Fish Farms. DATCP Fish Health 4/21/2009. Myron Kebus, MS, DVM. State Aquaculture Veterinary Epidemiologist

Transcription

1 Fish Farms Myron Kebus, MS, DVM State Aquaculture Veterinary Epidemiologist DATCP Fish Health National model for fish health programs Requirements: Import permits Health certificates Record-keeping Reportable diseases Veterinary education Fish farmer education Slide of map of WI Fish Farms Number of import permits for WI (see below) Slide of VHA paperwork, 42 farms have VHA s Ark. Ill. Iowa Kan. Canada Mich. Minn Neb. N.C. N.D. Del S.C. S. D. Vermont Wash New York Montana MO 1

2 What is VHS? Viral Hemorrhagic Septicemia VHSv-rhabdovirus NOT found in Wisconsin Reportable animal disease Hx: mortality-rainbow trout/turbot aquaculture (Europe/Pacific Coast) Great Lakes Basin-Type IVb Species: 16 coolwater & 3 coldwater freshwater drum, muskies, round gobies, gizzard, shad, white bass, yellow perch VHSv-Characteristics Slide of VHS rhabdovirus NOT a human pathogen Active <15 C, spring season Clinical signs Fish ataxia, swimming just below the surface Listless Bulging eyes Bloated abdomen Petechiae to large red patches Rapid death No external signs Internal lesions: multiple organ hemorrhage Death due to internal organ failure Picture of VHS positive fish (hemorrhaging, nasty) and normal fish which one has VHS?????? 2

3 VHSv-transmission Reservoir: clinically ill or carrier fish All age-groups are susceptible Urine, sexual fluids, cannibalism, +/- feces Vertical: eggs Routes of exposure: gills or wounds, orally is unlikely Free virus: ~14 days in water Fish that recover can shed virus VHS in North America Map of US, dots where VHS has been isolated. 2003: Lake St. Clair 2005: Lakes- Ontario, St. Clair, Huron 2006: St. Lawrence River, Lakes- Erie, Ontario, St. Clair Michigan, Ohio, Pennsylvania, New York, Ontario with reported die-offs NOT in commercial aquaculture facilities (yet) What? How? Who? Source is unknown One theory of origin: Maritime Provinces of Canada VHS normally in marine finfish Mutation to new strain, pathogenic to naïve freshwater fish 3

4 Regulations APHIS Emergency Order 10/24/06 Prohibits importation of certain species (37) of live fish from Ontario and Quebec, Canada Prohibits interstate movement of same species from New York, Pennsylvania, Ohio, Michigan, Indiana, Minnesota, Illinois, and Wisconsin Amendments 11/14/06 Permissable movement of susceptible species 1) Approved slaughter facility (human consumption) 2)Research, diagnostic laboratory 3)Other- require VHS-negative certification Reporting DATCP DNR (if affects wild populations) USDA (APHIS)- within 24 hours OIE- within 24 hours VHS Diagnosis American Fisheries Society Fish Health Section Blue Book Necropsies performed Gross pathologic lesions analyzed Tissue sections fixed for histology Microscopic lesions analyzed Tissue removed for infectious disease analysis Kidney and spleen for viral Kidney and liver for bacterial 4

5 VHS Diagnosis Slide of VHS + fish (from DNR) Process tissues to grow virus Homogenization Centrifugation Inoculation of supernatant onto plates Virus is grown in three cell lines for 28d CHSE Chinook salmon embryo EPC Epithelial papilloma of carp Fathead Minnow Epithelial origin CPE found further diagnostic tests No CPE found after 28d negative result Cytopathic Effects of VHS Rounded and granular cells in grape-like clusters Marginated chromatin VHS Diagnosis Further testing if CPE are found EM supporting evidence, not definitive IPN birnavirus IHN and VHS rhabdovirus PCR confirmatory, takes two days RNA isolation RT-PCR DNA PCR Gel electrophoresis Positive test at WVDL National Veterinary Services Lab to confirm 5

6 Formulating a Plan of Action First step: Quarantine How many fish do we need to sample to confirm our diagnosis? From which ponds should we sample? Do we want to sample in other locations? What containment steps should we take? What do we do if VHS is confirmed? Number Needed To Sample Farm Variables Number of ponds Total number of fish Test variables Sensitivity Specificity Likelihood ratio negative Likelihood ratio positive Positive predictive value Negative predictive value Expected prevalence (pre test odds) Post test odds Other variables Desired confidence interval And then a bunch of animated statistical things fly in. Formulating a plan of action continued What if we confirm VHS? What would you do? Myron s comments from the bottom of that slide are copied in red: What happens if we confirm that we have VHS on our hands? It s highly likely that on this farm at least, there will be slaughter of the fish. What next? Ring containment with quarrantine? Ring slaughter? Do we trace forward to where this farmer has sold fish recently? Do we trace backwards to where the Michigan fish came from? What do we do about the water ways we looked at in the last slide? There is currently NO official plan in the United States or Canada for this contingency There are plans in place in Denmark, Germany, but no one at the USDA seems to know about or have seen these plans, and we are still trying to come up with our own. So the question I want to leave you guys with is that Given that you are going to have to make these kind of decisions What would YOU do if you were faced with a potential outbreak like this? And now Misty is going to talk to you about our Fish Health Certification Program here in Wisconsin 6

7 Wisconsin Animal Health Department of Agriculture, Trade, and Consumer Protection First state to have an aquaculture veterinarian on staff 12 private practice veterinarians who serve fish farms Role of aquaculture veterinarians Disease treatment and prevention Risk assessment Food Safety Vet Training Talked about the Vet Training Course that he developed. 7