Congenital malformations occur sporadically in cattle; however, congenital structural and functional disorders of the nervous system are rather common in ruminants. Among the numerous causes of congenital nervous system defects, infectious agents are highlighted in this paper. Virus-induced congenital malformations are well known, among which those caused by bovine viral diarrhoea virus (BVDV), Akabane virus (AKAV), Schmallenberg virus (SBV), Bluetongue virus (BTV), and Aino virus (AV) are the most studied. In this study, we specify and categorise macroscopic and histopathological lesions in the brain of 42 newborn calves suffering from severe neurologic signs and diagnosed with BVDV and AKAV infection. Following a complete necropsy, specimens were collected from the brains to track the presence of BVDV, AKAV and SBV utilising reverse transcription polymerase chain reaction. Of the 42 examined calves, 21 were BVDV positive and 6 were AKAV positive, while 15 brains were negative for the studied agents. Regardless of the aetiology, cerebellar hypoplasia, hydranencephaly, hydrocephalus, porencephaly, and microencephaly were detected. Cerebellar hypoplasia was the most common lesion seen in both BVDV-positive and AKAV-positive cases. Virus-induced necrosis of the germinative cells of the external granular layer of cerebellum, as well as vascular damages, are believed to be the underlying causes of cerebellar hypoplasia. BVDV was the most important aetiological agent of such cases in this study.

Viral metagenomics characterizes known and identifies unknown viruses based on sequence similarities to any previously sequenced viral genomes. A metagenomics approach was used to identify virus sequences in Australian mosquitoes causing cytopathic effects in inoculated mammalian cell cultures. Sequence comparisons revealed strains of Liao Ning virus (Reovirus, Seadornavirus), previously detected only in China, livestock-infecting Stretch Lagoon virus (Reovirus, Orbivirus), two novel dimarhabdoviruses, named Beaumont and North Creek viruses, and two novel orthobunyaviruses, named Murrumbidgee and Salt Ash viruses. The novel virus proteomes diverged by ≥ 50% relative to their closest previously genetically characterized viral relatives. Deep sequencing also generated genomes of Warrego and Wallal viruses, orbiviruses linked to kangaroo blindness, whose genomes had not been fully characterized. This study highlights viral metagenomics in concert with traditional arbovirus surveillance to characterize known and new arboviruses in field-collected mosquitoes. Follow-up epidemiological studies are required to determine whether the novel viruses infect humans.

Ťahyňa virus (TAHV), a member of the Bunyaviridae family (California complex), is an important but neglected human mosquito-borne pathogen. The virus genome is composed of three segments, i.e., small (S), medium (M), and large (L). Previous studies on genetic variability of viruses within the California complex were focused on S and M segments, but the L segment remains relatively unstudied. To assess the genetic variation and the relation to virus phenotype we analyzed the L segment sequences of biologically diverse TAHV strains isolated in the Czech Republic and Slovakia. Phylogenetic analysis covering all available sequences of the L segment of TAHV clearly revealed two distinguished lineages, tentatively named as \"European\" and \"Asian\". The L segment strains within the European lineage are highly conserved (identity 99.3%), whilst Asian strains are more genetically diverse (identity 97%). Based on sequence comparison with other bunyaviruses, several non-synonymous nucleotide substitutions unique for TAHV in the L segment were identified. We also identified specific residue substitutions in the endonuclease domain of TAHV compared with the La Crosse virus. Since the endonuclease domain of the La Crosse virus has been resolved, we employed an all energy landscape algorithm to analyze the ligand migration of a viral polymerase inhibitor. This allowed us to demonstrate, at the atomic level, that this viral polymerase inhibitor randomly explored the specific residue substitutions in the endonuclease domain of the TAHV L segment.