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Diseases of Aquatic Organisms

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DAO 99:1-6 (2012)  -  DOI:

Reliability of non-lethal surveillance methods for detecting ranavirus infection

Matthew J. Gray1,*, Debra L. Miller2,3, Jason T. Hoverman1,4

1University of Tennessee, Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, 274 Ellington Plant Sciences Building, Knoxville, Tennessee 37996-4563, USA
2University of Georgia, College of Veterinary Medicine, Veterinary Diagnostic and Investigational Laboratory, 43 Brighton Road, Tifton, Georgia 31793, USA
3Present address: University of Tennessee, Center for Wildlife Health and Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, Knoxville, Tennessee 37996-4563, USA
4Present address: Department of Forestry and Natural Resources, Purdue University, 195 Marsteller Street, West Lafayette Indiana 47907–2033, USA

ABSTRACT: Ranaviruses have been identified as the etiologic agent in many amphibian die-offs across the globe. Polymerase chain reaction (PCR) is commonly used to detect ranavirus infection in amphibian hosts, but the test results may vary between tissue samples obtained by lethal and non-lethal procedures. Testing liver samples for infection is a common lethal sampling technique to estimate ranavirus prevalence because the pathogen often targets this organ and the liver is easy to identify and collect. However, tail clips or swabs may be more practicable for ranavirus surveillance programs compared with collecting and euthanizing animals, especially for uncommon species. Using PCR results from liver samples for comparison, we defined false-positive test results as occurrences when a non-lethal technique indicated positive but the liver sample was negative. Similarly, we defined false-negative test results as occurrences when a non-lethal technique was negative but the liver sample was positive. Using these decision rules, we estimated false-negative and false-positive rates for tail clips and swabs. Our study was conducted in a controlled facility using American bullfrog Lithobates catesbeianus tadpoles; false-positive and false-negative rates were estimated after different periods of time following exposure to ranavirus. False-negative and false-positive rates were 20 and 6%, respectively, for tail samples, and 22 and 12%, respectively, for swabs. False-negative rates were constant over time, but false-positive rates decreased with post-exposure duration. Our results suggest that non-lethal sampling techniques can be useful for ranavirus surveillance, although the prevalence of infection may be underestimated when compared to results obtained with liver samples.

KEY WORDS:  Iridovirus · Ranavirus · Molecular technique · PCR · Sampling · Surveillance

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Cite this article as: Gray MJ, Miller DL, Hoverman JT (2012) Reliability of non-lethal surveillance methods for detecting ranavirus infection. Dis Aquat Org 99:1-6.

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