Unusual Pathologic Brain Changes Associated with Zinc Toxicosis in a Blue-Fronted Amazon Parrot (Amazona aestiva).

An adult blue-fronted Amazon parrot (Amazona aestiva) was presented for a 6-wk history of ataxia and weight loss. Complete blood count, plasma chemistry panel, bile acids, and radiographic imaging were considered normal or unremarkable. The patient was hospitalized and supported with subcutaneous fluids, vitamin B complex, meloxicam, enrofloxacin, gavage feeding, and fenbendazole. While hospitalized, the ataxia significantly improved, and the bird began eating on its own and gaining weight. The bird was discharged from the hospital and prescribed enrofloxacin, meloxicam, and fenbendazole to be administered by the owner with recommendations for routine follow-up care. Medications were discontinued before emergent representation; at the time of reevaluation, the patient's condition had deteriorated severely. Given the poor prognosis, the owners elected for euthanasia. No gross abnormalities were noted on postmortem examination. Liver tissue zinc levels measured 125 ppm; normal limit is less than or equal to 25 ppm. Histopathologic changes to the brain were consistent with severe zinc toxicosis demonstrated by vasculopathy of the cerebral arteries and arterioles with multifocal areas of hemorrhage and astrocyte swelling. These findings have been reported in humans and other mammals but not birds. Although the source of this bird's heavy metal exposure is unknown, the high tissue zinc concentrations imply chronic exposure. This case presentation and unusual pathologic findings will be beneficial to the further understanding of avian zinc toxicosis.

Acetylcholinesterase concentrations in heparinized blood of Hispaniolan Amazon parrots (Amazona ventralis).

Organophosphate and carbamate pesticides inhibit acetylcholinesterase (AChE) at nerve synapses. Blood samples from 22 Hispaniolan Amazon parrots (Amazona ventralis) were assayed for cholinesterase levels by two different techniques. Using the modified Michel method, the whole-blood cholinesterase activity levels ranged from 0.082 to 0.616 deltapH/hr with a mean value of 0.35 deltapH/hr. A reference range (0.08-0.62 deltapH/hr) for cholinesterase was established in birds. The modified Ellman spectrophotometric method was used to measure AChE activity by adding acetylthiocholine or pseudocholinesterase (plasma cholinesterase) activity by adding butyrylthiocholine. The reference range of the AChE activity using the modified Ellman spectrophotometric method was 0-1.12 micromol/ml/min with a mean of 0.48 micromol/ml/min, and for pseudocholinesterase the range was 0.09-0.98 micromol/ml/min with a mean of 0.53 micromol/ml/min.