Prevalence and risk factors of tick-borne encephalitis virus in dogs in Lithuania

Abstract

Tick-borne encephalitis (TBE) is recognized as the most important zoonotic tick-borne viral disease in Europe. Causative agent of the disease is typically transmitted to human beings through bites of tick-borne encephalitis virus (TBEV)-infected ticks. However, an increasing number of case reports of TBE infection in dogs indicate that the virus might be an important tick-borne pathogen in dogs, especially in endemic areas. Therefore, the aim of the present study was to investigate the prevalence of TBEV RNA and TBEV-specific antibodies in serum samples of dogs living in a highly endemic region of Lithuania and to evaluate the main risk factors associated with the severe cases of TBE. The serum samples (n = 473) of dogs were randomly collected in two veterinary clinics in central Lithuania and analysed by commercially available ELISA kits and nested RT-PCR using primers targeting NCR5 region. To confirm TBEV propagation, Neuro-2a, Vero and MARC-145 cells were transfected with suspensions prepared from positive sera and viral replication in cells was confirmed via RT-PCR. Observed neurological symptoms in 31.8% (CI 95% 22.3-42.6) and a death rate of 18.2% (CI 95% 10.8-27-8) of PCR-positive dogs implies that TBE is a clinically important disease in dogs in endemic countries such as Lithuania. TBEV-specific antibodies were detected in 21.6% (CI 95% 17.9-25.6) of randomly collected dog blood samples and in 32.1% (CI 95% 15.9-52.4) of dogs with neurological symptoms. Males were more likely to develop neurological symptoms (p = 0.0084), while older dogs (p = 0.0032), dogs with neurological symptoms (p = 0.003) and the presence of TBEV-specific antibodies (p = 0.024) were more likely to experience worse outcomes of the disease. The results of the present study demonstrate that TBEV is a common and clinically important pathogen in dogs in Lithuania.