Noninfectious Disorders of Amphibians
Metabolic bone disease is frequently seen in amphibians consuming nonsupplemented invertebrates. Except for earthworms, most invertebrates used as food have an inverse calcium:phosphorus ratio. This results in mandibular deformity, long bone fracture, scoliosis, and eventually tetany and bloating. Diagnosis is made radiographically by finding thinning cortices of long bones, mandibular and hyoid bone deformities, pathologic fractures, and in severe cases, GI gas. Treatment includes correcting the diet and administering calcium glubionate 1 mL/kg/day, PO, for 30 days. Full-spectrum lighting with biologically active ultraviolet-B light should be provided. Vitamin D3 can also be administered in severe cases. Starvation, resulting in weight loss, lethargy, and dehydration, must be treated by providing proper nutrition through assist feeding.
Thiamine deficiency is seen in amphibians fed frozen fish containing thiaminase. Clinical signs include tremors, seizures, and opisthotonos. Initial treatment is the administration of thiamine at 25–100 mg/kg, IM or intracoelomic, followed by thiamine 25 mg/kg body wt, PO, with each meal. Thiamine deficiency can be prevented by routinely supplementing diets with 250 mg thiamine/kg of fish fed.
The carotenoids, including vitamin A, are not synthesized by amphibians and must be provided through diet. Excessive levels of vitamin A have been hypothesized to interfere with vitamin D metabolism and contribute to metabolic bone disease, whereas deficiency has been associated with lethargy, wasting, and inability to use the tongue to catch prey due to the development of squamous metaplasia of the tongue (short tongue syndrome). Treatment includes providing vitamin A supplementation and force feeding a proper diet.
Obesity is a disease. Overfeeding is the primary cause of obesity; many amphibian species will continue to consume prey as long as it is available and without regard for their energy needs. The oversized fat bodies may be palpated within the coelomic cavity; however, in females, ultrasound may be necessary to differentiate enlarged fat bodies from egg masses. Treatment for active species includes enlarging the size of the enclosure to allow increased activity. Maintaining the amphibian at the upper end of its POTZ will accelerate metabolic rate and increase caloric use. Reducing caloric intake also may be used to control weight.
Spontaneous neoplasia occurs in most organ systems but is rare except when caused by pollutants or an infectious agent, such as the virally induced Lucké renal carcinoma that affects populations of northern leopard frogs (see above) or epidermal papillomata in the Japanese firebelly newt. With increasing longevity in captivity and better health care, it is likely that more cases of neoplasia will be identified.
Traumatic injuries are common in captive amphibians and include lacerations, bone fractures, internal bleeding, desiccation, and the loss of digits, limbs, or tail. Rapid assessment followed by supportive care is required for a successful outcome. Desiccation is common in amphibians that escape their enclosure or do not receive proper care. For smaller amphibians (<30 g), most fractures can be managed conservatively with cage rest. For larger amphibians, the use of external or internal fixation may be beneficial. Pain management must be considered in traumatic cases. The presence of opioid receptors suggests using opioids may be beneficial (buprenorphine, 0.02 mg/kg, IM, SC, or PO). NSAIDs may also be used (meloxicam, 0.2 mg/kg) and appear to provide pain relief.