General information
Tick-borne encephalitis (TBE) is caused by an arbovirus. Arboviruses are an inhomogeneous group of viruses whose common feature is the transmission by blood-sucking arthropods. Like the West Nile virus, the TBE virus (TBEV) belongs to the genus Flavivirus and is transmitted by ticks.
In dogs, the disease was first described in 1972. Seroepidemiological studies conducted since then have shown that dogs have relatively frequent contact with TBEV (up to 30% in certain areas) without contracting the disease. If the disease is contracted, the symptoms in dogs are a multifocal occurrence involving the cerebrum, brain stem and sometimes also the spinal cord. The disease usually begins acutely to peracutely with a highly elevated body temperature (up to over 41 °C) and a further rapidly progressive course. Changes in behaviour, from being apathetic to overexcited or aggressive, gait disorders up to tetraparesis/tetraplegias and seizures can occur. Various brain nerve deficits are observed, e. g. facioplegia, strabismus, nystagmus, miosis, missing menace reflex. Hyperalgesia in the head and neck area as well as a generally increased painfulness are characteristic. A large part of the disorders ends lethally or by euthanasia within one week. Recently, there have been more and more literature reports on dogs with a chronic course of the disease that have survived. Sometimes slight neurological signs remained, sometimes the dogs were fully recovered.
Diagnosis should be confirmed serologically by antibody detection using ELISA. However, it must be taken into account that the antibodies could be the result of a previous subclinical infection. Antibodies may also appear in the CSF within the first week after infection and can be detected by ELISA.
In the peracute form, PCR can be used to try to detect the virus in the CSF. Due to the very rapid virus elimination from the brain, however, this is only possible in the early phase of infection. Virus detection by PCR from a collected tick is possible and especially useful if a person is affected by a tick.
TBE is also increasingly detected in neurologically affected horses. The clinical picture is similar to the disease caused by the West Nile virus.