Amphibian medicine (Proceedings)

For similar reasons as mentioned in the invertebrate lecture, more and more people are now bringing their pet amphibians to the veterinary office either as an emergency or for a husbandry consult. As previously mentioned, the owners of these exotic pets are often friendly and helpful who definitely can play an active role in the consultation. It is good practice to have a questionnaire filled out before the consultation. See below an example of the questionnaire my clients are asked to fill out prior to the consultation. This provides the clinician with information on general aspects of the husbandry, which is often the most common cause of problems.

The direct examination (arrive) should always be performed with gloves or with wet hands. The damp glove protects both the animal from our rough hands and us from the skin secretions of various amphibians. The investigation should be carried out systematically (e.g. head) to the tail. For most cases, a long, extensive investigation is often not necessary since most of the information comes from the interview with the owner. In small and ill patients it is often contraindicated to examine them directly as it can quickly lead to iatrogenic injuries.

As with other exotic pets the clinician should be aware of the major anatomically and physiologically different features of these animals. For example, the skin of most amphibians is very thin, which makes them so very vulnerable, however, this knowledge can also be used in our advantage for systemic therapy. Because of the thin skin most drugs can be given directly on the skin and by that route achieve high systemic concentrations. It is important to use pH neutral medications such as ophthalmological agents. Many injectable drugs are not pH neutral and can cause severe skin reactions if not diluted.

A good diagnostic tool for the general exam of even the sickest amphibians is the x-ray unit because many pathologies can be documented here.

A fecal exam will most often be positive for protozoans and these can be treated as the amphibian as a true carnivore does not need protozoans in the GI tract. A flotation test can also be performed to check for helminthes. Often a saline flush of the cloaca can produce feces.

A blood sample can be obtained by venipuncture of the ventral abdominal vein, which runs midline on the ventral abdomen. Often it can be visualized by transillumination.

Another great imaging method is the ultrasound exam as ultrasound waves travel nicely through water and a partially submersed amphibian will therefore provide the clinician with good quality images.

A direct exam of the coelomic cavity can be done via endoscopy. While this technique is minimally invasive, it has the added advantage that one can obtain tissue biopsies of different organs.

Anesthesia for invasive procedures or for surgery can be achieved by various agents such as MS-222, Eugenol or even Isoflurane (see references for details).

As mentioned above nearly all diseases seen in the pet amphibian are somehow traced to poor husbandry condition. Malnutrition is one of the most common causes among them. Since all adult amphibians are carnivores, they require a diet high in protein and low in fat. Often they develop lipid ceratopathy or obesity from a diet rich in fat or suffer from metabolic bone disease due to a lack of calcium in the diet. Larvae like tadpoles are often herbivores and feed well on fish food flakes. Environmental stress will eventually cause a suppression in the immune function and 'redleg' is a common presentation, this is a sign of systemic sepsis and needs to be addressed immediately with antibiotic that have a good range in the gram negative spectrum (e.g. gentamicin). The exact description of 'redleg' is actually a dermatosepticemia. While fungal disease in mammals are usually considered opportunistic pathogens, it has been shown that amphibians can be severely affected by fungal agents as a primary cause of infection. many species have been extinct by a chytrid fungus. While the fungus has been a notorius killer in many amphibian collection and in the wild, a successful treatment regime has recently been published.

Terrestrial amphibians are treated with itraconazole (Sporanox, 10 mg/ml) at 0.01% in 0.6% saline in a 5-min bath for 11 consecutive days. Aquatic amphibians, are treated with itraconazole administered directly in their primary tank water to achieve a concentration of 0.01% for 30 min every 5 days for four treatments. Itraconazole is then removed from the tank water after 30 min by high-rate-of-flow activated charcoal filters. This treatment and quarantine procedures are successful in eradicating the disease from a collection.

Due to their thin skin, amphibians are very sensitive to any environmental contamination (similar to fish and water contamination).

When confronted with a case, it is difficult to fnd a single cause immediately without culture and sensitivity. Very often a 'shotgun' therapy is initiated to save the animal. part sof this treatment often includes: Fluids, osmotic stabilization Enrofloxacin, Calcium gluconate, Vitamin B complex, +/- Dexamethasone SP

Cool temperatures, +/- metronidazole or itraconazole. Then the work-up starts once stabilized and samples are taken prior to the treatment. Very often samples grow slowly due to the lower temperatures that they need to be cultured at. It is important to inform the laboratory when submitting samples as amphibian cultures need to be incubated at room temperature and not in the incubator.

References:

Wright KM. 1996. Amphibian husbandry and medicine. In: Wright KM, Whitaker BR, editors. Amphibian medicine and captive hus- bandry. Malabar (FL): Krieger Publishing Company.

Reptile Medicine and Surgery by Douglas R. Mader;

The Reptile and Amphibian Problem Solver: Practical and Expert Advice on Keeping Snakes, Lizards, Frogs and Other Reptiles and Amphibians by Robert Davies, Valerie Davies

Guénette SA, Hélie P, Beaudry F, Vachon P. Eugenol for anesthesia of African clawed frogs (Xenopus laevis). Vet Anaesth Analg. 2007 May;34(3):164-70.

Guénette SA, Beaudry F, Vachon P. Anesthetic properties of propofol in African clawed frogs (Xenopus laevis). J Am Assoc Lab Anim Sci. 2008 Sep;47(5):35-8.

Lafortune M, Mitchell MA, Smith JA. 2001. Evaluation of medetomidine, clove oil, and propofol for anesthesia of leopard frogs, Rana pipiens. J Herpetol Med Surg 11:13–18.

Crawshaw GJ. 1993. Amphibian medicine. In: Fowler M, editor. Zoo and wild animal medicine: current therapy 3. Philadelphia: WB Saunders. p 131–139

Smith JM, Stump KC. 2000. Isoflurane anesthesia in the African clawed frog (Xenopus laevis). Contemp Top Lab Anim Sci 39:39–42

Rosenblum EB, Voyles J, Poorten TJ, Stajich JE. The deadly chytrid fungus: a story of an emerging pathogen. PLoS Pathog. 2010 Jan 29;6(1):e1000550.

Forzán MJ, Gunn H, Scott P. Chytridiomycosis in an aquarium collection of frogs: diagnosis, treatment, and control. J Zoo Wildl Med. 2008 Sep;39(3):406-11.