Tick-borne viral encephalitis in children

Tick-borne (spring-summer, or taiga) encephalitis is a natural focal viral disease with predominant damage to the central nervous system, manifested by general cerebral, meningeal and focal symptoms.

ICD-10 code

• A84.0 Far Eastern viral encephalitis (Russian spring-summer encephalitis).
• A84.1 Central European tick-borne encephalitis.
• A84.8 Other tick-borne viral encephalitides (Loping's disease, Powassan virus disease).
• A84.9 Tick-borne viral encephalitis, unspecified.

Epidemiology

The disease is characterized by pronounced natural foci. In Russia, foci of tick-borne encephalitis have been registered in the taiga regions of the Far East, in Siberia, in the Urals, and also in some areas of the European part of the country.

The main reservoir and carrier of the infection are the ixodid ticks Ixodes persulcatus (in the east) and I. ricinus (in the west). In some areas, other types of ticks may also be carriers. Ticks contain the pathogen for life and transmit it to their offspring transovarially. From infected ticks, the virus can be transmitted to rodents, hedgehogs, chipmunks and other animals, as well as birds, which serve as an additional reservoir of infection.

Humans become infected when bitten by an infected tick, with the virus entering the human bloodstream both directly with the tick's saliva and when it is crushed. The virus can also be transferred from the tick bite to the mucous membranes. In populated areas, cattle are involved in the epizootic process, and humans can become infected through alimentary means when consuming infected products, especially milk.

The disease has a pronounced spring-summer seasonality, which is associated with the maximum activity of ixodid ticks at this time of year.

Children get tick-borne encephalitis less often than adults. However, epidemic outbreaks of tick-borne encephalitis occur in holiday camps, near natural foci of infection. Children aged 7 to 14 years are most often affected.

Classification

There are typical and atypical forms of tick-borne encephalitis. Typical cases include all cases with CNS damage. Atypical cases include latent and subclinical forms, as well as cases that progress rapidly, in which death can occur within 1-2 days, even before the main clinical signs of the disease appear. Severity is determined by the degree of CNS damage.

Causes of tick-borne viral encephalitis

The causative agent of the disease belongs to the genus of flaviviruses. The virion is spherical, 40-50 nm in diameter, contains RNA, and reproduces well in many tissue cultures. Of the laboratory animals, white mice, hamsters, monkeys, and cotton rats are most sensitive to the virus. Many domestic animals are also susceptible to the tick-borne encephalitis virus.

What causes tick-borne viral encephalitis?

Symptoms of tick-borne viral encephalitis

The incubation period for tick-borne encephalitis is from 7 to 21 days, on average 10-14 days. The disease begins acutely, usually with a rise in body temperature to 39-40 ° C, severe headache, chills, fever, weakness, nausea and vomiting. From the first day of the disease, facial hyperemia, injection of scleral vessels, photophobia, pain in the eyeballs, often in the limbs and lower back are noted. The child is inhibited, drowsy. Meningeal symptoms quickly appear: rigidity of the occipital muscles, positive Kernig and Brudzinsky symptoms. On the 2nd-3rd day of the disease, encephalitic syndrome appears with impaired consciousness from mild stupor to deep cerebral coma, generalized seizures up to the development of epileptic status, sometimes there are signs of psychomotor agitation with delirium and hallucinations. Hand tremors, twitching of facial and limb muscles are often observed. Muscle tone is reduced, reflexes are depressed.

Symptoms of tick-borne viral encephalitis

Diagnostics of tick-borne viral encephalitis

Tick-borne encephalitis is diagnosed based on the acute onset of the disease, pronounced symptoms of intoxication, early signs of diffuse or focal damage to the brain, the occurrence of flaccid paralysis and hyperkinesis. Of decisive importance for diagnosis is the spring-summer seasonality, indicating the patient's stay in an endemic focus of tick-borne encephalitis, detection of a tick bite on the skin of the patient and detection of specific IgM antibodies by the ELISA method.

The virus is isolated from the blood and cerebrospinal fluid of patients by intracerebral infection of newborn white mice with material from the patient or in tissue culture (chicken fibroblasts).

Treatment of tick-borne viral encephalitis

Antibiotics are ineffective against tick-borne encephalitis. As an etiotropic treatment in the early stages of the disease, specific human immunoglobulin is administered at a rate of 0.5 ml/kg per day for 2-3 days. Dehydration (25% magnesium sulfate solution, mannitol, lasix, 20% glucose solution, etc.) and detoxification (reamberin solution, rheopolyglucin, albumin) are carried out.

Treatment of tick-borne viral encephalitis

Prevention of tick-borne viral encephalitis

In disease outbreaks, ticks are destroyed by spraying especially dangerous areas with insecticides. Treatment of free-ranging farm animals (cows, goats, sheep) with chlorophos has preventive value. Personal preventive measures include wearing special clothing and applying repellents to the skin, as well as carefully examining clothing and the body to detect ticks after visiting the forest, etc. Milk from goats and cows can only be consumed after boiling.

How to prevent tick-borne viral encephalitis?