Naturally occurring highly pathogenic avian influenza virus H5N1 clade 2.3.4.4b infection in three domestic cats in North America during 2023.

The Eurasian strain of highly pathogenic avian influenza (HPAI) H5N1 is a devastating pathogen for birds that also has the capacity to infect mammals. This report describes the presentation, clinical case findings (including haemogram and serum biochemistry), gross and microscopic lesions and virus detection in three HPAI H5N1-infected domestic cats from the USA in 2023. All three cats presented with neurological abnormalities and were euthanized due to a poor prognosis within 2 days (two cats) or 10 days (one cat) of known clinical disease onset. Necropsy consistently revealed pulmonary congestion and oedema, and cerebrocortical malacia with haemorrhage was also seen in the cat that survived for 10 days. On histology, all cats had necrotizing encephalitis and interstitial pneumonia with pulmonary congestion, oedema, vasculitis and vascular thrombosis. One cat also had microscopic multifocal necrosis in the liver, pancreas and an adrenal gland. To our knowledge, this report is the first to detail pathological findings in HPAI H5N1 naturally-infected cats during the widespread outbreak in North America beginning in 2021, and that describes a cat surviving for 10 days after onset of HPAI H5N1 encephalitis.

The Role of Histopathology in Ruminant Diagnostics.

Histopathology remains an important tool for ruminant disease diagnostic investigations. Some ruminant diseases require histopathology to make a definitive diagnosis. Clinical history, proper tissue sampling and handling, and proper fixation all increase the efficiency of a histopathologic examination and the likelihood of an accurate diagnosis. This article discusses some of the main organ systems of ruminants and highlights common ruminant diseases encountered by diagnosticians where histopathology is particularly important. Where applicable, correlative gross lesions, special considerations regarding tissue sampling, and histologic report interpretation are discussed.

Bovine Herpesvirus 1 Invasion of Sensory Neurons by Retrograde Axonal Transport Is Dependent on the pUL37 Region 2 Effector.

Following exposure and replication at mucosal surfaces, most alphaherpesviruses invade the peripheral nervous system by retrograde axonal transport and establish lifelong latent infections in the peripheral ganglia. Reactivation of ganglionic infections is followed by anterograde axonal transport of virions back to body surfaces where viral replication results in disease that can range from moderate to severe in presentation. In the case of bovine herpesvirus 1 (BoHV-1), replication in the epithelial mucosa presents as infectious bovine rhinotracheitis (IBR), a respiratory disease of significant economic impact. In this study, we provide a live-cell analysis of BoHV-1 retrograde axonal transport relative to the model alphaherpesvirus pathogen pseudorabies virus (PRV) and demonstrate that this critical neuroinvasive step is conserved between the two viruses. In addition, we report that the BoHV-1 pUL37 tegument protein supports processive retrograde motion in infected axons and invasion of the calf peripheral nervous system. IMPORTANCE A molecular and cellular understanding of the retrograde axonal transport process that underlies the neuroinvasive properties of the alphaherpesviruses is established from studies of herpes simplex virus and pseudorabies virus. The degree to which this phenotype is conserved in other related viruses has largely not been examined. We provide a time-lapse analysis of the retrograde axonal transport kinetics of bovine herpesvirus 1 and demonstrate that mutation of the pUL37 region 2 effector affords a strategy to produce live-attenuated vaccines for enhanced protection of cattle.

Fall panicum ( Panicum dichotomiflorum) toxicosis in three juvenile goats.

Consumption of certain grasses belonging to the genus Panicum has been found to cause hepatogenous photosensitization and crystal-associated cholangiohepatopathy in small ruminants, and liver disease in horses, in many areas of the world. We describe herein the clinical findings, microscopic lesions, and steroidal saponin analysis of Panicum dichotomiflorum associated with fatal toxicosis in 3 juvenile goats in Nebraska. The disease presentation in our case was fulminant, with anorexia, marked icterus, and death for all affected animals in less than a week. Photosensitization was not observed. The microscopic lesions consisted of severe crystal-associated cholangiohepatopathy and nephropathy, with aggregates of clear or refractile and birefringent, acicular crystals present within bile ducts, macrophages, hepatocytes, and renal tubules. High-performance liquid chromatography-mass spectrometry of the grass samples demonstrated that dichotomin was the major steroidal saponin present (0.89 µg/mg); protodioscin was also present (0.059 µg/mg). The findings were consistent with ingestion of steroidal saponins, and P. dichotomiflorum was identified as the predominant forage available.