Assessment of novel avian renal disease markers for the detection of experimental nephrotoxicosis in pigeons (Columba livia).

Renal disease is a major cause of illness in captive and wild avian species. Current renal disease markers (e.g., uric acid, blood urea nitrogen, and creatinine) are insensitive. Two endogenous markers, creatine and N-acetyl-beta-D-glucosaminidase (NAG), were selected for study in the pigeon (Columba livia). Representative organs from four pigeons were surveyed to determine those exhibiting the highest level of each marker. In a separate study, NAG and creatine from plasma and urine were assayed before and after gentamicin (50 mg/kg twice daily), administration for up to 9 days. Observer-blinded pathologic scoring (five saline solution controls, 17 treated birds) was used to verify the presence of renal disease that corresponded to marker increases. The first study revealed that kidney tissue had the highest NAG activity (by approximately six times), and pectoral muscle had the most creatine (>900 times). In response to gentamicin, plasma creatine (>five times) and NAG increased (approximately six times), which paralleled uric acid (>10 times). Urine creatine (approximately 60 times) and NAG increased dramatically (approximately 50 times) in response to gentamicin. In conclusion, NAG, especially in the urine, may be of value to noninvasively detect renal toxin exposures and to monitor potentially nephrotoxic drugs, and might be of value to screen free-ranging birds in large exhibits or in the wild by assaying fresh urate samples at feeding stations.

Urinalysis as a noninvasive health screening procedure in Falconidae.

Clinical signs of renal disorders in animals, including raptors, are not specific. Furthermore, serum or plasma biochemical parameters change only when 70% of kidney function is lost. In this study, reference values of urine variables were established in clinically healthy falcons. Urine samples were collected from 78 mature (> 1 year) and immature (6-12 months) male and female falcons belonging to 5 species. Droppings were assessed visually for urate color and consistency and color of the liquid urine. The liquid urine was collected by aspiration into a syringe and centrifuged, and the supernatant analyzed by commercial dipstick and by a wet chemistry analysis for alkaline phosphatase, gamma glutamyl transferase, glucose, chloride, and total protein concentrations. Sex, age, and species did not affect results of biochemical urine values (P > .05). Urine biochemical values did not differ significantly between fasted and fed birds. Total protein levels in urine samples decreased after 24-hour storage at 4 degrees C. Reference ranges for clinically normal birds are reported.

Hemoglobinuric nephrosis in a rhea (Rhea americana).

An eighteen-month-old female rhea (Rhea americana) was presented dead for necropsy. The owner reported having observed blood in the droppings. Gross examination revealed a rhea in good body condition with a copious amount of frank blood in the cloaca. Large masses of matted fescue grass (Festuca spp.) distended the ventriculus and jejunum. No hemorrhage was evident in the digestive tract, which was otherwise void of ingesta. The kidneys were dark brown in color. Renal histopathology revealed a severe accumulation of eosinophilic pigment in the tubular epithelial cells of the proximal convoluted tubules, with tubular nephrosis and eosinophilic casts in the collecting tubules. It was concluded that the renal pigment was hemoglobin and not myoglobin, based on lack of evidence of muscle injury and the severe erythrophagocytosis evident in hepatic macrophages. The renal pigment also stained positive with the hemoglobin-specific Okajima stain. Hemoglobinuric nephrosis has not previously been reported in an avian species.