Today's Veterinary Practice

NOV-DEC 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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CLINICAL INSIGHTS NOVEMBER/DECEMBER 2018 69 The areas of skin that tend to be the most affected are the areas of loose skin near the front legs and neck; those tissues eventually become swollen because of cell damage (when water-soluble vitamin A has been administered). 1,4 In reptiles with severe hypervitaminosis, the dermis and muscle can become exposed and they can die of secondary dehydration. 1 Commonly associated with skin lesions is secondary infection (bacteria or fungal), which can lead to sepsis. 1,2 In chameleons specifically, excess vitamin A can potentially lead to nutritional metabolic bone disease because of vitamin D interference. 5 DIAGNOSIS History and clinical findings are extremely important for diagnosing hypervitaminosis A, especially if vitamin A was administered weeks or months before you examine the animal. 1-3 The history should provide information about the patient's dietary intake of vitamin A (such as raw liver). 2 Information from liver biopsy results and serum vitamin A levels is also helpful; 3 however, although liver biopsy results can be considered more accurate, biopsy sample collection is obviously more invasive than blood collection. Skin biopsy results can help you determine primary or secondary causes, and culture and sensitivity should be considered for determining medical treatment. 1 Ideally, you can collect biopsy samples endoscopically or grossly (e.g., wedge biopsy) because fine-needle aspiration may not be diagnostic. Several laboratories can test for vitamin A; you can send serum samples to IDEXX Laboratories, Inc., the Animal Health Diagnostic Center at Cornell University, and the veterinary diagnostic laboratories at Michigan State University or Iowa State University. Before transport, the serum needs to be separated from the clot, kept refrigerated, and kept away from light. Turnaround times range from 3 to 7 business days after sample receipt (varying according to laboratory). Serum levels can vary significantly compared with hepatic vitamin A levels, and serum levels might therefore not be practical for a diagnosis because of these normal fluctuations. 4 Vitamin A levels in the blood can also be assessed through plasma retinol values. In captive aquatic turtles, plasma retinol levels are 0.03 to 0.364 mg/mL and in tortoises, 0.034 to 0.415 mg/mL. Plasma retinol levels in lizards and snakes have been reported between 0.049 to 0.372 mg/mL and 0.012 to 0.049 mg/mL. 2 Differential diagnoses for skin lesions in reptiles are infection (bacterial, fungal, viral, parasitic) and/or trauma. 1 TREATMENT Unfortunately, prior administration of vitamin A cannot be reversed. 2 Therefore, the treatment of hypervitaminosis A is typically supportive and includes prevention of secondary skin infections ( FIGURES 3 AND 4 ). Decreasing and potentially discontinuing vitamin A intake/usage are important. 2,3,6,7 Reptiles with acute hypervitaminosis A require supportive care and fluid therapy (10 to 30 mL/kg/ day). 1 Skin lesions can be treated with hydrotherapy, antiseptic solution soaks, systemic antimicrobials, and pain medication as needed. 1,2 Skin lesions should be treated like burn wounds; prevent secondary infections and relieve pain. Therapeutic laser therapy (photobiomodulation) is a newer form of wound management that has shown some promising results FIGURE 1. A turtle that had received an overdose of vitamin A by injection a few days earlier. Note the severe swelling and partial sloughing of the dermis. FIGURE 2. The dermal cast of the entire limb of the patient from Figure 1; the skin completely sloughed during the physical examination, revealing the raw dermis.

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