What is Crimean Hemorrhagic Fever?
Hemorrhagic fever of the Crimea-Congo is an acute infectious disease of a person, transmitted through tick bites, characterized by fever, severe intoxication and hemorrhages on the skin and internal organs. First discovered in 1944 in the Crimea. The pathogen was detected in 1945. In 1956, a similar disease was identified in the Congo. Virus research has established its full identity with the virus found in the Crimea.
Causes of Crimean Hemorrhagic Fever
The causative agent of the Crimean hemorrhagic fever is a virus from the family Bunyaviridae, a genus Nairovirus. Refers to arboviruses (Arboviridae). Discovered in 1945 by M.P. Chumakov in the Crimea, while examining the blood of sick soldiers and displaced persons who fell ill during the hay-harvesting work. In 1956, a virus similar in antigenic composition was isolated from the blood of a sick boy in Congo. The causative agent is called the Congo virus. Spherical virions, 92–96 nm in diameter, are surrounded by a lipid containing membrane. Most sensitive to the virus culture of the kidney cell embryo pigs, Syrian hamsters and monkeys. Poorly resistant to the environment. When boiling, the virus dies instantly, at 37 `C – after 20 h, at 45` C – after 2 h. In the dried state, the virus remains viable for over 2 years. In the affected cells is localized mainly in the cytoplasm.
The natural reservoir of the pathogen is rodents, cattle and small cattle, birds, wild mammals, also ticks themselves, capable of transmitting the virus to offspring through eggs, and are virus carriers for life. The source of the pathogen is a sick person or an infected animal. The virus is transmitted when a tick bites, or medical procedures associated with injections or blood sampling. The main carriers are ticks of Hyalomma marginatus, Dermacentor marginatus, Ixodes ricinus. Outbreaks of the disease in Russia annually occur in the Krasnodar and Stavropol Territories, Astrakhan, Volgograd and Rostov regions, in the republics of Dagestan, Kalmykia and Karachay-Cherkessia. The disease is also found in southern Ukraine and in the Crimea, Central Asia, China, Bulgaria, Yugoslavia, Pakistan, Central, Eastern and Southern Africa (Congo, Kenya, Uganda, Nigeria, etc.). In 80% of cases, people fall in age from 20 to 60 years.
Pathogenesis during the Crimean Hemorrhagic Fever
The basis of the pathogenesis of hemorrhagic Crimean fever is an increase in the permeability of the vascular wall. Increasing viremia causes the development of severe toxicosis, up to infectious-toxic shock with disseminated intravascular coagulation of the blood, depression of blood formation, which aggravates the manifestations of hemorrhagic syndrome.
Gates of infection is the skin at the site of a tick bite or minor injuries when in contact with the blood of sick people (with nosocomial infection). At the site of the gate of infection, no marked changes are observed. The virus enters the bloodstream and accumulates in the cells of the reticuloendothelial system. When a secondary more massive viremia appears signs of general intoxication, damage to the vascular endothelium and developing different severity of thrombohemorrhagic syndrome. Pathological changes are characterized by multiple hemorrhages in the mucous membranes of the stomach and intestines, the presence of blood in the lumen, but there are no inflammatory changes. The brain and its membranes are hyperemic, they show hemorrhages with a diameter of 1-1.5 cm with the destruction of the medulla. Small hemorrhages are detected throughout the brain. Hemorrhages are also observed in the lungs, kidneys, etc. Many questions about the pathogenesis of the Crimea-Congo fever remain unexplored.
At autopsy, multiple hemorrhages are found in the mucous membranes of the gastrointestinal tract, blood is in its lumen, but there are no inflammatory changes. The brain and its membranes are hyperemic, they show hemorrhages with a diameter of 1-1.5 cm with the destruction of the medulla. Small hemorrhages are detected throughout the brain. Hemorrhages are also observed in the lungs, kidneys, liver, etc.
Symptoms of the Crimean Hemorrhagic Fever
The incubation period is from one to 14 days. More often 3-5 days. Prodromal period is absent. The disease develops acutely.
In the initial (pre-hemorrhagic) period there are only signs of general intoxication characteristic of many infectious diseases. The initial period lasts more often 3-4 days (from 1 to 7 days). During this period, on the background of high fever, weakness, fatigue, headache, aches in the whole body, severe headache, pain in muscles and joints are noted.
Dizziness, impaired consciousness, severe pain in the calf muscles, signs of inflammation of the upper respiratory tract are more rare manifestations of the initial period. Only in some patients, even before the development of the hemorrhagic period, characteristic of this disease appear.
symptoms – repeated vomiting, not associated with eating, back pain, abdominal pain, mainly in the epigastric region.
A persistent symptom is fever, which lasts an average of 7-8 days, and the temperature curve is especially typical of Crimean hemorrhagic fever. In particular, with the onset of hemorrhagic syndrome, there is a decrease in body temperature to subfebrile, after 1-2 days the body temperature rises again, which causes the “double-humped” temperature curve characteristic of this disease.
The hemorrhagic period corresponds to the peak of the disease. The severity of thrombohemorrhagic syndrome determines the severity and outcome of the disease. Most patients on the 2-4th day of the disease (less often on the 5-7th day) develop a hemorrhagic rash on the skin and mucous membranes, hematomas at injection sites, there may be bleeding (stomach, intestinal, etc.). The patient’s condition is deteriorating. Hyperemia of the face is replaced by pallor, the face becomes puffy, there is cyanosis of the lips, acrocyanosis. A rash on the skin at the beginning is petechial, at this time an enanthema appears on the mucous membranes of the oropharynx, there may be larger hemorrhages into the skin. Nasal, uterine bleeding, hemoptysis, bleeding gums, tongue, conjunctiva are possible. The prognostic adverse appearance of massive gastric and intestinal bleeding. The condition of patients becomes even more severe, disturbances of consciousness are noted. Characterized by abdominal pain, vomiting, diarrhea; the liver is enlarged, painful on palpation, a symptom of Pasternack positive. Bradycardia is replaced by tachycardia, blood pressure is reduced. In some patients, oliguria is noted, residual nitrogen increases. In the peripheral blood – leukopenia, hypochromic anemia, thrombocytopenia, ESR without significant changes. Fever lasts 10-12 days. Normalization of body temperature and cessation of bleeding characterizes the transition to the recovery period. Asthenia lasts for a long time (up to 1-2 months). In some patients there may be mild forms of the disease, occurring without a pronounced thrombohemorrhagic syndrome, but they, as a rule, remain undetected.
As a complication, sepsis, pulmonary edema, focal pneumonia, acute renal failure, otitis, thrombophlebitis can be observed. Mortality ranges from 2 to 50%.
Diagnostics of the Crimean Hemorrhagic Fever
Diagnostics of the Crimean hemorrhagic fever is based on the clinical picture, data of the epidemiological history (stay in the zone of natural foci, attack of ticks, contact with patients with the Crimean hemorrhagic fever), the results of laboratory studies. In the blood there is a reduced number of red blood cells, leukopenia (up to 1×109-2×109 / l), neutropenia, thrombocytopenia. To confirm the diagnosis, virus isolation from the patient’s blood is used, from 6-10th day of illness, an increase in antibody titer is determined in repeated samples of the patient’s blood serum in the RAC, the reaction of diffuse precipitation in agar, the reaction of passive hemagglutination.
Differential diagnostics is carried out with other viral diseases that manifest hemorrhagic syndrome, especially if the patient was in countries with tropical and subtropical climates, with leptospirosis, hemorrhagic fever with renal syndrome, hemorrhagic vasculitis, sepsis, etc. during the last days before the onset of clinical manifestations of the disease.
Treatment of the Crimean Hemorrhagic Fever
Patients must be isolated in the infectious diseases department of the hospital. Treatment is symptomatic and etiotropic. Prescribed anti-inflammatory drugs, diuretics. Exclude the use of drugs that enhance kidney damage, for example, sulfonamides. Also prescribed antiviral drugs (ribavirin, reaferon). In the first 3 days, heterogeneous specific equine immunoglobulin, immune serum, plasma, or specific immunoglobulin, obtained from the blood serum of ill or vaccinated individuals, is administered. Specific immunoglobulin is used for emergency prophylaxis in patients in contact with the patient’s blood.
Prevention of the Crimean Hemorrhagic Fever
To prevent infection, the main efforts are directed at combating the carrier of the disease. They disinsect the premises for livestock, prevent grazing on pastures located on the territory of the natural hearth. Individuals should use protective clothing individually. Handle clothes, sleeping bags and tents with repellents. For tick bites in the habitat zone, immediately contact a medical facility for help. For those who are going to enter the territory of the South of Russia, preventive vaccination is recommended. In medical institutions, the high contagiousness of the virus should be considered, as well as its high concentration in the blood of patients. Therefore, patients should be placed in a separate box, and the service should be trusted only to specially trained personnel.