Characterization of Metarhizium viride Mycosis in Veiled Chameleons (Chamaeleo calyptratus), Panther Chameleons (Furcifer pardalis), and Inland Bearded Dragons (Pogona vitticeps)

Abstract

Metarhizium viride has been associated with fatal systemic mycoses in chameleons, but subsequent data on mycoses caused by this fungus in reptiles are lacking. The aim of this investigation was therefore to obtain information on the presence of M. viride in reptiles kept as pets in captivity and its association with clinical signs and pathological findings as well as improvement of diagnostic procedures. Beside 18S ribosomal DNA (rDNA) (small subunit [SSU]) and internal transcribed spacer region 1 (ITS-1), a fragment of the large subunit (LSU) of 28S rDNA, including domain 1 (D1) and D2, was sequenced for the identification of the fungus and phylogenetic analysis. Cultural isolation and histopathological examinations as well as the pattern of antifungal drug resistance, determined by using agar diffusion testing, were additionally used for comparison of the isolates. In total, 20 isolates from eight inland bearded dragons (Pogona vitticeps), six veiled chameleons (Chamaeleo calyptratus), and six panther chameleons (Furcifer pardalis) were examined. Most of the lizards suffered from fungal glossitis, stomatitis, and pharyngitis or died due to visceral mycosis. Treatment with different antifungal drugs according to resistance patterns in all three different lizard species was unsuccessful. Sequence analysis resulted in four different genotypes of M. viride based on differences in the LSU fragment, whereas the SSU and ITS-1 were identical in all isolates. Sequence analysis of the SSU fragment revealed the first presentation of a valid large fragment of the SSU of M. viride. According to statistical analysis, genotypes did not correlate with differences in pathogenicity, antifungal susceptibility, or species specificity.KEYWORDS Clavicipitaceae, Hypocreales, granulomatous glossitis, lizards, reptiles, ribosomal DNA, visceral mycosis N umbers of fungal infections caused by different emerging obligate and facultative pathogenic fungi in captive as well as in free-living reptiles have been increasing during the last decade (1, 2). Some of the most common reported fungal diseases in reptiles are yellow fungus disease in lizards and snake fungal disease in snakes, caused by keratinophilic ascomycetous fungi of the family Onygenaceae (Eurotiomycetes: Onygenales), identified as a member of the Chrysosporium anamorph of the Nannizziopsis vriesii complex (CANV) (3-6). Different reports in recent years have indicated that CANV is a reason for often fatal superficial or deep dermatomycosis in various lizard species, including veiled chameleons (Chamaeleo calyptratus) and inland bearded dragons (Pogona vitticeps) (7-12). Beside skin lesions, there have been rare cases of systemic infection (10). Another primary pathogenic species of the Onygenaceae family is Ophidiomyces ophiodiicola, causing snake fungal disease, a well-known disease in