Tick-borne encephalitis is an acute viral disease that mainly affects the nerve cells in the human body. These can be brain structures, peripheral innervation, or radicular nerve endings in the spinal cord.
The main source of infection is the Ixodes taiga tick. For the reproduction of these insects requires the blood of an animal or person. Spring-summer seasonality is associated with the biology of tick-carriers. The virus, entering the tick's stomach with the blood of infected animals, penetrates all organs of the tick and is then transferred to other animals, and is also transmitted to the offspring of the tick (transovarial transmission of the virus).
The penetration of the virus into the milk of farm animals (goats) has been proven; therefore, the alimentary ways of infection of people through goats and cows are possible. Alimentary “goat” endemic foci of encephalitis have been established in various regions of the former Soviet Union.
Where is tick-borne encephalitis?
Ticks are common in forest and forest-steppe zones with a temperate climate. There are several types of these parasites, but, as a rule, tick-borne encephalitis occurs after Ixodes Persulcatus (taiga tick) or Ixodes Ricinus (European forest tick) bites. The first is more common in Asia, the second - in the European region.
Currently, tick-borne encephalitis is registered in almost the entire territory of Russia (about 50 territories of the constituent entities of the Russian Federation are registered), where its main carriers are ticks. The most disadvantaged regions in terms of morbidity are: the Ural, West Siberian, East Siberian and Far Eastern regions, and from the adjacent regions of the Moscow Region - Tver and Yaroslavl.
The time from the moment of infection to the first symptoms of tick-borne encephalitis is about 10-14 days. The incubation period can be lengthened in people who received tick-borne encephalitis vaccinations in childhood.
There are also several stages of the disease:
- Lightning fast. With it, the initial symptoms appear already on the first day. In the absence of adequate treatment, a sick person quickly falls into a coma and dies from paralysis of the central nervous system.
- Protracted. In this case, the duration of the incubation period may be about a month, sometimes even slightly longer.
The first signs of illness (what you should pay attention to): usually one week after outdoor recreation, a person suddenly has a headache, nausea, vomiting, which does not bring relief, an increase in body temperature to 39-40 °, severe weakness. Then the brain symptoms join: limb paralysis, strabismus, pain along the nerve endings, convulsions, loss of consciousness.
The clinical classification of tick-borne encephalitis is based on determining the shape, severity and nature of the disease. Forms of tick-borne encephalitis:
- inapparent (subclinical):
By the nature of the flow, there are acute, two-wave and chronic (progressive) currents.
Symptoms of tick-borne encephalitis
After a tick bite, the virus multiplies in the tissues, penetrates the lymph nodes and blood. When the virus multiplies and when it enters the bloodstream, flu-like symptoms develop. The virus penetrates the blood-brain barrier and infects brain tissue - neurological symptoms occur.
But the brightness of clinical manifestations, the speed of their growth and specificity always depend on the type of the disease and the location of the virus.
- European - it is characterized by 2 phases. The first on manifestations is similar to the flu and lasts about a week. The second phase is characterized by lesions of the nervous system of varying degrees: from mild meningitis to severe encephalitis.
- Far East - usually begins with a feverish state, it is acute. Other symptoms can also increase rapidly, leading to paralysis and coma. The lethal outcome can be already in 6-7 days.
Despite the large variety of symptoms and manifestations of the disease, there are 4 main clinical forms of tick-borne encephalitis:
- Feverish. Tick-borne encephalitis virus does not affect the central nervous system, only fever symptoms appear, namely high fever, weakness and body aches, loss of appetite, headache and nausea. Fever can last up to 10 days. Cerebrospinal fluid does not change, symptoms of damage to the nervous system are absent. The forecast is most favorable.
- Meningeal. After a period of fever, a temporary decrease in temperature occurs, the virus penetrates the nervous system at this time, and the temperature rises again sharply, there are signs of neurological disorders. There are headaches with vomiting, strong photophobia and stiffness of the muscles of the neck, symptoms of irritation of the brain membranes, there are changes in the cerebrospinal fluid.
- Meningoencephalitic. It is characterized by damage to brain cells, which are characterized by impaired consciousness, mental disorders, convulsions, weakness in the limbs, paralysis.
- Poliomyelitis. The beginning of this form of the disease is manifested by severe fatigue, general weakness. There is numbness in the body, after which there are flaccid paralysis of the muscles of the neck and arms, proximal parts of the upper limbs. There is a “hanging head” syndrome. The increase in motor disorders occurs within a week, after which atrophy of the affected muscles occurs. Poliomyelitis form of the disease occurs quite often, in almost 30% of cases. For unfavorable, possible disability.
It should be noted that different people have different susceptibility to tick-borne encephalitis. With long-term residence in a natural focus, a person may be subjected to repeated suction of ticks with ingestion of minor doses of the virus. After that, antibodies are produced in the blood, the accumulation of which contributes to the development of immunity to the virus. If such people become infected, the disease will be mild.
Diagnosis of tick-borne encephalitis
In the case of tick-borne encephalitis, diagnosis is carried out using tomographic studies of the brain, serological and virological studies. Based on all indicators, an accurate diagnosis is established.
Brain damage is determined primarily based on complaints from a neurological examination by a doctor. It establishes the presence of inflammation and the nature of brain damage, and causes of encephalitis.
How to treat tick-borne encephalitis
In the case of tick-borne encephalitis, there is no specific treatment. If symptoms occur that indicate damage to the central nervous system (meningitis, encephalitis), the patient should be immediately hospitalized for maintenance therapy. As a symptomatic treatment often corticosteroid agents are used. In severe cases, there is a need for tracheal intubation followed by mechanical ventilation.
Etiotropic therapy consists in prescribing a homologous gamma globulin titrated against tick-borne encephalitis virus. Thanks to this drug, one can observe a clear therapeutic effect, especially if we are talking about a severe or moderately severe disease. Gamma globulin is administered in 6 ml intramuscularly, every day for three days. The therapeutic effect is observed after 13-24 hours after drug administration - the patient's body temperature returns to normal, the general condition improves, meningeal phenomena and headaches decrease, they may even disappear completely. In recent years, serum immunoglobulin and homologous polyglobulin have been used to treat tick-borne encephalitis, which are obtained from blood plasma of donors living in natural foci of tick-borne encephalitis.
Only 2-3 weeks after intensive treatment, subject to the normalization of body functions and the stabilization of the patient's condition is subject to discharge from the hospital. Contraindicated hard work, mental stress. Regular walks are recommended, it is advisable to use tick repellent products. A visit to the doctor is required for two years.
Tick-borne encephalitis and its prevention
Vaccination is used as a specific prophylaxis against tick-borne encephalitis, which is the most reliable preventive measure. All persons residing in endemic areas or leaving in them are subject to compulsory vaccination. The population in endemic areas is approximately half of the total population of Russia.
In Russia, vaccination is carried out by foreign (FSME, Encepur) or domestic vaccines according to the main and emergency schemes. The basic scheme (0, 1-3, 9-12 months) is carried out, followed by revaccination every 3-5 years. To form immunity to the onset of the epidemic season, the first dose is administered in the fall, the second in the winter. An emergency regimen (two injections with an interval of 14 days) is used for unvaccinated individuals who come to endemic foci in the spring and summer. Emergency vaccinated persons are immunized only for one season (immunity develops after 2-3 weeks), after 9-12 months they are given the 3rd injection.
As an emergency prophylaxis when sucking ticks to unvaccinated people, immunoglobulin intramuscularly is injected from 1.5 to 3 ml. depending on age. After 10 days, the drug is re-administered in the amount of 6 ml.
In tick-borne encephalitis, the prognosis for dysney depends on the degree of damage to the nervous system. When febrile, as a rule, all patients recover fully. In meningeal form, the prognosis is also favorable, but in some cases persistent complications from the central nervous system in the form of chronic headaches and migraine development can be observed.
The focal form of tick-borne encephalitis is the most unfavorable according to the forecast. Mortality can reach 30 people per 100 cases. Complications of this form is the occurrence of persistent paralysis, convulsive syndrome, mental decline.
Where to get tick-borne encephalitis inoculation 2016?
In 2016, in Moscow, in all administrative districts from March to September, vaccination centers operate annually at the bases of polyclinics, medical units, health centers of educational institutions: (in the Western administrative district - in children's polyclinic №119; in polyclinics for adults: No. 209, No. 162 and MSU polyclinic №202), as well as the Central Vaccination Center on the basis of Polyclinic № 13 (Trubnaya St., 19, building 1, telephone: 621-94-65)
Where to conduct a laboratory study of ticks?
Studies of ticks on infection by pathogens of natural focal infections are carried out at the Federal Center for Hygiene and Epidemiology, Federal Center for Hygiene and Epidemiology in Moscow, at the Federal Research and Development Institute of the Central Research Institute for Epidemiology of Rospotrebnadzor.
When contacting the laboratory, it is necessary to provide information on the date and territory on which the tick suction occurred (region, region, locality).
Where to conduct laboratory blood tests?
Persons affected by tick infestation in an endemic area can be subjected to laboratory blood tests (serological) for tick-borne encephalitis in the parasitological department of the microbiological laboratory of the Center for Hygiene and Epidemiology in Moscow, or in any other laboratory that performs this type of research.