Crimean hemorrhagic fever: causes and pathogenesis
Last reviewed: 23.04.2024
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Causes of Crimean hemorrhagic fever
The cause of the Crimean hemorrhagic fever is arbovirus of the family Bunyaviridae, genus Nairovirus: spherical or ellipsoid form, size 90-105 nm; covered with a lipid-containing membrane with spines. The genome of the virus contains 3 fragments (L-, M-, S-) of the single-stranded annular "minus" RNA chain encoding transcriptase, nucleocapsid protein (N), and enveloped glycoproteins (G1 and G2). The hemagglutinating ability of the causative agent of the Crimean hemorrhagic fever provides one of the surface glycoproteins. The causative agent of the Crimean hemorrhagic fever is able to multiply in the brain cells and abdominal cavity of newborn white mice, in newborn white rats and in the culture of transplanted kidney cells of piglets. After passage through a living organism, the virus increases virulence. The causative agent of the Crimean hemorrhagic fever can be inactivated with disinfectant solutions, fat solvents (ether, paraformaldehyde, alcohol). At 45 C, the virus dies within 2 hours, when boiled - instantly. Well preserved in the frozen state.
[Pathogenesis of Crimean hemorrhagic fever
Pathogenesis has not been studied enough. After penetration into the human body, the virus multiplies in the vascular endothelium, epithelial cells of the liver, kidneys and in the reticuloendothelial system, causing vasculitis with a predominant lesion of 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 course of the disease. As a result of direct vasotropic action of the virus, adrenal and hypothalamus damage, there is an increase in vascular permeability and an increase in disturbances in the hemostatic system, which is clinically expressed by symptoms of hemorrhagic diathesis.
Epidemiology of the Crimean hemorrhagic fever
The main natural reservoir of the causative agent of the Crimean hemorrhagic fever is mites of the genus Hyalomma (H. Plumbeum, H. Scupens, H. Marginatus), Rhipicephalus (Rh. Rossicus), Dermacentor (D. Marginatus and D. Reticulatus) and Boophilus (B. Annulatus ); as well as wild (rabbits, African hedgehogs) and domestic (sheep, goats, cows) animals. Human infection occurs transmissible (through the tick bite), contact (by contact with damaged skin and mucous membranes of blood and bloody discharge of the patient of the Crimean hemorrhagic fever and when crushing the mites) and aerogenic (in the laboratory) ways. Susceptibility to Crimean hemorrhagic fever is high regardless of age, but men aged 20-50 (hunters, shepherds, veterinarians, livestock breeders, field crop operators), and milkmaids, medical workers and persons involved in caring for patients are more often sick: laboratory assistants with blood: members of their families. Postinfectious immunity resistant. Natural foci are located in semi-desert, steppe, forest-steppe and floodplain landscapes with a warm climate. This area is unfit for farming and is used mainly for grazing cattle, which is the host of adult stages of ticks of the genus Hyalomma. The outbreaks are found in the territory of Bulgaria, Yugoslavia, Hungary. France (on the border with Spain). Greece, Iraq, Saudi Arabia, Asia (Iran, India, Pakistan) and Africa (Zaire, Nigeria, Senegal, Uganda, Kenya). Azerbaijan, Moldova, Tajikistan, Turkey and on the territory of Ukraine (in the Crimea, Donetsk region) and Russia: Dagestan. Kalmykia and Astrakhan. Volgograd and Rostov regions. Krasnodar and Stavropol territories. Seasonality - spring-summer (April-September) with a peak in June-July.