Yellow fungus disease (Chrysosporium anamorph of Nannizziopsis vriesii) in reptiles in Australia FACT SHEET

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1 Yellow fungus disease (Chrysosporium anamorph of Nannizziopsis vriesii) in reptiles in Australia FACT SHEET Introductory statement Yellow fungus disease, caused by the Chrysosporium anamorph of Nannizziopsis vriessi (CANV) has been reported in a variety of reptile species overseas. There are two reports of an outbreak of CANV infection in farmed crocodiles in the 1990s (Thomas et al 2002). It has also been isolated on two occasions from superficial lesions on Australian snakes, one of which was a filesnake (Ladds 2009). Recently this fungus has been isolated as a primary pathogen in captive coastal bearded dragons, Pogona barbata, in Australia (Australian Registry of Wildlife Health [ARWH] case reports, 6443/1, 6596/1, 6588/1, 6742/1). The CANV is found freely in the environment, and as such free-living reptile species are at risk of infection. Aetiology Yellow fungus, the Chrysosporium anamorph of Nannizziopsis vriessi (CANV) is an ascomycetous teleomorphic fungus in the order Onygenales, family Onygenaceae. Natural hosts CANV infection has been reported in a wide range of reptile species. There is no reported age or sex-linked predisposition. World distribution Cases of CANV infection in reptiles have been reported in North America, Europe and Australia. Occurrences in Australia Outbreaks of CANV occurred on two separate occasions in 1994 and 1997 in crocodiles sourced from the same crocodile farm (Thomas et al 2002). In an outbreak was reported in captive coastal bearded dragons, Pogona barbata, (ARWH case reports, 6443/1, 6588/1, 6596/1, 6742/1). PCR on cultured fungus confirmed the genus as Chrysosporium sp. in one case (6588/1). As a result CANV infection was thought to be the cause of death in all four animals. CANV infection has not previously been reported in coastal bearded dragons. A separate case of CANV has recently been diagnosed in a wild caught pet bearded dragon (pers.obs.). Epidemiology The number of cases of infections in reptiles caused by the CANV is high in relative contrast to reports of infections caused by fungi that are extremely common on reptilian skin (Paré et al 2006). Information on the mortality rate is not available other than infections can be fatal (Bowman et al 2007, Thomas et al 2002). Incubation period is 2-5 weeks (Paré et al 2006). Page 1 5/09/2009

2 Cutaneous mycosis in estuarine crocodiles (Crocodylus porosus) associated with the CANV may develop quickly with lesions apparent after one or two days (Thomas et al 2002). Transmission is by direct contact. Transmission studies in veiled chameleons (Chamaeleo calyptratus), fulfilling Koch s postulates, have demonstrated that the CANV can act as a primary pathogen. The CANV appears to be contagious and can readily spread either directly through contact or indirectly by fomites (Paré et al 2006). Suboptimal ambient temperatures provide an ideal environment for fungal infection (Thomas et al 2002). Clinical signs Yellow fungus disease is a slowly progressive and often fatal skin disease. Skin lesions slowly progress over several months from dry, hyperkeratotic plaques to exudative and necrotic ulcers (pers.obs). The mouth is commonly affected but lesions may occur anywhere on the body. Affected reptiles are often in poor condition. In later stages infection will extend to muscle, bone and deeper tissues. Figure 1. Yellow fungus disease in captive coastal bearded dragons, Pogona barbata (Courtesy R Johnson). Diagnosis Diagnosis is based on clinical signs, fungal culture, histopathology and PCR. Clinical Pathology Culture on Mycosel TM Agar and incubated at 28 C. Fungi identified to genus based on morphology. Page 2 5/09/2009

3 Pathology Lesions may begin as hyperkeratotic plaques that undergo necrosis, turn a darkish brown, and slough. The skin may be swollen, hard, and cracked with exudates seeping from the fissures. Lesions are often found around the mouth but may occur anywhere on the body. A whole limb may be affected (Paré and Jacobson 2007). In the later stages deeper tissues may be affected (pers.obs.). Histological lesions include a granulomatous fungal dermatitis, myositis, and osteomyelitis (ARWH case reports, 6443/1, 6596/1, 6588/1, 6742/1; Bowman et al 2007). PAS stained tissue sections revealed hyphae in the keratin layer, epidermis, dermis and occasionally skeletal muscle (Paré et al 2006). Two separate cases of granulomatous hepatitis, with intralesional hyphae morphologically consistent with those produced by the CANV have been reported (Bowman et al 2007, ARWH 6742/1). The latter case also had a granulomatous myocarditis with intralesional hyphae. Differential diagnoses Other dermatomycoses, bacterial dermatitis, stomatitis and osteomyelitis need to be excluded from the list of differential diagnoses. Previously the CANV has been misidentified as Trichophyton, or as other fungal species including Geotrichium or Trichosporon (Bowman et al 2007, pers.obs). Laboratory diagnostic specimens Procedures for specimen collection should follow those presented by Rose (2007). A complete range of tissue samples should be frozen and fixed. Representative biopsies of affected tissue should be taken from live reptiles. Histological and microbiological examination for hyphae typical of Chrysosporium sp. should be carried out. Laboratory procedures Histological and microbiological examinations include fungal culture, histopathology and PCR. Treatment Medical treatment of confirmed cases involves itraconazole (10 mg/kg, PO, q 24 h for 6 weeks) and topical treatment with chlorhexidine solution. Serum biochemistry should be monitored for signs of liver toxicity. Surgical excision of lesions should be carried out if possible, and in conjunction with medical therapy. Prevention and control Prevention of CANV infection in captive reptiles should focus on reducing the fungal load, with attention being paid to regular substrate changes and good hygiene in captive situations. Providing optimal heating for captive reptiles is also important as infection appears to be more common at low ambient temperatures (pers.obs.). Surveillance and management There is no targeted surveillance for CANV. There is no AUSVETPLAN or Import Risk Analysis for CANV. Statistics There is no information available on CANV infection in the National Wildlife Health Surveillance Database ( NOTE: access to this dataset is restricted. If you would like access please contact awhn@zoo.nsw.gov.au. Page 3 5/09/2009

4 Research Research is required to determine the incidence of CANV infection in both captive and free living reptiles. Continuing research into the origin and nature of the CANV as a reptile pathogen is being undertaken at Toronto Zoo. Human health implications CANV infection has been reported in humans. The fungus was isolated from a brain abscess in an HIV-infected human in Nigeria (Steininger et al 2005) and from a groin lesion in an immunosuppressed man in California (Paré and Jacobson 2007). The source of infection was unknown. Conclusions In Australia outbreaks of CANV infection have occurred in farmed crocodiles and more recently in captive bearded dragons. Overseas the fungus has been found to be a significant primary pathogen of the skin in bearded dragons. As the fungus is easily spread by contact, wildlife carers and veterinarians caring for captive and free living reptiles need to be vigilant in preventing the spread of the CANV. Further studies are warranted to understand fully the origin and nature of the CANV as a reptile pathogen, and its significance as a primary pathogen in reptiles in Australia, both captive and free living. References and other information Abarca M L, Martorell J, Castellá G, Ramis, A and Cabañes FJ. Cutaneous hyalohyphomycosis caused by a Chrysosporium species related to Nannizziopsis vriesii in two green iguanas (Iguana iguana). Medical Mycology 2008;46: Bowman MR, Paré, JA, Sigler L, Naeser JP, Sladky KK, Hanley CS, Helmer P, Phillips LA, Brower A and Porter R. Deep fungal dermatitis in three inland bearded dragons (Pogona vitticeps) caused by the Chrysosporium anamorph of Nannizziopsis vriesii, Medical Mycology 2007;45: Paré JA, Coyle KA, Sigler L, Maas III AK and Mitchell RL (2006) Pathogenicity of the Chrysosporium Anamorph of Nannizziopsis vriesii for veiled chameleons (Chamaeleo calyptratus). Medical Mycology 2006;44: Rose K. Wildlife health investigation manual. The Australian Registry of Wildlife Health, Sydney, Paré J and Jacobson ER. Mycotic diseases of reptiles. In: Jacobson ER, editor. Infectious Diseases and Pathology of Reptiles. CRC Press, Boca Raton, 2007: Steininger C, van Lunzen J, Tintelnot K, Sobottka I, Rohde H, Ansver Horstkotte M and Stellbrink HJ. Mycotic brain abscess caused by opportunistic reptile pathogen. Emerging Infectious Diseases 2005;11: Thomas A D, Sigler L, Peucker S, Norton J H and Nielan A. Chrysosporium anamorph of Nannizziopsis vriesii associated with fatal cutaneous mycoses in the salt-water crocodile (Crocodylus porosus) Medical Mycology 2002; 40: Acknowledgements The following people have had input into this document: Robert Johnson. Updated: 4 August 2009 Page 4 5/09/2009

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