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.

Acid-base balance and ventilation during sternal and lateral recumbency in field immobilized black rhinoceros (Diceros bicornis) receiving oxygen insufflation: a preliminary report.

Posture, ventilation, and acid-base balance using auricular venous blood values (pH, lactate, base excess [BE], HCO(3)(-), PO(2), SO(2), and PCO(2)), oxygen saturation of hemoglobin (SpO(2)), and end-tidal carbon dioxide (P(ET)CO(2)) were compared between sternal (STE) and lateral (LAT) recumbency in free-ranging black rhinoceros (Diceros bicornis bicornis) receiving oxygen insufflation. Data are reported as median, minimum, and maximum (median [minimum, maximum]). Thirty-six desert-adapted black rhinoceros (20 male, 16 female; age 8 [1.5, 33] yr) were immobilized in Namibia in March and April of 2008, from a helicopter, by remote intramuscular injection with etorphine HCl, azaperone, and hyaluronidase. Time from darting to recumbency was 6.0 (3, 15.5) min. Data were organized into two sampling periods: sample period 1 (P1, collected within 0-20 min postdarting; 13 [6.5, 19] min) and sample period 2 (P2, collected between 20-40 min postdarting; 32 [22.3, 39] min). All animals were acidemic (pH 7.24 [7.07, 7.32]) and hypoxemic (PO(2) 51 [38, 95.2]; SO(2) 78 [64, 96] mmHg) after capture. Lactate at P1 was 7.2 (3.2, 16.8) mmol/l and decreased (P=0.01) to 4.6 (1.2, 10.9) mmol/l at P2. At P2, lactate was less (P=0.06) in LAT 3.5 (1.2, 8.6) mmol/l than in STE posture 7.4 (3.1, 10.9) mmol/l. In P2, PO(2), SO(2), and SpO(2) were higher (P=0.02, 0.10, and 0.01, respectively) in STE than in LAT. End-tidal carbon dioxide in LAT was 38 (26, 47) mmHg and increased (P<0.001) rapidly to 48 (37, 55) mmHg when animals were moved into STE; no corresponding change in PCO(2) was observed. These preliminary findings suggest that STE posture in recumbent black rhinoceros reduces dead-space ventilation and improves oxygenation. Lateral posture was associated with lower blood lactate, quicker lactate recovery, or both. It is possible that the posture of recumbent rhinoceros after capture affects lactate accumulation and clearance, or both, and procedures should consider positioning in order to enhance perfusion.

Ultrasonographic characterization of ovarian events and fetal gestational parameters in two southern black rhinoceros (Diceros bicornis minor) and correlation to fecal progesterone.

A tremendous potential exists for the application of transrectal ultrasonography as a tool to enhance the captive management of endangered species. Reproductive study of two southern black rhinoceros (Diceros bicornis minor) females was performed daily to every other day for a approximately 60 day period to document ovarian changes, and three times weekly in early pregnancy to once monthly in late pregnancy in order to characterize changes in fetal parameters throughout gestation. All ovarian and fetal anatomical structures were measured in millimeters. The mean (+/- SD) length of the estrous cycle or interovulatory period was 26 +/- 1.4 days (n=2 cycles). Follicular growth rate of a dominant follicle was approximately 3 mm/day once the follicle reached 35 mm in diameter. Ovulation was observed to occur at a mean (+/- SD) follicular diameter of 49.5 +/- 2.6 mm (n=4) and within 48 to 72 h after observed estrus (n=2). Large ovarian structures [mean (+/- SD) diameter of 71.7 +/- 2.9 mm; n=3], considered analogous to equine anovulatory hemorrhagic follicles, were observed to form in the winter months and suggest seasonal periods of reduced fertility. Fecal progesterone assays confirmed ultrasonographic events. Although preliminary, the results of fetal sexing are presented and compared to the horse. Our data indicate that fetal eye or fetal foot diameter measurements can be used to accurately predict gestational age from about 2 months to term, providing useful information to managers of both captive and wild rhino populations. The ability to identify and quickly release animals in late term pregnancy in the wild and thereby reduce-abortions and neonatal mortalities in holding bomas is one potential practical conservation benefit of the fetal age predictive models.

Butorphanol and azaperone as a safe alternative for repeated chemical restraint in captive white rhinoceros (Ceratotherium simum).

Anesthesia in the white rhinoceros (Ceratotherium simum) has routinely involved potent narcotic anesthetic agents such as etorphine or carfentanil with their associated adverse side effects. In captive rhinoceroses conditioned to routine handling, a combination of butorphanol and azaperone at mean (+/- SD) doses of 69.3 +/- 18.0 mg and 103.1 +/- 20.9 mg, respectively, was used to produce levels of neuroleptanalgesia ranging from light "standing" sedation to deeper planes of anesthesia producing sternal and lateral recumbency. This combination was used for repeated (minimum repeat frequency of 3 days between events) anesthetic episodes (n = 26) in two animals, with the remaining episode performed in a white rhinoceros with chronic renal disease. The action of butorphanol was satisfactorily reversed with naltrexone (125 mg i.v. and 125 mg i.m.). Results (mean +/- SD) include sternal recumbency achieved in 14.1 +/- 8.1 min after i.m. dosing, standing and ambulation occurred in 1.7 +/- 0.6 min after reversal, heart rate was 62.0 +/- 10.1 beats/min, respiratory rate was 14.7 +/- 5.6 breaths/min, and percentage of oxygen saturation of hemoglobin (Spo2) was 89.2 +/- 3.0%. Without supplementation, the total elapsed time ranged from 44.9 min to 103.0 min, whereas elapsed times up to 214.3 min were achieved with supplementation (mean time to supplementation was 28.0 +/- 13.9 min after initial dosing). Butorphanol and azaperone produced adequate muscle relaxation and apparently adequate analgesia for minor surgical interferences, including abdominal laparoscopy. Respiratory rates and Spo2 measurements were improved compared with reports of using more potent opioids in this species.

Standing laparoscopic-guided uterine biopsy in a southern white rhinoceros (Ceratotherium simum simum).

Transrectal ultrasonography of a 35-yr-old captive female southern white rhinoceros (Ceratotherium simum simum) with a history of chronic mucohemorrhagic vulvar discharge revealed right transmural uterine horn enlargement. Abdominal laparoscopic surgery, although extremely difficult because of inadequate instrumentation, permitted uterine visualization and biopsy. Standing anesthesia, incorporating butorphanol and azaperone together with local anesthetic infiltration, facilitated the laparoscopy. A leiomyoma was suspected on the basis of history, physical examination, ultrasonographic appearance, and histopathology. Prior rhinoceros laparoscopies have failed, primarily from limitations imposed by recumbency.

Bilateral aural hyalohyphomycosis in sable antelope (Hippotragus niger).

Three juvenile sable antelope (Hippotragus niger) were diagnosed with bilateral aural hyalohyphomycosis based on histopathology. All three animals were suspected to be immunodeficient based on low IgG levels determined using the zinc sulfate turbidity test. The serum and hepatic copper levels of one animal were below the bovine reference range. Clinical signs in the three animals included bilateral ventral deviation of the pinnae with multifocal subcutaneous aural tumefaction and poor body condition. Numerous septate, nonpigmented fungal hyphae were found within the auricular cartilage, dermis, and subcutaneous granulomas. No significant fungal agents were isolated by culture, and no signs of systemic fungal dissemination were identified except for a concurrent fungal rhinitis in one animal.

Acute lymphoblastic leukemia in a juvenile southern black rhinoceros (Diceros bicornis minor).

A 21-mo-old female southern black rhinoceros (Diceros bicornis minor) developed acute upper respiratory dyspnea in association with lymphadenopathy and marked immature lymphocytosis. A diagnosis of acute lymphoblastic leukemia was reached on the basis of the morphologic and cytochemical characteristics of peripheral lymphoblasts. Antineoplastic chemotherapy included administration of cytarabine, cyclophosphamide, vincristine, and doxorubicin, with clinical remission achieved 19 days after initiation of treatment. The rhinoceros died, however, of congestive heart failure, presumably secondary to doxorubicin cardiotoxicity and a particular sensitivity of rhinoceros myocardial tissue to free hydroxyl radicals. The pharmacologic effects of any therapeutic agent need to be carefully considered before use in the black rhinoceros, especially within the context of the unique physiology of this species.

Anthracycline cardiotoxicity in a black rhinoceros (Diceros bicornis): evidence for impaired antioxidant capacity compounded by iron overload.

Two weeks before dying of congestive heart failure, a juvenile black rhinoceros (Diceros bicornis minor) received a single low dose of doxorubicin as part of combination chemotherapy for acute lymphoblastic leukemia. Diffuse hemosiderosis was present at necropsy in a pattern indicative of dietary iron overload, but unique iron-positive degenerative lesions were found in isolated myocardiocytes. Serum analyses revealed hyperferremia, 87% transferrin saturation, and 5- to 10-fold elevations in ferritin concentration, reflecting markedly increased tissue iron stores. Since both toxic and therapeutic effects of anthracyclines are mediated by formation of reactive free radicals via iron-catalyzed reactions, these observations suggest that iron overload may have enhanced myocardial susceptibility to cardiotoxic effects of doxorubicin. Impairments in other myocardial antioxidant defenses, such as deficiencies in catalase and glutathione S-transferase that are known to exist in rhinoceros erythrocytes, may have been underlying factors contributing to an inherent sensitivity of rhinoceros tissues to oxidant-induced injury.

Arthroscopic surgery in a reticulated giraffe (Giraffa camelopardalis reticulata).

An 8-mo-old captive male reticulated giraffe (Giraffa camelopardalis reticulata) developed an acute lameness (grade IV/V) of the right forelimb, with swelling of the metacarpophalangeal joint. A traumatic injury was suspected based on clinical, radiographic, and arthroscopic evaluation. Several abnormalities were identified arthroscopically, including synovitis, cartilage damage, and an osteochondral fragment. Medial collateral ligament damage was also suspected based on radiographic evaluation. Arthroscopy provided a means of diagnosis and treatment of the abnormalities identified. The lameness in this giraffe resolved within 6 wk following arthroscopic surgery.

Idiopathic distal esophageal dilation in a southern black rhinoceros (Diceros bicornis minor).

An adult female southern black rhinoceros (Diceros bicornis minor) experienced intermittent periods of regurgitation while eating, suggesting an esophageal disorder. Endoscopy for evaluation of the trachea, esophagus, and stomach revealed a 30-mm nasopharyngeal orifice with associated recess located in the caudodorsal pharynx and a 10-cm dilated segment of the distal esophagus that was presumably the cause of regurgitation. Dietary management of esophageal dilation through short-term utilization of a "soft feed" program successfully eliminated the regurgitation. This is the first report of esophageal dysfunction in a rhinoceros.