title: Ranavirus could facilitate local extinction of rare amphibian species.
abstract: There is growing evidence that pathogens play a role in population declines and species extinctions. For small populations, disease-induced extinction may be especially probable. We estimated the susceptibility of two amphibian species of conservation concern (the dusky gopher frog [Lithobates sevosus] and boreal toad [Anaxyrus boreas boreas]) to an emerging pathogen (ranavirus) using laboratory challenge experiments, and combined these data with published demographic parameter estimates to simulate the potential effects of ranavirus exposure on extinction risk. We included effects of life stage during pathogen exposure, pathogen exposure interval, hydroperiod of breeding habitat, population carrying capacity, and immigration in simulations. We found that both species were highly susceptible to ranavirus when exposed to the pathogen in water at environmentally relevant concentrations. Dusky gopher frogs experienced 100 % mortality in four of six life stages tested. Boreal toads experienced 100 % mortality when exposed as tadpoles or metamorphs, which were the only life stages tested. Simulations showed population declines, greater extinction probability, and faster times to extinction with ranavirus exposure. These effects were more evident with more frequent pathogen exposure intervals and lower carrying capacity. Immigration at natural rates did little to mitigate effects of ranavirus exposure unless immigration occurred every 2 years. Our results demonstrate that disease-induced extinction by emerging pathogens, such as ranavirus, is possible, and that threat may be especially high for species with small population sizes. For the species in this study, conservation organizations should incorporate ranavirus surveillance into monitoring programs and devise intervention strategies in the event that disease outbreaks occur.
authors.affiliation: Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK, 74078, USA. julia.earl@okstate.edu.
authors.forename: Julia E
authors.initials: JE
authors.lastname: Earl
authors.affiliation: Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Jordan C
authors.initials: JC
authors.lastname: Chaney
authors.affiliation: Department of Agricultural and Environmental Sciences, Tennessee State University, Nashville, TN, 37209, USA.
authors.forename: William B
authors.initials: WB
authors.lastname: Sutton
authors.affiliation: Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Carson E
authors.initials: CE
authors.lastname: Lillard
authors.affiliation: Conservation and Research Department, Memphis Zoological Society, Memphis, TN, 38112, USA.|Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Starkville, MS, 39762, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Kouba
authors.affiliation: Department of Biochemistry and Molecular Biology, Mississippi State University, Starkville, MS, 39762, USA.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Langhorne
authors.affiliation: Omaha's Henry Doorly Zoo and Aquarium, Omaha, NE, 68107, USA.
authors.forename: Jessi
authors.initials: J
authors.lastname: Krebs
authors.affiliation: Department of Biomedical and Diagnostic Sciences, University of Tennessee College of Veterinary Medicine, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Rebecca P
authors.initials: RP
authors.lastname: Wilkes
authors.affiliation: Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Rachel D
authors.initials: RD
authors.lastname: Hill
authors.affiliation: Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, 37996, USA.|Department of Biomedical and Diagnostic Sciences, University of Tennessee College of Veterinary Medicine, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Miller
authors.affiliation: Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Gray
mesh_terms: D000818:Animals; D004266:DNA Virus Infections; D004198:Disease Susceptibility; D007814:Larva; D017995:Ranavirus; D011898:Ranidae
keywords: Amphibian declines; Anaxyrus boreas boreas; Endangered species; Iridoviridae; Lithobates sevosus; Matrix model