Degenerative myelopathy and vitamin A deficiency in a young black-maned lion (Panthera leo)

Spinal disease in a captive population of Panthera species: Review of 86 cases (2003-2021)

This retrospective study aimed to characterize and determine the prevalence of spinal disease in nondomestic felids within a sanctuary population. A review of 304 postmortem examination reports in Panthera species from 2003 to 2021 revealed that 86/304 (28%) were diagnosed with spinal disease. Spinal lesions were categorized according to pathologic process: degenerative (78/86, 91%), developmental (8/86, 9%), inflammatory (6/86, 7%), or neoplastic (8/86, 9%). Degenerative lesions included intervertebral disk disease (IVDD; 66/78, 85%), spondylosis without concurrent IVDD (4/78, 5%), and idiopathic (noncompressive) degenerative myelopathies (8/78, 10%). Fourteen individuals had lesions in more than 1 category. Developmental cases were vertebral (4/8) or spinal cord (3/8) malformations or both (1/8). Inflammatory lesions included meningitis (4/6) and meningomyelitis (2/6). Neoplasia included vertebral multiple myeloma (4/8) and others (4/8). IVDD often involved multiple disks but primarily affected the cervical (41/66, 62%) and thoracic spine (32/66, 48%). A multivariate binary logistic model predicted the diagnosis of IVDD at postmortem examination, where odds of being affected were highest for males, lions (Panthera leo), and geriatric age group (>14 years). The spinal lesions documented in this study provide insight into high-risk signalment categories and predominant associated lesions affecting captive Panthera populations. Specifically, spinal disease, especially cervical IVDD, is common among Panthera species, and lions, males, and older felids are at increased risk.

Welfare concerns associated with captive lions (Panthera leo) and the implications for commercial lion farms in South Africa

Breeding and housing wild animals in captive environments can pose challenges for their welfare. In South Africa, thousands of lions (Panthera leo) are bred and raised at commercial captive breeding facilities, so called 'lion farms', for use in tourism, trophy hunting and traditional medicine. To gain a better understanding of the potential welfare challenges faced by lions on farms we reviewed 91 peer-reviewed articles relating to lion welfare, identified via a systematic review of the scientific literature. Across these studies, we identified 170 different terms relating to negative behaviours and physical health afflictions. The majority of these terms were associated with disease and injury (124; 73%), followed by negative behaviours (19; 11%), negative mental experiences (15; 9%), nutritional concerns (7; 4%), and environmental challenges or discomfort arising from the animal's surroundings (5; 3%). Of the 91 articles, 32 (35%) focused on data concerning captive lions. Only two studies focused specifically on data obtained from lion farms in South Africa, whilst the remainder reported on data collected from zoos, wildlife parks, sanctuaries, game reserves and private ownership. Our preliminary review of the scientific literature draws attention to some of the challenges associated with caring for lions in captivity, and outlines the potential significance of these welfare challenges for commercial lion farms. Our data highlight the apparent lack of scientific research involving captive lion welfare generally, particularly data collected at commercial breeding facilities in South Africa and the consequences this could have for the welfare of thousands of lions within the industry.

Radiographic analysis of the thickness of the cranial bones in captive compared to wild-living cheetahs and in cheetahs with hypovitaminosis A

Captive cheetahs often demonstrate a high incidence of diseases in which vitamin A imbalances are implicated. These can occur even under controlled and optimised feeding regimens, which is why surveillance of vitamin A status is mandatory in the successful health management of cheetahs. Serum levels of the vitamin do not reflect the true vitamin A status and liver tissue analysis is rather impractical for routine application in large felids. A biomarker for evaluating overt and subclinical vitamin A deficiency in cheetahs is needed. This study evaluates whether increased calvarial bone thickness can be detected on routine skull radiographs of vitamin A deficient cheetahs compared to unaffected animals, and secondly, evaluates whether there is increased bone thickness in clinically sound captive cheetahs in general compared to wild-living controls. Bone thickness in the neuro- and splanchnocranium was measured in 138 skull radiographs. Significant thickening of the parietal bones was found in latero-lateral radiographs of immature cheetahs (< 12 months) with vitamin A deficiency. This finding may allow a presumptive diagnosis of hypovitaminosis A in immature cheetahs. A general difference in skull thickness between free-living and captive cheetahs was not found.

Large felid leucoencephalomyelopathy in a Sumatran tiger (Panthera tigris sumatrae) from an Australian zoo

CASE REPORT

The clinicopathological features of a case consistent with large felid leucoencephalomyelopathy are described in a 19-year-old, zoo-based Sumatran tiger in which degenerative vertebral disease, renal insufficiency, diaphragmatic hernia and cataracts were comorbid. The principal presenting sign was ataxia, with concurrent deterioration of vertebral stiffness and vision loss. Histological features included marked destruction of the white matter, the formation of large, bizarre astrocytes and accumulation of numerous foamy macrophages (gitter cells). Immunohistochemical investigation of reactive astrocytes revealed several different cytoplasmic proteins.

CONCLUSION

This is the first reported case of large felid leucoencephalomyelopathy in Australia.

Leukoencephalomyelopathy of mature captive cheetahs and other large felids: a novel neurodegenerative disease that came and went?

A novel leukoencephalomyelopathy was identified in 73 mature male and female large captive felids between 1994 and 2005. While the majority of identified cases occurred in cheetahs (Acinonyx jubatus), the disease was also found in members of 2 other subfamilies of Felidae: 1 generic tiger (Panthera tigris) and 2 Florida panthers (Puma concolor coryi). The median age at time of death was 12 years, and all but 1 cheetah were housed in the United States. Characteristic clinical history included progressive loss of vision leading to blindness, disorientation, and/or difficulty eating. Neurologic deficits progressed at a variable rate over days to years. Mild to severe bilateral degenerative lesions were present in the cerebral white matter and variably and to a lesser degree in the white matter of the brain stem and spinal cord. Astrocytosis and swelling of myelin sheaths progressed to total white matter degeneration and cavitation. Large, bizarre reactive astrocytes are a consistent histopathologic feature of this condition. The cause of the severe white matter degeneration in these captive felids remains unknown; the lesions were not typical of any known neurotoxicoses, direct effects of or reactions to infectious diseases, or nutritional deficiencies. Leukoencephalomyelopathy was identified in 70 cheetahs, 1 tiger, and 2 panthers over an 11-year period, and to our knowledge, cases have ceased without planned intervention. Given what is known about the epidemiology of the disease and morphology of the lesions, an environmental or husbandry-associated source of neurotoxicity is suspected.

Vitamin A deficiency and hepatic retinol levels in sea otters, Enhydra lutris

Vitamin A deficiency has rarely been reported in captive or free-ranging wildlife species. Necropsy findings in two captively housed southern sea otters (Enhydra lutris nereis) included irregular thickening of the calvaria characterized by diffuse hyperostoses on the internal surface. One animal also had moderate squamous metaplasia of the seromucinous glands of the nose. There was no measurable retinol in the liver of either sea otter. For comparison, hepatic retinol concentration was determined for 23 deceased free-ranging southern and northern (Enhydra lutris kenyoni) sea otters from California and Alaska. Free-ranging otters were found to have similar hepatic retinol concentrations (316 +/- 245 mg/kg wet weight) regardless of their location and subspecies. All of these values were significantly higher than the levels in the affected animals. Consumption of a diet with very low vitamin A concentrations and noncompliance in daily supplementation are hypothesized as the causes of vitamin A deficiency in these two sea otters.

Needle biopsy for hepatic vitamin A levels in lions (Panthera leo)

Hypovitaminosis A (HA)-related skull malformations resulting in neurologic abnormalities and death have been, and still are, reported in captive lions (Panthera leo) worldwide. Liver vitamin A (VA) concentration is the most reliable indicator of animals' VA status, and its assessment is essential in prevention and treatment of HA in lions. A percutaneous needle liver biopsy using high-performance liquid chromatography ultraviolet retinoid analysis for VA concentration measurement was validated. It was first assessed in vitro using chicken liver. Later, the safety and feasibility of ultrasound-guided percutaneous needle liver biopsy was assessed in living lions. Hepatic VA concentrations in lion liver were measured using the above laboratory method. Mean chicken hepatic VA concentration in needle biopsy (NB) and wedge biopsy (WB) of the same liver lobes were 108.66 and 60.89 microg/g wet tissue, respectively, and were significantly (P = 0.03) correlated (r = 0.74). The calculated linear regression for predicting VA concentration in WB using NB VA for chicken liver was 25.194 + 0.3234x NB (microg/g). Four ultrasound-guided percutaneous needle liver biopsies were obtained from each of the four lions under general anesthesia. Mean hepatic VA concentration was 8.25 microg/g wet tissue (range 1.43-25.29 microg/g). Mean serum VA concentration, measured in these four lions was 1,011.1 nmol/L with a standard deviation of 337.91 nmol/L (range 590.26-1,077.2 nmol/L). The lions recovered uneventfully, and no complications were observed during a 4-yr follow-up period. In conclusion, the percutaneous needle liver biopsy technique is a reliable, practical, safe tool for obtaining liver tissue samples antemortem for assessment of the VA status in lions and can be used in future studies.

Serum vitamin A concentrations in captive sea otters (Enhydra lutris)

Individual dietary preferences and difficulty with animal training create challenges and nutritional concerns when evaluating a captive sea otter (Enhydra lutris) diet. The importance of vitamin A within the body reflects the necessity that it be ingested in adequate amounts to ensure optimal health. To compare levels of serum vitamin A concentrations from captive sea otters on daily oral vitamin A supplementation, serum samples from eight adult sea otters from three institutions were evaluated for serum vitamin A concentrations. The eight animals were fed a total of four different diets and received oral supplementation via three different methods. Multiple diet items were analyzed for vitamin A content and were found to have low to nondetectable levels of vitamin A. Oral vitamin A supplementation, as a slurry with dietary items, was shown to be effective and a mean serum concentration of approximately 170 +/- 51 microg/L was obtained for serum vitamin A concentrations in captive sea otters. Captive diets can be modified to increase vitamin A concentration and supplementation and, if accepted, can be used as a means to ensure adequate vitamin A intake.

The experimental induction of leukoencephalomyelopathy in cats

Leukoencephalomyelopathy of undetermined etiology has been described in specific pathogen-free cats. A study was established to assess if the long-term feeding of a gamma-irradiated diet could induce this disease. Cats fed exclusively on diet irradiated at 25.7-38.1 kGy ("typical" dose) and 38.1-53.6 kGy (high-end dose), respectively, developed typical lesions with attendant, progressively severe ataxia between study days 140 and 174. The onset of ataxia at day 140 and the number of animals affected at this time were similar in animals fed each ration. A maximum ataxia "score" was first reached by an animal on the high-end dose diet on day 167 and by 2 cats fed the "typical-end" dose diet 21 days later. Ataxic cats and 1 animal euthanized on day 93 prior to the onset of ataxia exhibited varying degrees of Wallerian degeneration in the spinal cord and brain, similar to the spontaneous disease. The elevated total antioxidant status of spinal cord segments and hepatic superoxide dismutase concentration of cats fed typical and high-end treated diets suggested free-radical involvement in the pathogenesis. The significantly elevated peroxide concentrations of the irradiated diets (1,040% and 6,440% of untreated values) may have resulted in increased oxidative insult, a factor possibly exacerbated by the treated diets' reduced vitamin A content. This study has reproduced leukoencephalomyelopathy in cats similar to spontaneous outbreaks by feeding a gamma-irradiated dry diet with elevated peroxide and reduced vitamin A concentrations.

Leukoencephalomyelopathy in specific pathogen-free cats

Investigations were carried out on 8 specific pathogen-free cats (5 male and 3 female) from a colony experiencing "outbreaks" of progressive hind limb ataxia in 190 of 540 at-risk animals ranging from 3 months to 3 years old. These studies identified moderate to severe bilateral axonal degeneration within white matter regions of the cervical, thoracic, and lumbar spinal cord and in the white matter of the cerebral internal capsule and peduncle, in the roof of the fourth ventricle and inferior cerebellar peduncle, and in the external arcuate and pyramidal fibres of the medulla. There were varying degrees of accompanying microgliosis, astrocytosis, and capillary hyperplasia. Such a clinicopathologic syndrome, termed feline leukoencephalomyelopathy, has previously been described in cat colonies in Britain and New Zealand, although its etiology has not been determined. The degenerative nature of the lesions and their bilateral distribution suggest possible nutritional, metabolic, or toxic causes. Although these findings provide circumstantial evidence that the exclusive feeding of a gamma-irradiated diet of reduced vitamin A content is associated with the development of the neuronal lesions, further tissue micronutrient and antioxidant analysis will be required to support this hypothesis.