Assessing the risk of introducing invasive pathogens through trade in wildlife: An amphibian case study
The live animal trade is a well-known route for the introduction of invasive species, parasites, and pathogens. Most amphibian imports occur through the pet and food trade, and some have been documented to carry pathogens, such as the fungal pathogens Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal). We evaluated the effectiveness and cost of four regulatory options designed to reduce the risk of introducing these pathogens through the live animal trade. We quantified amphibian imports using data provided by the U.S. Fish and Wildlife Service (USFWS), surveyed amphibian importers to quantify the amount and cost of existing disease testing, and created a risk assessment model using known rates of amphibian escape and establishment to quantify probability of disease establishment under four different regulatory options. We estimated the risk of disease establishment for the generalist amphibian pathogen Bd by quantifying imports of all species of amphibians and for the specialist pathogen Bsal by quantifying imports of all species of salamanders. We estimated the biological impact of chytridiomycosis on native species by assuming a 10-50% increase in the number of endangered species due to additional population declines, and estimated the financial cost based on costs reported in ESA recovery plans.
Results/Conclusions (200 words)
The U.S. imported approximately4 million amphibians (~ 270,000 salamanders) annually between 2003–2013. If there were no restrictions on amphibian imports (the status quo), our model predicts 212–1,693 Bd-infected amphibians and 21–168 Bsal-infected salamanders could escape and become established annually. If population declines occurred as a result of those introductions, annual costs to USFWS would be at least $0.93 million to recover an additional 10% of ESA-listed amphibians, and at least $ 0.59 million to recover an equal proportion of salamanders. Only 3 of 32 amphibian recovery plans featured chytrid-specific actions, costing $39,000 to $147,000/year. According to our model, changes to import regulations could reduce risk of chytrid pathogens entering the U.S. through the live animal trade by 90%. This reduction in risk would reduce the financial burden to USFWS via fewer ESA listings and recovery plans, but could increase costs to importers if disease testing and certification programs were required. Our analysis indicated that reduced profits to importers due to health certification could be offset by increasing sale price of individual amphibians by $0.40. The risk to native amphibians is high from both Bd and Bsal and could be significantly reduced with Bd- or Bsal-free health certifications.