Exploring whether native pathogens can be used to control AIS
Although ambitious, eradication of aquatic invasive species is an ultimate goal of MAISRC. One possible method would be through the introduction or promotion of species-specific pathogens. This high-risk, high-reward approach must be carefully assessed with thorough investigation and scientifically justified risk assessment. As a first step in Phase I of a multi-phase project, invasive carp species were surveyed to identify viruses circulating in these populations. Nearly 700 common carp were collected from Minnesota lakes, 120 silver carp from the Fox and Illinois Rivers, and a variety of carp species from eight mortality events. All fish were negative for cyprinid herpes viruses 1, 2, and 3, carp edema virus, and spring viremia of carp virus. However, advanced molecular approaches and virus isolation detected several known and unknown viruses of significance. This included novel viruses from at least seven RNA virus families: picornavirus, reovirus, hepatovirus, astrovirus, hepatitis virus, betanodavirus, and paramyxovirus. The novel carp paramyxovirus was associated with a mortality event and shows particular promise for further evaluation as a biocontrol agent. The standard operating procedures developed during Phase I will be essential to advance future work on this and related pathogen discovery research. Unfortunately, Phase I was met with several unforeseen challenges that hindered completion of all proposed activities, including laboratory renovation progress, service provider availability and delays, and access to mortality events. In spite of these setbacks, this project has significantly advanced our understanding of invasive carp viruses and positioned us well to for future research efforts. Phase I of this project provided researchers and managers with baseline data on viruses circulating in invasive carp populations in the region. These data have been broadly disseminated at scientific conferences, peer-reviewed and lay publications, and through MAISRC communications. Continued efforts to build upon this line of research will commence in Phase II of this long-term effort.
Phase II: Virus discovery and evaluation for use as potential biocontrol agents
Phase I of this project provided initial baseline data on viruses of carp species in the region. Phase II will build upon this work for carp species and now include zebra mussels to utilize newly developed techniques to more strategically identify viral biocontrol candidates for control of invasive carp and zebra mussels. More specifically, Phase II will:
- Collect apparently healthy invasive carp and mussel species in the Midwest region;
- Collect samples from mortality events of native and invasive fish and mussel populations in the Midwest region;
- Conduct virus discovery by next generation sequencing and culture potential pathogens;
- Determine the disease causing potential of two selected viruses, one for native and invasive fish and the other for native and invasive mussels; and
- Communicate findings to scientific, management, and public stakeholders.
This will provide the scientific foundation to begin to evaluate specific pathogens for invasive species control. Furthermore, 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.
Want to learn more about Koi Herpes Virus? Check out this presentation from MAISRC researcher Nick Phelps or these Frequently Asked Questions about KHV.
Researchers worked in 2017 and 2018 to collect samples rom fish kills events of both invasive and native fish around the state. Koi Herpes Virus (KHV) and Carp Edema Virus (CEV) have been identified in the state. KHV was found for the first time in wild fish in Lake Elysian in 2017. CEV was also found for the first time in Minnesota. Samples are now being processed and screened. Based on research and consultation with others, researchers have decided to move forward with the investigation of KHV as a potential biocontrol agent for invasive carp. Two specific cell lines required for the isolation of KHV have been received and are currently being grown for future in-vitro culture.
As of January 2019, researchers have confirmed the detection of 11 novel viruses from common carp mortality events and five novel viruses from mortality events of native fish species. They have also confirmed six additional lakes positive for KHV, two for CEV, and two lakes with both KHV and CEV. Researchers are currently finalizing the phylogenetics to better determine the origin of the viral strains that have been detected in Minnesota. Experiments are now underway to grow the virus in live fish.