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Objectives: Tick‐borne encephalitis virus and louping ill virus are neurotropic flaviviruses transmitted by ticks. Epidemiologically, tick‐borne encephalitis is endemic in Europe whereas louping ill's predominant geographical distribution is the UK. Rarely, these flaviviruses affect dogs causing neurological signs. This case series aimed to describe the clinical, clinicopathological, and imaging findings, as well as the outcomes in six dogs with meningoencephalitis and/or meningomyelitis caused by a flavivirus in the UK in 2021. Materials and Methods: Observational retrospective case‐series study. Clinical data were retrieved from medical records of dogs with positive serological or immunohistochemical results from three different institutions from spring to winter 2021. Results: Six dogs were included in the study. All dogs presented an initial phase of pyrexia and/or lethargy followed by progressive signs of spinal cord and/or intracranial disease. Magnetic resonance imaging showed bilateral and symmetrical lesions affecting the grey matter of the thalamus, pons, medulla oblongata, and thoracic or lumbar intumescences with none or mild parenchymal and meningeal contrast enhancement. Serology for tick‐borne encephalitis virus was positive in five dogs with the presence of seroconversion in two dogs. The viral distinction between flaviviruses was not achieved. One dog with negative serology presented positive immunohistochemistry at post‐mortem examination. Three dogs survived but presented neurological sequelae. Three dogs were euthanased due to the rapid progression of the clinical signs or static neurological signs. Clinical Significance: These cases raise awareness of the presence of tick‐borne encephalitis as an emergent disease or the increased prevalence of louping ill virus affecting dogs in the UK. [ABSTRACT FROM AUTHOR]

Background: Louping ill virus (LIV) is a tick-borne flavivirus that can cause fatal meningoencephalomyelitis in dogs. Four dogs with confirmed LIV infection and a case series of dogs with suspected flavivirus infection have been reported in the UK. However, underreporting of LIV infection due to lack of testing is suspected., Methods: Surplus serum/plasma from 220 dogs was used to determine the seroprevalence of LIV by haemagglutination inhibition (HAI) test. Signalment and environmental factors were investigated for potential correlations with a positive titre (serum dilution of 1:20 or more)., Results: Two hundred and two dogs were suitable for inclusion in the study, nine of which (4.5%) were seropositive. Among the dogs investigated for neurological disease (40/202; 19.8%), six (15%) were seropositive. Ectoparasiticide use approached significance (p = 0.055) for being protective against LIV seropositivity., Limitations: The main limitations were the specificity of the HAI test, the relatively small number of samples, the low number of seropositive dogs, the poor geographical distribution of the samples and the inherent limitations of questionnaire-based research., Conclusion: The seroprevalence of LIV in the UK dog population appears to be low. However, LIV should be considered in dogs presenting with unexplained acute or subacute progressive neurological clinical signs, especially because of the recent reports of several dogs with clinical flavivirus infections., (© 2024 British Veterinary Association.)

Case Description: A 9-month-old intact male domestic shorthair cat was evaluated for increasing frequency of generalized tonic-clonic seizures., Clinical Findings: The cat was reported to have had episodes of circling between the seizures. Upon examination, the cat had bilateral inconsistent menace response but otherwise normal physical and neurological examinations., Diagnostics: Magnetic resonance imaging (MRI) of the brain identified multifocal, small, rounded intra-axial lesions within the subcortical white matter containing fluid with similar characteristics as cerebrospinal fluid. Evaluation of urine organic acids showed increased excretion of 2-hydroxyglutaric acid. An XM_023255678.2:c.397C>T nonsense variant in the L2HGDH gene encoding L-2-hydroxyglutarate dehydrogenase was identified using whole genome sequencing., Treatment and Outcome: Levetiracetam treatment was initiated at 20 mg/kg PO q8h, but the cat died after a seizure 10 days later., Clinical Relevance: We report the second pathogenic gene variant in L-2-hydroxyglutaric aciduria in cats and describe for the first time multicystic cerebral lesions on MRI., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)