Tick-borne encephalitis virus (TBEV) infection in horses: clinical and laboratory findings and epidemiological investigations.

During a routine examination of 130 horse sera from 13 herds in Thuringia one TBEV antibody positive serum - with a very high titre - could be detected. The horse had been bought from a holding in Bavaria, and was reported to have clinical signs that may have been caused by a TBEV infection. To identify the source of the suspected TBEV infection, ticks from the surroundings of the barn in Thuringia as well as horse sera and ticks from two herds in Bavaria were examined. In the holding in Bavaria, where the horse was kept before, two out of ten horse sera were found to be TBEV antibody positive (20%), in a second herd nearby five out of 15 horse sera were TBEV antibody positive (30%), and in one serum TBEV-RNA could be detected. In addition, at both Bavarian sites, two different TBEV strains were detected in ticks collected in the vicinity of the respective holdings and in the surrounding areas. In contrast, no TBEV-RNA could be found in ticks collected in Thuringia. The suitability of horses as sentinels for the detection of natural TBEV foci supported by subsequent, targeted tick collection as well as the clinical importance of TBEV infection in horses are discussed.