Tick-borne encephalitis
Tick—borne encephalitis is a disease of an infectious nature, which is characterized by damage to the brain or spinal cord. Usually, the cause of such damage is flavivirus, which is most often transmitted by the bite of an ixod mite.
The content of the article:
Causes of tick-borne encephalitis
Classification of tick-borne encephalitis
Symptoms of tick-borne encephalitis
Feverish form
Meningeal form
Focal form
Progredient form
Diagnosis of tick-borne encephalitis
Treatment of tick-borne encephalitis
Prognosis and prevention of tick-borne encephalitis
Tick-borne encephalitis
Depending on the manifestation of the disease, its main symptoms will be:
fever;
characteristic convulsions;
headache;
nausea and vomiting;
impaired coordination of movement;
pain in the nerves;
paralysis;
paresis is possible.
The diagnosis is usually confirmed by PCR of blood or cerebrospinal fluid. As for the treatment, it will consist of a prescribed immunoglobulin, which best fights the causative agent of this disease. Antiviral drugs are also prescribed without fail. In the advanced form of tick-borne encephalitis, symptomatic treatment is carried out aimed at preventing a life-threatening critical condition.
The causative agent of tick—borne encephalitis – ixodes tick — is common in Siberia, China, Mongolia and the Far East. Individual foci of the disease are also found in some countries of Eastern Europe and even in Scandinavia.
In medicine, tick-borne encephalitis is classified as transmissible infections, that is, those that are transmitted to humans through a blood-sucking type of insects. According to health statistics, about 5 thousand people are infected with tick-borne encephalitis every year in our country.
Causes of tick-borne encephalitis
As mentioned above, the main causative agent of tick-borne encephalitis is a virus belonging to the genus of flaviviruses. In appearance, it resembles rounded particles with small protrusions on the surface, the size of which reaches no more than 50 nm. In size, the flavivirus is 2 times smaller than the influenza virus and 4 times smaller than the measles virus. It is such a small size that helps to instantly penetrate into the human body, bypassing the barriers of the immune system.
One of the main features of the virus of this disease is its weak resistance to high ambient temperatures, as well as to ultraviolet radiation or the use of disinfectants.
For example, if the virus is exposed to boiling, it usually dies within 2 minutes. Flavivirus is very difficult to maintain its capacity in hot weather, so it almost never occurs in the tropics and subtropics. The situation is different with the effect of low temperatures on the virus. It is at low temperatures that the flavivirus will be viable. It is also interesting that in the fermented milk environment, the causative agent of tick-borne encephalitis will be functional for at least 2 months.
In nature, the ixode tick is considered the main vector of flavivirus. In addition to humans, domestic animals, including cattle, can become the “target” of the virus. Thus, they talk about two ways of infection:
directly (in the case of a tick bite or when it is crushed in an attempt to extract from the skin);
when consuming contaminated dairy products that have not undergone appropriate heat treatment. It should be remembered that the risk of developing the disease increases the more time the tick is on the surface of the human body.
The greatest peak of tick-borne encephalitis infection occurs in late spring and early autumn, which is associated with an increase in the number of ticks at these times of the year. It is very easy to get infected with the virus by walking in forests, parks or plantings.
Classification of tick-borne encephalitis
The classification of tick-borne encephalitis is based on the most pronounced sign of the disease. So, for example, there are three forms of tick-borne encephalitis:
Feverish: in case of predominance of fever, it is inherent in about 50-55% of all patients.
Meningeal: in case of damage to the membranes of the spinal cord or brain, it is characteristic of 30-32% of patients with tick-borne encephalitis.
Focal: occurs when brain matter is also involved in the inflammatory process, after which pronounced focal symptoms of a neurological nature develop. This form is inherent in 20% of patients.
Symptoms of tick-borne encephalitis
The initial period of the disease (latent, aka incubation) lasts about two weeks. In some cases, there are rapid moments of infection (within a day from the beginning of the appearance of the first signs). The prolonged incubation period of tick-borne encephalitis can last up to a month.
The latent period of tick-borne encephalitis is characterized by the spread of viral particles at the site of infection (this may be a wound on the skin or one of the intestinal walls). After that, the virus penetrates into the blood, which spreads it already throughout the body. The latter entails the manifestation of the first symptoms. Repeated spread of the virus is observed in internal organs (primarily in the kidneys, liver, lymph nodes and even in the nervous system).
All forms of this disease have common symptoms:
acute onset (usually the patient can even tell clearly the time when he first felt bad);
chills;
muscle aches;
headache;
“lethargy” in the body;
vomiting;
convulsions;
arthralgia;
a sharp increase in body temperature;
red spots on the face and neck;
“bloodshot” eyes.
Further, the severity of the course of the disease will depend on the very form of tick-borne encephalitis.
Feverish form
The course of tick-borne encephalitis of the febrile form is usually characterized by a condition inherent in fever. The duration of this form is no more than 10 days. Very often it has a wave character: the first rise in temperature is replaced by a state of subsiding of the initial symptoms, after which it is possible to repeat the disease with characteristic new attacks that have been going on for several days.
After 8-10 days, the patient’s body temperature returns to normal, and his general well-being becomes much better. Nevertheless, such manifestations as general weakness, a strong heartbeat, poor appetite, sweating, may be present in the patient for a whole month, even after the person has already recovered.
Meningeal form
This form is characterized by the manifestation of symptoms of meningitis on the 3rd day from the onset of the disease. Usually such symptoms manifest themselves in the form of spinal cord and brain injuries:
headache (which does not go away even after taking strong painkillers);
vomiting;
nausea;
acute sensitivity of the skin (even when a person touches clothes, unpleasant painful sensations appear);
rigidity (tension) of the occipital muscles, which is externally manifested in the tilting of the head back;
Kernig’s symptom (inability to bend or unbend the leg at the knee joint in a sitting or lying position);
Brudzinsky’s symptom (upper and lower), which manifests itself when the patient tries to tilt his head forward, reaching with his chin to his chest, and when pressing on the pubis, involuntary bending of the leg in the joints (knee and hip) is usually observed.
All of the above symptoms are usually combined into meningeal syndrome, which means that the disease has moved to the level of damage to the brain and spinal cord.
Feverish symptoms, as well as the manifestation of meningeal syndrome, lasts about 2 weeks. After the patient’s temperature normalizes, for a long time he may have lethargy of the body and general weakness, intolerance to very bright lighting or sounds and constant bad mood.
Focal form
The focal form of tick-borne encephalitis is the most severe in its prognosis. The cause of its occurrence will be the penetration of the virus into the cerebrospinal substance and into the substance of the brain. The focal form is characterized by a strong increase in body temperature (sometimes the temperature can reach 40 ° C), frequent drowsiness, lethargy, vomiting, chills, convulsions, hypersomnia.
The focal form is characterized by symptoms indicating a clear brain lesion:
hallucinations are characteristic;
delusional states;
inability to navigate in space and time;
hallucinations.
If the brain stem is involved in the process and the centers with vital functions are affected, then deviations of the cardiovascular and respiratory systems are added to the usual symptoms.
If the virus enters the cerebellar tissue, then a person experiences an imbalance, a constant feeling of trembling in the upper and lower extremities. In the case of obvious spinal cord injury , there may be:
paresis;
paralysis of the shoulder and neck muscles;
paralysis of the upper chest or supra-scapular area;
decreased muscle activity.
If the virus penetrates into the roots of the spinal cord, then this contributes to the onset of sciatica, a painful sensation in the direction of nerve passage. This affects the manifestation of movement disorders or the normal functioning of internal organs. There may be a disorder of skin sensitivity in different parts due to the affected root.
If we talk about the focal form of tick-borne encephalitis, then it is characterized by two-wave development. In other words, the first attack usually resembles a feverish form. After some time (usually from a couple to several days) after the body temperature has normalized, the symptoms of the affected substance of the brain (or spinal cord) appear.
Progredient form
In a separate form, a progredient form of tick-borne encephalitis is isolated, which can occur on the basis of any other described above. It is characterized by the onset of prolonged disorders of the functioning of the brain (spinal cord), which manifests itself months or years after the end of the acute phase of the disease.
Diagnosis of tick-borne encephalitis
The diagnosis takes into account the clinical manifestations inherent in the patient, as well as the epidemiological data obtained. The results of laboratory tests are taken into account.
Clinical manifestations are assumed to be the characteristics of the disease inherent in the patient, which are established by a neurologist when examining a person. Such a clinic can include:
complaints of the patient himself;
a characteristic sequence of certain symptoms;
examination by a specialist that allows you to determine the areas of organ damage and the system of human organs.
As for epidemiological data, they are obtained by finding out the place and living conditions of the patient, data on his profession, the quality of nutrition, the use of seasonal products that could cause the disease. The specialist examines the place on the skin from where the patient could have extracted the ticks earlier.
Ongoing laboratory studies can confirm or refute the possible causes of infection with tick-borne encephalitis. To confirm the disease, it is enough to detect virus particles in the blood or cerebrospinal fluid. This is usually possible by PCR (the so-called polymerase chain reaction). The doctor can apply serological methods to determine the level of antibodies in the patient’s sera, which are usually taken with a difference of 2 weeks. It should be said that when performing this procedure, in addition to the antibody titer level, they also take into account the level of their increase per unit of time, from the moment of the onset of the disease.
Treatment of tick-borne encephalitis
Treatment of tick-borne encephalitis is carried out exclusively in a hospital. Since a person is the last link in the process of spreading the flavivirus, the patient is usually not considered contagious, that is, he does not pose a danger to the surrounding people and the environment. Any therapeutic manipulation will be carried out in the Department of neurology, instead of the infectious block.
Treatment of tick-borne encephalitis is aimed at eliminating the pathogen, that is, it includes pathogenetic and symptomatic therapy. The patient is shown bed rest.
Individual treatment and its implementation scheme, developed for each patient individually, will depend on how much time has already passed since the first characteristic symptoms. Interestingly, during the first week, the use of immunoglobulin will be particularly effective. It is usually used for 3 days. If tick-borne encephalitis is diagnosed at an early stage, then antiviral drugs such as interferon, ribonuclease, panavir or ribavirin will be particularly effective. However, these same drugs are completely ineffective if the disease has reached a late stage — when the virus affects the central nervous system itself. In this case, treatment should be focused not on eliminating the pathogen, but on eliminating various pathological changes that threaten human life.
For normal oxygen supply, a mask or ventilator is used (in case of respiratory disorders). In addition, diuretics are shown that can reduce intracranial pressure. The doctor may prescribe medications that can make the brain resistant to oxygen starvation.
Prognosis and prevention of tick-borne encephalitis
The prognosis of recovery depends on the severity of the lesion of the patient’s nervous system.
If the disease was of a febrile form, then usually all patients recover.
If the meningeal form develops, the prognosis for full recovery will also be positive, but in some cases a severe complication observed in the central nervous system may be diagnosed. Usually this complication is manifested by headaches and migraines.
As for the focal form, it is considered the most unfavorable form of tick-borne encephalitis. In the focal form, the number of deaths is 30-35 people out of 100. The main complications of this form will be paralysis, convulsive syndromes, a noticeable decrease in mental ability.
The prevention of tick-borne encephalitis is understood as the implementation of various kinds of preventive measures and vaccination. The first one provides for training among residents inhabiting endemic regions in order to consider the rules for visiting forests and various outdoor recreation areas during the greatest spread of ticks (spring-summer).
Such rules provide for:
wearing body-covering clothing (it is better to get out into nature in clothes with long sleeves and trousers, the head should be covered with a cap);
regular body examination to identify ticks;
timely access to a doctor if any insects are detected (it is highly not recommended to remove ticks yourself);
it is advisable to apply special repellents to clothes before going to nature;
use only boiled milk (you should also buy milk in proven and reliable places).
The second preventive method is vaccination, which includes the administration of immunoglobulin to those patients who have not been vaccinated before. Active immunization includes timely vaccinations for those people who live in areas of infection.
