An Overview of Reptile Fungal Pathogens in the Genera Nannizziopsis, Paranannizziopsis, and Ophidiomyces
Two recent molecular analyses of morphologically similar fungal isolates formerly grouped under the appellation “Chrysosporium anamorph of Nannizziopsis vriesii (CANV) complex” led to major taxonomic revisions and revealed new insights into the biology of these reptile pathogens. All CANV-complex isolates differed from N. vriesii and were assigned to 16 species, either within Nannizziopsis or within the new genera Paranannizziopsis and Ophidiomyces, and 14 of these species were newly described. From these revisions, a trend in host specificity clearly emerged that was not previously apparent. Nannizziopsis now includes nine species associated with chamaeleonid, gekkonid, cordylid, teiid, agamid, and iguanid lizards; crocodiles; and human hosts. Paranannizziopsis includes four species that infect squamates and tuataras. Ophidiomyces, with the single species Ophidiomyces ophiodiicola (formerly Chrysosporium ophiodiicola), is only associated with terrestrial or semiaquatic snakes. Nannizziopsi guarroi (formerly Chrysosporium guarroi) is the main causal agent of yellow fungus disease in captive bearded dragons (Pogona vitticeps), and O. ophiodiicola is the cause of mycoses in captive snakes and of snake fungal disease, an emergent global threat to populations of endangered wild snakes. Histopathology, polymerase chain reaction assays, and culture are crucial for confirming a diagnosis of fungal infection in reptiles; however, because fungal identification based on morphologic and physiologic features alone is difficult, sequencing should be sought to speciate reptile fungal isolates. Information gathered from PCR assays and molecular speciation will help in outlining pathogenic potential and contagion risks associated with each of these newly recognized fungal species and allow for a more comprehensive understanding of the ecology, distribution, and host range of these pathogens.Abstract
Extensive epidermal necrosis over the neck, dorsum, and right forelimb of an inland bearded dragon with yellow fungus disease, a mycosis usually caused by Nannizziopsis guarroi. The crust is sloughing, exposing the dermis. Photo courtesy of Bruce Henderson, DVM, and VIN.
Cytology of a touch preparation from a skin lesion of an inland bearded dragon with yellow fungus disease. Rectangular arthroconidia, typical of Nannizziopsis spp., are readily identifiable. Diff Quick, 100×. Photo courtesy of Kenny Crawford, DVM, and VIN.
Tentacled snake. Multifocal discoloration of the skin with swelling and thickening of the epidermis caused by infection with Paranannizziopsis crustacea. Photo courtesy of Wildlife Conservation Society.
Photomicrograph of the necrotic epidermis in the tentacled snake with Paranannizziopsis crustacea infection from Figure 3. Massive and dense arthroconidiation, or arthroconidial tuft, at the epidermal surface. H&E, 100×. Microphotograph courtesy of Wildlife Conservation Society.
Timber rattlesnake with multifocal labial and temporal scale necrosis and underlying soft tissue swelling from Ophidiomyces ophiodiicola infection. Necrotic scales occlude the loreal pit. Photo courtesy of Wildlife Conservation Society.
Distortion of rostral facial structures from soft tissue swelling and necrosis of overlying scales in a timber rattlesnake with Ophidiomyces ophiodiicola infection. Photo courtesy of Wildlife Conservation Society.
Ophidomyces ophiodiicola arthroconidia and hyphae in the necrotic epidermis of the rattlesnake from Figure 6. Gomori methenamine silver stain.
