Red neurons in ovine polioencephalomalacia (cerebrocortical necrosis) are strongly amyloid precursor protein immunopositive.

The signature pathological feature of the pseudolaminar cerebrocortical necrosis found in polioencephalomalacia (PEM) of ruminants is the development of red (eosinophilic) neurons. These neurons are generally considered to be irredeemably injured but we have shown, for the first time, in ovine PEM cases, that most strongly express amyloid precursor protein (APP), which has a neuroprotective role in the brain. By contrast, neurons in unaffected cerebral cortices from control sheep were APP immunonegative. This finding suggests that, rather than being inevitably destined to die, some of these APP immunoreactive cortical neurons may survive and regain structural and functional integrity.

Clinical and pathologic features of acute bovine liver disease in Australia.

Acute bovine liver disease (ABLD) is a sporadic hepatic disease affecting cattle in southern Australia, characterized histologically by striking periportal hepatocellular necrosis. The cause of ABLD is unknown; however, the seasonality and acute presentation of outbreaks suggest mycotoxin involvement. We describe here the clinical and pathologic findings of ABLD in 45 naturally affected cattle from 13 outbreaks occurring from 2010 to 2019 in Victoria, Australia. Outbreaks occurred in herds located along the southern coastal plain of Victoria and were observed most frequently in lactating dairy cattle. Clinical signs commonly included a combination of mild photosensitization, progressive neurologic signs, and hypogalactia, which preceded death by ≤ 48 h. All affected animals had marked elevations in activities of glutamate dehydrogenase, aspartate aminotransferase, and gamma-glutamyl transferase. At autopsy, the most common lesions were serosal petechiae and/or gastrointestinal hemorrhage, and hepatomegaly with a pronounced hepatic reticular pattern. The principal histologic lesion was widespread-severe periportal hepatocellular coagulative necrosis and erythrocyte pooling-which often extended to massive necrosis. Lesions in other organs were uncommon. Our study of ABLD suggests involvement of a potent hepatotoxin that is either directly cytopathic or requires bioactivation by periportal-specific enzymes.

Plant and Fungal Hepatotoxicities of Cattle in Australia, with a Focus on Minimally Understood Toxins.

Plant- and fungus-derived hepatotoxins are a major cause of disease and production losses in ruminants in Australia and around the world. Many are well studied and described in the literature; however, this is not the case for a number of hepatotoxicities with economic and animal welfare impacts, such as acute bovine liver disease (ABLD), brassica-associated liver disease (BALD) and Trema tomentosa, Argentipallium blandowskianum and Lythrum hyssopifolia toxicity. Additionally, significant overlap in the clinical presentation and pathology of these conditions can present a diagnostic challenge for veterinarians. This review summarizes the current and most recently published knowledge of common plant- and fungus-associated hepatotoxins affecting cattle in Australia, with a focus on the mechanisms of toxicity and distinguishing diagnostic features. Consolidation of the current understanding of hepatotoxic mechanisms in cattle provides insight into the potential mechanisms of lesser-known toxins, including cellular and subcellular targets and potential metabolic pathways. In the absence of specific etiological investigations, the study of epidemiological, clinical and pathological features of hepatotoxicity provides valuable insights into potential toxic mechanisms and is integral for the successful diagnosis and management of these conditions.

Diagnostic investigation of new disease syndromes in farmed Australian saltwater crocodiles (Crocodylus porosus) reveals associations with herpesviral infection.

Since 2006, 3 new disease syndromes have emerged in farmed saltwater crocodiles (Crocodylus porosus) in the Northern Territory of Australia. We describe the syndromes through a retrospective study of laboratory findings from 187 diagnostic cases submitted to Berrimah Veterinary Laboratories between 2005 and 2014. The first syndrome was characterized by conjunctivitis and/or pharyngitis (CP), primarily in hatchlings. Herpesviruses were isolated in primary crocodile cell culture, or were detected by PCR directly from conjunctiva or pharyngeal tissue, in 21 of 39 cases of CP (54%), compared with 9 of 64 crocodiles without the syndrome (14%, p < 0.0001). Chlamydiaceae were detected by PCR in conjunctiva or pharyngeal tissue of 55% of 29 CP cases tested, and of these, 81% also contained herpesvirus. The second syndrome occurred in juveniles and growers exhibiting poor growth, and was characterized histologically by systemic lymphoid proliferation and nonsuppurative encephalitis (SLPE). Herpesviruses were isolated or detected by PCR from at least 1 internal organ in 31 of 33 SLPE cases (94%) compared with 5 of 95 crocodiles without the syndrome (5%, p < 0.0001). The third syndrome, characterized by multifocal lymphohistiocytic infiltration of the dermis (LNS), occurred in 6 harvest-sized crocodiles. Herpesviruses were isolated from at least 1 skin lesion in 4 of these 6 cases. Although our study revealed strong associations between herpesvirus and the CP and SLPE syndromes, the precise nature of the role of herpesvirus, along with the pathogenesis and epidemiology of the syndromes, requires further investigation.

Primary ocular melioidosis due to a single genotype of Burkholderia pseudomallei in two cats from Arnhem Land in the Northern Territory of Australia.

Melioidosis was diagnosed in two domestic crossbred cats presented for unilateral ocular disease. One patient was born and bred in Nhulunbuy, Arnhem Land, while the other had moved there 6 months previously from Townsville, Queensland. Both patients were presented with sudden onset of a 'red eye' and blepharospasm, which progressed to an enlarged, painful, firm globe with loss of pupillary light reflexes and vision. An obvious primary focus of infection outside the eye was not detected in either cat. In both patients, the affected eye was surgically removed and vitreal culture revealed a pure growth of Burkholderia pseudomallei. In each instance, the infection had penetrated the sclera to produce retrobulbar cellulitis, and in one case frank retrobulbar abscessation. Histologically, there was a pyogranulomatous uveitis with extensive destruction of intraocular structures. The first case was still alive approximately 1 year following enucleation and limited antimicrobial therapy using amoxicillin clavulanate and doxycycline. The second was euthanased when a localised abscess developed on the same side of the face as the healed surgical incision, despite appropriate antimicrobial therapy. Both cases were caused by the same multilocus sequence type of B pseudomallei (ST 116), which had only been isolated previously from two human patients, both living in the same isolated geographical area as the cats of this report. Apart from the geographical clustering, no epidemiological links were evident between the two cats and/or the two people. The presumptive pathogenesis of these infections is discussed in relation to current knowledge about melioidosis in northern Australia.