Fungal Dermatitis in a central bearded dragon

Transcription

1 Vet Times The website for the veterinary profession Fungal Dermatitis in a central bearded dragon Author : PRU HARVEY Categories : Vets Date : April 14, 2014 Summary A central bearded dragon (Pogona vitticeps) was presented with a two-month history of hyperkeratosis, predominantly around the face. The male cage mate showed no clinical signs of disease. Biopsies were taken, revealing the presence of fungal hyphae within granulomas consistent with the Chrysosporium anamorph of Nannizziopsis vriesii. Therapy was initiated with ceftazidime, twice daily chlorhexidine facial scrubs and topical application of silver sulphadiazine cream and, on receipt of histopathology results, oral itraconazole was implemented. Although the dermatitis appeared to improve initially, two weeks later the bearded dragon died. Unfortunately, postmortem was declined. A SIX-MONTH-OLD central bearded dragon (Pogona vitticeps) presented as a referral from a neighbouring veterinary practice with a two-month history of hyperkeratosis predominantly around the face (Figure 1), but also over the right shoulder and brachial region (Figure 2) that had proven unresponsive to long-term treatment with enrofloxacin 2.5 per cent 5mg/kg twice a day. Due to the chronic, aggressively progressive nature of the condition blood was collected from the ventral tail vein for haematology and biochemistry, and the primary lesions were biopsied. The bearded dragon was premedicated with buprenorphine 0.05mg/kg IM (Mader, 2006) and meloxicam 0.2mg/kg IM (Mader, 2006). Anaesthesia was induced with alfaxalone 10mg/kg IV (Mader, 2006) injected into the ventral tail vein. Deep biopsies were taken with a 2mm biopsy punch from the upper and lower lips and face. The samples were placed in 10 per cent buffered formalin. Due to the small size of the biopsies and its hyperkeratotic nature the skin was not sutured, but left to heal by second intention. Remaining scabs were removed and the raw tissue underneath bathed in 10 per cent chlorhexidine solution (Figure 3). Antibiotic therapy was initiated on admission with ceftazidime 20mg/kg IM every 72 hours (Carpenter, 2005). While waiting for histology, the bearded dragon s wounds were cleaned twice daily with 10 per cent chlorhexidine solution and silver sulphadiazine cream (topically every 12 hours) was applied. Pain relief was continued with meloxicam and buprenorphine at the above dose rates. 1 / 13

2 Blood results showed elevations in urea, alkaline phosphatase (ALP), aspartate transaminase (AST) and white blood cells (WBC). Urea has low levels of production and variable excretion in reptiles, so is not generally clinically useful. ALP has widespread tissue distribution and its elevation may have been due to the extent and chronicity of the dermatitis. The WBC elevation supports the level of infection present. AST, however, is a very sensitive indicator of liver and muscle disease, and may also be elevated in renal disease (Mader, 2006). In retrospect these results may have indicated a level of liver compromise due to spread of the fungal disease, but may also simply have been indicative of the amount of tissue damage caused by primary fungal and secondary bacterial infection. Biopsy results initially revealed chronic moderate- to-marked inflammatory changes. Multifocal small granulomas were present in the superficial dermis and special stains revealed fungal hyphae in the dermal granulomas (Figure 4a and 4b). While waiting for the histology results, the dermatitis ran a waxing and waning course of improvement. The bearded dragon, however, remained bright throughout the process and was eating, drinking, urinating and defaecating consistently. As soon as fungal elements were recognised, treatment with itraconazole 10mg/kg by mouth every 12 hours (Carpenter, 2005) was initiated and the bearded dragon was sent home two days later, with a view to re-examination, anaesthesia and significant debridement of affected areas in a fortnight. A week later, the bearded dragon stopped eating and became lethargic. The following day, it died. Although a postmortem was declined, the author suspects the fungal infection had spread systemically. Its cage mate has shown no signs of infection to date. Discussion Fungal disease is found worldwide in nearly all orders and sub-orders of Reptilia (Mader, 2006). Although none of the fungi implicated in disease have been confirmed as true pathogens of reptiles that is, are usually opportunistic the Chrysosporium anamorph of Nannizziopsis vriesii (CANV) is consistently isolated from pet bearded dragons and is rarely found on normal reptile integument (Mader, 2006; Bowman et al, 2007). Infection with CANV or yellow fungus disease has been described in geckos (Bowman et al, 2007), chameleons (Paré et al, 2006a), snakes (Nichols et al, 1999) and crocodilians (Sigler et al, 2006b), and numerous case reports of infection in bearded dragons have been published in the literature (for example, Abarca et al, 2009; Bowman et al, 2007; Hedley et al, 2010). CANV is the leading cause of mortality in captive bearded dragons in North America, and is also seen in Europe and as far away as Australia. 2 / 13

3 Gross lesions associated with CANV infection consist of raised, crusting skin lesions; hyperkeratotic plaques; exudative and necrotic ulcers; discoloured, thickened and/ or necrotic skin; and focal cutaneous/subcutaneous swellings, often involving an entire limb (Abarca et al, 2009; Bowman et al, 2007; Hedley et al, 2010). Little is known about the origin, transmission or zoonotic potential of CANV (Abarca et al, 2009; Bowman et al, 2007); however, suspicions of an environmental origin and possible carrier state have been postulated (Bowman, 2007). Despite the fact environmental stressors, poor husbandry and inappropriate diet may predispose animals to infection with the CANV, evidence suggests it may behave like a primary pathogen (Bowman et al, 2007). Treatment Following histology results, the bearded dragon in this study was started on antifungal therapy with itraconazole. Itraconazole has been shown to have a broad spectrum of antifungal action, with lower toxicity than most other azoles (Plumb, 2005). However, Van Waeyenberghe et al (2010) treated CANV infections in naturally- infected bearded dragons with itraconazole and voriconazole, and found although those treated with itraconazole were cleared of external infection almost three weeks sooner than those treated with voriconazole, high levels of mortality occurred in those treated with the former product. Despite these findings and the evidence to support hepatotoxicity as a result of itraconazole therapy, Bowman et al (2007) monitored hepatic enzymes during treatment and found no evidence of either enzyme increase or postmortem changes associated with drug toxicity. Conclusion Yellow fungus disease is emerging as a significant cause of dermatomycosis in bearded dragons (Bowman, 2007) and, indeed, other reptilian species. Sadly, fungal disease in many reptiles is usually diagnosed at necropsy as it is not initially suspected and, as in this case, is grossly indistinguishable from bacterial infection (Pare et al, 2006b). It is important awareness of fungal disease in reptiles is increased in the veterinary community so cases are identified and treated rapidly. Please note some drugs mentioned within this article are not licensed for use in reptiles and are used under the cascade. 3 / 13

4 References and further reading Abarca M L, Martorell J, Castellá G, Ramis A and Cabañes F J (2009). Dermatomycosis in a pet inland bearded dragon (Pogona vitticeps) caused by a Chysosporium species related to Nannizziopsis vriesii, Veterinary Dermatology 20 (4): Bowman M R, Paré J A, Sigler L, Naeser J P, Sladky K K, Hanley C S, Helmer P, Philips L A, Brower A and Porter R (2007). Deep fungal dermatitis in three inland bearded dragons (Pogona vitticeps) caused by the Chrysosporium anamorph of Nannizziopsis vriesii, Medical Mycology 45 (4): Carpenter J W (2005). Exotic Animal Formulary (3rd edn), Saunders, St Louis. Girling S J and Fraser M A (2007). Systemic mycobacteriosis in an inland bearded dragon (Pogona vitticeps), The Veterinary Record 160 (15): Hedley J, Eatwell K and Hume L (2010). Necrotising fungal dermatitis in a group of bearded dragons (Pogona vitticeps), The Veterinary Record 166 (15): Mader D R (2006). Reptile Medicine and Surgery (2nd edn), Saunders Elsevier, St Louis. Nichols D K, Weyant R S, Lamirande E W, Sigler L and Mason R T (1999). Fatal mycotic dermatitis in captive brown tree snakes (Boiga irregularis), Journal of Zoo and Wildlife Medicine 30 (1): Paré A, Coyle K A, Sigler L, Maas A K 3rd and Mitchell R L (2006a). Pathogenicity of the Chrysosporium anamorph of Nannizziopsis vriesii for veiled chameleons (Chamaeleo calyptratus), Medical Mycology 44 (1): Paré A, Sigler L, Rosenthal K L and Mader D R (2006b). Microbiology: fungal and bacterial diseases of reptiles. In Mader D R (ed), Reptile Medicine and Surgery (2nd edn), Saunders Elsevier, St Louis: Plumb D C (2005). Veterinary Drug Handbook (5th edn), Iowa State Press, Ames, IA: Van Waeyenberghe L, Baert K, Pasmans F, van Rooij P, Hellebuyck T, Beernaert L, de Backer P, Haesebrouck F and Martel A (2010). Voriconazole, a safe alternative for treating infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii in bearded dragons (Pogona vitticeps), Medical Mycology 48(6): / 13

5 Figure 1a. Facial hyperkeratosis at initial presentation. IMAGES: Marina North. 5 / 13

6 6 / 13

7 Figure 1b. Facial hyperkeratosis at initial presentation. IMAGES: Marina North. 7 / 13

8 Figure 2. Skin lesions over shoulder (2a) and in brachial region (2b). IMAGES: Marina North. 8 / 13

9 Figure 2. Skin lesions over shoulder (2a) and in brachial region (2b). IMAGES: Marina North. 9 / 13

10 Figure 3. Lesions following removal of scabs, cleaning and application of silver sulphadiazine cream. IMAGES: Marina North. 10 / 13

11 Figure 3. Lesions following removal of scabs, cleaning and application of silver sulphadiazine cream. IMAGES: Marina North. 11 / 13

12 Figure 4a. Periodic acid-schiff staining. 12 / 13

13 Figure 4b. Haematoxylin and eosin staining. // 13 / 13 Powered by TCPDF (