History
A 1.4-kg (3.09-lb) 180-cm-long female emerald tree boa (Corallus caninus) with a 4-month history of anorexia and weight loss was evaluated because of emaciation, lethargy, dehydration, cloacal discharge, and occasional open-mouthed breathing. Treatment was instituted and included SC fluid therapy with reptile Ringer's solution (50% lactated Ringer's solution, 25% saline [0.9% NaCl] solution, and 25% solution of 5% dextrose in water) with vitamin B (30 to 35 mL, 2 times/wk), multiple oral tube feedings of an electrolyte solutiona or a nutritional recovery formulationb (20 mL/feeding given once daily and gradually tapered to once every 4 days until time of death), silver sulfadiazine cream application to the cloaca (once daily every 4 days for a total of 2 applications), and a single long-acting ceftiofurc injection (6.6 mg/kg [3 mg/lb], IM). After 2 weeks of treatment, the snake was found semicomatose in dorsal recumbency. Emergency care was provided, including manual ventilation with 100% oxygen and IV administration of fluids (3 mL of a solution of 50% dextrose in 7 mL of saline solution) and ceftazidime (22 mg/kg [10 mg/lb], IV). After 2 hours of emergency treatment, the snake had no signs of improvement and was euthanized. A necropsy was performed, and sections of large intestine, scaled skin, lungs, kidneys, ova, liver, pancreas, thyroid, spleen, heart and great vessels, and stomach were fixed in neutral-buffered 10% formalin and submitted to the University of Georgia College of Veterinary Medicine Department of Pathology for histologic examination. Sections of fresh tissue from the kidneys, liver, lungs, and pancreas and a swab of the endotracheal tube used during emergency treatment were submitted for aerobic bacterial, mycobacterial, and fungal cultures.
Clinical and Gross Findings
Reported gross necropsy findings included a small amount of serosanguineous fluid in the trachea and a small white nodule observed in the lungs. The serosal surface of the gas-distended colon had multiple petechia and ecchymoses, and its mucosal surface was dark red to black. A 1-cm-diameter black focus was present on the scaled skin on the lower left side of the body. Further sectioning of the formalin-fixed lungs revealed multiple, round, < 2-mm-diameter, firm, white nodules projecting into several central pulmonary lumens (Figure 1).
Gross photograph of a cross section of a lung from an emerald tree boa (Corallus caninus) that received treatment for anorexia, lethargy, and dehydration with occasional open-mouthed breathing. The snake was unresponsive to treatment and eventually euthanized. Notice the pale, nodular lesion (arrow) projecting into the central lumen of the lung.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Gross photograph of a cross section of a lung from an emerald tree boa (Corallus caninus) that received treatment for anorexia, lethargy, and dehydration with occasional open-mouthed breathing. The snake was unresponsive to treatment and eventually euthanized. Notice the pale, nodular lesion (arrow) projecting into the central lumen of the lung.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Gross photograph of a cross section of a lung from an emerald tree boa (Corallus caninus) that received treatment for anorexia, lethargy, and dehydration with occasional open-mouthed breathing. The snake was unresponsive to treatment and eventually euthanized. Notice the pale, nodular lesion (arrow) projecting into the central lumen of the lung.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page →
Histopathologic Findings
Formalin-fixed samples of lungs, large intestine, the lesion-bearing area of scaled skin, kidneys, ova, liver, pancreas, thyroid, spleen, heart and great vessels, and stomach were processed routinely for histologic examination. In sections of the lung tissue, smooth muscle bundles at the luminal end of several septae were expanded by multiple to coalescing granulomas that elevated the intact overlying respiratory epithelium and projected into the central pulmonary lumen (Figure 2).
Subgross photomicrograph of cross section of the lung from the snake in Figure 1. In snakes, faveoli (F) open into a central lumen (L), which is continuous with the bronchus. Adjacent faveoli are separated by a connective tissue septum, and there is a bundle of smooth muscle cells at the luminal end of each septum (SM). Multiple smooth muscle bundles project into the central lumen; the bundles are greatly expanded by coalescing granulomas (asterisks), which elevate the overlying intact respiratory epithelium. H&E stain; bar = 0.12 cm.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Subgross photomicrograph of cross section of the lung from the snake in Figure 1. In snakes, faveoli (F) open into a central lumen (L), which is continuous with the bronchus. Adjacent faveoli are separated by a connective tissue septum, and there is a bundle of smooth muscle cells at the luminal end of each septum (SM). Multiple smooth muscle bundles project into the central lumen; the bundles are greatly expanded by coalescing granulomas (asterisks), which elevate the overlying intact respiratory epithelium. H&E stain; bar = 0.12 cm.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Subgross photomicrograph of cross section of the lung from the snake in Figure 1. In snakes, faveoli (F) open into a central lumen (L), which is continuous with the bronchus. Adjacent faveoli are separated by a connective tissue septum, and there is a bundle of smooth muscle cells at the luminal end of each septum (SM). Multiple smooth muscle bundles project into the central lumen; the bundles are greatly expanded by coalescing granulomas (asterisks), which elevate the overlying intact respiratory epithelium. H&E stain; bar = 0.12 cm.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Each granuloma had a core of eosinophilic and basophilic necrotic cellular debris bordered by a layer of epithelioid macrophages up to 9 cells thick. This layer was admixed with fewer Langhans-type multinucleated giant cells, scattered heterophils, and a thick outer wall of fibrous connective tissue. At the periphery, moderate numbers of lymphocytes and fewer plasma cells were observed (Figure 3). Large numbers of acid-fast bacilli were present within the cytoplasm of epithelioid macrophages and extracellularly. Granulomas were limited to the lungs. Additional microscopic findings included multifocally extensive ulceration of the colon with intralesional gram-negative bacilli and focal mycotic dermatitis.
Photomicrograph of a section of one of the pulmonary granulomas in the lung tissue section in Figure 2. The granuloma is characterized by a central core of eosinophilic and basophilic necrotic cellular debris (C), surrounded by a layer (up to 9 cells thick) of epithelioid macrophages (M); in some foci, the macrophages are admixed with Langhans-type multinucleated giant cells (L) and low numbers of heterophils. This layer is surrounded by a thick layer of fibrous connective tissue (CT), further enveloped by moderate numbers of lymphocytes and fewer plasma cells. H&E stain; bar = 500 μm. Inset—Photomicrograph of an acid fast–stained section of another pulmonary granuloma. Notice the numerous acid-fast bacilli both free in the tissue and within epithelioid macrophages, consistent with Mycobacterium spp. Ziehl-Neelsen acid-fast stain; bar = 50 μm.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Photomicrograph of a section of one of the pulmonary granulomas in the lung tissue section in Figure 2. The granuloma is characterized by a central core of eosinophilic and basophilic necrotic cellular debris (C), surrounded by a layer (up to 9 cells thick) of epithelioid macrophages (M); in some foci, the macrophages are admixed with Langhans-type multinucleated giant cells (L) and low numbers of heterophils. This layer is surrounded by a thick layer of fibrous connective tissue (CT), further enveloped by moderate numbers of lymphocytes and fewer plasma cells. H&E stain; bar = 500 μm. Inset—Photomicrograph of an acid fast–stained section of another pulmonary granuloma. Notice the numerous acid-fast bacilli both free in the tissue and within epithelioid macrophages, consistent with Mycobacterium spp. Ziehl-Neelsen acid-fast stain; bar = 50 μm.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Photomicrograph of a section of one of the pulmonary granulomas in the lung tissue section in Figure 2. The granuloma is characterized by a central core of eosinophilic and basophilic necrotic cellular debris (C), surrounded by a layer (up to 9 cells thick) of epithelioid macrophages (M); in some foci, the macrophages are admixed with Langhans-type multinucleated giant cells (L) and low numbers of heterophils. This layer is surrounded by a thick layer of fibrous connective tissue (CT), further enveloped by moderate numbers of lymphocytes and fewer plasma cells. H&E stain; bar = 500 μm. Inset—Photomicrograph of an acid fast–stained section of another pulmonary granuloma. Notice the numerous acid-fast bacilli both free in the tissue and within epithelioid macrophages, consistent with Mycobacterium spp. Ziehl-Neelsen acid-fast stain; bar = 50 μm.
Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1159
Microbiological and Additional Laboratory Findings
Results of aerobic bacterial (maintained at 30°C), mycobacterial, and fungal cultures of tissue samples from the kidneys, liver, lungs, and pancreas and surface swab samples from the endotracheal tube used for manual ventilation were negative.
Samples of formalin-fixed large intestine underwent PCR assay for Salmonella enterica enterica, and results were negative.
Morphologic Diagnosis and Case Summary
Morphologic diagnosis: multifocal to coalescing pulmonary granulomas with intralesional acid-fast bacilli consistent with Mycobacterium spp, extensive ulcerative colitis with intralesional gram-negative bacterial rods, and diffuse dermal hyperkeratosis with intralesional fungal hyphae and subadjacent, focal, necrotizing dermatitis with intralesional gram-negative bacteria.
Case summary: pulmonary mycobacteriosis in an emerald tree boa.
Comments
Reptiles react to many bacterial, fungal, parasitic, and algal infections by developing granulomatous inflammation.1 Differential etiologic diagnoses for pulmonary granulomas in the snake of this report included bacteria (mycobacteria, Chlamydophila spp, Salmonella spp, and Nocardia spp) and fungi (Aspergillus spp and Paecilomyces spp).1–10 The presence of acid-fast bacilli in granulomas was consistent with a diagnosis of pulmonary mycobacteriosis. However, results of microbiological culture of lung tissue and a surface swab sample from an endotracheal tube used during emergency treatment of the snake were negative. Histologically, mycobacteria were confined to granulomas; it is possible that granulomas were not included in the tissue samples submitted for microbiological culture. Failure to isolate mycobacteria from the kidneys, liver, or pancreas was not unexpected, given that there was no microscopic evidence of systemic disease. Mycobacteriosis and the resultant chronic, granulomatous pneumonia was likely a major contributor to the deterioration in condition and death of this snake and possibly predisposed the snake to the acute bacterial colitis and fungal dermatitis. Histopathologic changes indicated that the colitis was induced by bacterial infection. Although results of the PCR assay of the large intestine tissue samples were negative for S enterica enterica, the presence of intralesional gram-negative bacilli detected via histologic evaluation supported a bacterial cause of the colitis, such as infection with Salmonella spp or Aeromonas spp.4,5,11
Infections with mycobacteria in numerous reptile species, including snakes, turtles, lizards, and crocodiles, have been reported.1 Although the causative agent was not isolated from the snake of this report, the most common mycobacterial isolates from reptiles are the atypical or nontuberculous Mycobacteriaceae, including Mycobacterium marinum, Mycobacterium chelonei, and Mycobacterium thamnopheos; identification of isolates such as Mycobacterium haemophilum and Mycobacterium kansasii is reported infrequently.12,13 Infections with Mycobacterium avium, Mycobacterium agri, Mycobacterium confluentis, Mycobacterium hiberniae, Mycobacterium neoarum, Mycobacterium nonchromogenicum, Mycobacterium ulcerans, Mycobacterium intracellulare, Mycobacterium fortuitum, Mycobacterium phlei, and Mycobacterium smegmati in reptiles have also been reported.1,12,14–16 Although some authors report a 0.1% to 0.5% annual incidence of mycobacteriosis in well-managed reptile collections, without adequate environmental control, the prevalence in a collection can be as high as 31.9%.14,17
Routes of transmission for mycobacteria include ingestion of infected material, entry through the integumentary or urogenital systems, or inhalation of aerosols generated during direct contact among animals or from contaminated surfaces.14,17 Clinical signs of systemic infection are nonspecific and include anorexia, listlessness, and chronic weight loss.14 Although the clinical signs in the case described in the present report may have been solely attributable to colitis, dyspnea in animals with pulmonary involvement of systemic mycobacteriosis has been reported.12,18 Mycobacteriosis is diagnosed by detection of acid-fast positive bacilli in exudate, aspirate, or biopsy samples from affected animals and by results of microbiological culture or PCR assay of tissue samples with gross or microscopic lesions consistent with Mycobacterium sp infection; additional techniques are necessary for speciation.
The pulmonary tract is the organ system most commonly affected in snakes with mycobacteriosis; however, disseminated mycobacterial infections are common in snakes and have been associated with debilitation from injury, malnutrition, or other concurrent disease.16,19 Although mycobacteriosis in reptiles may be acute or chronic, naturally occurring infections generally follow a chronic course.12 Grossly, grayish-white nodules may be observed in the subcutis as well as in visceral organs.1 Histologic lesions of chronic mycobacteriosis vary from condensed clusters of macrophages containing intracytoplasmic acid-fast bacilli to caseating granulomas.12
Because of the chronic nature of the disease as well as its zoonotic potential, difficulty and expense of treatment, poor prognosis for recovery, and potential for epizootic spread to other animals, mycobacteriosis in reptiles is usually not treated medically.16 To limit the extent of the disease in reptile collections, routine microbiological culture and screening should be performed on samples collected from dead or ill animals and nodules in any animal should be biopsied for further examination.17 In reptile collections, infected or newly introduced animals should be quarantined; exhibits and potential fomites should be routinely disinfected with sodium o-phenylphenol or sodium hypochlorite to limit potential spread of the organisms.17,20 These disinfection techniques should be routinely implemented, not just in instances of disease detection.17
Pedialyte, Abbott Laboratories, North Chicago, Ill.
Carnivore Care Gruel, Oxbow Enterprises Inc, Murdock, Neb.
Excede, ceftiofur crystalline free acid, Pfizer, New York, NY.
References
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