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

Urine Output Monitoring and Acute Kidney Injury in Non-mammalian Exotic Animal Critical Care

Acute kidney injury (AKI) is a sudden, severe decrease in kidney function which can occur in any species. There are various causes of AKI, some of which are seen in domestic species and some that are unique to birds, reptiles, and amphibians. These species present unique challenges with AKI management, such as differences in anatomy and physiology, intravenous and urinary catheterization, repeated blood sampling, and their tendency to present in advanced states of illness. This article will discuss AKI, diagnosis, treatment, and prognosis for non-mammalian exotic species.

EVALUATION OF SYMMETRIC DIMETHYLARGININE AS AN ENDOGENOUS MARKER OF RENAL DISEASE IN GREATER FLAMINGOS (PHOENICOPTERUS ROSEUS)

Detection of renal disease in birds is currently reliant on biochemical measures such as uric acid, which is only elevated after significant renal compromise has occurred. Symmetric dimethylarginine (SDMA) production has not been previously evaluated in birds and no reference intervals (RI) for measurement exist in avian species. This study aimed to develop an RI for SDMA in greater flamingos (Phoenicopterus roseus) and evaluate the association between SDMA levels and renal disease. Blood from 60 flamingos was collected for RI development and the RI of SDMA was found to be 11.8-34.2 µg/dl. Symmetric dimethylarginine showed a strong positive correlation with uric acid, a moderate positive correlation with creatine kinase, and moderate negative correlations with total protein, albumin, and glucose. No correlation was found with pododermatitis score or body condition. Using the SDMA RI, six clinical cases were included for assessment of the clinical relevance of SDMA in renally compromised patients. All birds that were euthanized had elevated SDMA levels and severe renal or systemic pathology on necropsy.

Pigeons (Columba livia domestica) Are Susceptible to Infectious Bursal Disease: A Comparative Study of Their Hematological and Serum Biochemical Alterations

The hematological and serum biochemical alterations following very virulent infectious bursal disease virus (IBDV) infection in pigeons and chickens were evaluated in this study. Sixty IBDV seronegative birds comprising 30 (3–6 weeks old) pigeons and 30 (3 weeks old) chickens were randomly divided as follows: 10 uninoculated pigeons only, 10 inoculated pigeons + 10 sentinel chickens, 10 inoculated chickens + 10 sentinel pigeons, and 10 uninoculated chickens. Inoculated birds were administered 0.20 ml of inoculum containing very virulent IBDV (vvIBDV). Blood was collected postinoculation/exposure (pi/pe) and processed for hematology and biochemistry. The results revealed significantly (P < 0.05) increased packed cell volume, decreased mean corpuscular hemoglobin (MCH), and MCH concentration (MCHC) in inoculated and sentinel chickens. Total leukocyte count (TLC), heterophil, and heterophil/lymphocyte (H/L) ratio were increased from 3 dpi/dpe in inoculated pigeons and from 3 to 14 dpi/dpe in inoculated and sentinel chickens. At 10 and 14 dpi/dpe, there was significantly (P < 0.05) increased serum total protein and globulin concentrations and decreased albumin/globulin ratio in pigeons and chickens. Serum urea concentration showed significant (P < 0.05) increase in inoculated and sentinel chickens at 3 and 4 dpi/dpe. To the authors' knowledge, this is the first report on hematological and serum biochemical alterations due to vvIBDV infection in pigeons.

COMPARATIVE RENAL DISPOSITION OF CREATINE, AND TECHNETIUM DIAGNOSTIC CONTRAST AGENTS IN THE PIGEON (COLUMBA LIVIA)

Clinical assessment of renal function in avian species often involves the measurement of plasma uric acid and blood urea nitrogen, relatively insensitive markers of renal dysfunction and dehydration. In mammals, endogenous creatinine is widely used as an indicator of renal glomerular dysfunction. However, avian species produce primarily creatine. Here, renal creatine, ^99mTc99-DTPA (diethylenepentaacetic acid, DTPA) and 99mTc-MAG3 (mercaptoacetyl triglycine, MAG₃) renal clearances are characterized in the pigeon avian model by infusing DTPA with inulin and creatine with each tracer and examining the slope of their blood disappearance curves. Clearance curves for inulin and DTPA were parallel, suggesting DTPA is cleared by renal filtration. MAG₃ clearance (slope: -2.74 × 10⁵, r² = 0.97) had a slope almost 10-fold steeper than for DTPA (slope: -6.29 × 10⁴, r² = 0.90), and orders of magnitude steeper than for creatine (slope: -1.4, r² = 1.0). These results suggest that DTPA is cleared by glomerular filtration like inulin, while MAG3 is filtered and actively excreted in a manner similar to mammals. In contrast, creatine is filtered and resorbed, has a larger volume of distribution (V_d), or exhibits a greater blood protein binding, making it more complex as a renal marker, when compared with creatinine handling in mammals. The two radiotracers can be readily adapted for use in birds, inviting both qualitative and semiquantitative functional evaluation of avian renal function for research and clinical purposes. The elimination of creatine appears to be more complex requiring further study.

Advances in Exotic Animal Clinical Pathology

Over the last 10 years, exotic animal clinical pathology has been evolving, improving health assessment in avian, mammal, fish, reptile, and amphibian patients. These advances are reviewed in this article. Species-specific reference intervals for blood parameters are becoming more available (eg, for ionized calcium, endocrine panels, and vitamin D plasmatic concentrations). In addition, new technologies are being developed to facilitate targeted metabolite detection and result acquisition by veterinarians. Novel techniques, biomarkers, and clinical changes related to disease have been described in avian, mammal, fish, reptile and amphibian species. The use of mobile applications may also be helpful.

Pharmacokinetics of meloxicam during multiple oral or intramuscular dose administration to African grey parrots (Psittacus erithacus)

OBJECTIVE To determine the pharmacokinetics of meloxicam in African grey parrots (Psittacus erithacus) during administration of multiple doses. ANIMALS 6 healthy African grey parrots. PROCEDURES Meloxicam was administered at each of 3 dosages (1 mg/kg, IM, q 24 h, for 7 days; 1 mg/kg, PO, q 24 h, for 12 days; and 1.6 mg/kg, PO, q 24 h, for 7 days) with an 8-week washout period between treatments. Blood samples were collected 12 and 24 hours after each drug administration (times of presumptive peak and trough drug concentrations) for pharmacokinetic analysis. Birds were visually assessed during all experiments and monitored for changes in selected plasma and urine biochemical variables after administration of the drug at 1.6 mg/kg. RESULTS Mean trough plasma concentrations at steady state were 10.7 and 9.16 μg/mL after meloxicam administration at 1 mg/kg, IM, and 1 mg/kg, PO, respectively. Plasma drug accumulation was evident (accumulation ratios of 2.04 ± 0.30 [IM treatment] and 2.45 ± 0.26 [PO treatment]). Plasma and urine N-acetyl-β-d-glucosaminidase activities were significantly increased at the end of meloxicam treatment at 1.6 mg/kg. CONCLUSIONS AND CLINICAL RELEVANCE Plasma concentrations of meloxicam were maintained at values greater than effective analgesic concentrations described for other avian species. Although administration of meloxicam at a dosage of 1 mg/kg IM and PO daily for 1 week and 12 days, respectively, was not associated with adverse clinical effects in this population, further studies are needed to assess the efficacy and safety of the drug during prolonged treatment and the clinical relevance of its accumulation.

Avian renal system: clinical implications

The avian renal system differs anatomically and physiologically from the mammalian renal system. However, it is affected by similar disease categories such as infectious, nutritional, degenerative, congenital, metabolic, and neoplastic conditions. The diagnosis of renal disease in birds can be challenging and, in many cases, diagnosis is made on postmortem examination. Successful treatment of avian renal disease requires early recognition of clinical signs and correct interpretation of diagnostic tools.