Using diseases in fish to our advantage
In lakes and rivers across the state, fish kills – localized die-offs of fish and other aquatic species – are an unfortunate reality. These events can be caused by oxygen depletion, overpopulation, or infectious diseases, which is what piqued the interest of MAISRC and fish health researcher Dr. Nicholas Phelps.
If infectious diseases can cause die-offs in native fish, might they cause die-offs for invaders as well? In fact, could we even use this approach to control invasive fish like Asian and common carp?
To further assess this approach, the Phelps lab has been working to characterize the virome of silver, bighead, and common carp. The virome – essentially a snapshot of all the viruses in a fish, whether problematic or not – is giving researchers, for the first time ever, a baseline understanding of what viruses exist in carp. Phelps is collecting samples from randomized sites in Minnesota, as well as from known fish kills across the country.
Samples of carp were gathered from lakes in Minnesota as well as the Chicago, Fox, and Illinois Rivers, where silver carp have become prolific. These samples are processed in the lab for virus isolation, followed by realtime PCR and next generation sequencing.
“Basically, we are conducting molecular tests that will give us a full list of viruses in each species of fish, with the hope of discovering a brand new virus that is only found in carp and which could be used as a very species-specific biocontrol,” Phelps said.
So far, approximately a year and a half into the project, two novel viruses have been identified from common carp and grass carp mortality events: novel picornavirus and novel paramyxovirus. The previously known grass carp reovirus (GCRV) was also confirmed, which was the first report of GCRV associated with fish mortality in the United States.
“Further down the road if we discovered a species-specific pathogen, we could theoretically grow the virus in a lab and release it to a lake or river where the carp are congregated to infect them,” Phelps added. “The virus can replicate itself and spread quickly – it would be like a kid with a cold at daycare.”
In addition to providing opportunities for biocontrol, understanding the virome of invasive species will serve as a potential early indicator for the movement and distribution of pathogens that may threaten native species.
