Objective: To determine aqueous humor flow rate (AHFR) in an avian species by use of anterior segment fluorophotometry. Animals: 9 healthy red-tailed hawks (Buteo jamaicensis; 4 males and 5 females) that ranged from 8 months to 8 years of age. Procedures: A protocol was developed for fluorophotometric determination of AHFR. Topical administration of 10% fluorescein was used to load the corneas, and corneal and aqueous humor fluorescein concentrations were measured approximately 5, 6.5, and 8 hours later. Concentration-versus-time plots were generated, and slopes and cornea-to-aqueous humor concentration ratios from these plots were used to manually calculate flow rates. Results: Mean ± SD AHFRs for the right eye, left eye, and both eyes were 3.17 ± 1.36 μL/min (range, 1.67 to 6.21 μL/min), 2.86 ± 0.88 μL/min (range, 2.04 to 4.30 μL/min), and 2.90 ± 0.90 μL/min (range, 1.67 to 4.42 μL/min), respectively. The AHFRs were similar for right and left eyes. These flow rates represented a mean aqueous humor transfer coefficient of 0.0082/min, which is similar to that of mammalian species. Conclusions and Clinical Relevance: The AHFR in red-tailed hawks was similar to that of most mammalian species, and the fractional egress was almost identical to that of other species. This information will allow a greater understanding of aqueous humor flow in avian eyes, which is crucial when evaluating diseases that affect avian eyes as well as medications that alter aqueous humor flow.

Objective—To evaluate the safety and efficacy of an experimental adjuvanted DNA-plasmid vaccine against West Nile virus (WNV) in red-tailed hawks (Buteo jamaicensis). Animals—19 permanently disabled but otherwise healthy red-tailed hawks of mixed ages and both sexes without detectable serum antibodies against WNV. Procedures—Hawks were injected IM with an experimental WNV DNA-plasmid vaccine in an aluminum-phosphate adjuvant (n = 14) or with the adjuvant only (control group; 5). All birds received 2 injections at a 3-week interval. Blood samples for serologic evaluation were collected before the first injection and 4 weeks after the second injection (day 0). At day 0, hawks were injected SC with live WNV. Pre- and postchallenge blood samples were collected at intervals for 14 days for assessment of viremia and antibody determination; oropharyngeal and cloacal swabs were collected for assessment of viral shedding. Results—Vaccination was not associated with morbidity or deaths. Three of the vaccinated birds seroconverted after the second vaccine injection; all other birds seroconverted following the live virus injection. Vaccinated birds had significantly less severe viremia and shorter and less-intense shedding periods, compared with the control birds. Conclusions and Clinical Relevance—Use of the WNV DNA-plasmid vaccine in red-tailed hawks was safe, and vaccination attenuated but did not eliminate both the viremia and the intensity of postchallenge shedding following live virus exposure. Further research is warranted to conclusively determine the efficacy of this vaccine preparation for protection of red-tailed hawks and other avian species against WNV-induced disease.

An applanation tonometer was used to estimate intraocular pressure in normal eyes of several species of raptors. No bird had active injury or illness, though some were nonreleasable to the wild because of previous injury. Mean (+/- SD) intraocular pressure was 20.6 (+/- 3.4) mm of Hg in red-tailed hawks (Buteo jamaicensis, n = 10), 20.8 (+/- 2.3) mm of Hg in Swainson's hawks (Buteo swainsoni, n = 6), 21.5 (+/- 3.0) mm of Hg in golden eagles (Aquila chrysaetos, n = 7), 20.6 (+/- 2.0) mm of Hg in bald eagles (Haliaeetus leucocephalus, n = 3), and 10.8 (+/- 3.6) mm of Hg in great horned owls (Bubo virginianus, n = 6). There was no significant difference in intraocular pressure between hawks and eagles. Mean pressure in great horned owls was significantly (P < 0.01) lower than pressure in hawks or eagles. Reliable intraocular pressure readings could not be obtained in barn owls (Tyto alba).

Objective: To evaluate the effects of dorsal versus lateral recumbency on the cardiopulmonary system during isoflurane anesthesia in red-tailed hawks (Buteo jamaicensis). Animals: 6 adult 1.1- to 1.6-kg red-tailed hawks. Procedures: A randomized, crossover study was used to evaluate changes in respiratory rate, tidal volume, minute ventilation, heart rate, mean arterial and indirect blood pressures, and end-tidal Pco2 measured every 5 minutes plus Paco2 and Pao2 and arterial pH measured every 15 minutes throughout a 75-minute study period. Results: Respiratory rate was higher, tidal volume lower, and minute ventilation not different in lateral versus dorsal recumbency. Position did not affect heart rate, mean arterial blood pressure, or indirect blood pressure, although heart rate decreased during the anesthetic period. Birds hypoventilated in both positions and Paco2 differed with time and position × time interaction. The Petco2 position × time interaction was significant and Petco2 was a mean of 7 Torr higher than Paco2. The Paco2 in dorsal recumbency was a mean of 32 Torr higher than in lateral recumbency. Birds in both positions developed respiratory acidosis. Conclusions and Clinical Relevance: Differences in tidal volume with similar minute ventilation suggested red-tailed hawks in dorsal recumbency might have lower dead space ventilation. Despite similar minute ventilation in both positions, birds in dorsal recumbency hypoventilated more yet maintained higher Pao2, suggesting parabronchial ventilatory or pulmonary blood flow distribution changes with position. The results refute the hypothesis that dorsal recumbency compromises ventilation and O2 transport more than lateral recumbency in red-tailed hawks.

OBJECTIVE To determine the pharmacokinetics of voriconazole administered PO with or without food to red-tailed hawks (Buteo jamaicensus) and whether any observed variability could be explained by measured covariates to inform dose adjustments. ANIMALS 7 adult red-tailed hawks. PROCEDURES In a crossover study design, hawks were randomly assigned to first receive voriconazole (15 mg/kg, PO) injected into a dead mouse (n = 3; fed birds) or without food (4; unfed birds). Sixteen days later, treatments were reversed. Blood samples were collected at various points to measure plasma voriconazole concentrations by ultraperformance liquid chromatography. Pharmacokinetic data were analyzed by noncompartmental methods and fit to a compartmental model through nonlinear mixed-effects regression, with feeding status and body weight investigated as covariates. RESULTS Voriconazole was well absorbed, with quantifiable plasma concentrations up to 24 hours after administration. Mean plasma half-life was approximately 2 hours in fed and unfed birds. Administration of the voriconazole in food delayed absorption, resulting in a significant delay in time to maximum plasma concentration. The final compartmental model included a categorical covariate to account for this lag in absorption as well as body weight as a covariate of total body clearance (relative to unknown bioavailability). CONCLUSIONS AND CLINICAL RELEVANCE A single dose of voriconazole (15 mg/kg) administered PO to red-tailed hawks resulted in mean plasma voriconazole concentrations greater than the targeted value (1 μg/mL). Additional studies with larger sample sizes and multidose regimens are required before the model developed here can be applied in clinical settings.

OBJECTIVE To determine the pharmacokinetics and adverse effects at the injection site of ceftiofur crystalline-free acid (CCFA) following IM administration of 1 dose to red-tailed hawks (Buteo jamaicensis). ANIMALS 7 adult nonreleasable healthy red-tailed hawks. PROCEDURES In a randomized crossover study, CCFA (10 or 20 mg/kg) was administered IM to each hawk and blood samples were obtained. After a 2-month washout period, administration was repeated with the opposite dose. Muscle biopsy specimens were collected from the injection site 10 days after each sample collection period. Pharmacokinetic data were calculated. Minimum inhibitory concentrations of ceftiofur for various bacterial isolates were assessed. RESULTS Mean peak plasma concentrations of ceftiofur-free acid equivalent were 6.8 and 15.1 μg/mL for the 10 and 20 mg/kg doses, respectively. Mean times to maximum plasma concentration were 6.4 and 6.7 hours, and mean terminal half-lives were 29 and 50 hours, respectively. Little to no muscle inflammation was identified. On the basis of a target MIC of 1 μg/mL and target plasma ceftiofur concentration of 4 μg/mL, dose administration frequencies for infections with gram-negative and gram-positive organisms were estimated as every 36 and 45 hours for the 10 mg/kg dose and every 96 and 120 hours for the 20 mg/kg dose, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Study results suggested that CCFA could be administered IM to red-tailed hawks at 10 or 20 mg/kg to treat infections with ceftiofur-susceptible bacteria. Administration resulted in little to no inflammation at the injection site. Additional studies are needed to evaluate effects of repeated CCFA administration.

Objective: To assess the agreement and reliability of cardiac measurements obtained with 3 echocardiographic techniques in anesthetized red-tailed hawks (Buteo jamaicensis). Animals: 10 red-tailed hawks. Procedures: Transcoelomic, contrast transcoelomic, and transesophageal echocardiographic evaluations of the hawks were performed, and cineloops of imaging planes were recorded. Three observers performed echocardiographic measurements of cardiac variables 3 times on 3 days. The order in which hawks were assessed and echocardiographic techniques were used was randomized. Results were analyzed with linear mixed modeling, agreement was assessed with intraclass correlation coefficients, and variation was estimated with coefficients of variation. Results: Significant differences were evident among the 3 echocardiographic methods for most measurements, and the agreement among findings was generally low. Interobserver agreement was generally low to medium. Intraobserver agreement was generally medium to high. Overall, better agreement was achieved for the left ventricular measurements and for the transesophageal approach than for other measurements and techniques. Conclusions and Clinical Relevance: Echocardiographic measurements in hawks were not reliable, except when the left ventricle was measured by the same observer. Furthermore, cardiac morphometric measurements may not be clinically important. When measurements are required, one needs to consider that follow-up measurements should be performed by the same echocardiographer and should show at least a 20% difference from initial measurements to be confident that any difference is genuine.