Tick-borne encephalitis - Causes, symptoms and treatment. MF.
Tick-borne encephalitis is a natural focal infectious disease caused by tick-borne encephalitis viruses that are transmitted by transmission( through insects) and by alimentary route( when milk is used in sick animals), but is clinically manifested by an infectious-toxic syndrome with a predominant lesion of the central and peripheral nervous system.
Tick-borne encephalitis is widespread with the presence of natural foci. There are the most endemic areas for tick-borne encephalitis( a high percentage of mites infected with this virus).According to the results of 2012, they include - Kirov Region, Perm Territory, Nizhny Novgorod Region, Udmurtia, Bashkortostan, MariEl, Tatarstan, Samara Region, Sverdlovsk Region, Tyumen Region, Chelyabinsk Region, Novgorod Region, Pskov Region, Leningrad Region, practically the entire Siberian FederalDistrict, Far Eastern Federal District, part of the districts of Yaroslavl, Tver regions. The disease is rare in the Central Federal District and does not occur at all in the Southern Federal District.
Symptoms of the disease are diverse, which makes it difficult to recognize, but they are all related to the damage to the nervous system. Certain fears are the formation of chronic forms of the disease with the development of disability.
The causative agent of tick-borne encephalitis is an RNA-containing virus belonging to the Vlaviviridae family. There are 3 varieties of the virus: 1) Far Eastern - the most virulent( can cause severe forms of the disease), 2) Siberian - less virulent, 3) Western - the causative agent of 2-wave encephalitis - causes non-severe forms of the disease.
Virus of tick-borne encephalitis
Features of causative agent:
a) tropism( a favorite lesion) to the nervous tissue, mainly affecting the motor structures of the brain;b) the possibility of persistence( prolonged presence) in the human body, which determines the virus carrier( the virus is inside cells and is not recognized by the immune system).
Properties of the virus: the ability to maintain resilience at low temperatures, but high temperatures( for example, boiling for 2 minutes) act on it fatal.
The causes of tick-borne encephalitis
The reservoir and vector of infection are ixodid mites, which are secreted by more than 15 species, but two species - Ixodes perculcatus( taiga) and Ixodes Ricinus( European) are of epidemiological importance. Iksodovy mite for 5-6 meters feels warm-blooded animal and man. The tick sucks in the skin and injects into the blood the tick-borne encephalitis virus. Why does not a person feel a bite? This is due to the presence of analgesic substance, vasodilating and hemolyzing substances in the mites. The result is anesthesia, good blood filling of the bite site and a decrease in blood clotting. The tick "eats" when it increases 120 times. In the foci of tick-borne encephalitis, after a tick bite, immunity may develop, there will be no illness-this is called pro-epidemic disease-that is, some local residents are already protected from this disease. There are two seasons of mite activity and the risk of infection of a person: spring( May-June) and late summer( August-September).
Transmission pathways:
is transmissible( with tick bite), and it should be remembered that the mite crawls on clothes in search of an open space, and over the body in search of a bite place, so after a visit to forest sites a bite can occur only after an hour;
- alimentary( the use of milk sick animals - goats, cows, in the blood of which there is a virus);
- infection possible when crushing ticks, which is strictly not recommended;
- transplacental( in case of a pregnant woman's bite, transmission of the virus from the mother to the fetus).
The patient with tick-borne encephalitis for others is NOT contagious.
Susceptibility to infection is high, all age groups are affected, but men are more likely to fall ill( up to 75%).Often there is a professional component of the disease, the risk group at which - foresters, loggers, geologists.
Symptoms of Tick-borne encephalitis
The virus penetrates the human skin when the tick is bitten. Allocate: 1 phase - latent - the virus accumulates in the human body( no symptoms, it is an incubation period that lasts an average of 7-12 days, but can vary from 1 to 30 days);further comes 2 phase - the virus penetrates into the blood - viremia - and enters the central nervous system( the patient has an infectious-toxic syndrome); 3 phase - neural( the patient has all the symptoms of the nervous system); 4 phase - formation of immunity( patient recovers).Sometimes the virus does not leave the human body, but is built into the genome of brain cells and forms a gradient course( recovery does not occur, the disease then subsides, then re-activated).
Isolate an acute and chronic form of tick-borne encephalitis. The acute form of the disease is characterized by 2 syndromes:
1. Infectious Toxic Syndrome( ITS) - patients complain of high temperature to 38-40 ° for 4-6 days, severe headache, which increases as the temperature rises, dizziness,vomiting for 1-2 days, sleep disturbance in the form of insomnia, muscle pain in the neck, upper arms, upper extremities, less often in the lumbar region, lower extremities, weakness and fatigue, numbness in the upper limbs, muscle twitching, increased sensationpheno- skin( hyperesthesia).
Features in children: can be loss of consciousness, the appearance of delusions, excitement, convulsive syndrome.
This syndrome occurs in all forms of tick-borne encephalitis.
2. Cranio-cervical syndrome - in most patients reddening of the face, neck, upper limbs and conjunctivitis.
Further symptoms depend on the form of the disease.
Feverous form of tick-borne encephalitis ( prevalent, recorded in 50-60% of patients).Only ITS and indistinct reddening of the skin. The flow is favorable.
Meningeal form. occurs in a third of patients. To two syndromes on 3-4th day of the disease joins: meningeal syndrome( strong persistent impassable headache, vomiting) and meningeal signs( a symptom of Kernig, Brudzinsky, rigidity of the occipital muscles) - only the doctor checks. Meningeal signs persist throughout the febrile period, then can persist against the background of normal temperature for another 6-8 weeks. With spinal puncture: an increase in the number of cells up to several cells in 1 μl, lymphocytes predominate, the liquid is clear and flows out under pressure.
Meningoencephalitic form of tick-borne encephalitis. It is diagnosed in 10-20% of patients. It flows heavily, as a focal or diffuse lesion of the brain is formed. Patients, in addition to the 2 syndromes described above, describe complaints characteristic of cerebral syndrome: a violation of consciousness from states of stupor to sopor( prolonged sleep), there may be a coma of varying degrees, convulsive syndrome, spastic hemiparesis( sharp and pronounced weakness in the upper andlower extremities from one or the other side).A fatal outcome can occur on 2-4 days of the disease in 20-30% of patients. In 20% of patients, a gradient course develops with epileptic seizures, memory loss.
Poliomyelitis-like form. Characterized by the appearance of flaccid paresis and paralysis mainly upper limbs, cervico-brachial musculature. On the 1-4 day from the appearance of temperature there is a symptom of the "hanging head", a symptom of the "falling hand", the tendon reflexes from the hands are not caused. Muscle atrophy is formed( on the 2-3th week of the disease).There may be muscle twitching, a feeling of numbness in the limbs. In 50% of patients, there is an improvement and recovery, while in 50% there is a gradual course and disability.
Polyradiculoneuric form. Peripheral nerves are affected: patients complain of pain along the nerve trunks, paresthesia( the feeling of chills in the limbs), symptoms of nerve tension - Lassega, Wasserman, descending paralysis of Landry( determined by the doctor).In 70% of cases, residual phenomena, paresis, paralysis remain.
Two-wave form of the disease. Patients have a first wave of fever for a week without brain damage, then a period of normal temperature for 7-14 days, followed by a second wave and a detailed picture of the brain lesion.
Chronic form of tick-borne encephalitis can be: primary-gradient( the symptoms of the disease are aggravated and do not pass in the acute period of the disease, despite the treatment) or secondary-gradient( the symptoms of the disease resume again after the period of complete or partial restoration of the impaired functions).
Immunity after the transmitted infection is produced type-specific, long-lasting: antibodies to the virus persist for life. Repeated diseases are almost not found. Complications of tick-borne encephalitis
Complications include the development of epilepsy after meningeal form, cerebral edema with a lethal outcome after the meningoencephalitic form, the defeat of the cranial nerves with the development of strabismus, nasal congestion, difficulty swallowing, speech, paralysis of the muscles of the neck, trunk and extremities after poliomyelitis-likeforms, immobility and muscle atrophy after the polyradiculoneuritic form of encephalitis and other serious consequences.
Diagnosis of tick-borne encephalitis
A doctor may presume tick-borne encephalitis after a review of complaints, a thorough examination and collection of an epidemiological anamnesis( visit to forest, field territory, especially during ticks, tick bites).
What should I do if I bite a tick? Do not scratch the bite place and crush the mite yourself, do not try to pull it out with tweezers or something else. It is advisable to go to the surgeon for removal, but if this is not possible, then tie the thread into the knot as close as possible to the proboscis of the tick, then gently rock and slightly lift until it is removed. Remove carefully, because inside there may be a head, which then is very difficult to remove.
Place the bite with iodine. The mite itself should not be discarded, placed in a glass container with a wet fleece, and placed in a refrigerator. As early as possible, carry the tick to a laboratory test in the virological laboratory. It is desirable to deliver the tick for research alive. The result of the analysis is extremely important for you, because on its basis the following activities will be carried out against you, as bitten.
Laboratories can be at infectious hospitals, medical diagnostic centers, hygiene centers, trauma centers.
The final diagnosis is made after laboratory tests:
1) Detection of the EE of the tick-borne encephalitis virus with the help of ELISA in mites( the result is usually ready within 24 hours), cerebrospinal fluid of the patient, when examining the milk of a sick animal;or PCR diagnosis of the tick.
2) PCR-diagnosis of tick-borne encephalitis RNA virus in the patient's blood - no earlier than 10 days after tick bite;
3) ELISA detection of IgM antibodies in the blood not earlier than 2 weeks after the bite;
4) ELISA diagnosis of IgG antibodies in the blood not earlier than 3 weeks after the bite.
Treatment of patients with tick-borne encephalitis
1) Organizational-regime measures: hospitalization in an infectious hospital of all patients, bed rest for the entire fever period and 7 days of normal temperature.
2) Etiotropic treatment( directed at the virus) involves the introduction of a specific anti-malignant immunoglobulin. Immunoglobulin is administered during the febrile period, when a second wave occurs, is repeated at the same dose. It is possible to prescribe iodantipyrine, interferon preparations( roferon, intron A, reaferon and others), interferon inducers( tsikloferon, amixin, neovir).
3) Pathogenetic treatment includes disintoxication therapy, dehydration, postdromal therapy( antipyretic, anti-inflammatory, drugs that improve microcirculation, cerebral circulation and others).
At home, you can not try to treat tick-borne encephalitis. You can wait for complications, transfer the disease into a chronic form, get disability.
Patient discharge is carried out at 14-21 days of normal temperature. The dispensary observation turns out to be an infectionist and neuropathologist for 1 year after a febrile form with a checkup every 6 months. After other forms of the disease - 3 years with a quarterly inspection.
Tick-borne encephalitis prevention
1) Specific prevention includes vaccination against tick-borne encephalitis. There are as far as vaccines: cultural inactivated( Russia), Enceevir( Russia), Encepur adult and children's( Germany), FSME-immune-injection( Austria).This is a planned prophylaxis, it needs to be vaccinated from the autumn( September-October).The course consists of 3 doses, the first two with an interval of 1 month, the third one a year after the second. Immunity persists for 3 years, then you need to make 1 revaccination for the next 3 years.
2) Passive prevention - the introduction of a specific anti-malignant immunoglobulin to persons who have been attacked by ticks. It is carried out and effective in the first 3 days after the bite.
3) Prevention of iodantipyrine. Several schemes are known - after a bite for 9 days( treatment course);- before visiting places with possible attack by ticks.
4) Nonspecific prevention - use of repellents, acaricides, wearing special protective clothing( or at least pants to fill in socks plus a long sleeve with a dense rubber band on the end), self-examination during and after visiting the forests, eating boiled milk.
The doctor infektsionist Bykova N.I.