Coccidiosis in Wild Eastern Newts (Notophthalmus viridescens): An Unexpected Finding in Consecutive Mortality Events in Tennessee, USA.

Wildlife diseases are a major threat for species conservation, and there is a growing need to implement more comprehensive disease response programs to better identify these diseases of concern. During March 2017, we observed moribund and dead eastern newts, Notophthalmus viridescens, in a single pond in middle Tennessee. All moribund individuals were emaciated. We euthanized and processed all individuals immediately on-site and later performed histopathology and quantitative PCR for ranavirus, the protist Perkinsea, and chytrid fungi Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans. One newt was positive for ranavirus. Histopathology showed no evidence of ranavirosis but did reveal overwhelming coccidiosis. Overlapping partial sequences of coccidian 18S subunit DNA showed a 96.4% match with Eimeria steinhausi, suggesting that lesions were due to a previously undescribed Eimeria sp. In 2019, two more moribund newts were encountered at the same pond. Histopathology revealed the same suspicious parasitic organisms, and one individual was positive for B. dendrobatidis. Further research on how seasonal and other environmental parameters may influence coccidia-associated morbidity and mortality is warranted. These events highlight the importance of histopathologic evaluation of mortality events and provide guidance for investigation of future outbreaks.

Prevalence of Ophidiomyces ophiodiicola, the Causative Agent of Snake Fungal Disease, in the Interior Plateau Ecoregion of Tennessee, USA.

The fungal pathogen Ophidiomyces ophiodiicola, the causative agent of snake fungal disease, has been implicated in declines of North American snake populations since 2006 and the geographic range of this pathogen is still not fully known. In Tennessee, US, O. ophiodiicola has been detected since 2012, but large portions of the state have not been surveyed for this pathogen. Our primary objective was to monitor the prevalence of O. ophiodiicola in the Interior Plateau ecoregion of Tennessee by swabbing all snakes that were encountered during road cruising survey efforts in 2017 and 2018. Eleven snakes of four species, copperhead (Agkistrodon contortrix), common water snake (Nerodia sipedon), black kingsnake (Lampropeltis nigra), and smooth earthsnake (Virginia valeriae), tested positive for the presence of O. ophiodiicola. Overall, 9.2% (11/120) of snakes sampled tested positive for the presence of O. ophiodiiola, and we further observed a seasonal trend in detections with summer months having the greatest frequency of detections. Our results extend the known geographic range of O. ophiodiicola in Tennessee by adding four previously unconfirmed O. ophiodiicola-positive counties. Further sampling will need to be conducted across west Tennessee because this is the most data-deficient region of the state. Our results offer additional evidence of the presence of this pathogen in Tennessee and will help researchers further understand the geographic distribution and host range.