Shell Lesions Associated With <i>Emydomyces testavorans</i> Infection in Freshwater Aquatic Turtles

Abstract

A newly described onygenalean fungus, <i>Emydomyces testavorans</i>, has been isolated from ulcerative shell and skin lesions of freshwater aquatic chelonians. To investigate the shell lesions associated with infection and determine if any lesional features were unique to <i>E</i>. <i>testavorans</i>, tissues from turtles housed in zoological institutions (<i>n</i> = 45) in the United States and free-living turtles (<i>n</i> = 5) submitted for diagnostic biopsy or necropsy were examined. Free-living turtles were from geographically distinct habitats in Florida (<i>n</i> = 1) and Washington (<i>n</i> = 4) at the time of sampling. Histologic shell sections were evaluated for the presence or absence of specific lesional features. Infection with <i>E. testavorans</i> was evaluated in all cases by screening GMS (Grocott-Gomori's methenamine silver)-stained histologic sections for the presence of morphologically consistent fungi and by quantitative PCR (polymerase chain reaction) on representative frozen tissue or formalin-fixed paraffin-embedded sections. Additionally, culture was performed for 15 cases with available fresh/frozen tissue. In total, there were 17 PCR-confirmed <i>E. testavorans</i> cases, 29 cases with morphologically consistent fungi on GMS-stained sections, and 21 cases of shell lesions without histologic or molecular evidence of <i>E. testavorans</i> infection. Epithelial inclusion cysts, defined as cystic structures within the dermis lined by keratinized stratified squamous epithelium and containing necrotic bone and keratin debris, were significantly (<i>P</i> < .01) associated with <i>E. testavorans</i> infection. Other significantly associated shell lesions included squamous metaplasia, hyperkeratosis, inflammation, and osteonecrosis (<i>P</i> < .05). This study identified characteristic shell lesions associated with <i>E. testavorans</i> infection. Further studies to prove causality are needed.