Incidence and risk factors for bumblefoot (pododermatitis) in rehabilitated raptors

Blood Vessel Topography of the Feet in Selected Species of Birds of Prey and Owls

Birds of prey and owls are susceptible to diseases of and traumatic injuries to their feet, which regularly require surgical intervention. A precise knowledge of the blood vessel topography is essential for a targeted therapy. Therefore, the metatarsal and digital vasculature was examined in eight species of birds of prey and owls. The study included contrast micro-computed tomography scans and anatomical dissections after intravascular injection of colored latex. In all examined species, the dorsal metatarsal arteries provided the main supply to the foot and their branching pattern and number differed between species. They continued distally as digital arteries. All examined species showed a basic pattern of four collaterally located digital blood vessels per toe: a prominent artery and small vein on one side and a small artery and prominent vein on the other side. Digital veins united to form common digital veins, most of which joined into a superficial, medially located metatarsal vein. This vein provided the main drainage of the foot. The detailed visualization of the topography of pedal blood vessels will help veterinary surgeons during surgical procedures. In addition, differences in the plantar arterial arch between hawks and falcons were discussed regarding their possible influence on the prevalence of pododermatitis (bumblefoot).

Changes in Environment and Management Practices Improve Foot Health in Zoo-Housed Flamingos

Foot lesions are a highly prevalent phenomenon among zoo-housed flamingos, with up to 99.8% of birds affected. These lesions are a recognized welfare concern, increasing the likelihood of bacterial infections, and even septicemia. Although several risk factors have been linked to foot lesions in flamingos (including age, climate, and substrate), there have been few studies looking at changes in foot lesions over time. This study tracked changes in foot lesions for an individual flock of Chilean Flamingos (97 birds) at Dublin Zoo, Ireland, over an 18-month period in response to a mandatory indoor housing order imposed by the Irish Government as a seasonal precautionary measure to prevent the spread of avian influenza. Using a pre-defined scoring system for four common types of foot lesions (hyperkeratosis, fissures, nodular lesions, and papillomatous growths), we show that providing unrestricted access to outdoor habitats and natural substrates (both terrestrial and aquatic) can improve the health and wellbeing of zoo-housed flamingos. This longitudinal study highlights the importance of regular foot health monitoring in flamingos, and the importance of natural aquatic substrates when managing flamingos. As many zoo-housed birds have been spending more time indoors on artificial substrates over recent years due to avian influenza housing orders, it is critical that we assess the impact of such changes in management and habitat access on bird health and welfare.

EVALUATION OF β-HYDROXYBUTYRATE, AMINO ACIDS, AND SELECTED CHEMISTRY VALUES IN THE PLASMA OF FREE-RANGING RED-TAILED HAWKS (BUTEO JAMAICENSIS)

The red-tailed hawk (Buteo jamaicensis) is a raptor species native to North America that is commonly presented to wildlife rehabilitators and veterinarians, but little is known about biomarkers of metabolic status in this species. This study evaluates plasma β-hydroxybutyrate (BHB) and free amino acids in 24 free-ranging red-tailed hawks in good body condition in order to establish reference intervals for these values. Standard biochemical analytes were also measured. The mean plasma BHB level measured was 13.9 mg/dl. Plasma amino acids were not similar to the few available reports in avian species. Standard biochemical analytes were similar to those previously reported for red-tailed hawks. These data serve as a foundation for further investigation into the use of these biomarkers to assess metabolic status of this species in health and disease.

Species, causes, and outcomes of wildlife rehabilitation in New York State

Wildlife rehabilitation is a publicly popular practice, though not without controversy. State wildlife agencies frequently debate the ecological impact of rehabilitation. By analyzing case records, we can clarify and quantify the causes for rehabilitation, species involved, and treatment outcomes. This data would aid regulatory agencies and rehabilitators in making informed decisions, as well as gaining insight into causes of species mortality. In New York State, the Department of Environmental Conservation (NYSDEC) has licensed rehabilitators since 1980 and annual reporting is required. In this study, we analyzed 58,185 individual wildlife cases that were attended by New York rehabilitators between 2012 and 2014. These encompassed 30,182 (51.9%) birds, 25,447 (43.7%) mammals, 2,421 (4.2%) reptiles, and 75 (0.1%) amphibians. We identified patterns among taxonomic representation, reasons for presentation to a rehabilitation center, and animal disposition. Major causes of presentation were trauma (n = 22,156; 38.1%) and orphaning (n = 21,679; 37.3%), with habitat loss (n = 3,937; 6.8%), infectious disease (n = 1,824; 3.1%), and poisoning or toxin exposure (n = 806; 1.4%) playing lesser roles. The overall release rate for animals receiving care was 50.2% while 45.3% died or were euthanized during the rehabilitation process. A relatively small number (0.3%) were permanently non-releasable and placed in captivity; 4.1% had unknown outcomes. A comparable evaluation in 1989 revealed that wildlife submissions have increased (annual mean 12,583 vs 19,395), and are accompanied by a significant improvement in release (50.2% in the study period vs 44.4% in 1989) (χ²(1) = 90.43, p < 0.0001). In this manuscript, we aim to describe the rehabilitator community in New York State, and present the causes and outcomes for rehabilitation over a three-year period.

A RETROSPECTIVE STUDY OF FEMORAL FRACTURES IN WILD BIRDS OF PREY: 119 CASES

A retrospective study was performed to describe patient and fracture characteristics, treatments, complications, and outcomes associated with femoral fractures in free-ranging birds of prey. Cases were identified from the electronic database and included raptors admitted with femoral fractures at the Bird of Prey Clinic of the Université de Montréal, from 1986 to 2018. In total, 119 individuals from 24 species, with 123 femoral fractures, were included in the study. Twenty-seven birds (23%) were declared dead upon arrival. Ninety-two birds (77%) were admitted alive; 80 with acute fractures and 12 with a fracture that had already healed. A conservative treatment (cage rest) was used to manage eight fractures. Surgical repair was attempted on 34 femoral fractures in 33 birds. An intramedullary pin alone was used in 28 cases (82%), and an external skeletal fixator-intramedullary pin tie-in fixator was used in 6 cases (18%). For surgically treated fractures, 19 healed (in 18 birds), 4 did not heal, and 11 birds died or were euthanized before healing could be achieved. Of the 23/34 fractures where the healing process could be assessed, healing rate for comminuted fractures (11/23) was 91% (10/11). Surgical complications occurred in 10 cases (including 7 cases of migration and loosening of the pin, and 1 case of osteomyelitis), leading to euthanasia in 4 cases. Out of the 21 birds with acute femoral fracture upon presentation that were released, 14 had received a surgical treatment and 7 had received a conservative treatment. Nine of the 21 released birds (43%) had at least one other fractured bone. The majority of deaths and euthanasia occurred within 2 wk after admission (51/59; 86%). Thirteen birds were euthanized primarily because of their femoral fracture. Thirteen birds died in treatment and 33 were deemed nonreleasable and euthanized because of a comorbidity not related to the femoral fracture.

Pilot Study: Correlation of the Surface Skin Temperature Between the Leg and Foot Using Thermographic Imaging in Captive Hawks

The purpose of this study was to determine whether the thermal image temperatures of the tibiotarsal scaled region of the raptor leg and the plantar surface of ipsilateral foot while perching were correlated. The correlation between leg and foot temperature was sought to determine whether remote imaging of the legs can be used as a reliable predictor of foot temperature. The right and left tarsometatarsal region (Leg) and metatarsal pad (Foot) of 10 captive hawks, including 8 red-tailed hawks (Buteo jamaicensis), 1 Harris's hawk (Parabuteo unicinctus), and 1 Swainson's hawk (Buteo swainsoni) were imaged once daily over 3 consecutive days. To account for conditions of the metatarsal pad that might affect the thermal image, 3 groups were identified: Normal, Active when mild hyperemia was present, and Suspect when abrasions were noted. A significant correlation was evident when thermography readings of the tarsometatarsal region (R.Leg and L.Leg) of the unrestrained bird were compared with readings from the plantar surface of the ipsilateral metatarsal pad when restrained (R.Foot and L.Foot). The correlations for R.Leg versus R.Foot (r = 0.81) and L.Leg versus L.Foot (r = 0.74) suggest that temperatures of the tarsometatarsal region of perching hawks measured by infrared thermography may be useful to screen and monitor for the presence of thermal changes associated with inflammation of the metatarsal pad in captive hawk species.

Effects of Perching Surfaces and Foot Bandaging on Central Metatarsal Foot Pad Weight Loading of the Peregrine Falcon (Falco peregrinus)

Pododermatitis is prevalent in falcons and is characterized by inflammation and infection of the plantar aspect of the feet, particularly at the central metatarsal pad. Suboptimal perch design and increased weight loading on the plantar skin have been proposed as major risk factors for the development of pododermatitis. Prevention and treatment are challenging, but weight load reduction on the affected area of the foot is an accepted goal of initial treatment. To date, to our knowledge no studies have compared the performance of different bandage-perch surface combinations on weight redistribution away from the central metatarsal pad. An ex vivo factorial experiment was designed using the feet from a peregrine falcon cadaver to quantify weight load reduction on the central metatarsal pad with different combinations of perch surfaces (wood, neoprene, artificial turf) and bandages (none, interdigital, silicone shoe). Feet were attached to a digital force gauge mounted on a manual test stand for compression testing. Weight loading at the central metatarsal pad was measured using a small force sensor. Perch-surface combinations in randomized order were tested at 250 g, 500 g, and 1 kg with 9 replicates per foot. At 250 g, all combinations reduced measured metatarsal pad forces, but otherwise performed similarly. As compression forces increased, differences emerged with the shoe combinations performing better overall, followed by a group including the neoprene and artificial turf-interdigital bandage combinations, and a third group including the interdigital/wood and no bandage-artificial turf. All combinations performed better than control (no bandage on wood). This study may assist veterinarians in selecting appropriate perching surface/bandage combinations when treating falcons with pododermatitis.

Squamous cell carcinoma of the footpad with systemic metastasis in a captive crowned solitary eagle (Buteogallus coronatus)

Squamous cell carcinomas (SCC) are one of the most common tumors of the tegument that can have a misdiagnosis of chronic skin wounds. An adult captive crowned solitary eagle presented an indolent wound-like ulcer on the footpad and a fatal outcome. An infiltrating tumoral mass in the foot and multiple tumoral metastatic nodules in visceral organs were detected. The neoplasm was composed of atypical squamous cells with strong positivity for cytokeratin, “keratin pearl” structures, and marked invasion of tissues confirming a diagnosis of metastatic SCC. This might be the first report of an SSC with metastasis on the footpad in a captive Chaco eagle, which is one of the endangered species of birds of prey.

Pododermatitis in raptors admitted in a wildlife rehabilitation centre in central spain

Pododermatitis is a chronic and progressive bacterial infectious disease of birds´ footpads, especially associated with captivity, which could represent an important problem in wildlife rehabilitation centres, delaying the release of the birds to the environment and harming their conservation. The objectives of the present study were i) to estimate the incidence rate of pododermatitis, ii) to analyse the influence of environmental, physiological, and pathological factors which may influence the onset of the infection in raptors after their admission to a rehabilitation centre, and iii) to follow up the evolution and macroscopic characteristics of the lesion. An observational retrospective study was carried out on clinical cases of raptors (n = 2004) admitted in a rehabilitation centre in central Spain from 2009 to 2015. The proportion of pododermatitis was 6.9%, with an incidence density of 6.8 cases/100 bird-years at risk. Our results showed that the disease was more likely to occur in birds staying longer (P < 0.001). According to Cox analysis, the variables 'raptor family' (P < 0.001) and 'age' (P = 0.002) may have significant effects on pododermatitis development. Raptors from the Falconidae and Strigidae families were less likely to develop pododermatitis than those from the Accipitridae family, with a hazard ratio (HR) of 0.31 and 0.13, respectively. Regarding age, fully feathered raptors had a three-fold higher risk of having pododermatitis than non-fully feathered birds. Survival analysis of time of pododermatitis development revealed significant differences associated with the variables 'raptor family' (P < 0.03); 'age' (P < 0.001) and 'cause of admission' (P = 0.001). Duration of the pathology (P < 0.05) and lesion location (P < 0.001) seemed to be phylogenetic dependent. Injuries were primarily located in the toes area or the whole footpad of birds belonging to the Accipitridae or Falconidae families, respectively (P = 0.003).

Advancement flap as a novel treatment for a pododermatitis lesion in a red-tailed hawk (Buteo jamaicensis)

Pododermatitis is a pathologic condition commonly reported in captive raptors and characterized by swelling, excoriation, ulceration, cellulitis, or abscessation of the plantar aspect of the foot. Its cause can be multifactorial, often involving abnormal weight bearing or poor sanitation, and medical and surgical techniques, in addition to environmental alterations, are hallmarks of treatment. In this case, a single pedicle advancement flap was used to treat chronic, nonresponsive grade V/VII pododermatitis of the right metatarsal pad in a red-tailed hawk (Buteo jamaicensis). The advancement flap was formed by using the interdigital skin between digits 3 and 4. The double layer of skin was incised and separated, and the leading edge of the flap was then advanced over the defect and secured with simple interrupted subcutaneous and skin sutures. The foot was bandaged after surgery to take pressure off the surgical site. At 58 days after the surgery, the hawk was deemed medically sound with no signs of pododermatitis and was released to a wildlife rehabilitator. The use of a single pedicle advancement flap has not previously been reported for the treatment of pododermatitis.

Effects of feeding enrichment on the behaviour and welfare of captive Waldrapps (Northern bald ibis) (Geronticus eremita)

One of the contributing factors leading to the development of serious foot problems such as bumblefoot (pododermatitis) in captive birds is an abnormally sedentary lifestyle. This study investigated the effects of feeding enrichment on the activity levels of a captive colony of seven Waldrapps or Northern bald ibis (Geronticus eremita) at Tilgate Nature Centre in Sussex. After the introduction of a simple and inexpensive feeding enrichment device, the proportion of time the ibis spent inactive on perches was significantly reduced, with a corresponding increase in the proportion of time allocated to active behaviours such as walking, flying and foraging on the ground. Feeding enrichment, over the longer term, also resulted in a significant reduction in levels of aggression between individuals within the colony. The scope of this study is limited by the relatively small sample size, but nevertheless the findings suggest that the use of feeding enrichment for captive Waldrapp ibis has a number of beneficial effects.

A possible relationship between bumblefoot responsive to potassium arsenite and micrococci in the blood of three birds of prey

Pododermatitis (bumblefoot) is a major health problem of falcons world-wide because healing processes in the talons are difficult and lengthy. A peregrine (Falco peregrinus), a merlin (Falco columbarius) and a saker falcon (Falco cherrug) with bumblefoot at different stages ranging from III to V, were all found to be carriers of micrococcus-like organisms in the blood and two of them were successfully treated with 0.5% potassium arsenite in low dosage given intravenously. A number of considerations are made on the immune dysfunction aspects of bumblefoot in birds of prey and on the emerging role of arsenic-based medicaments in the treatment of animal and human immune dysfunction syndromes.