Discovery of a Novel Alveolate Pathogen Affecting Southern Leopard Frogs in Georgia: Description of the Disease and Host Effects Andrew K. Davis, 1 Michael J. Yabsley, 1,2 M. Kevin Keel, 2 and John C. Maerz 1 1 D.B. Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA 30602, USA 2 Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine, The University of Georgia, Athens, GA, USA Abstract: In April of 2006, we observed southern leopard frog (Rana sphenocephala) tadpoles in a pond in northeast Georgia that were dying from an unknown pathogen. Examination of affected specimens, as well as PCR characterization, revealed that all were infected with a novel alveolate pathogen closely related to fresh- water and marine eukaryotic organisms and, to a lesser degree, to members of the genus Perkinsus. This pathogen has been documented in numerous mortality events in anuran tadpoles in the United States, al- though it has not yet been named nor clearly described. We subsequently conducted a systematic survey of this and four other ponds in the same area to document the extent of the pathogen and to describe the nature of infections in leopard frog tadpoles. Of 87 live tadpoles examined, 25% were infected with the alveolate pathogen, based on visual inspection of tadpole liver tissue. Affected tadpoles frequently had enlarged abdo- mens, swam erratically, and could be captured by hand. All organs of infected tadpoles were infiltrated but typically to a lesser extent than the liver and kidneys, which often had hundreds of thousands of the spherical, 6-lm organisms. Infected tadpoles tended to weigh more than noninfected ones, likely due to the massive organ swelling that coincided with infections. Infected tadpoles did not differ in developmental stage from noninfected tadpoles. Infection prevalence varied widely among ponds, and in one pond, we witnessed a rapid die-off of R. spenocephala tadpoles during our surveys, although we did find infected metamorphic frogs. The rapid mortality we observed as well as the vast number of organisms seen in specimens suggests that this pathogen has tremendous transmission potential, and therefore deserves further monitoring and study. Keywords: Rana sphenocephala, southern leopard frogs, amphibian disease, alveolate pathogen INTRODUCTION Infectious diseases can play important roles in wildlife populations, from influencing host genetic diversity to causing widespread declines in terrestrial and marine sys- tems (e.g., Harvell et al., 1999; Daszak et al., 2000; Lafferty and Gerber, 2002; Altizer et al., 2003). Amphibians repre- sent a group of organisms that have been particularly im- pacted by infectious diseases (Daszak et al., 1999). Indeed, reports of large-scale amphibian population declines and the potential role of emerging pathogens in these declines (e.g., Kiesecker, 2002; Lips et al., 2005; Forson and Storfer, 2006; Pounds et al., 2006) have raised awareness of their Published online: September 6, 2007 Correspondence to: Andrew K. Davis, e-mail: akdavis@uga.edu EcoHealth 4, 310–317, 2007 DOI: 10.1007/s10393-007-0115-3 Original Contribution Ó 2007 EcoHealth Journal Consortium