Country-wide distribution of bluetongue virus with expanding host spectrum and evidence of vector competence in Hungary.

Following the introduction of bluetongue virus type 4 (BTV-4) in 2014, country-wide monitoring of bluetongue (BT) disease was performed to see whether the virus has become enzootic in Hungary. To analyse the epizootiology of BT, over 110,000 samples collected from domestic and wild ruminants were screened for the presence of BTV RNA and virus-specific antibodies using real-time RT-PCR assay and commercial ELISA kit, respectively. During laboratory analysis, specimens collected from 333 (0.8%) cattle, 79 (2.2%) sheep, 4 (0.9%) goats, and 1 (2.3%) mouflon were found to be positive by viral RNA-detection assay. In addition, antibody to BTV was detected in 5.5% (3158/57,250) of cattle, 10.1% (517/5120) of sheep, 40% (116/290) of goat, and 5.6% (16/284) of buffalo origin samples. The majority of positive samples originated from south-western counties; however, 18 out of 19 counties reported cases or antibody prevalence in the examined animals. Genome sequencing of a representative BTV-4 strain from 2015 was also performed. When comparing this strain with the isolate BTV4-HUN2014 detected only a year earlier in Hungary, mutations at 14 sites were identified within the amplified and sequenced genome. Our findings reinforce the need for continued surveillance of BT disease in Hungary. Keywords: reoviridae; orbivirus; cattle; sheep; goat; biting midge.