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US - Nebraska: Highly Pathogenic Avian Influenza in Mammals: A Case Report of Two Domestic Cats - April 7, 2023

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  • US - Nebraska: Highly Pathogenic Avian Influenza in Mammals: A Case Report of Two Domestic Cats - April 7, 2023

    University of Nebraska



    Written by Dr. Sarah Sillman, DVM, PhD, dip. ACVP

    Highly Pathogenic Avian Influenza in Mammals: A Case Report of Two Domestic Cats

    In January, an outdoor, adult, domestic longhaired cat presented to the University of Nebraska Veterinary Diagnostic Center for postmortem examination after a history of rapid decline with clinical signs of anorexia, recumbency, anisocoria, pyrexia, seizures, tremors, nystagmus, loss of proprioception, and hyperesthesia. Gross necropsy revealed only a few visible changes to the organs including pulmonary congestion and edema, mild pericardial transudative effusion, and a subtle darkening of areas of the cerebrocortical grey matter. Complete histopathology examination revealed necrotizing lesions in the kidney, liver, adrenal gland, and pancreas; encephalitis with patches of extensive neuronal degeneration and necrosis, particularly in the cerebral cortex; and edema, vessel congestion, and mild inflammation in the lung and epicardium. The lesions were recognized as suspicious for highly pathogenic avian influenza virus infection, which was confirmed with molecular diagnostics. The PCR Ct value for avian influenza in the brain of this cat was remarkably low (12), indicating a very large amount of virus in the brain, as consistent with an acute infection. Highly pathogenic avian influenza Eurasian strain H5N1 was verified by molecular assay at National Veterinary Services Laboratories

    Three other outdoor domestic cats of this household were noted at risk, and one of them developed clinical signs shortly after the first affected cat. This cat was described as somnolent and had episodes of walking in circles (circling). The cat was responsive to stimuli and seemed to eat and drink normally. It lived 10 days with neurologic impairment, when the cat suddenly became laterally recumbent with continual tremors, necessitating euthanasia. Gross necropsy documented major lesions only in the brain. There was excessive bloody cerebrospinal fluid from the subarachnoid space and obvious areas of malacia and hemorrhage in the cerebral cortex. On histopathology of affected brain, there was extensive loss of neurons with severe vacuolation and collapse of the supporting parenchyma, accompanied by reactive changes including astrogliosis and lymphocytic perivascular cuffs. Avian influenza was detected in the brain, although the PCR Ct value was higher (30), a consequence of the infection being chronic and/or less initial virus burden. Eurasian strain H5N1 was verified at NVSL. Acute hemorrhage from the damaged cortex leading to increased intracranial pressure could have caused the neurological crisis in this second cat. The remaining two cats in the household have been reportedly normal and nasal swabs collected from them did not detect avian influenza virus. ...