VHSV in smallmouth bass and round goby: What have we learned?

Transcription

1 VHSV in smallmouth bass and round goby: What have we learned? presented by Geofrey E. Eckerlin Thousand Islands Biological Station

2 Background - Description of pathogen (i.e. what is it?) Where did it come from? Where is it now? VHSV in smallmouth bass and round goby Major findings Future lines of investigation

3 Viral Hemorrhagic Septicemia Virus Type IVb The Pathogen (VHSV): Bullet-shaped, enveloped, virions (Rhabdoviridae) The Disease (VHS or Egtved Disease): first described among cultured rainbow trout in France and Germany (1879 and 1882, respectively) Genotype IVb = 1st intro to N American freshwater and several species Externally: Darkening, bulging eyes, very pale to white gills Internally: petechiate hemorrhaging on the liver, swim bladder, visceral and adipose tissues extreme cases with internal bleeding NOT HARMFUL TO HUMANS

4 III Ib, II, III I, Ia, IVa IVa IVb Theory: endemic to marine systems - introduced to freshwater IVb IVb Elsayed et al. 2006, Gagne et al maps.google.com

5 VHSV 2005, 2006, 2007, 2008 South Milwaukee, Lake Michigan Clear Fork Reservoir

6 As of November 2007: Officially 28 species Photo: David Figura Black crappie Bluegill Bluntnose minnow Brown bullhead Brown trout Burbot Channel catfish Chinook salmon Emerald shiner Freshwater drum Gizzard shad Lake whitefish Largemouth bass Muskellunge Shorthead redhorse Northern Pike Pumpkinseed Rainbow trout Rock bass Round goby Silver redhorse Smallmouth bass Spottail shiner Trout-Perch Walleye White bass White perch Yellow perch

7 A trophic interaction with an invasive species resulting in tradeoffs for smallmouth bass Prey on SMB eggs Prey on RG confirmed high VHSV levels hyper-abundance prey on SMB embryos increased condition - goby diet increased nest guarding costs increased exposure to VHSV? (Groocock et al. 2007) (Steinhart et al. 2004a, 2004b, 2005)

8 month M J J A S O N D J 31.2% (Fisher s exact test, p=0.002) F M A M J J natural log viral RNA quantity % 1.6% 1.7% 9.1% mean daily water temperature ( C) % Sp1 PS S LF PrS Sp2 n=61 n=71 n=62 n=60 data not available n=17 n=77 0

9 Concept definitions: Reservoir host- One or more epidemiologically related populations or environments where a pathogen can be permanently maintained and from which infection is transmitted to a target populations (Haydon et al. 2002) Reservoir competence- the probability of a given species infecting another species (adapted from Brunner et al. 2008) -Cambridge City Council, UK

10 What defines a competent or effective reservoir host? High reproductive rates High densities Habitat plasticity Aggressive/social interactions within or between species Relatively unaffected by the disease Think Hantavirus (Douglass 2007), Lyme disease (LoGuidice et al. 2003), plague (Collinge et al. 2008), Nipah, Ebola and SARS-CoV (Dobson 2005), Brucellosis (Al Dahouk et al. 2005), etc -

11 Round goby (RG) as a reservoir host - High densities, serially stressed Highly affected by VHSV, though still hyper-abundant Aggressive, social and highly integrated into food web Virus present among RG during pre-spawn when not found among SMB Extremely high viral levels ( ) -AP, M. Spencer Green

12 Goby frequency among SMB Gut Contents estimate round goby density (number / m 2 ) 62.31% n= % n=80 NO DIFFERENCE (Fisher s exact test p=0.7031) 65.82% n=79 INDICATIONS: DIET DOES NOT = CONTACT DIET PREFERENCE? 2006 fine mesh 2006 course mesh 2007 fine mesh 2007 fine mesh Cape Vincent Clayton Alex Bay Seining index data from JM Farrell

13 estimate round goby density (number / m 2 ) VHSV prevalence among SMB 13.5% n=96 Fisher s exact test, p= % n= % n= fine mesh 2006 course mesh 2007 fine mesh 2007 fine mesh Cape Vincent Clayton Alex Bay Seining index data from JM Farrell

14 Major Lessons: Strong yearly VHSV outbreak trend can be used to focus monitoring effort VHSV IVb affected our juvenile SMB more Smallmouth may be selecting goby Round goby densities follow same general spatial pattern as VHSV prevalence

15 Where are we going from here? Proposing to combine VHSV work with St. Lawrence food web study to expand our understanding of the entire viral reservoir I hope to continue to investigating the role of round goby as reservoir host Investigate efficacy of round goby control methods in disease prevention

16 Acknowledgements: Without the support, coordination and collaboration of all of you, this body of work would not have been possible. New York State Seagrant Federal Sportfish Restoration Program New York State Department of Environmental Conservation The Great Lakes Research Consortium Jessica E. Schneider, Elizabeth Elkins, Dr. John Farrell, Dr. Paul Bowser, Steve Lapan, Dr. Jacqui Frair, Dr. Chris Whipps, Dr. James Casey, Rufina Casey, Dr. Geoffrey Groocock, Dr. Rod Getchell, Greg Wooster, Krissy Hope, Tom Heath and the rest of the folks at CAAHL, Jana Lantry, Lee Calhoun, Steve Lapan, Dr. John Coll and collaborators at the Lamar USFWS Lab, Roger Klindt and the Brownville crew, Eric Reynolds, Katie Woodside, Kevin Kapuscinski, Chuck Curry, Jarrod Hughes, Brain Kelder, Dan Zangari, Tom Bell, Scott Copey, Chris Mickle, Jenna Rossenwasser, Jen Raino, Maureen Gregory, Francis Reynolds, Colby Bowman, Carly Fairbanks, Anne Strodel, Reinman s, O Briens, Mom and Ferrous Oxide.