A Test of Non-Invasive Detection Methods for Snake Fungal Disease

The emerging fungal pathogen, Ophidiomyces ophidiicola, (snake fungal disease; SFD) has been recently reported in wild pit viper populations from at least ten states. Specifically, SFD has affected two species of conservation concern, the Timber Rattlesnakes Crotalus horridus and and Eastern Massasauga Sistrurus catenatus. Symptoms reported for SFD include scabs or crusty scales, subcutaneous nodules, cloudiness of the eyes, skin ulcers, lesions, and swelling of the face. Although biopsies of infected tissue are the preferred diagnostic technique, they are not practical given conservation, logistical, and safety concerns. Non-invasive methods to detect SFD in wild individuals have produced inconsistent results. Therefore, to determine the most effective method for detecting SFD in the field, we performed a laboratory challenge study in which we infected the Cottonmouth (Agkistrodon piscivorous), with a cultured strain of O. ophidiicola. Our goal was to assess efficacy of two sampling methods: cotton tipped swabs and saline flushes of the loreal pits. To evaluate each technique, we sampled each pit using cotton swabs and saline flushes twice weekly for a period of 120 days. Only cotton-tipped swabs were found to be an effective means of DNA collection. Gross necropsy and histopathology were performed on all individuals following the study to confirm infection and identify internal effects of SFD.