Routes of transmission of tick-borne encephalitis: can you get infected from a person? Interesting video: how to reliably protect yourself from tick-borne encephalitis. Meningoencephalitic form of tick-borne encephalitis

Tick-borne encephalitis– severe acute viral pathology, the main clinical syndrome of which is damage to the structures of the brain and spinal cord. Severe damage to the subcortical nuclei and meninges in humans leads to persistent neurological symptoms, irreversible complications, respiratory arrest and heartbeat.

What to do if you are bitten by an ixodid tick, how do the symptoms of the disease manifest, where should you go?

Properties of the pathogen

This is what the tick-borne encephalitis virus looks like

The duration of incubation, clinical picture and stages of remission differ depending on the subtype of tick-borne encephalitis virus:

European - causes a mild clinical picture with a short acute period, rapid and complete recovery;
Siberian – is the cause of short-term incubation period, two-phase course, damage to the central nervous system, persistent complications;
Far Eastern - dangerous due to frequent deaths, leads to severe clinical symptoms and subsequent disability.

Vectors of infection

These are six species of ixodid ticks. The encephalitis tick itself does not get sick; it is a carrier of a viral infection. It becomes infected from wild (less often domestic) birds and animals, which are also carriers. Tick-borne encephalitis is a severe anthroponosis, the disease occurs exclusively in humans. The bite of an encephalitis tick is the main route of transmission of a viral infection.

By sucking the blood of animals, the tick becomes infected with a virus, which spreads throughout the tick’s body over the course of 3–4 days. The virus multiplies in the host tissue cells and lives until the death of the animal. Highest value for human infection, the localization of viruses in salivary glands ah tick.

Ticks are carriers of the dangerous disease encephalitis

To reduce human blood clotting when piercing the skin, the tick secretes an anticoagulant from the salivary glands, and with it a viral mass.

Routes of infection

The period of tick activity occurs in late spring and summer, so cases of tick-borne encephalitis occur during this season. Infection occurs when:

bite of an infected tick: the virus enters the human blood with saliva (the disease is diagnosed in 6% of those bitten);
consumption of milk from carrier animals that has not undergone heat treatment;
accidental crushing of a tick removed from the skin, the organs of which contain a lot of viruses;
failure to comply with safety regulations in biological laboratories.

Sources of infection with tick-borne encephalitis

The mechanism of pathology development

After an encephalitis tick bite, swelling and redness of the skin and itching develop. With sensitization to the components of insect saliva, necrotic changes develop with the formation of deep scar defects. A similar clinical reaction also occurs when the mite body is removed incorrectly, when its elements remain inside the skin.

If bitten by a tick, skin immune cells, protecting the body from infection, absorb viruses. Replication of the virus ribonucleic acid by cell organelles begins. New virions appear, enter the bloodstream and spread throughout the tissues of the body. They settle in the organs of the reticuloendothelial system: lymph nodes, spleen, liver, where they undergo repeated replication.

Once again entering the bloodstream, the viruses penetrate the cerebrospinal fluid and infect the membranes and motor nuclei of the central nervous system. The clinical manifestations of the disease depend on how many replications have occurred. Double viremia in humans causes a biphasic form of the disease. Periods of remission correspond to intracellular replication.

Clinical picture of the development of tick-borne encephalitis

Clinical forms

The manifestation of pathology depends not only on the subtype of the pathogen, but also on its quantity, the reactivity of the body, age, repeated viral infection. The clinical form of tick-borne encephalitis depends on the location of the main damage, intensity and duration of symptoms.

The febrile form develops in 25–30% of cases and is associated with the inability of the virus to penetrate the cerebrospinal fluid. The disease is characterized by symptoms similar to the clinical course of influenza: hyperthermia up to 39 ° C, headaches, dizziness, aches throughout the body, and weakness. Neurological symptoms in this form are absent or minimal, due to general intoxication. The course is short-term (up to 5 days), uncomplicated. The patient may not know about the disease; it can only be detected by laboratory tests.
The meningeal form of tick-borne encephalitis is the most common pathology (if you do not take into account the febrile form, which occurs under the guise of another viral pathology). It is characterized by symptoms of irritation of the dura mater, increased intracranial pressure, and pronounced manifestations of general intoxication. Hypersensitivity to light, sound and tactile stimuli appears. High body temperature lasts up to 2 weeks, sometimes with a biphasic increase. Traces of protein, leukocytosis, and subsequently lymphocytosis are determined in the cerebrospinal fluid. Changes in the composition of the cerebrospinal fluid will appear for a long time, even after clinical recovery.
The meningoencephalitic form occurs in two phases. The first phase of the viral disease lasts up to a week and is characterized by general symptoms. Then comes a period of apparent clinical well-being for up to 2 weeks.

The second phase is difficult to tolerate due to damage to the brain substance and lasts up to 7 days. In addition to meningeal manifestations, focal manifestations develop, which depend on the location of damage to the subcortical nuclei. Function is impaired cranial nerves, disorders of vital centers occur, which is manifested by impaired breathing and heartbeat, and a drop in blood pressure.

When motor neurons are damaged, paresis, paralysis, and muscle tremors develop. There is clouding of consciousness with disorientation, hallucinations, and epileptic convulsions. Protein and pronounced cytosis are detected in the cerebrospinal fluid.

Tick-borne encephalitis is a dangerous disease

The clinical outcome of the viral disease is favorable, residual effects are missing.

Poliomyelitis form - characterized by symptoms of damage to the nervous system cervical region and shoulder girdle, which subsequently manifests itself as persistent muscle atrophy. The course is two-phase, one week of exacerbation with two weeks of remission.
The polyradiculoneuritic form of the viral disease is caused by damage to the peripheral nervous system, characterized by “volatility” of changes: movement of symptoms from bottom to top. Sensitivity disturbances, pain along the nerves, paresis and flaccid paralysis develop.

Features of pathology in childhood

A characteristic feature of tick-borne encephalitis in children is the massiveness tick bites. The growth of a child allows insects to easily infest the entire surface of the skin. More often than in adults, a child’s viral disease can occur from consuming raw, contaminated milk.

Signs of encephalitis after a tick bite in childhood develop in 3–4 weeks. The clinic begins with hectic fever (40 ° C), sore throat, which simulates a sore throat. Neurological symptoms increase rapidly. In children, an atypical, mild clinical course or fulminant (like acute sepsis) development of tick-borne encephalitis with mortality within 1–2 days after infection is possible.

Habitats

Endemic tick-borne encephalitis is contracted in cold and wooded regions: Siberia, the Urals, and the Far East. The incidence rate in the Baltics, Belarus and Kazakhstan is much lower. Human infection occurs in the habitats of ixodid insects - in the forest, city parks and squares; the insect can be carried by an animal.

The most dangerous species encephalitis ticks

Diagnostics

Specific diagnosis of a viral disease is carried out in a virological laboratory, it is represented by serological methods: hemagglutination inhibition reaction and enzyme immunoassay. The point is to determine antibodies to the virus. What to do if serological tests become positive only on days 5–7 of the disease, and treatment of viral tick-borne encephalitis must be started as early as possible?

A properly collected epidemiological history from a person is the key to success in diagnosing tick-borne encephalitis. And if an encephalitis mite is still present on the skin, it is sent for molecular biological research.

Nonspecific diagnostics consists of blood tests, cerebrospinal fluid, hardware research central nervous system - computed tomography or nuclear magnetic resonance.

Treatment

When establishing a diagnosis of tick-borne encephalitis and determining its form, prescribe antiviral drugs, anti-tick γ-globulin, immunized serum. Symptomatic therapy aimed at normalizing the functions of the nervous, cardiovascular, respiratory immune system, temperature reduction, pain relief. Do not self-medicate, only a specialist knows what to do for viral encephalitis!

Consequences

Consequences of tick-borne encephalitis

The consequences of a viral illness in the form of residual neurological and mental dysfunction depend on the pathogen and the form of the clinical course. Infection with the European virus, mild forms end favorably, residual effects are observed in 10% of patients, death is possible in 2% of cases. The Far Eastern virus and severe clinical forms of the disease lead to 20% disability or 20–25% mortality.

Prevention

Residents of endemic areas are vaccinated. The first vaccine is administered at birth, then according to the vaccination schedule up to 12 months. Subsequently, every 3–5 years they are revaccinated with two vaccinations: in the fall and in the winter. What to do upon arrival in an endemic area during the disease season? People who do not have immunity are given a two-time urgent vaccination.

During outbreaks, it is undesirable to unnecessarily visit tick habitats. This is especially true for children. When going into the forest, stay away from tall grass. Wear tight, light-colored, closed clothing. Lubricate exposed skin surfaces with insecticides.

Vaccination is an effective prevention of tick-borne encephalitis

When you get home, carefully remove your clothes, inspect them and wash them in hot water. Also inspect skin. If a bloodsucker has attached itself to you, you should not rip it out. Grease or overlay vacuum can will have an effect after a certain time.

What to do to urgently stop the virus from entering the body? The tick must be unscrewed using slow rotational (clockwise) movements, being careful not to damage the insect. But it is better to have the procedure performed by a specialist.

A tick is a small animal that can present the bitten person with a deadly gift. If you brought a “trophy” from the forest, it needs to be removed and preventive treatment with globulin. At the first symptoms of a viral pathology, immediately consult a doctor; the consequences of a tick bite can cost your life!

Video

How scary is this disease? Watch a video about the unpleasant consequences of tick-borne encephalitis.

Tick-borne encephalitis is a dangerous disease infectious nature. Modern medicine has created enough drugs for treatment; the mortality rate is about 4% of all cases of infection. Some people neglect timely appeal to the doctor, which provokes horrible consequences. If you know how encephalitis is transmitted from person to person and whether it is transmitted at all, you can learn to identify the first dangerous symptoms and manage to contact a medical facility in time.

Foci of infection in nature are carried by rodents and other animals. For them, encephalitis is absolutely safe, unlike in humans. As for the ticks themselves, dangerous virus exists in their body constantly. Encephalitis, transmitted from adults to larvae, never ceases to exist. Infection is increasing in numbers because the tick population in areas close to cities and residential buildings increases tenfold every year.

The greatest risk of infection with the encephalitis virus exists during periods of tick activity, in spring and summer. In autumn, cases of infection are recorded in minimal quantities. People who frequently visit forest areas are at risk.

Through the circulation of the virus between different animal species. Scientists have identified two mechanisms of infection:

transmissible;
nutritional.

The first mechanism of infection is characterized by entry of the virus through the skin. When a tick bites, pathological microorganisms enter the bloodstream. As a result of research, it was revealed that the longer the tick is on the skin, the more virus it will release. Accordingly, the more dangerous it is for humans. In this way, a large amount of the virus can be transmitted through the blood from an infected tick, in doses fatal to humans. Encephalitis will also be difficult to treat.

In a situation where, when removing an insect, it is accidentally crushed or not completely removed, then infection is also possible. Therefore, it is not recommended to try to do this on your own, but rather trust a doctor. It is important to know that the tick does not bite immediately. It moves on clothes, hair, branches, flowers and other things. Only after a period of time does it reach the skin.

Encephalitis causes damage to brain tissue. The inflammatory process can affect any part of the brain and even the spinal cord. Encephalitis may be purulent or non-purulent. The acute period of infection appears on days 6-10. There are cases when the disease became chronic. Then it becomes deadly.

Nutritional mode of transmission

It is important to know! Encephalitis cannot be transmitted from person to person. There are two specifically studied methods of infection: through the skin, through a bite, and through the mucous membranes of the gastrointestinal tract.

Infection with the virus through the alimentary method occurs as a result of consuming milk from a sick animal. Encephalitis in animals is completely asymptomatic. The infection enters milk through the blood, which in turn is a dangerous source.

Unprocessed milk that has not been boiled is dangerous. Scientists have found that the encephalitis virus lives in milk for about 2 months. Even derivative products such as cheese and cottage cheese are very dangerous to eat from an infected animal. The particular risk of this mode of transmission is that a large number of people can become ill.

Encephalitis can be determined by external signs:

the face and neck acquire a reddish tint;
the conjunctiva of the eyes becomes cloudy and red;
The upper part of the chest is also distinguished by redness.

The deterioration in health occurs suddenly. The pathology is often confused with other diseases, because the symptoms are common:

a sharp rise in temperature;
severe headaches;
nausea and vomiting;
sleep disorders;
sometimes loss of consciousness.

Infection occurs through a direct tick bite and through consumption of encephalitic milk. As a result of complications, paralysis develops. The formation of adhesions and cysts in the brain tissue is observed. The patient remains disabled. A fatal outcome is also possible when treatment does not bring results or the virus has spread throughout important bodies and systems.

Japanese encephalitis - how not to get infected

This type of encephalitis is also called mosquito encephalitis. The virus is transmitted by mosquitoes, which spread the infection in hot weather. The risk group includes people who are constantly outdoors in the evenings, when there are especially many mosquitoes. This type of virus is classified as naturally occurring. Distributed in almost all countries of the world.

Infected mosquitoes spread the infection through their bites. Children under 10 years of age are most often affected. However, mosquitoes infect various animals and rodents. In turn, animals can become carriers of the virus to people.

Encephalitis transmitted through milk from a sick goat or cow affects the human body, provoking pathological processes, primarily on the mucous membranes of the stomach. The virus develops not only in the intestinal tract and subcutaneous tissue. Sometimes during examination it is found in the lymph nodes or spleen. Treatment of this type of infection is long-term and complicated by disruption of the digestive system. This significantly impairs the use of medications.

Development of the virus in the body

It is known that the incubation period of encephalitis lasts on average from 7 to 10 days. It can last 30 days. Developments in modern medicine make it possible to use very effective means treatment of encephalitis. More often, the prognosis depends on when the person sought help.

It is customary to determine the form of encephalitis based on what signs of the disease appear:

febrile;
meningeal;
meningoencephalitic;
polio;
polyradiculoneuritic.

According to statistics, about 70% of ticks living in mid-latitudes are infected with a dangerous virus. In places where there is an increased risk of spreading tick-borne encephalitis, vaccination is carried out. This measure is an excellent preventative method.

The clinical symptoms of encephalitis infection are very complex. It all starts with a mild fever and an increase in temperature to 40.5 degrees. Then vomiting, convulsions, joint pain, numbness of part of the face or torso are observed. Often the patient loses consciousness.
Already in the first hours after a tick bite, the administration of immunoglobulin is indicated. This drug begins the fight against the encephalitis virus during the incubation period. To make a diagnosis, blood and cerebrospinal fluid must be analyzed. Antibody tests are carried out in a hospital setting. A number of specialists are involved in the treatment of infection, performing strict monitoring of the patient’s condition.

Intramuscular injections of immunoglobulin are indicated for 5-7 days. Complex treatment necessarily includes taking such devices as Prednisolone, Dextran, Procaine, Ibuprofen and others. Bed rest is mandatory. It is recommended to supplement the diet with vitamins and nutrients.

Is it possible for a healthy person to become infected from a sick person?

Several years ago, in Novosibirsk, scientists conducted a unique experiment on encephalitis infection with mice. Absolutely healthy females were placed in cages with virus-infected males. After a while, offspring appeared that were much weaker and smaller than those of healthy couples.

During the observation process, slow development of embryos was revealed. Some of the mice did not survive at all. During the research, scientists discovered an encephalitis virus in the cubs. The experiment caused a huge resonance in the scientific and medical community also because some people do not remember that they could ever be bitten by a tick. They also deny drinking milk. However, at the same time, they are carriers of the encephalitis virus.

The community of scientists who conducted these studies took the initiative that patients with encephalitis should be advised to abstain from sexual intercourse for a certain period. However, so far there have been no adherents of scientists among medical representatives.

Tick-borne encephalitis is seasonal and appears only in the spring-summer period - the time of activation of tick activity. The carrier lives in grass and treetops, has very low mobility and does not have the ability to pursue its prey.

The ixodid tick itself is not a source of the virus - it becomes infected with it from sick animals. Total infected ticks are approximately 20%, so an arthropod bite does not always lead to infection.

What it is?

Tick-borne encephalitis (spring-summer tick-borne meningoencephalitis) is a natural focal viral infection characterized by fever, intoxication and damage to the gray matter of the brain (encephalitis) and/or the membranes of the brain and spinal cord (meningitis and meningoencephalitis). The disease can lead to persistent neurological and psychiatric complications and even death of the patient.

According to statistics, six ticks out of a hundred are carriers of the virus (at the same time, from 2 to 6% of people bitten can get sick from an infected individual).

How does infection occur?

The main reservoir and source of infection are ixodid ticks. How does the tick-borne encephalitis virus enter the insect's body? 5–6 days after the bite of an infected animal in a natural outbreak, the pathogen penetrates all organs of the tick and concentrates mainly in the reproductive and digestive systems, and the salivary glands. The virus remains there for the entire life cycle of the insect, which is from two to four years. And all this time, after a tick bites an animal or person, tick-borne encephalitis is transmitted.

Absolutely every resident of an area where there are outbreaks of infection can become infected. These statistics are disappointing for humans.

Any animal can be a natural reservoir of infection: hedgehogs, moles, chipmunks, squirrels and voles and about 130 other species of mammals.
Depending on the region, the number of infected ticks ranges from 1–3% to 15–20%.
Some species of birds are also among the possible carriers - hazel grouse, finches, thrushes.
According to epidemiology, tick-borne encephalitis is widespread from Central Europe to Eastern Russia.
The first peak of the disease is recorded in May-June, the second - at the end of summer.
There are known cases of human infection with tick-borne encephalitis after consuming milk from tick-infected domestic animals.

Routes of transmission of tick-borne encephalitis: transmissible, during a bite by an infected tick, and nutritional - after eating contaminated foods.

Forms of the disease

Symptoms after an encephalitis tick attack are very diverse, but in each patient the period of the disease traditionally proceeds with several pronounced signs.

In accordance with this, there are several main forms of tick-borne encephalitis:

Feverish. The tick-borne encephalitis virus does not affect the central nervous system; only symptoms of fever appear, namely high temperature, weakness and body aches, loss of appetite, headache and nausea. Fever can last up to 10 days. The cerebrospinal fluid does not change, there are no symptoms of damage to the nervous system. The prognosis is most favorable.
Meningoencephalitic. It is characterized by damage to brain cells, which are characterized by impaired consciousness, mental disorders, convulsions, weakness in the limbs, and paralysis.
Meningeal. The virus penetrates the meninges, infecting neurons. At the same time, it develops focal form diseases. In addition to fever, symptoms of encephalitis include severe headache, vomiting, and photophobia. Signs of involvement of the meninges in the inflammatory process develop - stiff neck. When performing a lumbar puncture in the cerebrospinal fluid, you can see signs of inflammation: plasma cells appear, the level of chlorides decreases, etc.
Poliomyelitis. It is characterized by damage to the neurons of the cervical spinal cord and resembles polio in appearance. The patient has persistent paralysis of the muscles of the neck and arms, which leads to disability.

A special form of tick-borne infection has a two-wave course. The first period of the disease is characterized by febrile symptoms and lasts 3–7 days. The virus then penetrates the meninges and neurological signs appear. The second period lasts about two weeks and is much more severe than the febrile phase.

Tick-borne encephalitis - symptoms

The incubation period for transmissible transmission lasts 7-14 days, for nutritional transmission - 4-7 days.

The Far Eastern subtype of tick-borne encephalitis is characterized by a rapid course with high mortality. The disease begins with a sharp increase in body temperature to 38-39 °C, severe headaches, sleep disturbances, and nausea begin. After 3-5 days, damage to the nervous system develops.

The clinical picture of symptoms of tick-borne encephalitis of the European subtype is characterized by biphasic fever. The first phase lasts 2-4 days, it corresponds to the viremic phase. This stage is accompanied by nonspecific symptoms, including fever, malaise, anorexia, muscle pain, headache, nausea and/or vomiting. Then comes an eight-day remission, after which in 20-30% of patients there follows a second phase, accompanied by damage to the central nervous system, including meningitis (fever, severe headache, stiff neck) and/or encephalitis (various disturbances of consciousness, sensitivity disorders, motor disorders up to paralysis).

In the first phase, leukopenia and thrombocytopenia are detected in the laboratory. A moderate increase in liver enzymes (ALT, AST) in a biochemical blood test is possible. In the second phase, pronounced leukocytosis is usually observed in the blood and cerebrospinal fluid. The tick-borne encephalitis virus can be detected in the blood starting from the first phase of the disease. In practice, the diagnosis is confirmed by the detection of specific acute-phase IgM antibodies in the blood or cerebrospinal fluid, which are detected in the second phase.

What should I do if bitten by a tick?

If a tick has embedded itself in a person's skin, it should be removed in a medical facility. It is not recommended to do this on your own, as you can damage its body and not remove it completely. If there are no hospitals nearby, but you urgently need to remove a tick, you need to do the following:

the skin is generously lubricated with Vaseline or oil (to stop the flow of oxygen to the tick)
then it is grabbed with tweezers and carefully rotated counterclockwise and removed from the human skin
after extraction, it is necessary to go to the hospital on the first day after the bite for vaccination - specific donor immunoglobulin is injected intramuscularly, 3 ml.

Diagnostics

Tick-borne encephalitis can be suspected in case of trips to nature in endemic areas, tick bites, fever, headache, neurological symptoms. But the clinic does not make a diagnosis.

To accurately confirm the diagnosis, it is necessary to determine specific antibodies -

immunoglobulin class M for encephalitis (IgM) – the presence indicates an acute infection,
IgG - the presence indicates contact with an infection in the past, or the formation of immunity.

If both types of antibodies are present, this is a current infection.

The virus is also determined in the blood by PCR and PCR of the cerebrospinal fluid is performed. In addition, another infection in the blood is determined in parallel - tick-borne borreliosis.

Tick-borne encephalitis - treatment

All sick people are required to be hospitalized in a hospital. They are shown strict bed rest. Patients should be kept in intensive care units or under constant supervision medical personnel due to the unpredictability of the pathology. If complications develop, patients are transferred to the intensive care unit.

Drug treatment of tick-borne encephalitis is as follows:

infusion therapy - solutions of glucose, Ringer, Trisol, Sterofundin;
etiotropic therapy (directly aimed at destroying the pathogen) - specific donor immunoglobulin, homologous donor polyglobulin, leukocyte donor interferon, reaferon, laferon, intron-A, neovir, etc.;
glucocorticosteroids (methylprednisolone, prednisolone) - drugs in this group prevent damage to the brain and spinal cord, reduce their swelling;
antipyretic drugs - paracetamol, infulgan. It is prohibited to use acetylsalicylic acid because of possible complications on the liver;
decongestants – mannitol, furosemide, l-lysine escinate;
anticonvulsant therapy – sodium hydroxybutyrate, magnesium sulfate, sibazon;
substances that improve microcirculation in the brain - thiotriazoline, trental, dipyridamole, actovegin;
neurotrophics – complex B vitamins (neurorubin, milgamma);
hyperbaric oxygenation.

During the recovery period, exercise therapy procedures, therapeutic massage, and classes with a rehabilitator are indicated.

Features of the use of immunoglobulin

The drug interrupts the cycle of viral development in the initial route of infection and prevents its reproduction. The antigenic structures of immunoglobulin recognize the virus, bind antigen molecules and neutralize them (0.1 g of serum can neutralize about 60,000 lethal viral doses).

The effectiveness of the drug has been proven when administered within the first 24 hours after a tick bite. Further, its effectiveness drops sharply, since with prolonged exposure to the virus, the cells of the body are already affected, and cell walls are an insurmountable barrier for our molecular guardians.

If more than 4 days have passed after contact with a tick, it is dangerous to administer the drug throughout the entire incubation period of the virus; this will only complicate the disease and will not prevent its development.

Prevention

As specific prevention Vaccination is used, which is the most reliable preventive measure. Mandatory vaccination All persons living in or entering endemic areas are subject to this. The population in endemic areas accounts for approximately half of the total population of Russia.

In Russia, vaccination is carried out with foreign (, Encepur) or domestic vaccines according to the main and emergency schemes. The basic regimen (0, 1-3, 9-12 months) is carried out with subsequent revaccination every 3-5 years. To build immunity by the beginning 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 persons arriving in endemic areas in the spring and summer. Emergency vaccinated individuals are immunized for only one season (immunity develops in 2-3 weeks); after 9-12 months they are given the 3rd injection.

In the Russian Federation, in addition to tick bites, unvaccinated people are given intramuscular immunoglobulin from 1.5 to 3 ml. depending on age. After 10 days, the drug is re-administered in an amount of 6 ml. The effectiveness of emergency prophylaxis with specific immunoglobulin needs to be confirmed in accordance with modern requirements of evidence-based medicine.

Today, tick-borne encephalitis is not incurable and, if detected in a timely manner, does not cause significant damage to the body. The key in this case is the timely detection of the tick, so you should especially carefully examine the surface of the skin (especially in children) after visiting a forest area.

It should also be remembered that tick-borne encephalitis is not transmitted from one patient to another, it is not dangerous, like a viral disease, to others.

Medical newspaper. No. 34 - 2003

Tick-borne encephalitis is a zooanthroponotic viral disease, the causative agent of which is transmitted mainly by ixodid ticks. And it is characterized by fever, intoxication and damage to the central and peripheral nervous system. The first clinical description was given by the domestic researcher A. Panov in 1935. In 1937-1938. complex expeditions of E. Pavlovsky, A. Smorodintsev, L. Zilber, V. Solovyov, E. Levkovich and others studied in detail the epidemiology, clinical picture and prevention of this disease. The tick-borne encephalitis virus was first isolated in 1937 by L. Zilber and his colleagues from the brains of the dead, the blood and cerebrospinal fluid of patients, as well as from ixodid ticks and wild vertebrates of the Far East.

Epidemiology

Natural foci of tick-borne encephalitis were first discovered in the taiga regions of the Far East. Currently, outbreaks are known in a number of areas of the forest zone of Russia, Ukraine, Belarus, Kazakhstan, Kyrgyzstan, Lithuania, Latvia and Estonia.

In Russia, natural foci of tick-borne encephalitis are distributed from the Kaliningrad region in the west to Sakhalin in the east. In Ukraine, a relatively constant incidence is characteristic only of the Transcarpathian region. Sporadic diseases are known in the western and northern regions. On the territory of Belarus, diseases are found in all regions. In Kazakhstan, diseases are regularly observed in the Alma-Ata region and East Kazakhstan regions. Isolated cases are registered in other areas. In Kyrgyzstan, there are isolated diseases that occur irregularly. Natural foci are located in the mountain-forest belt of the Tien Shan in the northern regions bordering Kazakhstan.

In the Baltic states, diseases are recorded sporadically from 1 to 50 cases of tick-borne encephalitis per year. Foci of tick-borne encephalitis have been registered in the Czech Republic, Poland, Germany, Finland, Sweden, Ireland, Australia, Hungary, Yugoslavia, and China. Spontaneous virus carriage or antibodies to the tick-borne encephalitis virus have been found in most species of vertebrate animals associated with forest biocenoses within the range of this infection. The virus has also been isolated from arthropods of various groups. However, not all warm-blooded animals and arthropods play the same role in the circulation of tick-borne encephalitis virus.

Natural foci of tick-borne encephalitis in different parts of its nosoareal vary in the degree of epizootic activity: from low in forest-steppe landscapes to high in a number of forest ones. The epidemic activity of tick-borne encephalitis foci depends not only on the degree of their epizootic activity, but also on a number of social factors, primarily on the population density in endemic areas and the nature of its economic activities.

The tick-borne encephalitis virus circulates in natural foci of infection along a chain; ixodid ticks - wild vertebrates - ixodid ticks.

Infection with the tick-borne encephalitis virus has been established in 14 species of ixodid ticks: Ixodes persulcatus, Ix. ricinus, Ix. pavlovskyi, Ix. trianguliceps, Ix. hexagonus, Ix. gibbosus, Haemaphysalis concinna, H. japonica, H. inermis, Dermatocentor marginatus, D. silvarum, D. reticulatus, D. nuttali. Despite the significant number of species of ixodid ticks from which the tick-borne encephalitis virus was isolated, only two species of ticks, which are the main carriers and long-term keepers of the virus in nature, are of real epidemiological significance: Ix. persulcatus in Asia and in a number of areas of the European nosoarea, Ix. ricinus - in the European part. Absolute and relative number of animal species feeding tick larvae, nymphs and adults Ix. persulcatus and Ix. ricinus, unequal in different parts area of tick-borne encephalitis and is determined primarily by the number of ticks.

The tick body is a favorable environment for the virus to multiply. At Ix. persulcatus infected experimentally, the virus multiplies intensively and reaches its maximum concentration by the 40th day after infection. During this period, the amount of virus increases 1000 times. By the 6th day after feeding, the virus penetrates all organs of the tick. The largest amount of virus accumulates in the intestines, reproductive system and salivary glands. The latter contribute to the dissemination of the virus among animals that feed ticks, into whose bodies the virus penetrates from the salivary glands during the period of blood sucking. A significant concentration of the pathogen in the ovary creates the prerequisites for transovarial transmission of the virus to offspring.

The virus is able to overwinter in the body of a tick and be transmitted transphasically. The number of ticks infected with the virus in outbreaks can vary from single individuals to 2-5% and even up to 40%.

Humans are attacked almost exclusively by adult ticks, which determines the main role in infection. Human infection occurs when an infected tick sucks blood. The majority of patients indicate a history of sucking ixodid ticks. The frequency of tick bites in sick people in various areas is about 80%. The likelihood of contact with ticks in areas of tick-borne encephalitis is very high. Typically, ticks lie in wait for their hosts along animal trails, where they are found in the greatest number. Ticks can also crawl onto people caring for livestock, which brings a lot of ticks after grazing, on the edges of the forest. The tick penetrates under a person’s clothing and most often attaches itself to the area of the shoulder, chest, neck and head. The tick's blood sucking, which lasts 4-6 days, is usually insensitive, since its saliva contains an anesthetic substance.

The main cause of severe forms of tick-borne encephalitis is multiple tick bites, which often lead to death.

The causative agent of tick-borne encephalitis is transmitted by ticks during any, even short-term, suction. Removing a tick does not eliminate infection with tick-borne encephalitis, since already in the first portions of the liquid fluid of a hungry tick there is a virus, and the case of cemented saliva that forms during the first hour often contains the same amount of virus as in the rest of the tick’s body.

Large mammals (deer and other ungulates) are feeders not only of imagoes, but also large quantity nymphs Ix. persulcatus and Ix. ricinus. Thus, these wild animals, being feeders of imagoes and nymphs of ixodid ticks, have important epizootic significance. They determine the existence of a short chain of transmission of the pathogen by ticks from adults or adults and nymphs to uninfected nymphs when they simultaneously suck blood on wild mammals. This significantly complements the well-known long route of transmission of the virus - transovarian and transphase.

In large wild and domestic animals and small mammals, antibodies that appear in the blood as a result of infection with tick-borne encephalitis do not persist for a long time. Their titers are constantly decreasing, and in the absence of re-infection, antibodies disappear relatively quickly. Many animals become seronegative by the end of the tick season, following the appearance of antibodies in their blood. The rapid disappearance of humoral antibodies in wild and domestic animals is one of the characteristic features of the epizoology of tick-borne encephalitis. The possibility of multiple viremia in long-living mammals gives reason to believe that it is the hosts of adult ticks that are important for maintaining the circulation of the tick-borne encephalitis virus in the outbreak, since they determine the level of infection of well-fed imago ixodid ticks and their offspring. Under experimental conditions, the possibility of exchange of tick-borne encephalitis virus between donor ticks and recipient ticks during joint feeding on animals with a “subthreshold” level of viremia was proven. This exchange occurs when infected and uninfected ticks suck blood from one focus of inflammation on the skin of a vertebrate. This route of transmission of the virus is called transptial (from the Greek ptialon - saliva). Transptial transmission of the tick-borne encephalitis virus, as well as other tick-borne viruses, occurs in natural foci.

The most common route of human infection with the tick-borne encephalitis virus is transmissible, that is, associated with the sucking of infected ticks - adults or nymphs. Serologically it has been established that birds of a number of species can regularly become infected with tick-borne encephalitis. However, the total population density of birds is, as a rule, significantly less than the population density of mammals, so the absolute number of birds that can become infected with tick-borne encephalitis during the epizootic season is relatively small. Therefore, birds are only additional feeders of larvae and nymphs, and they do not determine the structure of natural foci in an epizootic situation. Birds are weakly susceptible to the causative agent of tick-borne encephalitis, are only additional hosts of the virus and can take a significant part in the process of its circulation only in foci where they are attacked by many ixodid ticks.

Human infection with tick-borne encephalitis is also possible through the nutritional route - by consuming raw milk from infected goats and cows. Goats suffer from tick-borne encephalitis. Infected animals experience loss of appetite, lethargy, meningeal symptoms, paralysis hind limbs. Their milk takes on a reddish tint, and when it settles, a mucous-bloody sediment appears at the bottom of the vessel. The virus remains in the blood of goats for three days, and in milk for 8 days after illness. Cows are not susceptible to the virus, but they also exhibit viremia.

Everywhere in all foci of tick-borne encephalitis, a spring-summer seasonality of incidence is observed, which is due to the activity of ixodid ticks at this time of year. When the epidemic period lasts 4-5 months, the first isolated diseases are most often observed in the second half of April - the first half of May. The maximum incidence is usually recorded in June, then it decreases and from the second half of July it is recorded again in the form of isolated cases. Overwintered virus-forming ticks are the source of the encephalitis virus, and their first attack on people is directly related to the onset of spring warming and melting snow cover.

Determining the beginning of the epidemic season is very important for the timely organization of anti-epidemic measures (vaccination, anti-tick measures). The end of the epidemic season occurs in July, but isolated cases can be observed in September, more often they occur in the first half of August.

Etiology

The disease is caused by a virus of the B-arbovirus group, which belongs to small RNA viruses (genus Flavivirus, family Flaviviridae). The virus consists of a protein shell, which is associated with antigenic and hemagglutinating properties, and ribonucleic acid, which is the carrier of genetic information. There are eastern and western nosogeographic variants of the virus.

The virus is not resistant to high temperatures, ultraviolet irradiation. Lysol in a 5% solution kills the virus after 1 minute, a 5% solution of trichloroacetic acid inactivates the virus after 10 minutes. In cow's milk at refrigerator temperature, the tick-borne encephalitis virus persists for 2 weeks, and in sour cream for up to 2 months. Gastric juice of normal acidity at a temperature of 37° almost completely inactivates the virus after 2 hours. However, low acidity gastric juice and the alkalization of the latter by the introduction of milk under the same conditions does not lead in most cases to inactivation of the virus.

The virus persists for a long time in the body of ixodid ticks, in which transphase transmission of the virus is observed. The pathogen remains in the body of hungry gamas ticks for at least a month. Mosquitoes infected under experimental conditions are freed from the virus within 5 days. Among laboratory animals, monkeys and white mice are susceptible to the tick-borne encephalitis virus.

Pathogenesis

The virus enters the human body through the bite of an infected tick through the skin or through the raw milk of domestic animals. After sucking on a tick, the virus spreads hematogenously and quickly penetrates the brain, fixing itself here with cells, causing degenerative changes. The nerve cells of the anterior horns of the cervical spinal cord and the nucleus of the medulla oblongata are especially strongly affected, where necrotic and dystrophic changes. In parallel with the accumulation of the virus, inflammatory changes in the blood vessels and membranes of the brain develop. The correspondence of the site of the tick bite to the subsequent localization of segmental disorders indicates the possibility of a lymphogenous route of penetration of the virus into the central nervous system. In some cases, one way or another predominates, which affects clinical features diseases. The occurrence of meningeal and meningo-encephalitic syndromes corresponds to the hematogenous, and poliomyelitis and radiculoneuritic syndromes correspond to the lymphogenous route of spread of the virus. The nature of the course of the disease is determined by the route of introduction, the properties and dose of the pathogen, as well as the resistance and reactivity of the macroorganism.

Viremia in tick-borne encephalitis has a two-wave nature: short-term primary viremia, and then repeated (at the end of the incubation period), coinciding with the multiplication of the virus in the internal organs and its appearance in the central nervous system. Long-term virus carriage is possible, which can be different in its manifestations and consequences: latent infection (the virus is integrated with the cell or exists in a defective form), persistent infection (the virus reproduces, but does not cause clinical manifestations), chronic infection (the virus reproduces and causes clinical manifestations with a recurrent, progressive or regressive course), slow infection (the virus reproduces after a long incubation period, causes clinical manifestations with steady progression, leading to death).

Clinical course

The incubation period lasts 4-14 days, for milk infection - 7-10 days. The disease begins suddenly with an increase in temperature to high numbers, the appearance of meningeal symptoms, and damage to the central nervous system. Then disturbances in sensitivity and coordinated movements appear. The form of the disease can be different - from asymptomatic and erased to very severe, complicated by persistent paralysis and paresis, sometimes leading to death.

In the initial period of the disease, fever is observed in 80% of cases, headache and vomiting (in 24%), symptoms of damage to the central nervous system (in 12%), and at the height of the disease - in 25, 62 and 65% of cases, respectively. Damage to the central nervous system is characterized by pronounced changes in the brain stem and basal ganglia of the brain. Of the patients with clinical symptoms About 1/3 of CNS lesions recover completely. Mortality ranges from 20-44%. In case of lethal outcomes, death occurs in 70% of cases in the first week, in 25% - in the 2nd week, in other cases - up to a month from the onset of the disease. The ratio of clinical and asymptomatic forms in different countries fluctuates between 1:300 - 1:1000, in India in the 70-80s it was 1:20 - 1:30.

The acute period of tick-borne encephalitis lasts from 3 to 14 days, more often 6-8 days. In the acute period it is very characteristic appearance sick. There is hyperemia of the skin of the face, neck and chest, mucous membrane of the pharynx, injection of the sclera and conjunctiva. Often, erythema of various sizes appears at the site of tick suction. Changes in the respiratory system are rare and manifest themselves in the form of bronchitis or focal pneumonia. Disorders of the cardiovascular system are functional in nature. In patients, muffled heart sounds are heard, absolute or relative bradycardia, arterial and venous hypotension are determined. An electrocardiogram reveals disturbances in the contractile function of the myocardium, and, to a lesser extent, the functions of automaticity, excitability and conductivity. The state of these functions is determined by shifts in electrolyte metabolism, in particular hypokalemia. There is a decrease secretory function stomach, antitoxic, absorption-excretory, carbohydrate, protein-forming functions of the liver; febrile albuminuria is observed. Their dependence on the period of the disease and the severity of its course has been established. Changes in internal organs completely disappear in the long term of recovery. In the peripheral blood there is moderate leukocytosis with a shift to the left, lymphopenia and aneosinophilia, increased ESR.

Despite the variety of manifestations of the acute period of tick-borne encephalitis, in each individual case the leading syndrome of the disease can be identified. Based on this, and also taking into account the severity and persistence of neurological symptoms, five clinical forms of the disease are distinguished: 1) febrile (erased); 2) meningeal; 3) meningoencephalitic; 4) poliomyelitis; 5) polyradiculoneuritis.

The febrile form is characterized by a favorable course with rapid recovery. The duration of fever is 3-5 days. Its main clinical signs are toxic-infectious manifestations: headache, weakness, nausea - with mild neurological symptoms. CSF values are without deviations from the norm.

The meningeal form is the most common form of tick-borne encephalitis. Patients complain of severe headache, worsening with the slightest movement of the head, dizziness, nausea, single or repeated vomiting, pain in the eyes, photophobia. They are lethargic and inhibited. Rigidity of the neck muscles, Kernig's and Brudzinski's symptoms are determined. Meningeal symptoms persist throughout the febrile period. Sometimes they are determined by normal temperature. The duration of fever is on average 7-14 days. In the cerebrospinal fluid there is moderate lymphocytic pleocytosis up to 100-200 per 1 mm3, an increase in protein.

The meningoencephalitic form is observed less frequently than the meningeal one (the national average is 15%, in the Far East up to 20-40%). This form has a more severe course. Delusions, hallucinations, psychomotor agitation with loss of orientation in place and time are often observed. Epileptic seizures may develop. There are diffuse and focal meningoencephalitis. With diffuse meningoencephalitis, general cerebral disorders are expressed (profound disorders of consciousness, epileptic seizures up to status epilepticus) and scattered foci of organic brain damage in the form of pseudobulbar disorders (breathing disorders in the form of brady- or tachypnea, like Cheyne-Stokes, Kussmaul, etc.), irregularities deep reflexes, asymmetric pathological reflexes, central paresis of facial muscles and tongue muscles. With focal meningoencephalitis, capsular hemiparesis, paresis after Jacksonian convulsions, central monoparesis, myoclonus, epileptic seizures, and, less commonly, subcortical and cerebellar syndromes quickly develop. In rare cases (as a consequence of disturbances in the autonomic centers), a syndrome may develop stomach bleeding with bloody vomiting. Characteristic are focal lesions of cranial nerves III, IV, V, VI pairs, somewhat more often VII, IX, X, XI and XII pairs. Later, Kozhevnikov epilepsy may develop, when general epileptic seizures with loss of consciousness appear against the background of constant hyperkinesis.

The polio form is observed in almost a third of patients. It is characterized by a prodromal period (1-2 days), during which general weakness and increased fatigue are noted. Then periodically occurring muscle twitching of a fibrillar or fascicular nature is detected, reflecting irritation of the cells of the anterior horns of the medulla oblongata and spinal cord. Suddenly, weakness may develop in any limb or a feeling of numbness may appear in it (later, severe motor disturbances often develop in these limbs). Subsequently, against the background of febrile fever (1-4 days of the first febrile wave or 1-3 days of the second febrile wave) and general cerebral symptoms, flaccid paresis of the cervicobrachial (cervicothoracic) localization develops, which can increase over several days , and sometimes up to 2 weeks. The symptoms described by A. Panov are observed ("head hanging on the chest", "proud posture", "bent, stooped posture", techniques of "torso throwing the arms and throwing back the head." Poliomyelitis disorders can be combined with conduction disorders, usually pyramidal: flaccid paresis of the arms and spastic - legs, combinations of amyotrophy and hyperflexion within one paretic limb. In the first days of the disease, patients with this form of CE often have a pronounced pain syndrome. The most typical localization of pain is in the neck muscles, especially along the back surface, in the area of the shoulder girdle and arms. Increasing motor disorders with FE lasts up to 7-12 days. At the end of the 2-3rd week of the disease, atrophy of the affected muscles develops.

The polyradiculoneuritic form is characterized by damage to peripheral nerves and roots. Patients develop pain along the nerve trunks, paresthesia (a feeling of “crawling goosebumps”, tingling). The symptoms of Lasseg and Wasserman are determined. Sensitivity disorders appear in the distal parts of the extremities of the polyneural type. Like other neuroinfections, CE can occur as Landry's ascending spinal palsy. Flaccid paralysis in these cases begins from the legs and spreads to the muscles of the torso and arms. The ascent can also begin from the muscles of the shoulder girdle, involving the cervical muscles and the caudal group of nuclei of the medulla oblongata.

A fundamentally special variant is tick-borne encephalitis with a two-wave course. The disease is characterized by an acute onset, chills, headache, nausea, vomiting, dizziness, pain in the limbs, sleep disturbance, anorexia and the presence of two-wave fever. The first febrile wave lasts 3-7 days and is characterized by a mild course. There are moderate meningeal symptoms without damage to the cranial nerves. In the peripheral blood - leukopenia and accelerated ESR. The first febrile wave is followed by a period of apyrexia, lasting 7-14 days. The second feverish wave begins as acutely as the first, the temperature rises to high numbers. Patients are lethargic, inhibited, nausea and vomiting appear, and meningeal and focal symptoms of damage to the nervous system are detected. In peripheral blood - leukocytosis. This is a qualitatively new phase of the disease; it is always more severe than the first and lasts longer.

During the first feverish wave, normal cytosis and increased cerebrospinal fluid pressure are detected in the cerebrospinal fluid. During the second wave, cytosis is 100-200 or more cells per 1 μl, lymphocytes predominate. The protein and sugar content increases.

The course of the disease is acute, recovery is complete. There are isolated cases of chronic progressive course.

In different areas of the range of tick-borne encephalitis, differences in the clinical course of the disease are noted. Tick-borne encephalitis caused by the Western variant of the virus (European part of Russia, Western and Eastern Siberia), characterized by a milder course and lower mortality (below 1%), a large number of erased forms of the disease. The febrile period is longer (11 days) than with the eastern nosogeographical variant (8-9 days), and is of a two-wave nature. The eastern variant of tick-borne encephalitis (Far East) is characterized by an encephalitic symptom complex, and the western nosoform is characterized by a meningeal complex. The constant symptoms of the Western nosogeographical variant are radicular pain and distal type of paresis; damage to the nuclei of the brain stem and cervical spinal cord is rare. The course of the acute period is easier: it does not happen comatose state with respiratory distress and generalized seizures. In the Far East, there is a severe course of tick-borne encephalitis with paralysis and an average mortality rate of up to 20%.

Susceptibility and immunity

Human susceptibility to tick-borne encephalitis is universal. The disease is most common among people of working age. The professional composition of the sick is determined by the characteristics of the location of natural foci, the nature of the organizational and economic activities of the population and the prevailing way of life. The greatest risk of morbidity is among those directly working in the forest. In most foci of encephalitis, males predominate among the sick. This is explained by the fact that forest work is usually carried out by men. The disease affects people of all age groups. Among old-timers, an immune layer gradually forms with age, resulting from a latent or clinically pronounced infection. Most infections with the virus lead to an inapparent course of infection with the development of immunity: 1 clinical case accounts for 60 inapparents. IN last years The ratio of different professional groups of the population among the sick has noticeably changed, since the contact of urban residents with natural foci of tick-borne encephalitis during walks in the forest, picking mushrooms and berries began to play a large role in the incidence.

After a person recovers, tick-borne encephalitis leaves long-lasting and lasting immunity. In the blood of convalescents, as a rule, specific antibodies are detected, which can be detected in neutralization reactions, complement fixation and inhibition of hemagglutination.

Virus-neutralizing antibodies accumulate in the blood rather slowly, reaching a maximum after 1.5-2.5 months and persist for many years. The accumulation of virus-neutralizing antibodies is also observed in vaccinated people and people living for a long time in areas of encephalitis.

Virus-neutralizing antibodies are also found in wild and domestic animals attacked by infected ticks.

The process of natural immunization of the population is one of the important epidemiological features of tick-borne encephalitis. A high incidence was always observed in groups that first came into contact with active natural foci of encephalitis. Therefore, the intensity of the incidence of tick-borne encephalitis does not always correspond to the level of tick infestation and virality of ticks. Morbidity and natural immunization of the population are parallel processes. Their ratio is determined a large number factors, the most important of which are the spread of virus-carrying ticks, susceptibility to infection and the conditions of contact of people with a natural focus.

Laboratory diagnostics. Laboratory confirmation of the diagnosis is a serological examination of patients to identify the presence and increase in antibody titer. For this purpose, complement fixation reactions (FFR), hemagglutination inhibition (HAI), hemagglutination inhibition (RPHA), neutralization (RN), indirect hemagglutination (RIHA), diffuse priming in agar (RDPA), on bioassay mice or in cell cultures etc. A 4-fold increase in antibody titer is diagnostic. In the absence of an increase in antibody titer, patients are examined three times: in the first days of the disease, after 3-4 weeks and after 2-3 months from the onset of the disease. In tissue culture, the virus and its antigens are detected in the first 7 days of illness. The enzyme-linked immunosorbent diagnostic method has proven itself well, with the help of which antibodies to the tick-borne encephalitis virus are detected earlier and in higher serum dilutions than in RTGA and RSK, and also more often determine changes in the strength of specific immunity.

By using virological methods the pathogen and its antigens can be detected in the acute period of the disease in the blood or cerebrospinal fluid. U dead people the virus is isolated from the brain.

Treatment

Treatment of patients with CE is carried out according to general principles, regardless of previous preventive vaccinations or the use of specific gamma globulin for prophylactic purposes. In the acute period of the disease, even in mild forms, patients should be prescribed bed rest until the symptoms of intoxication disappear. Almost complete restriction of movement, gentle transportation, and minimization of painful stimuli clearly improve the prognosis of the disease. No less important role in treatment has balanced diet sick. The diet is prescribed taking into account functional disorders stomach, intestines, liver. Taking into account the vitamin imbalance observed in a number of patients with CE, it is necessary to prescribe vitamins B and C. Ascorbic acid, which stimulates the function of the adrenal glands, as well as improves the antitoxic and pigment functions of the liver, should be administered in an amount of 300 to 1000 mg per day.

Etiotropic therapy consists of prescribing homologous gamma globulin titrated against the TBE virus. The drug has a clear therapeutic effect, especially in moderate and severe cases of the disease. Gamma globulin is recommended to be administered 6 ml intramuscularly, daily for 3 days. The therapeutic effect occurs 12-24 hours after the administration of gamma globulin: body temperature drops to normal, the general condition of patients improves, headaches and meningeal symptoms decrease and sometimes completely disappear. The earlier gamma globulin is administered, the faster the onset of healing effect. In recent years, serum immunoglobulin and homologous polyglobulin, which are obtained from the blood plasma of donors living in natural foci of TBE, have been used to treat TBE. On the first day of treatment, serum immunoglobulin is recommended to be administered 2 times at intervals of 10-12 hours, 3 ml at mild flow, 6 ml - for moderate and 12 ml - for severe. In the next 2 days, the drug is prescribed 3 ml once intramuscularly. Homologous polyglobulin is administered intravenously at 60-100 ml. It is believed that antibodies neutralize the virus (1 ml of serum binds from 600 to 60,000 lethal doses virus), protect the cell from the virus by binding to its surface membrane receptors, neutralize the virus inside the cell, penetrating it by binding to cytoplasmic receptors.

For specific antiviral treatment CE also uses ribonuclease (RNase), an enzyme preparation prepared from the tissues of the pancreas of a large cattle. RNase inhibits the multiplication of the virus in the cells of the nervous system, penetrating the blood-brain barrier. It is recommended to administer ribonuclease intramuscularly in saline (the drug is diluted immediately before the injection) in a single dose of 30 mg after 4 hours. The first injection is performed after desensitization according to Bezredko. Daily dose the enzyme introduced into the body is 180 mg. Treatment continues for 4-5 days, which usually corresponds to the moment of normalization of body temperature.

A modern method of treating viral neuroinfections is the use of interferon preparations, which can be administered intramuscularly, intravenously, endolumbarally and endolymphatically. It should be taken into account that large doses of interferon 1-3-6x10 IU have an immunosuppressive property, and the resistance of cells to virus penetration is not directly proportional to IFN titers. Therefore, it is advisable to use relatively small doses of the drug or use interferon inducers (double-stranded RNA of phage f2, tilorone, etc.), which provide low titers of IFN and have immunomodulatory properties. Double-stranded RNA of phage f2 (larifan) is injected intramuscularly in 1 ml doses with an interval of 72 hours from 3 to 5 times. Tilorone in a dose of 0.15-0.3 g is administered orally at intervals of 48 hours from 5 to 10 times.

Pathogenetic therapy for febrile and meningeal forms of TBE, as a rule, consists of measures aimed at reducing intoxication. For this purpose, oral and parenteral administration of fluid is carried out, taking into account the water-electrolyte balance and acid-base state. In meningoencephalitic, poliomyelitis and polyradiculoneuritic forms of the disease, additional administration of glucocorticoids is mandatory. If the patient does not have bulbar disorders or disorders of consciousness, then prednisolone is used in tablets at the rate of 1.5-2 mg/kg per day. The drug is prescribed in equal doses in 4-6 doses over 5-6 days, then the dosage is gradually reduced ( general course treatment 10-14 days). At the same time, the patient is prescribed potassium salts and a gentle diet with sufficient protein content. For bulbar disorders and disorders of consciousness, prednisolone is administered parenterally, increasing the above dose by 4 times. In case of bulbar disorders (with swallowing and breathing disorders), from the moment the first signs of respiratory failure appear, conditions must be provided for transferring the patient to mechanical ventilation. Lumbar puncture is contraindicated and can be performed only after removal of the bulbar devices. To combat hypoxia, it is advisable to systematically administer humidified oxygen through nasal catheters (20-30 minutes every hour), hyperbaric oxygen therapy(10 sessions under pressure pCO2=0.25 MPa), use of neuroplegics and antihypoxants: intravenous administration sodium hydroxybutyrate 50 mg/kg body weight per day or seduxen 20-30 mg per day. In addition, with psychomotor agitation, lytic mixtures can be used.

Preventive and anti-epidemic measures

The main measure in the prevention of tick-borne encephalitis is the fight against ixodid ticks. Their destruction in limited areas leads to the elimination of the conditions necessary for the circulation of pathogens and the cessation of diseases among people for a long time. Measures to combat ixodid ticks can be divided into preventive, to protect people from tick attacks, and exterminatory.

Preventive measures consist of preventing people from staying in tick habitats, or taking measures that lead to the death of ticks. Preliminary reconnaissance of areas of residence (temporary or permanent) of people is carried out to identify the places and nature of the spread of ticks, with the subsequent adoption of measures to protect people from their attacks.

Specific prevention is carried out by vaccination with a liquid adsorbed vaccine against tick-borne encephalitis and a lyophilized form of culture fluid. Vaccinations are carried out for persons aged 4 to 70 years if there is a risk of contracting tick-borne encephalitis. The full course of vaccinations consists of four subcutaneous injections.

By epidemic indications recommended before the epidemic season after full course vaccinations, carry out annual revaccinations for 3-4 years in a row. If revaccination is missed within one or two years, it can be resumed before the start of the epidemic season without repeating the full course of vaccinations.

Contingents are subject to general immunization, among which the following infection risk indicators have been determined: incidence - 10-20 or higher per 100 thousand population; bitten by ticks - 1-2% and higher; the immune layer among indigenous people is 30-40% and higher. The effectiveness of culture-adsorbed vaccine in controlled epidemiological experiments reaches 70-80%. It increases to 92-97% or more after individual revaccinations.

In those vaccinated with a tissue vaccine, if the disease develops, it proceeds benignly without deaths and severe defeats. There is a predominance of febrile forms and a significant decrease in the incidence of meningeal forms with the complete disappearance of paralytic tick-borne encephalitis.

In cases requiring the rapid creation of a protective barrier (during infection with ticks or in laboratory conditions), seroprophylaxis with purified anti-encephalitis serums and specific gamma globulin is used.

An important non-specific measure in relation to tick-borne encephalitis is the protection of people from tick attacks, which includes self- and mutual examinations to detect attached ticks, wearing special protective clothing and the adaptation of ordinary outer clothing to protect against ticks, and the use of repellents. Self- and mutual examinations are carried out without removing clothing approximately every 2 hours of work or being in areas of mass spread of ticks (on pastures, wild animal trails, etc.). During these inspections, ticks found on outer clothing and exposed parts of the body are removed. This is one of the main very effective measures for the prevention of infectious diseases transmitted by ixodid ticks.

In areas where ticks are spreading, special anti-tick overalls are used with tightly tightened sleeves and at the bottom of the trousers (rubber strips are sewn into the edges of the cuffs), zipper fasteners, and a hood sewn to the collar, leaving only the face exposed. To reduce the likelihood of some types of ticks crawling under clothing, the shirt is tucked into trousers, trousers into boots or the bottom of trousers, as well as sleeve cuffs, tightly buttoned (pressed with rubber bands) or tied with braid, and the collar is buttoned tightly. Most species of ixodid ticks tend to crawl only upward, and with this method of fitting clothing, they are less likely to crawl onto it, and therefore can be detected during self- and mutual examinations on the surface of clothing.

good prophylactic is the impregnation of clothing with deterrents. The best repellents against ixodid ticks are considered to be diethyltoluamide, Kyuzol-A (acyl-tetrahydroquinoline), and hexamide (N-benzene hexamethylenamine). They are used to impregnate outerwear (overalls, shirts, trousers), Pavlovsky nets, or applied to the skin of exposed parts of the body (arms, neck). Overalls treated with Kyuzol-A reliably protect against Ix ticks. persulcatus in the taiga for 45 days. If in 1 hour of stay in the taiga up to 20-25 ticks attach to an untreated overalls, then on the overalls soaked with Kyuzol-A, single ticks were found, which fell off after 1-2 minutes. Diethyltoluamide applied to the overalls repel ticks Ix. persulcatus for one month. The preparations are applied to clothing at a rate of about 25 ml per set (shirt, trousers).

To prevent tick-borne encephalitis and some other diseases transmitted by ixodid ticks, large areas (forests) are treated on a large scale in places where tick-borne encephalitis is widespread (usually anthropurgic foci - forest pastures of domestic animals) by spraying various insecticides from airplanes or helicopters, at the rate of 0.3-0.5 g of technical substance per 1 m2, or up to 50 kg per 1 ha. The use of helicopters is preferable, since, thanks to the downward air currents that occur during the rotation of the main rotor, dust (or granular preparations) in mass penetrates to the surfaces of the forest floor, settles to a much lesser extent on foliage and needles, and is less affected by the wind. Helicopters can pollinate forests when wind strength is up to 5 m/s, and airplanes only when wind strength is less than 2 m/s. Helicopters are more convenient due to greater maneuverability, a large speed range, and low requirements for the take-off site.

In steppe areas and forest clearings, early spring fires give good results when dead grass is burned before the beginning of the growing season (especially in pastures), which leads to the death of ticks along with the dead wood. In the spring, during the period of adult activity, it is possible to use aerosols for the immediate and rapid destruction of ticks in the area. At this time, ticks are active, located in the upper layer of litter or on vegetation, and if you apply an insecticidal aerosol under favorable meteorological conditions (for example, early in the morning), when it spreads along the ground, you can get a good, albeit temporary, acaricidal effect.

Burrowing forms of ixodid ticks are destroyed by blowing insecticides into the burrows, which is especially important when conducting excavation work, since some types of ticks (for example, Ix. laguri laguri) can attack people under these conditions.

Treatment of large and small livestock with acaricidal preparations (1-2% chlorophos solution) in the spring is a measure of the destruction of ixodid ticks (adults) on host animals, and at the same time leads to the gradual elimination of tick foci. This method is effective when carried out over a number of consecutive years, since not all adult ticks feed annually.

To exterminate ixodid ticks, the most effective are organophosphorus insecticides, as well as DDT and hexachlorane preparations: 4% dust and 3% karbofos emulsion, 0.5% trichlorometaphos-3 emulsion, 0.5% metathion or cyclophos emulsion. The consumption rate for dusts is 10-20 g/m, for aqueous emulsions and suspensions - 100 mg/m2 of the treated surface. In the form of dusts and granules, they are used before snow falls (for snow) and before spring melting (for snow) with the help of airplanes, helicopters, various aerosol generators and other devices at the rate of 30-50 kg of the drug per 1 hectare of area, when using the above emulsions, the consumption of working fluid is 100 l/ha. However, due to the discovery of disinfectants in vegetables, fruits, livestock products, in water and their accumulation in the human body, as well as the destruction of natural biogeocenoses and the damage caused to them by disinfectants, the latter can be used over large areas only for vital epidemiological indications.

Anti-epidemic measures consist of a thorough epidemiological examination of the outbreak, hospitalization of sick people, vaccination and seroprophylaxis. Measures to combat rodents and ixodid ticks are being intensified.