One Small Step for Rhinos, One Giant Leap for Wildlife Management- Imaging Diagnosis of Bone Pathology in Distal Limb

Abstract

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.

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

“…But animal models show that enthesopathy can also occur without tendon microtears or inflammation and may be an adaptive response to loading (Benjamin, Rufai & Ralphs, 2000). Remodelling and enthesopathy are both frequently observed in rhinos and thought to reflect tissue loading (Regnault et al, 2013; Galateanu et al, 2013; Stilson, Hopkins & Davis, 2016). The linear appearance and the location of soft tissue mineralisation in our elephants suggest that the digital flexor tendons are the affected structures.…”

“…Over the recent years advanced imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) have been more commonly used in veterinary practice for musculoskeletal and other problems, but their use for elephants is precluded by body size and transport issues. As a result of the limited availability of imaging, the frequencies of these bony conditions in captive elephants are unknown and they are almost certainly under-reported based on what we know in other large animals such as cows (Nigam & Singh, 1980; Kofler, Geissbühler & Steiner, 2014) or rhinoceroses (Regnault et al, 2013; Galateanu et al, 2013). …”

RADIOGRAPHIC PROTOCOL AND NORMAL ANATOMY OF THE HIND FEET IN THE WHITE RHINOCEROS (CERATOTHERIUM SIMUM)

“…The developed protocol focused on all three phalanges of each digit and their associated joints and focused on sites of pathologies previously identified; thus employment of this protocol should increase successful diagnosis of osteopathologies in the pedes of rhinoceroses. The protocol and described anatomy are also relevant for use in radiography of anesthetized rhinoceroses. Anatomical knowledge of rhinoceros feet is currently fairly limited.…”

“…The radiographs were then assessed for diagnostic quality by a large animal veterinary radiology specialist (RW). Assessment criteria focused on visualization of gross anatomic features and visibility of areas where pathology has been previously identified …”

“…The main lesions were enthesiophyte formation, osteoarthritis, remodeling, osteitis/osteomyelitis, fracture, and subluxation . Another recent study found significant bone pathology by CT examination of the cadaver feet of two white and one Indian rhinoceros . None of the lesions were diagnosed ante mortem and in some cases the rhinoceroses were euthanased due to diseases of the soft tissue structures of the foot.…”