Tick-borne encephalitis

Content

Introduction

Introduction

Tick-borne encephalitis (TBE) or spring encephalitis-summer, is a viral infectious disease of humans that involves the central nervous system and is caused by a virus of the same family as those responsible for yellow fever and dengue.

The virus is transmitted by the bite of infected ticks.

The disease is present in many countries of northern and central eastern Europe, including Italy, where it was first identified in 1994 in the province of Belluno.

Ticks can infect various wild and domestic animals with the encephalitis virus, including rodents, roe deer, sheep and goats which, in turn, can retransmit the virus to other ticks, contributing to its spread.

Tick-borne encephalitis, in a first phase, often manifests itself with disorders (symptoms) similar to those of the flu but, subsequently, symptoms of meningitis and encephalitis may be highlighted.

The risk of TBE can be reduced by using insect repellants and protective clothing that protects against tick bites. Additionally, a vaccine is available.

Symptoms

Symptoms

In 70% of cases, the bite of a tick carrying the virus occurs in "humans with" an infection that does not cause disturbances or causes very mild ones. For this reason it can go unnoticed.

In the remaining 30% of cases, a first phase appears characterized by disorders (symptoms) similar to those of the flu:

  • high fever
  • bad headache
  • sore throat
  • tiredness
  • pain in muscles and joints

Such ailments appear 3-28 days after the bite and last 2-4 days. Thereafter the temperature drops and, generally, no further consequences occur.

In a small percentage, however (10-20% of these cases), the virus continues to spread into the meninges (protective membranes that cover the brain and spinal cord) or into the brain itself, causing symptoms of meningitis or encephalitis. Usually, in this second phase, after an interval without disturbances of 8-20 days, the following may appear:

  • sudden fever
  • nausea and vomit
  • stiff neck
  • headache
  • changes in mental state, such as confusion, sleepiness or disorientation
  • convulsions
  • sensitivity to light (photophobia)
  • difficulty speaking
  • paralysis

If tick-borne encephalitis reaches this stage it is necessary to see a doctor or go to the hospital quickly. Generally the disorders (symptoms) tend to improve slowly in a few weeks, although in a small percentage of cases long-term complications develop , or permanent, which include:

  • memory problems
  • speech problems
  • epilepsy
  • behavioral and mood changes
  • problems with concentration
  • movement problems
  • tiredness

Tick-borne encephalitis occurs milder in children and younger people, becoming progressively more severe as they age.

Causes

Causes

Tick-borne encephalitis is caused by a virus transmitted by the bite of an infected tick. The virus responsible for the disease is a arborvirus (belonging to the flavivirus genus), very similar to the one that causes yellow fever and dengue. Ticks carrying this disease are mainly ticks "hard"and can be hosted by many wild and domestic animals such as rodents, roe deer, sheep and goats. These animals can become infected and transmit the virus to new ticks, thus contributing to the spread of the infection." Birds most likely carry ticks over a considerable distance.

The environments where there is the highest risk of being bitten are woods, areas rich in bushes, humid and shaded areas, areas with low vegetation and leaf beds, undergrowth, uncultivated meadows, the border areas between lawn and forest, especially if in the presence of water. Little-traveled trails with wildlife are also at risk. The period of greatest transmission of the disease is between spring-summer and autumn, the period which corresponds to the maximum activity of ticks.

If you realize that you have been bitten by a tick, it is best to remove it quickly. To remove them from the skin, you have to grasp them firmly with tweezers as close to the skin as possible, pull them up firmly but not abruptly, with a gentle rotation to avoid breaking them. If the part of the mouth with which you bite, called rostrum, remains inside the skin, must be extracted with a sterile needle. The operation must be carried out with the hands protected by gloves or a handkerchief, to avoid the possibility of infection through small lesions of the skin. Afterwards, it is good to thoroughly disinfect the area and apply an antibiotic ointment.

Diagnosis

Diagnosis

The disorders (symptoms) alone do not allow to ascertain (diagnose) tick-borne encephalitis (TBE). In particular, without specific tests carried out on the blood or on the cerebrospinal fluid it is not possible to distinguish this disease from others that these animals can transmit. Diagnosis is therefore based on laboratory analyzes through which to verify:

  • presence of specific antibodies (IgM)
  • increased antibodies specific to the TBE virus greater than or equal to 4 times the normal value
  • TBE virus in blood and, in fatal cases, in nerve tissue samples

The cases identified are reported to the competent authorities to allow an assessment of the spread of this disease in our country.

Prevention

Prevention

The main form of prevention for tick-borne encephalitis is to avoid being bitten.

The presence of these animals in areas at risk can be contained by removing dry leaves and brushwood, removing wood piles, pruning trees and bushes and keeping lawns and paths clean. Pest control is only useful in confined areas.

In case of permanence, or excursions, in areas at risk, the most useful form of prevention is the protection of all parts of the body with appropriate clothing: light-colored clothing to make the possible presence of ticks more evident, t-shirts with long sleeves and long trousers. It is advisable to put the trousers in your socks to prevent the tick from entering between the trousers and the leg; the shoes should be high; it would also be good to wear gloves. For the uncovered parts it is good to protect yourself with products against insect bites based on N, N-diethyl-n-toulamide (DEET), dimethyl-phthalate, benzyl benzoate, permethrin and acaricides, repeating the application every 2-3 hours. Avoid putting the product on wounds and be careful not to bring it into contact with the eyes.

In case of work or stop in areas at risk, it is advisable to inspect clothing and uncovered parts every 3 - 4 hours and remove any ticks.

There is also a vaccine against tick-borne encephalitis which provides for the administration of three doses with boosters every three years. The best time to get vaccinated is the winter one, in order to be already protected in the period of maximum tick activity. Vaccination is recommended. only for people exposed to the tick bite for work reasons and for the population residing in areas at risk (established by evaluating the spread of the disease).

Bibliography

Bibliography

EpiCentro (ISS). Tick-borne meningoencephalitis

European Center for Disease Prevention and Control (ECDC). Tick-borne encephalitis (English)

Ministry of Health. Tick-borne encephalitis

In-depth link

In-depth link

EpiCentro (ISS). Tick-borne diseases. Brochure for travelers

EpiCentro (ISS). Tick-borne diseases. Free from ticks

EpiCentro (ISS). Tick-borne diseases. Travelers: beware of ticks

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