Tick-borne encephalitis (TBE) is a serious viral disease, the pathogens of which are mostly transmitted by ticks and can proceed to several severe stages. There were 352 cases of TBE diagnosed and reported in Germany in 2016.
Tick-borne encephalitis (TBE) is a disease caused by the TBE virus. The virus can attack the brain and the nervous system in humans.
The TBE virus is primarily transferred to humans by ticks. However, there have been cases where the disease was caused by drinking the raw milk of cows and goats infected with TBE virus.
According to estimates, the chances of suffering from TBE due to a tick bite in a risk area is around 1 in 150. The calculation is based on the assumption that around 2 percent of the ticks in areas of risk are infected with the TBE virus, but not every infection leads to an illness. Of the people bitten by a tick infected with the TBE virus, only a third develop the disease. For most people the infection does not produce noticeable symptoms of the disease.
There were 352 cases of TBE diagnosed and reported in Germany in 2016. Not every TBEV infection results in a severe progression of the disease. Scientists have yet to discover why it is that some people suffer severely and even die from an infection while others experience little to no illness. What is certain is that the age of the persons infected plays a significant role: the older the patient the more seriously TBE tends to develop. Gender also appears to be important, with TBE affecting men around twice as often as women. The proportion is even higher for severe TBE cases: around three times higher in men than in women.
Symptoms and progression of TBE
Typical cases of TBE develop in two stages:
Common initial symptoms are fever, headache and aching joints, similar to a summer flu. A fraction of patients moves on to the second stage of the disease, while others have overcome TBE at this point.
During the second stage of the disease, the TBE virus affects the meninges and/ or the central nervous system. The mildest form is meningitis. The symptoms of meningitis are high fever, severe headaches and frequently a stiff neck.
In more severe cases of TBE, meningoencephalitis and meningoencephalomyelitis develop. Not only are the meninges (membranes surrounding the brain and spinal cord) affected in these cases, but also the brain, or even the spinal cord and nerve roots. In addition to the symptoms of meningitis, it can also lead to other serious issues, including impaired consciousness, speech disorders and swallowing difficulties, to mental instability or paralysis of parts of the body.
Long-term effects of TBE
Previously it was assumed that about 10 to 20 percent of patients who underwent acute clinical progressions of TBE would suffer long-term or permanent neuropsychological damage.
The results of a study by the Neurology Clinic of the HELIOS Hospital in Pforzheim provided data regarding the possible long-term consequences of a TBE illness for the first time based on the study of 731 persons who suffered from TBE in the state of Baden-Württemberg between 1994 and 1999. 81 patients developed acute conditions involving the spinal cord (myelitis) and of these, 57 agreed to take part in a long-term study over ten years. The results of the study showed that 50 percent of the severely ill TBE patients suffered consequential long-term damage from the disease, such as paralysis of the extremities and of the breathing and throat muscles, breathing difficulties, balance problems, swallowing and speech difficulties. 30 percent of the severely ill patients who took part in the study died during the period of observation. Only 20 percent of the patients recovered fully.
Source: (in German): Kaiser, R. (2011). Long-term prognosis with primary myelitis manifestations of TBE – an analysis of progression over 10 years. Der Nervenarzt, 82(8), pp.1020-5
How do you catch TBE?
The TBE virus is contained in the saliva of a tick. The virus migrates across the wound immediately following a bite. Even when a tick is removed right after being bitten, the risk of TBE remains. Nevertheless, the longer the tick is allowed to feed the higher the risk of an infection with further pathogens.
Medical TBE treatment
There is no cure for TBE. As there are no medicines to combat the virus, treatment is limited to mitigating the symptoms. Drugs to reduce fever and relieve pain are mostly given. Ultimately though, the body is left alone to tackle the virus. That is why it is vital to take precautions against the disease before it is contracted. There are two main precautions a person can take: avoiding tick bites, and vaccination for protection against TBE.
The German Standing Committee on Vaccination (STIKO) at the Robert Koch-Institute recommends that residents of and travelers to risk areas who are exposed to ticks should get vaccinated against TBE.