Abstract
Snake fungal disease (SFD) is a clinical syndrome associated with dermatitis, myositis, osteomyelitis, and pneumonia in several species of free-ranging snakes in the US. The causative agent has been suggested as Ophidiomyces ophiodiicola, but other agents may contribute to the syndrome and the pathogenesis is not understood. To understand the role of O. ophiodiicola in SFD, a cottonmouth snake model of SFD was designed. Five cottonmouths (Agkistrodon piscivorous) were experimentally challenged by nasolabial pit inoculation with a pure culture of O. ophiodiicola. Development of skin lesions or facial swelling at the site of inoculation was observed in all snakes. Twice weekly swabs of the inoculation site revealed variable presence of O. ophiodiicola DNA by qPCR in all five inoculated snakes for 3 to 58 days post-inoculation; nasolabial flushes were not a useful sampling method for detection. Inoculated snakes had a 40% mortality rate. All inoculated snakes had microscopic lesions unilaterally on the side of the swabbed nasolabial pit, including erosions to ulcerations and heterophilic dermatitis. All signs were consistent with SFD; however, the severity of lesions varied in individual snakes, and fungal hyphae were only observed in 3 of 5 inoculated snakes. These three snakes correlated with post-mortem tissue qPCR evidence of O. ophiodiicola. The findings of this study conclude that O. ophiodiicola inoculation in a cottonmouth snake model leads to disease similar to SFD, although lesion severity and the fungal load are quite variable within the model. Future studies may utilize this model to further understand the pathogenesis of this disease and develop management strategies that mitigate disease effects, but investigation of other models with less variability may be warranted.
Highlights
Emerging wildlife diseases are increasing in prevalence worldwide, and can have dramatic impacts on local populations [1]
The eastern massasauga and timber rattlesnake are both are under local threats to their sustainability, studying Snake fungal disease (SFD) in these target species is limited to observational studies
Cottonmouth snakes inoculated with O. ophiodiicola showed clinical signs and histopathological evidence consistent with SFD
Summary
Emerging wildlife diseases are increasing in prevalence worldwide, and can have dramatic impacts on local populations [1]. Snake fungal disease (SFD) is one such disease syndrome associated with high morbidity and mortality in free-ranging snakes, predominantly eastern massasaugas (Sistrurus catenatus) and timber rattlesnakes (Crotalus horridus) [2,3,4,5,6,7,8,9]. A model is needed to characterize the pathogenesis of SFD through experimental challenge. Experimental transmission studies are historically used in model species to demonstrate the ability of a pathogen to study a disease syndrome in threatened species [13]. The eastern massasauga and timber rattlesnake are both are under local threats to their sustainability, studying SFD in these target species is limited to observational studies. Cottonmouths (Agkistrodon piscivorous) are an abundant pit-viper species overlapping in distribution with both the eastern massasauga and timber rattlesnake
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