Ranavirus epidemics constitute a serious emerging threat to wild populations of fishes, amphibians, and reptiles. Ranaviral outbreaks have now been documented on six continents, in 43 countries, and in more than 173 species of fishes, amphibians, and reptiles (Global Ranavirus Consortium) and ranaviral disease is now considered a Notifiable Pathogen (World Organization for Animal Health). Infection can move quickly through these ectothermic vertebrate populations or communities and mortality rates can reach 100 percent. And with greater occurrence, co-pathogens are being identified in box turtles, namely other upper respiratory pathogens: herpesvirus and Mycoplasma. These pathogens are less likely to cause mortality and may better represent individual or environmental stress. Clinical signs include nasal discharge, ocular swelling and discharge, and oral plaques.
Snake Fungal Disease
Ophidiomyces ophiodiicola is currently placed in the order Onygenales (Ascomycota) within the family Onygenaceae. This fungus is closely related to other species of Onygenaceae within the Chrysosporium anamorph Nannizziopsis vriesii (CANV) complex that causes dermal lesions in reptiles. The genus Ophidiomyces currently contains only one species, O. ophiodiicola, and it is known to infect only snakes. It leads to the syndrome Snake Fungal Disease (SFD), which causes widespread morbidity and mortality across the eastern United States.
Historically, several case reports of skin disease in snakes were confirmed or suspected to be CANV or CANV-like. However, since publication of the description of the genus Ophidiomyces in 2013 and with the use of advanced molecular techniques, it is now thought that many of these infections may have been caused by O. ophiodiicola.
Clinical signs consist of skin swelling, flaking, nodules, pustules, and displaced scales. The manifestation of SFD in colubrid snakes is variable and has included pneumonia, ocular infections, and subcutaneous nodules. A case of O. ophiodiicola was observed in a black rat snake (Elaphe obsoleta obsoleta) with a subcutaneous nodule. In addition, mycosis was observed in the skin as well as a more systemic invasion involving the lungs and eye (one case) and lungs and liver (one case) of garter snakes.
Diagnosis Offered at Illinois
The Wildlife Epidemiology Laboratory is a collaborative research diagnostic lab for new or ongoing studies in free-ranging and captive amphibians, reptiles, birds, and mammals. We have developed diagnostic assays for ranavirus, Terrapene herpesvirus 1, box turtle Mycoplasma, and Ophidiomyces. These assays utilize qPCR technology to detect pathogen DNA. Sample types and submission guidelines are now available through the Veterinary Diagnostic Laboratory. Concurrent histopathology and culture tests are still available as well.
—Matt Allender, DVM, MS, PhD, DACZM