Vesicular and Ulcerative Dermatopathy Resembling Superficial Necrolytic Dermatitis in Captive Black Rhinoceroses (Diceros bicornis)

Abstract

The histopathology, clinical presentation, and epidemiology of a cutaneous and oral mucosal disease affecting 40 black rhinoceroses (Diceros bicornis) at 21 zoological parks (50% of the captive US population) were investigated. Twenty-seven biopsies were examined from recent lesions, and clinical information was available from 127 episodes. The cutaneous lesions began as plaques that progressed to vesicles, bullae, or ulcers. Lesions waxed and waned in individual cases. Lesions were predominantly bilaterally symmetrical, affecting pressure points, coronary bands, tips of the ears and tail, and along the lateral body wall and dorsum. Oral lesions were first noticed as ulcers and were present on the lateral margins of the tongue, palate, and mucocutaneous junctions of the lips. All recent lesions had similar histopathologic findings of prominent acanthosis, hydropic degeneration of keratinocytes in the stratum spinosum, spongiosis, intraepithelial vesicles, and parakeratosis without dermal inflammation. Chronic lesions were ulcerated. No pathogens were identified by culture or electron microscopy. Most episodes coincided with stress events (transportation, sudden cold temperatures, intraspecific harassment, estrus, advanced pregnancy) or concurrent diseases (toxic hepatopathy, hemolytic anemia, respiratory or urinary tract infections). Affected rhinoceroses usually were lethargic and had weight loss. Affected rhinoceroses also had lower hematocrit, serum albumin, and cholesterol values than captive healthy or wild rhinoceroses. The clinical patterns and histopathologic findings are similar to those of superficial necrolytic dermatitis in dogs and necrolytic migratory erythema in humans. The high prevalence of this skin disease in captive black rhinoceroses under many circumstances suggests that their epidermis is acutely sensitive to any disruption of metabolic homeostasis. We propose that metabolic changes secondary to a stress response from maladaptation or nutritional inadequacy of captive diets may contribute to the development of this disease in rhinoceroses without hepatopathies.

Hypoaminoacidemia is not Associated with Ulcerative Lesions in Black Rhinoceroses, Diceros bicornis

“…Thus, age-related hepatic pathologies may be responsible for the observed hypoaminoacidemia. 6 By contrast, skin and oral lesions occur in black rhinos of all ages, 14 and, in this study, the animals were 2, 6, 17, and 23 yr of age. Some dogs with SND and humans with necrolytic migratory erythema, a syndrome clinically similar to SND, have hyperglucagonemia secondary to a glucagon-secreting pancreatic tumor.…”

“…A decade ago, ulcerative lesions were described in black rhinos, and it was suggested that they exhibited clinical similarities to SND in domestic dogs. 14 The lesions begin as raised plaques, which progressively lead to vesicles and erosions, and finally to ulcers. Ulcers are usually bilaterally symmetrical and tend to expand peripherally, with most lesions seen on pressure points, such as the back, feet, lateral body wall, tail, head, ears, and vulva and/or prepuce.…”

“…In one report, 23 of 34 affected rhinos had concurrent health conditions, including liver disease, anemia, gastrointestinal diseases, respiratory tract infections, and urinary tract disease. 14 Other associated symptoms can include weight loss, lameness, depression, anorexia, weakness, pregnancy, and estrus and/or breeding. A recent survival analysis performed on 296 of 334 black rhinos (88.6%) in the captive United States population identified that skin lesions were a significant mortality risk.…”

Evidence for Chronic Stress in Captive but Not Free-Ranging Cheetahs (Acinonyx Jubatus) Based on Adrenal Morphology and Function

“…Species survival cannot be assured through captive breeding programs alone because captive cheetahs reproduce poorly and are prone to develop unusual diseases that cause considerable morbidity and mortality (Marker et al, 1989;Munson, 1993;Munson et al, 1999). A reproductive survey of the North American captive cheetah population found that poor fecundity was mainly due to gonadal inactivity.…”

“…Captive cheetahs have a high prevalence of unusual diseases, such as veno-occlusive disease and glomerulosclerosis, that rarely occur in other species (Munson, 1993;Bolton and Munson, 1999). Also, common infectious agents, such as Helicobacter and feline infectious peritonitis (FIP), cause persistent and severe inflammatory disease in cheetahs (Eaton et al, 1993;Munson, 1993).…”