginatus), Rhipicephalus (Rh. rossicus), Dermacentor (D. marginatus and D. reticulatus) and Boophilus (B. annulatus); as well as wild (hares, African hedgehogs) and domestic (sheep, goats, cows) animals. Humans become infected by transmission (through a tick bite), contact (when blood and bloody secretions of a patient with Crimean hemorrhagic fever come into contact with damaged skin and mucous membranes and when ticks are crushed) and airborne (in laboratory conditions). Susceptibility to Crimean hemorrhagic fever is high regardless of age, but men aged 20-50 (hunters, shepherds, veterinarians, livestock breeders, field workers) and milkmaids, health workers and persons involved in patient care are more likely to get sick: laboratory technicians working with blood: members of their families. Post-infection immunity is persistent. Natural foci are located in semi-desert, steppe, forest-steppe and floodplain landscapes with a warm climate. This territory is unsuitable for agriculture and is used mainly for grazing cattle, which are the host of adult stages of ticks of the genus Hyalomma. Foci have been identified in Bulgaria, Yugoslavia, Hungary, France (on the border with Spain), Greece, Iraq, Saudi Arabia, in Asian countries (Iran, India, Pakistan) and Africa (Zaire, Nigeria, Senegal, Uganda, Kenya). Azerbaijan, Moldova, Tajikistan, Turkey and in Ukraine (in Crimea, Donetsk region) and Russia: Dagestan, Kalmykia, Astrakhan, Volgograd, Rostov regions, Krasnodar and Stavropol territories. Seasonality - spring-summer (April-September) with a peak in June-July.