Read the German translation: Dermatologische Krankheiten bei Reptilien
Introduction
In Europe and North America, reptiles are gaining increasing popularity as pets. According to Schröter et al. (2004), 3% of US and European households keep reptiles, mainly tortoises.1 The increasing number of reptiles kept as pets results in rising numbers of reptiles presented as patients in the veterinary clinic, especially in small animal practices. Langenecker (2006) reported in the period from 1994 to 2003 an increase of 50% for the Clinic for Zoo Animals, Exotic Pets and Wildlife of the Vetsuisse Faculty University of Zurich.2
Dermatologic problems are frequently diagnosed in reptiles. Langenecker (2006) found that lizards and snakes are more frequently affected than tortoises.2 The ten most frequent diagnoses included dermatologic problems such as dysecdysis, ectoparasites, and abscesses. The main reason for skin diseases in reptiles is related to the management, of special importance are the ambient humidity and the temperature.
Basic Anatomy of the Reptile Skin
To understand the pathophysiology resulting in dermatologic problems, it is important for the clinician to acquire a basic knowledge about the anatomy and physiology of the reptile skin. For more details, readers are referred to textbook chapters.3,4 The reptile skin is composed of epidermis and dermis. Glands are usually absent.
The epidermis consists of three layers: the stratum corneum, the stratum intermedium, and the stratum germinativum. The stratum corneum is six to eight cell layers thick and it is heavily keratinized. The scales grow from the stratum germinativum. In tortoises, the stratum corneum produces the shell consisting of carapax and plastron. The keratinized scutes cover bony plates that have evolved from parts of the skeleton such as the vertebral column and the ribs. Within the dermis, pigment cells are found, which play an important role in the colour changes that affect reptiles, especially lizards.
Reptiles are growing throughout their life and they shed their skin in regular intervals, a process called ecdysis. An exception are the scutes of the shell in tortoises, which are constantly worn down. The skin of lizards and tortoises is shed in several pieces, whereas in snakes the skin is shed in one piece. In the latter, it is of special importance to be aware that the spectacle, which covers the eye, must also be shed.
Infectious Diseases
A well known cause for dermatological problems in reptiles are parasites, especially mites. In snakes Ophionyssus natricis is typically diagnosed, in lizards Hirstiella trombidiformis. Often the disease is subclinical, but clinical signs include pruritus, nervousness, secondary bacteriological dermatopathies, and anaemia. Diagnosis is made by detection of mites, which macroscopically are visible as small red dots. Treatment is with topical application of ivermectin as a spray in a concentration of 5 mg/l, which is applied three to four times at weekly intervals. Parenteral ivermectin application is also possible (0.2 mg/kg sc, repeat in 10 to 14 days). Beware that ivermectin is toxic in tortoises and indigo snakes (Drymarchon corais).
As an alternative, fipronil may also be used, as long as animals are not directly sprayed onto. The spray is first applied to the hand of the clinician, a latex glove must be worn, and subsequently the fipronil is brought onto the reptile. The treatment may need to be repeated within 10 to 14 days. Adverse reactions to this treatment have been observed in chameleons and young boas. It is important to treat cage mates and also thoroughly disinfect the terrarium.
During summer months myasis is diagnosed in tortoises. Treatment consists in mechanical removal of maggots and flushing with physiologic saline solution, topical disinfection. In wild-caught reptiles, leeches and ticks may be found. Treatment is by removal.
Fungal dermatopathies often reveal Aspergillus spp., Mucor spp., Candida spp., Penicillium spp. and Geotrichum spp.5 The relevance of these agents is controversial as Aspergillus spp. and Paecilomyces spp. have been found in the skin of healthy snakes.
Recently a fungal dermatopathy caused by Chrysosporium anamorph of Nannizziopsis vriesii (CANV) has been recognized as an important disease. It is of major importance in lizards, especially the bearded dragon (Pogona vitticeps), but it has also been found in snakes.6 Clinically, the disease becomes apparent as severe dermatitis and often results in the death of the patient. The obvious hyperkeratosis is of yellowish appearance, hence the name yellow fungus disease. Treatment has been attempted with itraconazole (5-25 mg/kg SID po) for two to four weeks.
A well known bacterial disease complex in tortoises is "shell rot", which typically is an ulcerative dermatitis. Snakes may be affected as well. Different bacteria have been cultured such as Beneckea chitinovora or Citrobacter spp.. It is recommended to base treatment on microbial culture and sensitivity testing, followed by wound debridement. Topical treatment with 2% chlorhexidine or iodine solutions are used as well as ointments (e.g., silver sulphadiazine, Flammazine®, Solvay Pharma AG, Bern)
Advances in the diagnosis of viral diseases has also revealed possible involvement of viruses in skin diseases, of special interest are herpesviruses and iridoviruses (Ranavirus).
Non-Infectious Diseases
The aetiology of many dermatopathies in reptiles is trauma. This can be caused by biting either by cage mates (esp. in lizards) or other animals (e.g., prey in tortoises and snakes), impact on hard materials (e.g., terrarium glass). Another well-known aetiology is burns due to heating mats, hot rocks or lamps. Treatment is similar to that of mammals. Shell fractures in tortoises may need to be stabilized with cerclage wires. Topical treatment as described for bacterial dermatitis may be needed as well as analgesia, for which morphine appears to be offering the best effect in reptiles.
Inadequate climatic conditions within the terrarium frequently lead to problems with the physiologic shedding of the skin, this condition has been termed dysecdysis. In mild cases, soaking in warm water for 15 to 20 minutes per day might resolve the problem. In more severe cases, retained skin (e.g., spectacles in snakes) may need to be surgically removed.
References
1. Schröter, et al. Appl. Environ. Microbiol. 2004; 70: 613.
2. Langenecker 2006; Retrospektive Untersuchung zur Entwicklung der Artenverteilung und den häufigen Krankheitsbildern bei exotischen Heimtieren im Zeitraum von 1994-2003. Vetsuisse-Fakultät Universität Zürich, Zürich.
3. O'Malley. 2005. Clinical anatomy and physiology of exotic species. Elsevier Saunders, London.
4. Cooper. Dermatology, 2006; 196.
5. Jacobson, et al. S. Avian Exot. Pet Med. 2000; 9: 94.
6. Bowman, et al. Med. Mycol. 2007; 45: 371.