What is taiga encephalitis. Spring-summer tick-borne encephalitis (taiga encephalitis) - Symptoms, Diagnosis, Treatment. How soon can you get it

A number of flaviviruses carried by ticks have been found on the territory of Eurasia. Many of them are known to cause diseases in farm animals, such as sheep rolls (in the UK).

The incidence is characterized by very strong geographical differences. The main risk factors are being in nature and drinking raw milk, especially goat's.

The incubation period lasts 7-14 days, possibly longer.

Taiga spring-summer encephalitis, as a rule, is more acute and more severe than Central European encephalitis, immediately starting with neurological symptoms. It is characterized by high mortality and a high incidence of residual neurological defects, mainly flaccid paralysis of the muscles of the neck, shoulder girdle, shoulder and trunk.

On early stage disease virus can be isolated from the blood. After the addition of neurological symptoms, IgM antibodies are detected in the blood and CSF. Sometimes thrombocytopenia develops at an early stage, as with some other flavivirus infections transmitted by ixodid ticks (for example, with Kyasanur forest disease).

There is no etiotropic treatment for these infections.

In Austria, Germany and Russia, effective inactivated vaccines against tick-borne encephalitis with aluminum salts as an adjuvant are produced. The Austrian-made tick-borne encephalitis vaccine provides antiviral immunity if it is administered twice with an interval of 0.5-3 months. Other vaccines are about as effective. In rare cases, vaccination is complicated by Guillain-Barré syndrome, therefore, it is indicated only for people living in natural foci or visiting them in the spring and summer.

In vitro, neutralizing antibodies to Central European encephalitis virus cross-react with taiga spring-summer encephalitis virus and vice versa, but whether vaccination provides cross-protection in the field is not known.

In natural foci, from 0.2 to 4% of ticks are infected, therefore, if ticks are found on the body, the question of immunoprophylaxis arises. Immunoglobulin against tick-borne encephalitis can be administered immediately, although its effectiveness has not been studied in controlled studies. In any case, the drug should not be administered after the development of the infection, as this may aggravate its course.

Biology of ixodid

Ixodid ticks (pasture or forest) are small arachnids that spend part of their lives on the body of the host, feed on the blood of humans and animals. Ticks have a small head, eight legs, a small body, a sharp harpoon-shaped proboscis for sucking blood. They navigate with the help of the organs of touch and smell, they are able to feel a warm-blooded organism at a distance of up to 10 meters.

The most voracious individual is female, because for the development of eggs she needs nutrients. Having sucked blood, the female increases a hundred times, becomes like a shiny large droplet. But be careful - an awkward movement, and the abdomen can burst, and its contents can splash into the eyes or a wound on the body. Males are not so bloodthirsty - after all, they do not need to take care of their offspring, they just need to eat and fertilize the female.

From an epidemiological point of view, female ticks will be the most dangerous. Suspended for several days, they, together with saliva, inject a large number of viral particles into human blood.

Why are ixodid ticks dangerous to humans?

Scary stories about ticks have a real basis - you can get infected with such a terrible disease as encephalitis. How can a person become infected? It is enough to take a walk in nature, pick up a tick, a bloodthirsty creature will find a secluded place, stick its head almost completely into the skin and drink and suck for ten to twelve days, if a person does not notice it earlier, or accidentally hooks it, breaking off the bloody belly. But the deed has already been done - the tick bite has launched the mechanism of infection transmission.

True, not every close encounter with a tick can cause encephalitis, it is necessary that the animal has this insidious active virus in its saliva. The number of bites from an encephalitic animal increases the risk of developing the disease, although sometimes one bite is sufficient. Vaccination carried out on time, a sufficient level of antibodies is a guarantee that the disease will not develop. How ticks get infected, where the virus came from, the transmission mechanism is studied by the science of epidemiology.

How ticks get infected

The source of infection is mouse-like rodents (shrews, voles, shrews), moles, hares and other small animals. Epidemiologists have counted more than 200 animals that are natural reservoirs of the encephalitis virus. natural foci tick-borne encephalitis - taiga regions of the Far East, the forest zone of Russia from Kaliningrad to Sakhalin.

The disease is characterized by a spring-summer periodicity, with an increase in the activity of ticks, the number of infected increases. Ticks become infected by feeding on the blood of these animals, often change 3–4 hosts, and have a complex life cycle:

1. Fertile females lay a huge number of eggs, from which larvae develop.
2. The larvae live on small animals, birds, sometimes on large insects; before the onset of the next phase of development, they fall to the ground, turning into a nymph.
3. A nymph is an immature tick that lives on large animals and humans; when satiated, the nymph molts and also falls to the ground.
4. After a while, an adult crawls onto the blades of grass, sits with its paws apart, and waits for its “prey” - the owner.

Diagram of the life cycle of a tick

Adult individuals live 3–4 months, die by autumn, only immature females hibernate.

How does a person become infected?

The prey of a tick can be not only a large animal, but also a person. Tick ​​activity begins to show in early spring, therefore, in April, a meeting with these creatures is possible. The peak of activity falls in May (you need to be careful when going on May picnics) and lasts almost until the end of June. With the onset of dry and hot days, activity decreases.

The second August peak is typical for the European part of Russia. In the Urals, Siberia and the Far East, there is only one spring-summer peak. Tick-borne encephalitis has two sources of the virus carrier to humans:

• taiga tick (found in the taiga forests of Siberia and the Far East);
• canine (range - the European part of Russia, Central and Northern Europe).

With saliva, substances that prevent blood clotting enter the wound, so animals can drink a lot of it. Painkillers are also injected into the wound, the bite is painless, a person does not always notice small monsters that have stuck to his skin. After the animals have drunk, they stretch their proboscis, fall to the ground.

By appearance tick, it is impossible to find out if it is infected. You can determine in the laboratory by making a test.

Etiology

The etiology (causes), ways of infection and transmission of tick-borne encephalitis have been studied quite well. The causative agent of infection multiplies in the cells of mammals, birds and arthropods. It does not live long in the external environment, it is quickly destroyed by boiling, the action of disinfectants. Tick-borne encephalitis is characterized by natural foci - the disease occurs only where ixodid ticks live.

Infection with encephalitis occurs when eating raw milk, other dairy products obtained from sick animals. Ways of infection - transmissible (through blood when bitten), alimentary. The gate of infection is the skin, the epithelium of the digestive tract. The virus moves through the blood, lymphatic vessels, infecting cells and tissues on its way. Reaching the brain, it is localized in the cells.

The disease is often acute, rarely chronic, lasting for life. Complications that arise during the development of the disease can end in paralysis or death - in 70–80% of patients complications persist for life, in 20% the development of the pathology ends in death.

The pathogenesis of the disease in humans

Tick-borne encephalitis is characterized by deep damage to the white and gray matter of the brain, sensory and motor roots of the spinal, cranial and peripheral nerves. In patients, the meninges swell and become hyperemic, the internal organs are affected - the kidneys, liver, lungs. There are irreversible processes of death of neurons, cerebral vessels.

The pathogenesis of encephalitis is diverse:

• with an insufficient dose of the virus, the disease does not develop,
• sometimes clinical symptoms do not appear, the disease is hidden;
• distinguish between such forms as meningitis, meningoencephalitis, febrile forms, encephalomyelitis;
• according to another classification, a form with brain damage and feverish is distinguished.

All people with tick-borne encephalitis should be tested for borreliosis at the same time, since ticks can be infected with both infections.

Clinic

The incubation period is 7‒14 days, sometimes up to 20 days. The disease develops acutely, patients complain:

• weakness, numbness of the skin of the neck and face, increased fatigue;
• fever up to 40°C, hyperemia skin and mucous;
• pain in the whole body, muscle pain;
• the occurrence of paresis, paralysis.

There may be clouding of consciousness, stupor, coma. If symptoms of the disease appear, it is urgent to deliver the sick person to the infectious diseases department to clarify the diagnosis and conduct intensive medical treatment.

findings

The source of infection with encephalitis are small wild animals, in which the virus lives in the blood cells. Animals infect ticks that feed on them. Adult ticks bite a person - the chain closes. Compliance with safety rules, timely vaccination is a guarantee of human health.

Tick-borne encephalitis is a viral natural focal disease affecting the central nervous system. The causative agent of tick-borne encephalitis is the tick-borne encephalitis virus, which belongs to the group of arboviruses.

It has varying degrees of stability. When heated to 60 ° C, it dies within 10 minutes, when boiled - 2 minutes. Rapidly destroyed by ultraviolet irradiation, exposure to

disinfectants.

There are the following nosogeographical types: eastern, western and two-wave. The carrier of the causative agent of fever are ixodid ticks:

Ixodes persulcatus predominates in the Eastern regions;

Ixodes ricinus lives in the Western regions.

3-6 days after the bloodsucking of an infected animal, the virus penetrates into all organs of the tick, concentrating in the reproductive apparatus and salivary glands. The virus lives in a tick for 2-4 years. In various localities, tick infestation reaches from 1 to 20%.

The reservoir of tick-borne encephalitis virus are rodents, wild mammals and some birds.

Human infection occurs when bitten by infected ticks. The longer the blood sucking, the greater the chance of infection.

When crushing ticks, infection can occur through damaged skin, mucous membranes of the eye.

There is also an alimentary route of infection: when eating raw goat or cow's milk.

There are the following types of foci of the disease:

Natural foci in the wild;

Foci that have arisen as a result of human economic activity;

Secondary foci - near settlements when ticks live on domestic animals.

In Russia, tick-borne encephalitis is recorded in the Far East, the Urals, Siberia, and the European part of Russia.

The peak incidence occurs in May, July, the end of the summer - the beginning of autumn.

This is due to an increase in the number and increased activity of ticks.

The entrance gate for a tick bite is the skin, and for the alimentary route of transmission, the mucous membrane of the digestive tract.

The virus hematogenously and lymphogenously enters the internal organs, the central nervous system, causing an inflammatory reaction in nerve cells. AT pathological process the gray matter of the brain and spinal cord is involved, including the motor neurons of the spinal cord and brain (brain stem).

The incubation period lasts from 3 to 21 days.

Currently, in areas endemic for tick-borne encephalitis, preventive vaccinations are carried out according to epidemiological indications.

The population living in an enzootic area for tick-borne encephalitis;

Persons who arrived in this territory and perform the following works: agricultural, irrigation and drainage, construction, excavation and movement of soil, procurement, commercial, geological, deratization, pest control;

Persons working in logging, clearing forests;

Persons working with live cultures of the causative agent of tick-borne encephalitis.

Vaccination is carried out from the age of four, revaccination - after 1 year, then every 3 years.

There are several types of vaccines against tick-borne encephalitis (Table 1).

Emergency prevention of tick-borne encephalitis is carried out with human immunoglobulin against tick-borne encephalitis (Russia). It is available in ampoules of 1.0 ml.

For the prevention of tick-borne encephalitis, the dose is 0.1 ml / kg of body weight, after a tick bite, 0.1 ml / kg is administered no later than 4 days (Table 34).

The protective effect of the vaccine appears after 24 hours and lasts for 1 month.

Table 34. Schedules for the use of vaccines against tick-borne encephalitis

- Who is this - taiga enemy?

This terrible disease, called "taiga encephalitis", affected the brains of people. They found it in the Siberian taiga, where more than half of the sick people died.

- When did she appear?

The development of Siberia in the pre-war years was accompanied by the arrival there of a large number of people from the European part of the country. They became victims of the disease.

During the years of the first five-year plans, our country, which began the construction of heavy industry enterprises on an unprecedented scale, needed a large amount of raw materials - coal, ore, and oil. The reserves explored in the western regions were limited, it was necessary to look for new deposits.

The Soviet government allocated huge funds for the development of unexplored regions of Siberia and the Far East. The first detachments of scouts went to the taiga: geologists, engineers, topographers. They were looking for ore deposits, oil, coal and other minerals. The construction of new settlements and cities began.

It was a restless time. Our country fortified its eastern borders, fearing an attack by the Japanese militarists. Dozens of echelons with people moved to the East. They carried civil engineers and workers.

At the call of the party, a large number of volunteers went out to build new cities in the taiga, lay roads, develop mineral resources, build power plants, and explore the vast expanses of Siberia. There was enough space for everyone in the taiga.

Already in 1934 and 1935, neuropathologists A. Panov and A. Shapoval, who worked in the Far East, began to receive messages in Moscow that some new, previously unknown disease had appeared among people who were exploring the taiga. Hundreds of people got sick. An incomprehensible ailment affected the human brain and motor system.

The disease began with severe convulsions, severe headache, vomiting, clouding, and then loss of consciousness. Very often a tragic end came: paralysis developed, followed by death. Experiencing excruciating suffering, every third or fourth sick person died. Those who recovered had paralyzed arms or legs, their necks could not hold their heads, and many lost their hearing. Young, strong, healthy people turned into severe invalids within a few days.

Doctors understood that some disease-causing principle affects the parts of the brain that control muscle movement, vision or hearing. That, perhaps, is all that was known about the mysterious disease.

Military doctors noted two features. The disease, as a rule, occurred only in the warm season, in spring and summer. With the onset of autumn, the diseases ceased, and in winter the disease completely disappeared, so that next spring re-emerge. Later, for this reason, it was called: "spring-summer taiga encephalitis."

Another feature: the young, the strongest, fell ill. The disease mainly affected only people who had come to the taiga again, and not local residents. The cause of the illness was unknown. How and by what it was called, it is not clear. The old-timers said only that it was impossible to go to certain areas of the taiga: death lurks there, and local residents bypass them. However, now people had to go there and went. The disease sometimes affected entire detachments of pioneers.

One massive case of an incomprehensible illness was diagnosed in 1934, when a party of topographers and geologists suffered in the taiga. Twenty people, having disembarked from the train in the Khabarovsk region, loaded their horses and set off for reconnaissance in the taiga. On the way, the expedition stopped for the night in several villages, and then went deeper into the taiga jungle. Topographers were to map the area, and geologists were to look for valuable minerals. It was at the beginning of summer.

Taiga welcomed the expedition with fresh greenery and flowers. Everything seemed interesting and tempting. Young people rejoiced interesting work who was waiting for them.

Two weeks later, two saddled horses returned from the taiga. On one of them was an unconscious man in a very serious condition. He was admitted to the hospital. For five days, without leaving him alone for a minute, doctors and sisters fought death, trying to save the patient. But nothing helped.

And what could they do if not a single doctor on earth knew how to cure this unknown disease. She overtook the young man immediately, and now, a week later, the mysterious microbe, rapidly multiplying, spread throughout the body, hit the nervous system, reached the most important vital centers. Countless hordes of small enemies ruled in the human body.

In search of a geological party, several detachments of Red Army soldiers went with guides from local hunters-trappers. The search lasted about a week, and finally the camp of geologists was found. At the edge of the forest, by the stream, there were tents, horses were grazing peacefully, but there were no people in the camp who could tell about the misfortune. All geologists were in tents, most of them had already died, and the rest were unconscious. The survivors were brought to the hospital and treated for a long time.

At first, doctors thought that people got sick with a severe flu, since the disease hit everyone at the same time. However, later, when they began to recover, it was found that most developed severe paralysis of the arms, legs, muscles of the neck and back. It became clear that the disease affected the brain and in its nature resembled encephalitis already known at that time - inflammation of the brain.

Then, outbreaks of this disease began to be increasingly detected in various parts of Siberia, where geologists worked looking for minerals, topographers laying new routes through the taiga, builders erecting bridges, roads and new villages. The disease also affected the detachments of the Red Army soldiers, who were stationed in the taiga, guarded and strengthened our border.

Many died, others became disabled. Thousands of people were in danger. Science did not know any serums and medicines for the treatment of a new disease.

By 1937, such a situation had developed that the task of developing the Siberian wealth, its open spaces and subsoil was threatened with failure. People were afraid to go to the taiga, because many of them either did not return from there, or remained paralyzed or deaf crippled for life. The disease blocked the road to the taiga.

- What was done?

- Everything possible and even impossible.

But it was very dangerous, wasn't it?

Yes, and some scientists paid with their lives or health. Now the whole world knows their names, more precisely, the scientific world. After all, people quickly forget, and more often do not know at all, what is happening outside the walls of laboratories.

The study of taiga encephalitis has become one of the most exciting pages in the history of Soviet medicine. Fearless doctors and virologists went to the taiga. These were truly obsessed people, and they went to Siberia to uncover the secret. The minimum time was released, the deadlines were given tough. They had to find the reason that caused the death of thousands of people. But it was important to do more than that; the main task of the researchers was to develop means for the prevention and treatment of a serious illness, the creation of a drug for the reliable protection of those traveling on Far East hundreds of thousands of people.

In those years, there were only two laboratories in our country that studied viral diseases in people. In Moscow there was a Central Virological Laboratory of the People's Commissariat of Health of the RSFSR, and it was headed by a well-known scientist, Professor L. Zilber. Very young virologists E. Levkovich, M. Chumakov, A. Shubladze also worked there. In Leningrad, at the L. Pasteur Institute of Epidemiology and Microbiology, the department of virology and bacteriology was headed by Professor A. Smorodintsev, who was then 36 years old. His faithful companions were A. Drobyshevskaya, O. Chalkina, V. Korshunova, with whom he studied influenza and made the world's first vaccine against this disease.

From 1937 to 1940, the Soviet government and the People's Commissariat of Health of the USSR regularly sent research expeditions to the taiga jungle of the Far East to study encephalitis.

There were four such expeditions in total. The first was led by Professor L. Zilber, and the other three - by Professor A. Smorodintsev. Entomologists who were looking for insects - carriers of infection, were commanded by a military doctor, the most famous specialist in this field - Academician E. Pavlovsky.

Without hesitation, the scientists left Moscow and Leningrad, sparkling with the surgical whiteness of the laboratory, quiet, flooded spring sun library halls and went to the East, to the taiga wilderness, to fight with an unknown enemy. The brave explorers had no means of protection against the mysterious enemy. Many members of these expeditions paid with their health, even own life for the right to reveal the secret and defeat the causes of a serious illness.

The first expedition set off in the spring of 1937 to the Far East from Moscow. Together with the scientists, several thousand small four-legged members of the expedition rode: mice, guinea pigs, rabbits. There was a long way to go: after all, at that time, trains to Khabarovsk went 13 days.

From the very beginning, the expedition was divided into two groups.

The northern detachment, upon arrival at its destination, was supposed to remain in Khabarovsk, study all the reports about the mysterious disease, deal with the supply and organization of work. This detachment was headed by the head of the expedition L. Zilber. The southern detachment was led by a young woman, a virologist E. Levkovich. They unloaded at the Obor station and went deeper into the taiga. It was raining continuously and the road was wet. It was necessary to shelter animals well from rain and cold. In addition to animals, the scientists took with them to the taiga complex equipment: thermostats, a glacier, a centrifuge, and microscopes.

Immediately upon arrival, the expedition settled in the camp of lumberjacks, where several new houses were built, tents were stretched. They also set up houses for a large vivarium, where they placed cages with laboratory animals, on which scientists were going to conduct experiments, looking for the causative agent of a mysterious disease.

The expedition worked in difficult conditions. We had to sleep in bad barracks, not protected from heat or rain. Mosquitoes and midges attacked people in clouds. In one of the houses, lost among the swamps, they set up a laboratory, a taiga hospital was located nearby.

People who had suffered a terrible disease and remained crippled reached the hospital. Most of them were pale, thin, with twisted spines, drooping heads, twisted faces. Some had paralyzed arms, others had legs. Many people were struck with hearing, observed general weakness, apathy, memory loss.

The work began with the analysis of case histories and a survey of those who had been ill. Soon after the expedition arrived in the Far East, it was possible to establish that people who communicated with a sick person never fell ill. A healthy person did not become infected directly from the patient: this was confirmed by observations of family members of the sick, of the medical personnel who treated them. It was necessary to look for some other ways of transmitting the infection from one person to another.

The found prey was brought to the laboratory, and there the virologists took blood from the animals, then euthanized them, removed the lungs, liver, spleen, brain and other organs, ground them in mortars, and prepared tissue suspensions. Suspensions were also prepared from insects, and with all these materials they infected, infected and infected more and more laboratory animals from morning to evening.

Materials were injected into the bloodstream and through the mouth, injections were made into the brain and into the abdominal cavity. After all, no one knew exactly where the causative agent of the mysterious disease could be located and how it should be introduced to a laboratory animal. Nor did they know which animals to choose - mice, rats, guinea pigs, rabbits or monkeys - so that they would develop a disease similar to what was observed in humans.

Dead animals were not found in the taiga, and this testified that the disease does not affect animals, even if the pathogen is in their body. You can imagine this colossal work. After all, even if the infection is hidden in some kind of chipmunk or squirrel, it does not necessarily sit in the animal that the scientists caught. Maybe only one hundred or thousandth of forest animals are infected, or maybe they are even rarer.

Researchers spent days and nights in a small laboratory. Thousands of mice passed through their hands. Animals were labeled, infected, caged, observed, and recorded in laboratory journals.

Somehow, in the midst of work, heavy rains began. The raging river broke through the dam, the water penetrated into the vivarium, into the room where the animals were. The results of many months of observations were in jeopardy. Working waist-deep in water, scientists pulled out cages with mice and rabbits onto land.

Having made many analyzes and blood cultures of patients, the expedition found that ordinary microbes were not responsible for the occurrence of encephalitis: there were no such microbes in the blood of patients. It remained only to suspect the viral nature of the disease.

Where should the supposed virus be located in patients with encephalitis? scientists asked themselves. Logically, there was only one answer: not otherwise than in the brain.

To test this assumption, scientists performed an autopsy of people who died from encephalitis, took tissue from their brain and spinal cord, prepared a suspension and infected laboratory animals with it. After 8-10 days, some of the mice fell ill. They lay helpless, with paralyzed legs. The mice developed typical paralysis, then the animals began to die. This testified that the contagious beginning is really located in the brain of sick people.

The scientists took the brains of diseased mice, crushed them, prepared a suspension and filtered it through porcelain filters that kept germs out. The filtrate was infected with fresh mice. They developed encephalitis, which confirmed the assumption about the viral nature of the disease. The first strains of the encephalitis virus were isolated almost simultaneously in the Northern Detachment by E. Levkovich and M. Chumakov and in the Southern Detachment by A. Sheboldaeva, A. Shubladze and L. Zilber.

The danger that lay in wait for researchers at every turn made itself felt. The first misfortune happened in August 1937 with one of the virologists of the expedition, a very young man M. Chumakov.

Two years before leaving for the expedition, he defended his Ph.D. thesis in microbiology, but now the disease has overtaken him. Chumakov fell ill with typical encephalitis. In the worst condition, he was taken from the taiga, first to a hospital in Khabarovsk, and then taken to Moscow. It so happened that the virus, for which the scientist hunted and finally caught, lay in wait for him and entered the brain.

M. Chumakov was saved by inoculating him with a serum prepared from the blood of a person who had recovered from encephalitis. However, Chumakov remained hearing impaired and paralyzed hands. In this case, infection occurred during the autopsy or during experiments on feeding ticks on mice and forest voles infected with the encephalitis virus.

Entomologists in the taiga continued to hunt for ticks, mosquitoes, horseflies and other insects, and midges, in turn, hunted people. Gluttonous hungry insects from all sides rushed to the live bait, as the scientists sat quietly, baring one hand so as not to frighten off the midges. When the insect was attached to drink blood, it was carefully removed and lowered into a test tube. Exhausted from the heat, bitten by midges, people often felt that they were close to fainting. But their postures were invariably calm, and their movements careful and precise.

For several hours, entomologists hunted in the forest, extracting the necessary material. In addition to flying, they also collected crawling bloodsuckers - ticks. They were taken from cattle, which were grazing in glades near fires that repel midges. Ticks were also searched for in the grass, by cutting it and then shaking it. This monotonous work was carried out from day to day. In the end, it was possible to draw up curves for the appearance and disappearance of certain insects.

Doctors sat in local hospitals, studying case histories.

And finally, the work has borne some fruit. It was found that in all past years, diseases occurred only in the spring and summer. Scientists have compiled a special curve of the appearance of the disease, the development of the largest number of cases, and then its disappearance. When comparing the curves, it turned out that the disease appeared no earlier than in the first ten days of May. Consequently, infection with encephalitis occurred even earlier - in mid-April. And horseflies, for example, began to fly only at the end of May and could not be carriers of the disease.

From the very beginning, scientists thought that the disease was spread by mosquitoes. Mosquitoes generally have a poor reputation. However, much was not linked to the true state of affairs. Mosquitoes hatch only in summer: their earliest appearance was recorded in the second decade of May. In addition, they live in damp places. Cases of encephalitis always appeared in the spring and struck many people where there were no swamps at all.

In the end, suspicion fell on ticks. Many people who, fortunately, did not die, but recovered, said that, before getting sick, they were bitten by ticks. Yes, and everything coincided in time: it was in the spring that most ticks multiplied. There was only one snag: dozens of various kinds ticks, and which of them could be infectious, was unknown.

Indirect indications of tick-borne transmission of encephalitis to humans, the ability of ticks to receive the virus from a sick animal and transmit it to a fresh animal through a bite were obtained in 1937 by M. Chumakov.

The study of ticks continued.

It has been traced that the female mite lays its eggs in the ground. The eggs hatch into larvae. A hungry larva climbs onto grass or bushes and sits with its front legs up. When any animal runs past, she attacks him and sticks. A nymph comes out of the larva - small tick, which then develops into an adult insect.

The tick sits on the paths laid in the taiga and waits for prey. Having stuck to it, he drinks blood for three to six days and swells so that his size increases to one centimeter. Only after that it falls off. In each of its transformations, the tick feeds only once. The larva and nymph usually stick to small rodents, and the adult tick - to large animals and humans.

Scientists, comparing the time of appearance and reproduction of ticks, found that this exactly coincides with the curve of encephalitis diseases. Ticks appear, and after a few days encephalitis begins. Disappear - ticks, and the epidemic stops by itself.

Academician Pavlovsky and Professor Smorodintsev came to the conclusion that encephalitis must have a permanent focus in nature, a "fortress" hidden from the human eye. To test this assumption, dozens of different animals and birds inhabiting the taiga were caught. Many pets were examined.

The work was facilitated, since at that time a large batch of monkeys was purchased from Japan. They were taken by steamer to the Far East, and scientists infected these animals with the collected materials. Many of them contained a virus that caused a disease in monkeys very similar to the spring-summer encephalitis that develops in humans.

Fritillaries and thrushes, hedgehogs, chipmunks and field mice, many domestic animals - they all carried an infectious principle in the body. Thus, the "reservoir" of the virus was found. It turned out that ticks transmit the encephalitis virus to chipmunks, voles and other animals living in the taiga.

In addition, the preservation of the virus helps domestic animals: goats, sheep, horses, pigs, cows, dogs. They are also bitten by ticks and infect their body, but these animals do not suffer from encephalitis.

But the most important thing was that the virus can remain in the intestines of these blood-sucking insects for a very long time and even be transmitted to offspring. Moreover, scientists later proved that the virus multiplies in the tick, which is the long-term and permanent host of this pathogen.

Academician Pavlovsky formulated a theoretical justification for the natural foci of tick-borne encephalitis. In certain areas of the country, the virus is helped to survive and persist in nature for a long time by interconnected animals and blood-sucking insects. The virus multiplies in the body of the tick, the tick bites an animal or bird living in the taiga and infects them, from these animals new ticks carry the infection to other animals. Thus, the disease is continuously maintained.

If a person came to this zone, he necessarily became an object for the attack of ticks, and if these ticks were contagious, the person could consider himself doomed.

There was one more mystery to be solved. Sometimes among the sick were small children and old people who did not go to the forest and could not be bitten by ticks. In addition, there were many cases when entire families fell ill.

Scientists have been looking for a clue for a long time and finally found an elementary simple answer: in all such cases, goats were the source of infection. Living near forested areas where ticks infected with the virus are located, goats became the object of attack. The encephalitis virus, as it turned out, multiplies well in the body of a goat and enters the milk. By consuming unboiled goat milk, people become infected and fall ill with encephalitis. This is the second way of spreading this terrible infection.

Already in Moscow, upon returning from the expedition, the laboratory assistant N. Utkina fell ill, and later N. Kagan, a researcher in the virus department of the All-Union Institute of Experimental Medicine.

At that time, it was believed that encephalitis could only be contracted in the taiga, from a tick bite, so although the laboratory staff followed all the precautions when working with infectious material, no one was insured against accidental infection, especially since protective vaccines did not yet exist . It is not known exactly how Utkina and Kagan became infected. Both of them died. The therapeutic serum prepared from the blood of the ill person did not help either. All attempts by doctors to save them ended in failure. The urns with their ashes are still kept in the museum of the D. Ivanovsky Institute of Virology.

- How did you manage to protect people from tick-borne encephalitis?

- The only reliable way was a vaccine.

How soon could you get it?

- A year later.

When the first expedition returned to Moscow, the question immediately arose of what to do next. After all, it was not enough to find out that tick-borne encephalitis - as scientists began to call this disease - is caused by viruses and is transmitted to people by ticks living in the taiga. This will not stop the disease. I had to find some effective means, using which the state could protect people traveling to the taiga.

At that time, relations with militaristic Japan in the Far East deteriorated sharply. She concentrated the huge Kwantung Army near our borders, aimed, and then attacked friendly Mongolia,

The Red Army soldiers guarding the eastern borders of our Motherland became victims of encephalitis. The first thing that scientists could recommend was to carry out sanitary and epidemiological health measures in the villages, cities and army camps located in Siberia: to destroy ticks near populated areas. The number of diseases decreased, but about two thousand people fell ill every year, and about half of the patients, as a rule, died. Destroying ticks proved to be extremely difficult, expensive and not effective enough.

At this time, the All-Union Institute of Experimental Medicine was organized in Moscow. He was faced with many problems important for public health, but the most responsible task was to find the means to overcome tick-borne encephalitis. A 36-year-old professor Smorodintsev, invited from Leningrad, was appointed to lead the department of virology. By this time he was already well known for developing the world's first influenza vaccine.

In the laboratory where they worked with encephalitis viruses, access was prohibited for all outsiders. Entering the laboratory, people stepped over a high threshold-barrier. The laboratory assistants worked in two thick overalls, rubber gloves and special masks. They were protected from the experimental animals by a large protective glass bent by an arc, so that the virus from a syringe or pipette, if some mistake occurs, would not splash onto the face or body of the researcher.

There are dozens of healthy and infected mice on the laboratory table. And a high threshold is made in case the experimental mouse runs away. After all, the animals that escaped from the laboratory can spread the infection by biting someone.

Observations carried out in the Far East showed that people who had been ill with encephalitis acquired a long-term immunity to this disease and were not re-infected. Then A. Smorodintsev set the task for his team to learn how to artificially create the same immunity, to find a vaccine that protects against the disease. Nobody knew how to cook it.

The scientist decided that it was necessary to accumulate a sufficient amount of the virus in the laboratory, and then weaken it or inactivate it. It is possible that the resulting drug will retain the ability to induce the formation of antibodies, as encephalitis viruses did in natural conditions.

Any vaccine is a kind of concentrate of viruses, weakened or inactivated. Usually these are the same viruses that cause the disease. Scientists subject them to special treatment, during which the destructive properties of viruses are eliminated.

The introduction of the vaccine stimulates the mobilization of the body's defenses: antibodies are formed that can neutralize the "wild" street virus. They appear in the blood shortly after vaccination and already after 2-4 weeks reach very high concentrations. It is they who neutralize the virus if it enters the body.

started endless experiences. Scientists worked literally in three shifts, many even spent the night in the laboratory. Time hastened. Smorodintsev, together with Kagan and Levkovich, were looking for ways to create a vaccine. To do this, mice were infected, and then their brains were used to transfer the virus from one animal to another. Scientists have conducted many such passages of the virus.

Testing the safety of the vaccine in healthy mice, it was eventually realized that the live virus was not attenuated even by repeated passage through animals. He remained as disease-producing as he had been in the beginning. It was at this time that Kagan died.

When it turned out that the live virus was unsuitable for vaccination, it was decided to neutralize the pathogen, but in such a way as to preserve its ability to cause immunity to encephalitis in humans.

Smorodintsev and Levkovich accumulated the virus in the brains of mice, infecting thousands of animals. Then they were put to sleep, the brain was taken out, crushed and ground in mortars with glass beads. This made it possible to obtain a thin homogeneous mass, which was dissolved in a special saline solution. The liquid was purified from fragments of brain cells in centrifuges with a high rotation speed. As a result, a transparent material was obtained, which contained significant concentrations of the virus. This solution then only had to be inactivated with formalin.

When the vaccine was ready, the question arose of where and how to test it. The first experiments were carried out on small laboratory animals, and then on monkeys. Experiments have shown that the vaccine does not cause harm, stimulates the formation of antibodies and protects the monkeys from subsequent infection with a live tick-borne encephalitis virus.

Already in the spring of 1938, Smorodintsev and Levkovich prepared the first ampoules with a drug that they considered suitable for people. It was necessary to prove that the vaccine would not harm those vaccinated. After all, it contained large amounts of encephalitis virus, however, inactivated by formalin.

Scientists did not even think about who would be the first to receive injections of the vaccine in order to prove its harmlessness. It was self-evident. The creators of the vaccine and the laboratory staff administered it to themselves and, after careful medical supervision, made sure that no side effects occurred for several months after vaccination.

When the safety of the vaccine was found out, it was necessary to be sure of its protective effectiveness. Having discovered that antibodies to the encephalitis virus formed in the blood after vaccination, the researchers took a huge risk and infected themselves with a wild taiga virus. They introduced very large amounts of the virus into their bloodstream, much larger than what enters the human body when bitten by ticks. Belief in success was justified: the vaccine protected the scientists, they did not get sick.

After further testing, the vaccine began to be produced in large enough quantities to be able to vaccinate everyone who needed protection against encephalitis due to travel to work in the taiga. By spring, more than 20,000 people who were leaving for the Far East had been vaccinated. The activities had a tangible effect. By autumn, it was possible to find out that almost all the vaccinated were protected. They successfully worked in the taiga, although they were repeatedly bitten by ticks. Most of them did not get sick.

Evaluation of the effectiveness of the vaccine against tick-borne encephalitis, conducted a year later, showed that the number of diseases decreased by 2.5-4 times. This was good to begin with, but not enough, because a certain percentage of those vaccinated did get sick.

Examining the blood sera obtained from many thousands of people vaccinated that year, and analyzing the data on the incidence of encephalitis in Siberia, scientists came to the conclusion that the first vaccinations protect people for only one year. Only during this short time did sufficient amounts of antibodies remain in the blood.

The encephalitis vaccine was made from killed viruses. To the introduction of such a killed virus that could not multiply in the body, the response was weaker, a much smaller amount of antibodies was formed. This amount was enough for a year. Then the antibodies were destroyed, and the person again became susceptible. He risked getting infected again and getting sick.

Scientists have found that protection is greatly enhanced if the vaccine is administered not once, but three or four times. This vaccination cycle was to be repeated every two years. Naturally, this was not very convenient, but it allowed everyone who started working in the conditions of the uninhabited Siberian taiga (hunters, lumberjacks, members of geological and other expeditions, and primarily the military) to be reliably protected from tick-borne encephalitis.

One can imagine the scale of this huge preventive work, which was designed to protect the health of millions of people in the vast territory of Siberia and the Far East.

In 1941, the approval of the State Prizes of three degrees for outstanding scientific developments made in our country was announced. The Soviet government highly appreciated the selfless work of researchers who fought tick-borne encephalitis in the taiga, studied the nature of this disease and created the world's first effective vaccine. In 1941, the work of E. Pavlovsky, A. Smorodintsev, E. Levkovich, P. Petrishcheva, M. Chumakov, V. Solovyov and A. Shubladze was awarded the State Prize of the first degree.

- Did this mean that encephalitis was over?

No, only the initial stage of work has been completed. Scientists were only able to move the cornerstone and answer the first two questions: what causes and how encephalitis spreads.

- But since the vaccine was created, all that remained was to vaccinate everyone who needed it, right?

This approach is too simplistic. After all, the vaccine was inactivated, and the immunity it created turned out to be not only short-term, but also not strong enough.

In the post-war period, many expeditions sent to various zones of the Soviet Union found that tick-borne encephalitis occurs not only in the Siberian taiga, but affects people literally in all forest areas of the country. The disease was also found in the Urals, and in Karelia, and in the southern regions.

These studies of virologists and epidemiologists, led by Chumakov and Smorodintsev, found out the nature of previously unknown diseases, called "Omsk hemorrhagic fever", "two-wave meningoencephalitis", etc.

The tick-borne encephalitis virus gathered its harvest everywhere: from the shores of the Pacific Ocean to the White Sea and Belarus. Moreover, the research of Soviet scientists advised virologists of other countries to do the same work. In less than a few years, foci of tick-borne encephalitis were identified first in Czechoslovakia, and then in Hungary and Romania, in Finland and Poland. Foci of tick-borne encephalitis associated with very related viruses were also found in various states of Asia and America.

True, in Siberia, encephalitis has a more severe clinical course and kills 20-30 percent of the sick, while in the European regions of the country the disease is milder and the mortality rate is 10 times lower.

Human economic activity has a significant impact on the preservation of foci of tick-borne encephalitis. Often it generally leads to their elimination or reduction as a result of deforestation and subsequent plowing of the land.

On the other hand, foci of encephalitis often expand if people intensively develop forests, replace coniferous trees with deciduous ones. A person always brings domestic animals with him into the forests, which become the targets of tick attacks, and then transmit the virus to people who consume their milk.

AT last years experts have calculated that in our time on the territory of the Soviet Union about 20 million people are in constant danger of contracting tick-borne encephalitis. And in those places where forest areas are saturated with a large number of infected ticks, up to 25-40 percent of the inhabitants can become infected annually. True, not everyone gets sick, but these numbers are significant.

Studying the habits of insects, scientists have found that, attacking a person, a tick always crawls on his clothes only from the bottom up. Therefore, in order to protect yourself from the tick and prevent it from getting on the skin, trousers should be well tucked into boots, and a shirt under the belt of trousers. If at the same time the shirt cuffs are still tightly fastened, the tick will practically not be able to get on the human body. Various liquids or ointments produced by our industry that repel insects reliably protect a person from ticks.

In many regions of the country, where the infestation of forests with ticks is very high, in recent years the state has been actively exterminating them with the help of various insecticides. To do this, planes and helicopters spray or pollinate forests around settlements, forestry facilities, rest houses and sanatoriums with poisons that are deadly for insects. Pollination of forests is carried out in autumn, and then in spring, when the poison more easily reaches the ticks on the trees. Annual pollination with such insecticides drastically reduces the number of mites and greatly reduces the risk of human infection with encephalitis.

Some zealous opponents of the vaccine proposed to fight tick-borne encephalitis by destroying animals that carry the virus. But this is unrealistic. It is now known that on the territory of the Soviet Union more than 100 species of mammals and birds are constantly infected with the tick-borne encephalitis virus. Them total number amounts to many hundreds of millions of individuals, which means that nothing can be done with them. They maintain in nature constant foci of infection, and at the same time the ecological balance, which is always dangerous to disturb.

At present, it is possible to protect against this disease, and the only reliable way is to actively vaccinate all people who will work or live in the forests where the infection nests.

All these years, virologists have been actively working to improve the quality of the vaccine, given that the old drug, produced on the brain tissue of white mice, often caused the development of local inflammatory reactions, and in some, albeit very rare, cases, gave general complications.

In 1964, researchers used single-layer tissue cultures instead of mouse brains to grow tick-borne encephalitis viruses. This method turned out to be so successful that since 1966, all inactivated vaccine against tick-borne encephalitis produced in the USSR has been prepared only on tissue culture. As a result, all side effects completely disappeared, since the vaccine no longer contained the mouse brain tissue protein that had previously contaminated it.

Curious are the works of statisticians who are interested in everything in the world, including tick-borne encephalitis. They recently calculated that of all people who have been infected with tick-borne encephalitis in recent years, 90 percent were bitten by ticks and only 10 percent became infected as a result of using contaminated milk.

If ticks bite mainly adults, since it is they who work in forest areas, then more than half of those infected from milk are children. The bulk of encephalitis infections through milk occurred in the Cis-Urals and Middle Ural. These are the Kirov, Perm, Sverdlovsk regions and the Udmurt ASSR. The answer was simple: here the population contains a lot of goats, and ticks, carriers of tick-borne encephalitis viruses, live in large numbers here.

If in previous years, ticks mainly infected only people who worked in the taiga, now 80 percent of the victims are tourists or vacationers. And here the matter is explained simply: those who work in the forests are necessarily vaccinated with a vaccine, and it creates reliable protection. And people who go to the forest for mushrooms, relax or travel do not go to doctors for vaccinations and therefore get sick after being attacked by infected ticks.

Today, the attention of the whole country is riveted to the unprecedented scale construction of the Baikal-Amur Mainline. This railway line opens up access to the wealth of Eastern Siberia. After all, there are deposits of coal, iron, copper, nickel ores. There are hidden underground reserves of oil and gas.

The construction of this road with a length of more than three thousand kilometers is carried out in very difficult geographical conditions. It crosses dozens of rivers, overcomes mountain ranges and impenetrable taiga. Builders have to cross swamps and swamps, demolish hills and mountains, go through many kilometers of tunnels.

Before the start of construction, a very thorough biological reconnaissance of the entire area was carried out. And they found that many sections of the highway must cross the taiga, where there are massive foci of tick-borne encephalitis. Started production immediately significant amount vaccines to vaccinate construction workers, engineering personnel and all persons who will live on the track.

The inactivated vaccine now in use is being prepared in large quantities in tissue cultures at the Moscow Institute of Poliomyelitis and Viral Encephalitis and at the Tomsk Institute of Serums and Vaccines. All people are vaccinated multiple times. Initially, three injections with an interval of two weeks. Then all those who have been vaccinated must undergo a single revaccination every year for four years in order to acquire reliable protection.

In recent years, Moscow scientists have significantly improved the quality of the vaccine by subjecting it to additional purification on specially designed coarse glass filters. This method made it possible to remove all contaminating proteins from vaccines, which sometimes gave undesirable local reactions, and also to significantly increase the protective activity of the drug.

Observations of many thousands of those vaccinated have shown that the incidence of disease is reduced by at least four times as a result of vaccination. In addition, for those who do get sick, the disease is much easier, and mortality has generally ceased.

The selfless work of Soviet scientists and the widespread use of killed vaccines made it possible to defeat encephalitis, this taiga killer.

The risk of contracting a severe viral disease - not all campers think about tick-borne encephalitis. This is due to the lack of information about the disease, methods of infection, symptoms and preventive measures. About 400 thousand cases of tick bites are recorded annually. During examination, the virus is found in 4-6% of those bitten. The encephalitis mite is active in late spring when a stable warm temperature is established. At this time, caution should be exercised in forest areas. To protect yourself and your children, doctors recommend vaccination against tick-borne encephalitis.

Carriers of the disease - who should be afraid

Attention. There are two ways of infection with the virus - transmissible (tick bite), alimentary - eating raw milk of goats or cows carriers of the disease.

Dangerous types of ticks

The carriers of the causative agent of tick-borne encephalitis are. There are up to 650 species of them, in Russia the dog tick is also dangerous. The first species is widely distributed in the forests of Siberia, the Urals and the Far East. The second is in the European strip. In late spring and early summer, their number reaches peak levels, so the number of bites increases dramatically. The virus is carried by adults, nymphs and larvae. Not only people, but also animals become victims.

• egg;
• larva - feeds once on small rodents;
• nymph;
• an adult.

The transition from one phase to the next is accompanied by molting. At the end of summer, the nymphs become sexually mature, having saturated with blood, females mate with males and lay eggs and die. Males die immediately after fertilization.

Attention. The female can stay on the human body for up to 2 days. It is drunk with blood and grows to a size of 10 mm. The color of the swollen body changes to light gray. The male sucks blood for 4-5 hours, then falls off, its size changes slightly.

How does a tick bite?

An arthropod bite does not cause pain, so a person does not notice it. The predator injects a special anesthetic into the blood. The individual makes its way deep into the skin, gradually plunging into the epidermis. To do this, she selects areas where the blood vessels are closest to the surface. The structure of the proboscis and jaws of an arthropod predator is designed specifically to easily dig into the skin and suck out the blood of the victim.

The bite of an encephalitic tick leaves redness and inflammation on the skin due to an allergic reaction and microtrauma.

How to remove a tick

• cosmetic tweezers;
• strong thread;
• a special device for taking out a tick (sold in a pharmacy).

Outwardly, it is impossible to recognize whether or not a tick is a carrier of viral diseases. It is placed in a glass jar and delivered to the laboratory within 2-3 days. If this is not possible, then they are burned. The wound is disinfected with alcohol or iodine. When separating the proboscis, it is taken out of the wound like a splinter.

Attention. It is not advisable to remove the attached individual with your fingers, if there is nothing at hand, it is advisable to wrap them with a bandage or scarf.

Information about the disease

Tick-borne encephalitis refers to natural focal viral infections. It is accompanied by inflammation of the brain and spinal cord. Late initiation of treatment leads to neurological and psychiatric complications. The virus is divided into three subtypes:

• European - common in the western part of the Russian Federation, transmitted by a dog tick, mortality - 2%, complications and disability - 20%;
• Siberian - found throughout Russia and northern Asia, the source of infection is the taiga tick;
• Far Eastern - common in the east of the Russian Federation, in China and Japan, transmitted by a taiga species of ticks, the number of deaths is up to 40%.

Attention. Worse than other cases of encephalitis are patients over the age of 50 years.

The clinical picture of the disease of the European subtype includes two phases. The first lasts 2-4 days, it is characterized by loss of appetite, muscle pain, fever, vomiting. Then comes relief for 7-8 days. After remission, 25-30% of patients enter the second phase. It is accompanied by damage to the central nervous system, manifestations of meningitis and encephalitis (fever, impaired consciousness and motor functions).

The Far Eastern subtype is characterized by more pronounced symptoms. The rapid course of the disease often ends in death. The defeat of the nervous system occurs after 3-5 days. There is no specific treatment for tick-borne encephalitis. Patients are hospitalized, they are prescribed maintenance therapy and corticosteroid drugs.

Encephalitis tick virus symptoms

The bite of a tick infected with the encephalitis virus can lead to serious health problems. The incubation period of the disease is 7-14 days, in some cases it can last up to 30-60. At this time, you need to carefully monitor your health, pay attention to the appearance of malaise. The time of appearance of the first symptoms of the disease depends on the state of the body's defenses, with a weakened immune system, the consequences appear after 3-4 days. They are similar to acute respiratory infections or influenza:

• temperature rise to 38-39 0 ;
• nausea;
• body aches;
• lethargy and lethargy;
• pain in the muscles of the shoulder girdle and neck;
• loss of appetite;
• lack of coordination.

Clinical picture

With a mild course of the disease, the symptoms are blurred, not all of them appear. The disease has two phases, after some relief of febrile symptoms, complications occur in the form of damage to the nerve centers and the brain. How is encephalitis treated? To combat the causative agent of the disease, the introduction of immunoglobulins is necessary. These compounds, synthesized from blood plasma, prevent the development of the virus and the release of toxic substances. After a few days, the condition of patients improves, meningeal symptoms subside. Treatment necessarily includes taking drugs for intoxication. For a full recovery of health, it is very important to start therapy on time.

The final disposal of the consequences of the disease occurs depending on its severity. With a mild form, residual effects disappear after a month, with an average form - after 2-4 months. After a complex form, it will take several years to recover.

Do not forget that ticks are carried by others infectious diseases. One individual can infect a person with several diseases at the same time.

Vaccination against encephalitis

Several types of vaccines are used in the country, they are divided according to the age of patients. Children are given special preparations designed for the age of 1-11 years.

Who should be vaccinated?

Vaccination against tick-borne encephalitis is not mandatory. It is recommended for residents of areas with a high incidence of encephalitis and those who are going to visit this area. In Russia, these regions include Siberia, the Urals, the Far East, the North-West region and the Volga region. This applies not only to recreation in the country or in the forest, but also to work on agricultural plots, construction and surveys.

Vaccination can be carried out at any time, preferably before the start of the peak tick season (April, May). The scheme of the event depends on the type of drug chosen. The standard schedule provides for the introduction of 3 doses - the first in the fall, the second after 1-3 or 5-7 months, the third - after a year. Revaccination is carried out after 3 years.

Attention. Like any medical procedure, vaccination against tick-borne encephalitis can have contraindications. They include: a period of exacerbation of chronic diseases, general malaise, pregnancy, an allergy to vaccination.