James G. Johnson

Disseminated histoplasmosis (Histoplasma capsulatum) in a pet rabbit: case report and review of the literature

A 2.5-year-old intact male miniature lop rabbit (Oryctolagus cuniculus) was presented with multiple nodules surrounding the eyes, nose, mouth, and prepuce. Cytological evaluation of the periocular nodules revealed the presence of intracellular (within macrophages) and extracellular yeast organisms. The yeast organisms were approximately 3–5 µm in diameter, round to oval, with a thin clear capsule, and contained an eccentrically placed basophilic crescent-shaped nucleus. The clinical pathological interpretation was granulomatous inflammation with intralesional yeast of a morphology consistent with Histoplasma spp. The rabbit was treated with microsized griseofulvin (25 mg/kg, orally, once a day) for 12 days pending final cytological diagnosis of histoplasmosis. No significant improvement was noted during the treatment period, and humane euthanasia was performed. Postmortem examination revealed the presence of intracellular and extracellular yeast organisms in the small intestine, skin (antebrachium, perioral, palpebral, perianal, and pinnal), penis, penile urethra, rectum, axillary lymph node, and conjunctiva. Postmortem fungal culture yielded Histoplasma capsulatum. Based on clinical and postmortem findings, a definitive diagnosis of disseminated histoplasmosis was made. Disseminated histoplasmosis appears to be unreported in rabbits. Although the treatment used did not provide noticeable improvement, available information on histoplasmosis treatment in other species has been reviewed to provide useful information for future management of this condition in rabbits.

Cardiomyopathy in a Harris hawk (Parabuteo unicinctus)

CASE DESCRIPTION An adult sexually intact female Harris hawk (Parabuteo unicinctus) housed at a wildlife hospital was evaluated because of acute collapse during an educational exhibition. CLINICAL FINDINGS Physical examination and hematologic analysis revealed no abnormalities; radiography revealed findings consistent with a previous tibiotarsal fracture. Coelioscopy with histologic examination and fungal culture of lung and air sac samples revealed anthracosis but no fungal infection. The hawk was discharged and temporarily removed from the education program; 1 month later, upon reintroduction into the program, it collapsed again. Physical examination and hematologic findings were similar to those after the first episode. Transcoelomic and transesophageal echocardiography and CT angiocardiography findings were consistent with cardiomyopathy. TREATMENT AND OUTCOME Initial cardiac treatment included furosemide (0.5 mg/kg [0.23 mg/lb], PO, q 24 h) and pimobendan (10 mg/kg [4.5 mg/lb], PO, q 12 h). After 10 days of treatment, peak and trough plasma concentrations of pimobendan were measured at 25, 196 and 715.97 ng/mL, respectively; the dosage was decreased to 0.25 mg/kg (0.11 mg/lb), PO, every 12 hours. No overt signs of toxicosis were detected. A sample was collected to reevaluate plasma pimobendan concentration after 30 days of treatment; results were not obtained prior to the patients death but revealed a peak concentration of 16.8 ng/mL, with an undetectable trough concentration. The hawk was found dead 6 months after initial evaluation. Necropsy revealed cardiomegaly, but histologic examination did not reveal an inciting cause of cardiac dysfunction. CLINICAL RELEVANCE Cardiac disease in raptors may be underreported. Transcoelomic and transesophageal echocardiography and CT angiography provided useful information for the diagnosis of cardiac disease in the hawk of this report.

HYPERCALCEMIA AND METASTATIC MINERALIZATION INVOLVING FOOTPADS IN ROCK HYRAXES (PROCAVIA CAPENSIS)

Abstract:  Three rock hyraxes (Procavia capensis) maintained in a zoological collection had chronic hypercalcemia and azotemia. In addition, all animals displayed signs of lameness due to footpad lesions that were histologically characterized as marked metastatic mineralization with granulomatous inflammation, reminiscent of calcinosis circumscripta. Although the animals were managed with aggressive fluid therapy, calciuresis, and dietary modification, all were eventually humanely euthanized due to the severity of their footpad lesions and/or progression of renal disease. Metastatic mineralization was also noted in other soft tissues among the three cases, including the stomach, colon, lung, vascular wall, ovary, and kidney. Varying degrees of interstitial nephritis were confirmed on postmortem examination, and in the absence of other causes for hypercalcemia, metastatic mineralization was presumably the consequence renal dysfunction. The renal pathway is the primary mode of calcium excretion in the rock hyrax. In renal dysfunction, hypercalcemia may develop secondary to decreased calcium excretion. Footpad mineralization is an uncommon sequel to renal dysfunction in domestic animals but has not been reported in rock hyraxes. A retrospective review of mortality data in this collection revealed a notable prevalence of renal lesions, including two additional animals with metastatic mineralization and renal dysfunction. Expanding knowledge of renal diseases will further guide preventative and clinical measures, including screening for metastatic mineralization and therapeutic trials for management of hypercalcemia and calcium mineral deposition in the footpads and other soft tissues.

Atypical fibrosarcoma in the skin of a Roborovski hamster (Phodopus roborovskii)

A 2.5-year-old intact male Roborovski hamster (Phodopus roborovskii) was presented with a large subcutaneous mass overlying the abdomen, affecting the animals ambulation and access to different compartments of the cage through narrow tubing. Ultrasound examination delineated a well-circumscribed mass in the subcutis of the caudoventral abdominal region. The mass was surgically excised and on cytologic examination showed, in a background of blood, a small population of individually arranged oval to spindle-shaped cells that exhibited a moderate degree of anisokaryosis, coarsely stippled chromatin, one or more prominent nucleoli, and lightly basophilic well-defined cytoplasmic processes. Histologically, the mass was composed of interlacing streams and bundles of pleomorphic spindle cells (ganglion-like cells) with variable amounts of collagenous stroma. The neoplastic cells exhibited moderate features of malignancy. These cells stained intensely with vimentin, but not with any other markers, including antibodies to cytokeratin AE1/AE3, S100 protein, desmin, smooth muscle actin, synaptophysin, neurofilament, and androgen receptor. Based on histologic features, the mass was diagnosed as an atypical fibrosarcoma. This is the first report of an atypical fibrosarcoma in a Roborovski hamster and one of few reports of atypical fibrosarcoma in domesticated hamsters overall.

TREATMENT OF DIABETES MELLITUS IN A GOLDEN LION TAMARIN (LEONTOPITHECUS ROSALIA) WITH THE GLUCAGON-LIKE PEPTIDE-1 MIMETIC EXENATIDE

Abstract An 8-yr-old male golden lion tamarin (Leontopithecus rosalia) was diagnosed with diabetes mellitus based on hyperglycemia and persistent glycosuria. Initial treatment consisted of the oral antihyperglycemic medications glipizide and metformin that resulted in decreased blood glucose concentrations; however, marked glycosuria persisted. Insufficient improvement on oral antihyperglycemic therapy and poor feasibility of daily subcutaneous insulin therapy led to an investigation into an alternative therapy with extended-release exenatide, a glucagon-like peptide-1 (GLP-1) mimetic, at a dosage of 0.13 mg/kg subcutaneously once per month. Following treatment with exenatide, the persistent glycosuria resolved, the animal maintained normal blood glucose concentrations, and had lower serum fructosamine concentrations compared to pretreatment levels. Based on these findings, extended-release exenatide could be considered as a therapeutic option in nonhuman primates with diabetes mellitus that do not respond to oral antihyperglycemics and in which daily subcutaneous insulin is not feasible.

MANDIBULAR OSTEOSARCOMA IN A NUTRIA (MYOCASTOR COYPUS)

Abstract:  A four-year-old neutered male nutria (Myocastor coypus) was presented for a one-day history of lethargy and anorexia. A right-sided facial swelling and loose right mandibular fourth molar that exuded caseous exudate from the root were noted; however, the animal continued to decline despite removal of the affected tooth and antibiotic and anti-inflammatory therapy. Radiographs showed a lytic proliferative bony lesion on the right mandible that appeared to expand in size over the course of a week. Due to its declining clinical condition and poor response to therapy, the animal was euthanized. Necropsy revealed an invasive bony neoplasm of the right mandible, histologically consistent with an osteosarcoma, that was invading the mandible and dental arcade, likely contributing to tooth root infection and osteomyelitis. Endocardiosis of the tricuspid valve was incidentally found as well with early cardiac remodeling of the right ventricle. This is the first report of an osteosarcoma and endocardiosis in a nutria.

RADIOGRAPHIC EVALUATION OF CARDIAC SILHOUETTE IN CLINICALLY HEALTHY HUMBOLDT PENGUINS (SPHENISCUS HUMBOLDTI)

Abstract Wild populations of Humboldt penguins (Spheniscus humboldti) on the coasts of Chile and Peru have been declining because of food scarcity caused by the El Niño Southern Oscillation and human interference. Part of conserving this vulnerable and threatened species is maintaining the health of penguins within zoo collections. A variety of cardiovascular diseases has been reported in individuals from the Spheniscidae family including ventricular septal defects, Dirofilaria immitis infection, pulmonary hypertension, and valvular dysplasia, ultimately resulting in congestive heart failure. An accurate clinical picture of cardiovascular disease in Humboldt penguins requires diagnostics tailored to this specific species. The aim of this study was to establish a routine methodology for evaluating the cardiac silhouette of clinically healthy Humboldt penguins using vertebral heart scale (VHS), cardiocoelomic width ratio (CCWR), and a novel cardiac silhouette-to-keel ratio (CKR). Ventrodorsal and right lateral radiographs were taken of 10 mature Humboldt penguins during routine health evaluations. An echocardiographic exam of each penguin was performed to confirm that there was no evidence of cardiac structural remodeling from disease. Two penguins were excluded on the basis of echocardiographic findings; therefore, data from eight penguins were used to calculate objective cardiac measurements for the clinically healthy population. Right lateral radiographs were used to determine VHS (7.4–10.4) and CKR (3.4–4.4). Ventrodorsal radiographs were used for calculating CCWR (0.45–0.59). The excluded penguins had CCWRs that were outside the 95% confidence interval for the range generated by this study. This initial work supports that standardizing radiographic views provides objective measures for cardiac silhouette evaluation in this species. Further research in larger populations and comparison with birds having confirmed cardiac disease is needed to determine the value of these three measurement techniques in Humboldt penguins.

Rhabdomyolysis and Artifactual Increase in Plasma Bicarbonate Concentration in an Amazon Parrot (Amazona species)

Abstract A 7-year-old male Amazon parrot housed outdoors presented with acute collapse, marked lethargy, and open-mouth breathing. The patient had stiffness of the pectoral muscles, and petechiation and ecchymosis noted around the eyes and beneath the mandible. Laboratory data revealed markedly increased aspartate aminotransferase, creatine kinase, and lactate dehydrogenase activity consistent with rhabdomyolysis, as well as markedly increased plasma bicarbonate concentration. Marked clinical improvement and resolution of laboratory abnormalities occurred with fluid therapy, administration of a nonsteroidal anti-inflammatory medication, and husbandry modifications, including indoor housing and dietary alteration. A spurious increase in bicarbonate measurement as documented in equine and bovine cases of rhabdomyolysis also occurred in this avian patient and must be considered for accurate interpretation of acid–base status in exotic species presenting with consistent clinical signs.