One small step for rhinos, one giant leap for wildlife management--imaging diagnosis of bone pathology in distal limb

CT based 3D reconstruction of the forefoot's blood supply in a white rhinoceros

BACKGROUND

The white rhinoceros (Ceratotherium simum) is close to extinction, listed as "Near Threatened", with a decreasing population on the Red List of Threatened Species of the International Union for Conservation of Nature. In at least 50% of the specimens in captivity, podiatric diseases, such as osteitis, osteomyelitis, chip fractures, enthesophytes, fractures and osteoarthritis were found during necropsy. These osteal deformations cause further pathogenic alterations in the soft tissues, particularly in the digital cushion. The literature provides good description of the skeleton of the rhino's limbs, but similar for the vascular system is non-existent. In order to recognize the symptoms in an early state and for a successful surgical treatment, precise knowledge of the vascular anatomy is essential. The purpose of our study was to provide detailed anatomical description of the blood supply of the digits and that of the digital cushion.

RESULTS

The blood supply of the distal foot, digits and digital cushions were perfectly visible on the reconstructed and coloured 3D models. The deep palmar arch provided not only the blood supply to the digits but had a palmaro-distal running branch which developed a trifurcation proximal to the proximal sesamoid bones of the third digit. Two of its branches participated in the blood supply of the digits' proximal palmar surface, while the major branch supplied the digital cushion from proximal direction.

CONCLUSIONS

Our findings show a unique blood supply: the main vessels of the digital cushion stem both directly from the deep palmar arch and from the digits' own arteries. The detailed description of vessels may be useful in planning surgery of the region and also in cases where the veins of the ear are not accessible.

Foot shape and radiographs of free-ranging Nubian giraffe in Uganda

Foot health in zoo giraffe has been a topic of recent research, although little is known about the foot health of free-ranging giraffe. This study describes the foot shape and radiographic pathological changes in 27 young adult Nubian giraffe (Giraffa camelopardalis camelopardalis) from a translocation in Uganda (August 2017). Giraffe feet were observed to have a concave sole, the hoof wall was longest by the toe tip, and the weight-bearing surface of the foot was primarily along the periphery of the foot including hoof wall, parts of the heel, and the edge of the sole. Radiographs showed that pedal osteitis and sesamoid bone cysts were relatively uncommon (3/24 giraffe with osteitis, 1/24 giraffe with sesamoid cysts), and that no giraffe in the study had P3 joint osteoarthritis, P3 rotation, or P3 fractures. Radiographs consistently demonstrated a positive palmar/plantar angle with the sole of the hoof thicker at the heel than by the toe tip, with the non weight-bearing palmar/plantar angle measuring 1.6°- 4.3°. This is the first systematic review of foot shape and radiographs in free-ranging giraffe and demonstrates a low prevalence of foot pathologies. This study suggests qualitative differences in foot shape, foot health, radiographic anatomy, and foot pathologies when comparing free-ranging and zoo giraffe. Further research is needed to identify why these differences occur and whether husbandry modifications could help improve zoo giraffe foot health and prevent associated lameness.

Phenylbutazone pharmacokinetics in southern white rhinoceros (Ceratotherium simum simum) after oral administration

Southern white rhinoceros (Ceratotherium simum simum) frequently develop painful conditions, such as traumatic injuries or osteoarthritis, necessitating the administration of pain-relieving medications. One of the preferred treatments is the nonsteroidal anti-inflammatory drug phenylbutazone because of the availability of oral formulations and the familiarity of its use in horses. For the main study, a single oral dose of phenylbutazone at 2 mg/kg was administered to healthy adult rhinoceros (n = 33) housed at six North American zoological institutions. Each rhinoceros had up to four blood samples collected under voluntary behavioural restraint at up to four predetermined time points (0, 1, 1.5, 2, 3, 4, 6, 8, 10, 24, 30 and 48 h). Drug analysis was performed by high-performance liquid chromatography. The population pharmacokinetic parameters were calculated with nonlinear mixed-effects modelling, and analysis showed a peak concentration (C_MAX ) of 3.8 µg/ml at 1.8 h and an elimination half-life of 9 h. The concentrations achieved were similar to what has been reported for horses and were within the half maximal effective concentration for horses for at least 10 h. A multi-dose trial in five rhinoceros receiving 2 mg/kg orally once daily for five days found mild accumulation at a predicted factor of 1.2. This study represents the first pharmacokinetic data of phenylbutazone in any rhinoceros species.

IMPROVED DIAGNOSIS OF FOOT OSTEOARTHRITIS IN ELEPHANTS (ELEPHAS MAXIMUS, LOXODONTA AFRICANA) USING STEREORADIOGRAPHY

Diagnosis of foot disease in elephants is challenging. Owing to their large size, the available diagnostic tools and the expense of imaging are diagnostically limiting. Stereoradiography is the preparation of paired radiographs that form a three-dimensional (3D) image when viewed stereoscopically. Clinicians and veterinary students graded osteoarthritis in the feet of African (Loxodonta africana) and Asian (Elephas maximus) elephants taken postmortem with standard 2D radiographs, as well as 3D stereoradiographs. These gradings were compared with the actual gross pathology identified in the specimens. Although veterinary students diagnoses were no better than chance from 2D radiographs, 83.6% of the students could correctly differentiate severity between joints on stereoradiography; this is an absolute improvement of 30.1% (95% confidence interval [CI] = 19.6%-40.6%). Overall, participants were 27.4% (95% CI = 18.4%-36.3%) more successful at diagnosing pathology on stereoradiographs. Half of participants were shown standard 2D radiographs first, the others stereoradiographs first, but the difference in gradings between the two groups was not statistically significant. Stereoradiography appears to hold the potential to improve diagnosis of osteoarthritis in elephant feet, particularly by less experienced clinicians, and the technique is low-cost and applicable under field conditions.

CLINICAL CONDITIONS FOUND RADIOGRAPHICALLY IN THE FRONT FEET OF RETICULATED GIRAFFE (GIRAFFA CAMELOPARDALIS RETICULATA) IN A SINGLE ZOO

Front foot radiographs from 22 giraffe (Giraffa camelopardalis reticulata) at one zoo were analyzed to better understand causes of lameness in this giraffe population. The herd had a history of front hoof overgrowth and intermittent lameness. Radiographic findings included distal interphalangeal joint osteoarthritis (OA), distal phalangeal bone (P3) osteitis, P3 fractures, P3 rotation, and sesamoid bone cysts. OA of the distal interphalangeal joint occurred in at least one front foot of 73% (16/22 giraffe) of the herd, and all giraffe had OA by 7 yr of age. Pedal osteitis was present in at least one front foot in 86% (19/22) of the giraffe, starting in animals as young as 1 yr old. P3 fractures were present in 36% (8/22) of the herd. These fractures were near the site of the deep digital flexor attachment and were diagnosed in giraffe as young as 10 yr old. The presence of severe osteitis was associated with the presence of P3 fractures. This study is unique in that a large herd was trained to participate in voluntary front foot radiographs so multiple causes of foot disease could be diagnosed antemortem and without anesthesia. Although the underlying causes of these lesions are likely multifactorial and currently unknown to us, the high prevalence of foot disease in relatively young animals warrants further investigation across zoos. In this study, OA, osteitis, and P3 fractures were common radiographic findings among giraffe that were limping. Subsequent monitoring and management changes suggest that proactive management of foot health can decrease morbidity and mortality in zoo giraffe.

Micro-anatomy of the ear of the southern white rhinoceros (Ceratotherium simum simum)

The white rhinoceros is the largest of the five extant rhinoceros species. The population is declining rapidly because of intense poaching. However, normal anatomical descriptions in this species are lacking. The purpose of this study is to describe the osseous anatomy of the middle and inner ear of the southern white rhinoceros using micro-focus X-ray computed tomography imaging. Four temporal bones obtained from two 1-day old southern white rhinoceros preserved in 10% formalin were scanned. Tri-dimensional reconstructions were obtained and volumes of the middle ear ossicles and inner ear structures were calculated. Excellent high spatial resolution 3D images were obtained for all samples and virtual models of the auditory ossicles and bony labyrinth were generated. Visualization of the tympanic membrane, middle ear and inner ear structures was possible in all samples. Whereas the stapes and incus had a shape similar to their human or equine counterparts, the malleus showed a unique appearance with a long rostral branch projecting latero-distally to the manubrium. The cochlea described 2 turns rostro-laterally around its axis, with a medial direction of rotation. However, identification of the soft tissue structures of the middle ear was sometimes difficult and visualization of the small structures of the membranous labyrinth was not possible using this formalin fixation and alternative techniques should be investigated. Further investigations are needed in order to provide a complete virtual model including both soft and bone tissues of this difficultly accessible region.

Biomechanical insights into the role of foot pads during locomotion in camelid species

From the camel’s toes to the horse’s hooves, the diversity in foot morphology among mammals is striking. One distinguishing feature is the presence of fat pads, which may play a role in reducing foot pressures, or may be related to habitat specialization. The camelid family provides a useful paradigm to explore this as within this phylogenetically constrained group we see prominent (camels) and greatly reduced (alpacas) fat pads. We found similar scaling of vertical ground reaction force with body mass, but camels had larger foot contact areas, which increased with velocity, unlike alpacas, meaning camels had relatively lower foot pressures. Further, variation between specific regions under the foot was greater in alpacas than camels. Together, these results provide strong evidence for the role of fat pads in reducing relative peak locomotor foot pressures, suggesting that the fat pad role in habitat specialization remains difficult to disentangle.

Foot pressure distribution in White Rhinoceroses (Ceratotherium simum) during walking

White rhinoceroses (Ceratotherium simum) are odd-toed ungulates that belong to the group Perissodactyla. Being second only to elephants in terms of large body mass amongst extant tetrapods, rhinoceroses make fascinating subjects for the study of how large land animals support and move themselves. Rhinoceroses often are kept in captivity for protection from ivory poachers and for educational/touristic purposes, yet a detrimental side effect of captivity can be foot disease (i.e., enthesopathies and osteoarthritis around the phalanges). Foot diseases in large mammals are multifactorial, but locomotor biomechanics (e.g., pressures routinely experienced by the feet) surely can be a contributing factor. However, due to a lack of in vivo experimental data on rhinoceros foot pressures, our knowledge of locomotor performance and its links to foot disease is limited. The overall aim of this study was to characterize peak pressures and center of pressure trajectories in white rhinoceroses during walking. We asked two major questions. First, are peak locomotor pressures the lowest around the fat pad and its lobes (as in the case of elephants)? Second, are peak locomotor pressures concentrated around the areas with the highest reported incidence of pathologies? Our results show a reduction of pressures around the fat pad and its lobes, which is potentially due to the material properties of the fat pad or a tendency to avoid or limit "heel" contact at impact. We also found an even and gradual concentration of foot pressures across all digits, which may be a by-product of the more horizontal foot roll-off during the stance phase. While our exploratory, descriptive sample precluded hypothesis testing, our study provides important new data on rhinoceros locomotion for future studies to build on, and thus impetus for improved implementation in the care of captive/managed rhinoceroses.

Skeletal pathology and variable anatomy in elephant feet assessed using computed tomography

Foot problems are a major cause of morbidity and mortality in elephants, but are underreported due to difficulties in diagnosis, particularly of conditions affecting the bones and internal structures. Here we evaluate post-mortem computer tomographic (CT) scans of 52 feet from 21 elephants (seven African Loxodonta africana and 14 Asian Elephas maximus), describing both pathology and variant anatomy (including the appearance of phalangeal and sesamoid bones) that could be mistaken for disease. We found all the elephants in our study to have pathology of some type in at least one foot. The most common pathological changes observed were bone remodelling, enthesopathy, osseous cyst-like lesions, and osteoarthritis, with soft tissue mineralisation, osteitis, infectious osteoarthriti, subluxation, fracture and enostoses observed less frequently. Most feet had multiple categories of pathological change (81% with two or more diagnoses, versus 10% with a single diagnosis, and 9% without significant pathology). Much of the pathological change was focused over the middle/lateral digits, which bear most weight and experience high peak pressures during walking. We found remodelling and osteoarthritis to be correlated with increasing age, more enthesopathy in Asian elephants, and more cyst-like lesions in females. We also observed multipartite, missing and misshapen phalanges as common and apparently incidental findings. The proximal (paired) sesamoids can appear fused or absent, and the predigits (radial/tibial sesamoids) can be variably ossified, though are significantly more ossified in Asian elephants. Our study reinforces the need for regular examination and radiography of elephant feet to monitor for pathology and as a tool for improving welfare.

SOLITARY OSTEOCHONDROMA OF THE DISTAL THIRD METACARPAL BONE IN A TWO-YEAR-OLD WHITE RHINOCEROS (CERATOTHERIUM SIMUM)

A privately owned, 2-yr-old, 600-kg, intact male white rhinoceros presented with a progressive lameness of the left front limb of 8-mo duration with a focal swelling situated over the dorsoproximal aspect of third metacarpophalangeal joint. Radiographs of the affected limb showed a 28 mm × 26 mm exostosis at the dorsodistal third metacarpal bone. Surgical removal of the exostosis was performed and histopathologic examination confirmed a solitary osteochondroma. A follow-up examination 1 yr after surgical removal revealed total abolishment of the left front limb lameness. This report documents the first diagnosis and treatment of solitary osteochondroma in a white rhinoceros.

CLINICAL MANAGEMENT OF BILATERAL CUTANEOUS SQUAMOUS CELL CARCINOMA OF THE HIND FEET PADS IN A SOUTHERN WHITE RHINOCEROS (CERATOTHERIUM SIMUM SIMUM)

The current report describes the temporary regression, due to intensive symptomatic treatment, of ulcerative skin lesions caused by squamous cell carcinoma in a white rhinoceros. A captive, 40-yr-old southern white rhinoceros (Ceratotherium simum simum) developed profound, ulcerative skin lesions on the pads of both hind feet. At the peak of the disease, at least one quarter of the pads was affected. A diagnosis of squamous cell carcinoma was made via biopsy. Treatment included anti-inflammatory drugs, antibiotics, and local care. The lesions regressed on both feet until they seemed clinically healed. It was presumed that long-term, anti-inflammatory treatment and local bandaging had induced the temporary regression of the lesions. Two years later, however, a small ulcerative lesion reappeared on one pad and post mortem examination confirmed that the carcinoma was also histologically present in the clinically intact tissue. No metastasis was found and computed tomography showed normal digital bones.

Osteopathology in Rhinocerotidae from 50 Million Years to the Present

Individual elements of many extinct and extant North American rhinocerotids display osteopathologies, particularly exostoses, abnormal textures, and joint margin porosity, that are commonly associated with localized bone trauma. When we evaluated six extinct rhinocerotid species spanning 50 million years (Ma), we found the incidence of osteopathology increases from 28% of all elements of Eocene Hyrachyus eximius to 65-80% of all elements in more derived species. The only extant species in this study, Diceros bicornis, displayed less osteopathologies (50%) than the more derived extinct taxa. To get a finer-grained picture, we scored each fossil for seven pathological indicators on a scale of 1-4. We estimated the average mass of each taxon using M1-3 length and compared mass to average pathological score for each category. We found that with increasing mass, osteopathology also significantly increases. We then ran a phylogenetically-controlled regression analysis using a time-calibrated phylogeny of our study taxa. Mass estimates were found to significantly covary with abnormal foramen shape and abnormal bone textures. This pattern in osteopathological expression may reflect a part of the complex system of adaptations in the Rhinocerotidae over millions of years, where increased mass, cursoriality, and/or increased life span are selected for, to the detriment of long-term bone health. This work has important implications for the future health of hoofed animals and humans alike.

Rhinoceros feet step out of a rule-of-thumb: a wildlife imaging pioneering approach of synchronized computed tomography-digital radiography

Currently, radiography is the only imaging technique used to diagnose bone pathology in wild animals situated under “field conditions”. Nevertheless, while chronic foot disease in captive mega-herbivores is widely reported, foot radiographic imaging is confronted with scarcity of studies. Numerous hindrances lead to such limited numbers and it became very clear that the traditional perspective on bone imaging in domestic animals based on extensive studies and elaborated statistical evaluations cannot be extrapolated to their non-domestic relatives. For these reasons, the authors initiated a multi-modality imaging study and established a pioneering approach of synchronized computed tomography (CT) and digital radiography (DR), based on X-ray projections derived from three-dimensional CT reconstructed images. Whereas this approach can be applied in any clinical field, as a case of outstanding importance and great concern for zoological institutions, we selected foot bone pathologies in captive rhinoceroses to demonstrate the manifold applications of the method. Several advances were achieved, endowing the wildlife clinician with all-important tools: prototype DR exposure protocols and a modus operandi for foot positioning, advancing both traditional projections and, for the first-time, species-related radiographic views; assessment of radiographic diagnostic value for the whole foot and, in premiere, for each autopodial bone; together with additional insights into radiographic appearance of bone anatomy and pathology with a unique, simultaneous CT-DR correlation. Based on its main advantages in availing a wide range of keystone data in wildlife imaging from a limited number of examined subjects and combining advantages of CT as the golden standard method for bone diseases' diagnostic with DR's clinical feasibility under field conditions, synchronized CT-DR presents a new perspective on wildlife's health management. With this we hope to provide veterinary clinicians with concrete imaging techniques and substantial diagnostic tools, which facilitate straightforward attainment and interpretation of field radiography images taken worldwide.

Reproductive tract tumours: the scourge of woman reproduction ails Indian rhinoceroses

In Indian rhinoceros, extensive leiomyoma, a benign smooth muscle tumour, was sporadically diagnosed post mortem and commonly thought of as contributing factor for reduced fecundity of this species in captivity. However, to date, the prevalence of reproductive tract tumours and their relevance for fecundity are unknown. Our analysis of the international studbook now reveals that females cease reproducing at the age of 18.1±1.2 years; equivalent to a reproductive lifespan of just 9.5±1.3 years. This short reproductive life is in sharp contrast to their longevity in captivity of over 40 years. Here we show, after examining 42% of the captive female population, that age-related genital tract tumours are highly prevalent in this endangered species. Growth and development of these tumours was found to be age-related, starting from the age of 10 years. All females older than 12 years had developed genital tumours, just 7–9 years past maturity. Tumour sizes ranged from 1.5–10 cm. With age, tumours became more numerous, sometimes merging into one large diffuse tumour mass. These tumours, primarily vaginal and cervical, presumably cause widespread young-age infertility by the age of 18 years. In few cases, tumour necrosis suggested possible malignancy of tumours. Possible consequences of such genital tract tumour infestation are hindered intromission, pain during mating, hampered sperm passage, risk of ascending infection during pregnancy, dystocia, or chronic vaginal bleeding. In humans, leiomyoma affect up to 80% of pre-menopause women. While a leading cause for infertility, pregnancy is known to reduce the risk of tumour development. However, different from human, surgical intervention is not a viable treatment option in rhinoceroses. Thus, in analogy to humans, we suggest early onset and seamless consecutive pregnancies to help reduce prevalence of this disease, better maintain a self-sustained captive population and improve animal welfare.

One small step for rhinos, one giant leap for wildlife management--imaging diagnosis of bone pathology in distal limb

Chronic foot disease poses a threat to the general health, represents a tremendous clinical challenge, and often is a reason for euthanasia in captive megaherbivores, among them the elephant and rhinoceros. Nevertheless, apart from the elephant, foot pathology is handled as being confined only to soft tissues whereas bone pathology is often overlooked. As a case in point, the authors selected the second largest mammal on land, the rhinoceros. We performed a computed tomographic (CT) study using the highest resolution available in veterinary world, followed by digital radiography of eight distal limbs from two white and one Indian rhinoceroses. Our study demonstrated that bone pathology in rhinoceroses’ foot is present and in large numbers, yet none of these were diagnosed ante mortem. Even when the animals were euthanized due to foot problems, the decision was based on soft tissue pathology rather than orthopedic reasons. Even more worrying is the fact that the largest number of osteopathologies was present in one of the white rhinoceroses that showed no discernable related clinical signs. This study describes for the first time the existence of bone pathology in white rhinoceros foot, in addition to the two previously described rhinoceros species - Indian and black rhinoceroses. Furthermore, the chronic foot disease reported for the Indian rhinoceros in our study was not restricted to soft tissue structures as was presumed ante mortem but included severe bone pathology. New evidence suggesting that osteopathology in rhinoceroses’ distal limb is more widespread than it was thought before could force us to rethink of radiographic diagnosis in captive megaherbivores as routine examination incorporated into their health management. The anticipated improvements in radiologic examinations in megaherbivores will increase the effectiveness of their management and husbandry and open the way for improved animal welfare and better wildlife conservation.