Abstract
Veronaea botryosa is a ubiquitous, saprobic, dematiaceous mold capable of causing cutaneous and subcutaneous lesions in humans, as well as systemic infection in a variety of other species.1 In the last decade, V. botryosa has been associated with emergent systemic fungal infections in aquatic animals, including cultured sturgeon (Acipenser spp.),2 captive amphibians,3 and wild reptiles4. Recently, intraspecific variability among V. botryosa isolates from different clinically affected hosts and geographic regions was found using repetitive extragenic palindromic PCR fingerprinting (rep-PCR);5 however, little is known regarding zoonotic potential of the different genetic clades, and no animal model currently exists to investigate V. botryosa phaeohyphomycosis. In this study, immune-competent Hsd:Athymic Nude-Fox1nu heterozygote (nu/+) and immune-deficient homozygote (nu/nu) mice were inoculated by subcutaneous injection (SC) or orogastric gavage (OG) with three representative V. botryosa strains recovered from white sturgeon, green sea turtle (Chelonia mydas), and human previously typed via rep-PCR.5 Daily mortality and morbidity were recorded, and dissemination of the fungus in surviving mice was investigated by plating splenic samples on agar media 30 days post-inoculation. Additionally, histological analysis of the injection site, regional lymph node, salivary gland, spleen, liver, mesenteric lymph node, and gastrointestinal tract was performed to assess fungal-associated changes at the site of inoculation, as well as dissemination to other tissues. No mortality was observed in any of the treatment groups, and there were no histological changes observed in the OG exposed animals. Fungus was not recovered from splenic samples regardless of the fungal strain, mouse strain, or route of infection. Mice did not develop systemic phaeohyphomycosis, but histopathological changes at the site of injection mimicked the condition seen in humans with fungal hyphae and local inflammation. In conclusion, nu/+ mice appear to be a useful animal model of subcutaneous fungal infection with V. botryosa. Moreover, the results suggest that V. botryosa isolates present low zoonotic risk. The methods used in the current study can be followed or modified to study zoonotic risk of emergent and previously recognized pathogens of aquatic animals.
Acknowledgments
The authors wish to thank the University of California-Davis, School of Veterinary Medicine for their financial support, Susan C. Yun for her guidance, the Teaching and Research Animal Care Services staff for their assistance, and Dr. Laurie Brignolo for donating the mice used in this study.
* Presenting author
+ Student presenter
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