Pathological characterization of natural Ophidiomyces ophiodiicola infection in wild-caught Lake Erie watersnakes: A standardized approach to documentation of disease

Ophidiomyces ophiodiicola (formerly Chrysosporium ophiodiicola), the causative agent of ophidiomycosis (Snake Fungal Disease; SFD), is a serious emerging fungal pathogen causing morbidity and mortality in both wild and captive snakes. SFD has been documented in terrestrial and aquatic captive snake populations in the United Kingdom, Germany, Australia, and North America. The most common presenting clinical signs of SFD infection include severe dermatitis, facial swelling, and emaciation. It was previously thought that lesions associated with SFD were limited to the skin of the head and neck; however, recent reports show well-documented cases of SFD skin lesions throughout many regions of the body. These case reports predominantly focus on grossly visible cutaneous lesions. Rarely, systemic lesions within the lungs, spleen, liver, eye, and kidneys have been documented. SFD can be fatal; however, the complications of this disease leading to mortality, particularly concerning the pathology and role of comorbidities, are poorly understood. This lack of understanding limits the ability and success of clinicians and rehabilitators to treat snakes infected with SFD and inhibits our ability to prevent transmission in both captive and wild settings. Treatment and preventing transmission are particularly important for those species that are endangered or threatened. The aim of this study was to gain insight into the cutaneous disease severity, subclinical manifestation, systemic involvement, and comorbidities associated with SFD. I hypothesized the following: 1) the systematic mapping protocol derived from this methodology will identify characteristic lesions of SFD in a cohort of wild-caught Lake Erie water snakes, 2) as the number of survey sections affected by SFD increases, so too will the overall cutaneous severity score, 3) histopathological examination will allow for detection of subclinical lesions that are not associated with gross disease, 4) individuals with visceral granulomas will have more severe cutaneous disease, 5) there will be a range of infectious and non-infectious conditions associated with ophidiomycosis, and finally 6) individuals with decreased visceral adipose tissue will have a higher overall cutaneous severity score as well as head cutaneous severity score than those with adequate visceral adipose tissue. This study established a detailed necropsy protocol that identified a positive correlation between cutaneous severity and a wider distribution in cutaneous lesions throughout an individual. The results also highlighted a high prevalence (45.3%) of subclinical, or grossly inapparent, cutaneous lesions as well as a lack of correlation between cutaneous severity and visceral granulomas. Finally, this study documented numerous comoribidities, including verminous pneumonia, heterophilic enteritis and splenitis, cutaneous mites, and coccidiosis. The most-prevalent comorbidity was decreased visceral adipose tissue stores which was not associated with cutaneous disease severity. The results of this study suggest that SFD alone is able to cause mortality; however the pathogenesis by which O. ophiodiicola does this remains unclear. Additionally, these results provide a process for those studying SFD to evaluate cutaneous severity of disease with clincal (grossly visible) and subclinical (grossly absent) disease.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

VMS-Veterinary Clinical Medcne

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Pohly, Andrea E.

Contributors dc:contributor

• Allender, Matthew
• LoBato, N Denae
• Hoyer, Lois
• Terio, Karen

• Snake
• Fungal
• SFD

Statement dc:rights

• Copyright 2020 Andrea Pohly

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108509

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108509