Abstract
The oak is a common tree or shrub in the Quercus genus, with a number of species native to the Northern hemisphere. In large amounts, the leaves and acorns of Quercus can be highly toxic to ruminants and horses.1,3,4 Large outbreaks of poisoning, with fatal results, have been documented in hoofstock, generally in the fall when acorns or leaves fall, or when forage food is scarce.3,4 Oak plant parts contain tannins, or naturally occurring plant polyphenols: hydrolysable tannins (HTs) and condensed tannins (CTs).3-5 HTs cause protein denaturation and cell death with lesions in the kidney and liver. CTs on the other hand are not absorbed from the gastrointestinal mucosa, damage mucosal lining and can disrupt absorption of nutrients.5 The most common clinical signs of Quercus toxicity in hoofstock are anorexia, depression, rumen atony, and constipation turning to bloody diarrhea.1,3,4 Histologically, renal lesions, typically renal tubular necrosis, are often present.3,4 Aspergillus sp., an opportunistic pathogen, is a widespread environmental contaminant in aquaria.6 Aspergillosis, an important cause of fatality in cetaceans, is usually associated with pneumonia but also rarely affects the brain.2
A mature female captive beluga ingested over 20 lbs of White Oak leaves that had blown into the outdoor pool after a succession of windy days in the fall. The whale then became acutely anorexic. When handled, it regurgitated a foul-smelling brown fluid containing bits of oak leaves into its mouth and sometimes through its blowhole. Stomach contents were evacuated on multiple occasions using hydrogen peroxide and warm water through an orogastric tube, as well as by manual evacuation. On one attempt, over 8 lbs of oak leaves were removed from the stomach and esophagus. Each of the 5 gastric emptying attempts was followed by a 2–3 day recovery. By the 4th week after the onset of clinical signs, the animal was still anorexic, and force-feeding was then started until the 7th week, when the whale died. In addition to nutritional support, the animal was treated with a series of antibiotics and stomach protectorants. Bloodwork showed leukocytosis, fibrinogenemia, and a regenerative anemia. BUN, creatinine, and phosphorus remained normal.
Postmortem examination showed severe ulceration of the distal esophageal mucosa, with oak leaves and fish bones found in the thoracic portion of the esophagus and a markedly distended forestomach containing mostly oak leaves and fish spines. A large (9 x 3 x 4 cm) hematoma was present within the left parietal lobe of the brain, and the overlying meninges were affected by severe suppurative necrotizing vasculitis extending into the cortex with intralesional hyphae consistent with Aspergillus sp. There was evidence of aspiration pneumonia and no evidence of renal tubular necrosis. Considered together, the anamnesis and the clinical and pathological findings suggest that CTs damaged the esophageal mucosa, which served as an entry point to the fungal hyphae, causing the meningeal and intracerebral vasculitis that led to a large intracerebral hematoma.
References
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