Pathogen Host Switching in Commercial Trade with Management Recommendations

Abstract

Global wildlife trade exacerbates the spread of nonindigenous species. Pathogens also move with hosts through trade and often are released into naïve populations with unpredictable outcomes. Amphibians are moved commercially for pets, food, bait, and biomedicine, and are an excellent model for studying how wildlife trade relates to pathogen pollution. Ranaviruses are amphibian pathogens associated with annual population die-offs; multiple strains of tiger salamander ranaviruses move through the bait trade in the western United States. Ranaviruses infect amphibians, reptiles, and fish and are of additional concern because they can switch hosts. Tiger salamanders are used as live bait for freshwater fishing and are a potential source for ranaviruses switching hosts from amphibians to fish. We experimentally injected largemouth bass with a bait trade tiger salamander ranavirus. Largemouth bass became infected but exhibited no signs of disease or mortality. Amphibian bait ranaviruses have the potential to switch hosts to infect fish, but fish may act as dead-end hosts or nonsymptomatic carriers, potentially spreading infection as a result of trade.

Widespread Occurrence of Ranavirus in Pond-Breeding Amphibian Populations

“…We identified fish because they are an amphibian predator and could affect densities (Wellborn et al 1996). Although fish may be a reservoir for ranaviruses (Picco et al 2010), they were not sampled for ranavirus infections. There were two cases when we were unable to identify the amphibian larvae to species.…”

Distribution and Host Range of Ranaviruses

“…Experimental infection of largemouth bass was successful, but inoculated animals experienced no mortality or disease (Picco et al 2010 ). There is also evidence that multiple FV3-like and ATV-like strains may circulate in ponds and may affect both urodeles and anurans (Schock et al 2008 ).…”

Ranavirus Ecology and Evolution: From Epidemiology to Extinction

“…In particular, it appears that fi sh and at least some reptiles are less susceptible to ATV and FV3-like ranaviruses than amphibians (Jancovich et al 2001 ;Picco et al 2010 ;Allender et al 2013b ;Brenes et al 2014a ). Several studies have demonstrated little or no transmission of ATV (Jancovich et al 2001 ;Picco et al 2010 ) and FV3 to fi sh (Ariel et al 2010 ;Gobbo et al 2010 ;Bang Jensen et al 2011a ;but see Bang Jensen et al 2011b ). Similarly, amphibians may be less susceptible to fi sh ranaviruses.…”