News and Highlights: May 2006

Accepted abstract for the 2006 Annual Conference of the Wildlife Disease Association and the American Association of Wildlife Veterinarians, University of Connecticut, August 6 - 10.

THE INFLUENCE OF CATTLE ON PATHOGEN PREVALENCE IN GREEN FROG (RANA CLAMITANS) AND AMERICAN BULLFROG (RANA CATESBIANA) TADPOLES IN CUMBERLAND PLATEAU WETLANDS

A. Chandler Schmutzer, Department of Forestry, Wildlife and Fisheries, University of Tennessee, 274 Ellington Plant Sciences Building, Knoxville, TN 37996; Matthew J. Gray, Department of Forestry, Wildlife and Fisheries, University of Tennessee, 274 Ellington Plant Sciences Building, Knoxville, TN 37996; Debra L. Miller, Veterinary Diagnostic and Investigational Laboratory, The University of Georgia, College of Veterinary Medicine, 43 Brighton Road, Tifton, GA 31793

Diseases have been associated with amphibian declines worldwide.  It is hypothesized that anthropogenically induced stress may increase pathogen prevalence in amphibian populations by compromising immunity.  Cattle grazing in wetlands may induce stress in resident tadpole populations by altering water quality.  Therefore, we compared pathogen prevalence in green frog (Rana clamitans; n=80) and American bullfrog (Rana catesbiana; n=101) tadpoles residing in eight cattle-access and non-access wetlands on the Cumberland Plateau, Tennessee.  Tadpoles were collected during winter, summer, and fall 2005, and were screened for pathogens using standard viral and microbial isolation techniques and PCR for frog virus 3 (FV3) confirmation.  Two pathogens (FV3 and Aeromonas hydrophila) known to be associated with amphibian die-offs were isolated from both tadpoles species.  Frog virus 3 was more prevalent (P=0.02) in green frog tadpoles residing in cattle-access (45%) versus non-access (15%) wetlands.  No differences were detected (P=0.78) between treatments in FV3 prevalence for bullfrog tadpoles.  A season trend in FV3 prevalence existed, with prevalence greater (P<0.02) in the fall and winter than in summer for both tadpole species.  Prevalence of A. hydrophila was greater in cattle-access (45%) than in non-access (0%) wetlands for bullfrog tadpoles during fall.  Also, prevalence of A. hydrophila was greater in fall than in summer for both tadpole species.  Our results suggest that cattle use of wetlands may increase prevalence of amphibian pathogens in tadpoles, although this effect may be species and season dependent.

Read more about the Center's Amphibian Disease Program 

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