Group Summaries - Fish Health

 

May 22-24, 2006 UF Tropical Aquaculture Laboratory

This Information Exchange Group did not meet.

 

June 5-7, 2005 Virginia State University

Attendees:      There were 20 participants from 11 institutions.
Facilitator:      Dr. Jimmy Avery

SESSION SUMMARY:

Jimmy Avery – MSU
· David Wise has conducted experiments looking at whole-pond treatments with copper sulfate to control snails.  The test were done in ponds with alkalinities ranging from 150-300 ppm.
Jesse Chappel – AU
· There is a new instrument that can be added to microscopes that can produce electron-microscope quality images.  The instrument could be useful as a diagnostic tool.
Craig Watson – UF
· Spring Viremia of Carp is a hot issue in the ornamental industry.  Federal agencies are looking at import restrictions to prevent further introductions. A florida lab can now identify the virus and certify lots.  Certification could cost as much as $400-500 per lot.
Craig Tucker – MSU
·

Fish health research is currently the largest program at the National Warmwater Aquaculture Center.  The two main approaches are evaluation of treatments (such as vaccines) and epidemiology/risk.  Florfenicol is close to receiving approval from FDA.  Trematode research continues to be a big research issue.
Gary Burtle – UG
· Posed a question to the group concerning which form of copper sulfate (crystal vs. liquid) was most effective.   Craig Tucker stated that form doesn’t matter when you compare 1 ppm copper (as crystal) vs. 1 ppm copper (as liquid). The difficulty in dissolving CuSO4 may be why liquid copper may be appearing more effective.
James Steeby
· He stated that he is continuing to work with Dave Strauss at Stuttgart regarding clearance of copper sulfate.

 

June 6-8, 2004 University of Arkansas, Pine Bluff

Attendees:  The groups represented at the fish health section were USDA/ARS/SNARC, LSU, MSU, UG, TAMU, and UAPB.
Facilitator:  Drew Mitchell, USDA/ARS/SNARC
Co facilitator:  Kelly Winningham, UAPB

SESSION SUMMARY:

USDA/ARS/SNARC (Harry K. Dupree Stuttgart National Aquaculture Research Center) - Ken Davis, David Straus, Steve Rawles, and Drew Mitchell
· Looking at cortisol levels as an indicator of stress in fish and the relationship between susceptibility to disease and cortisol levels. 
· Examining amino acid and essential fatty acid concentrations of feed for hybrid striped bass
· Examining several drugs for potential use in aquaculture after taking them through the FDA approval process.  Looking at copper sulfate as an external treatment for ich in channel catfish ponds and also for control of fungus on fish eggs. Additionally, there will be research conducted on the use of diquat, hydrogen peroxide, and formalin as an antifungal treatment for fish eggs and side-by-side comparisons will be made between the chemicals to determine which is the safest and most effective treatment to use. Also looking at potassium permanganate and diquat as an external treatment for columnaris -- expanding on diquat work done by Andy Goodwin and Swapna Thomas.  Will be focusing on defining range values for diquat treatment levels.  Examining use of florfenicol as medicated feed for controlling streptococcus in Hybrid Striped Bass.
· Defining best hydrated lime pond shoreline treatment rate for snails that vector the catfish trematode and then compare with the established copper sulfate shoreline pond treatment (working with Dr. David Wise, MSU-Stoneville).  Will test the best treatment in a commercial application study.
· Also will be looking at the gill trematode (serious problem in the aquarium trade in Florida and in wild fish Texas and Utah). In addition to snails, it is carried by the green heron and possibly other birds.  The snail host is found all over the county and in warm springs as far north as Wyoming.  Will be examining other birds to determine if additional species beside green heron serve as carriers.  Will also be continuing work on the bird hosts of catfish trematode and yellow grub.
Louisiana State University -- Robert Reigh
· Currently not working in fish health area, but interested in seeing what areas of fish health are being researched and additional work that is needed.
Thad Cochran National Warmwater Aquacultural Center - Brian Small
· Examining genetics of channel catfish to produce a more disease resistant fish.
· Working on identification of candidate genes for ESC and CCV.
· Developed a real time PCR assay for the detection of ESC in channel catfish.
· Developing micro rays to aid in the identification of candidate genes.
· Examining innate immunity in channel catfish.
· Examining the clearance rate of ESC and viruses in catfish.
· Examining the role of cortisol in regulating the clearance of ESC.
· Examining role of stress and the effects of low level feeding on cortisol – fish families with really low stress responses tend to have higher survival rates.
· Examining embryonic development and time to hatch.
· Examining use of hydrogen peroxide as treatment for Saprolegnia in hybrid catfish.
· Examining which stages in development are most critical, have found that the first 24 hours are critical due to calcium levels.
· Working with Harvest Select to create hybridized catfish (possible gamete incompatibility causing high die off rate among fry).
· Examine effects of stress and cortisol on reproduction in channel catfish.
Jim Steeby
· Examine PGD in channel catfish ponds.
· Use of FHM in catfish ponds to reduce the dero worm that vectors PGD --minnows stocked at even high stocking rates were not effective in controlling or reducing PGD outbreaks in catfish ponds.
· Examine use of buffalo fish as a control for dero worms and as a possible control agent for snails (alternative for black carp).  No apparent effect on snails.
· When 1-year-old small mouth buffalo were stocked in channel catfish ponds, no significant difference in the number of fish with PGD was observed among sentinel fish in the spring, but by the fall there was approximately a 50% decrease in the number of fish with PGD.  The disadvantage was that by the fall the buffalo were approximately 2.5 to 3 lbs in size and would be seined up with the catfish and would become a sorting issue.  In fingerling ponds they would be much easier to sort. An advantage was that the buffalo fed on the benthos and did not eat the floating catfish feed.  Outside of grading issues, the small mouth buffalo might be used as an effective biological control species for PGD in channel catfish ponds.
· ESC vaccine- debate over application and cost efficiency.  Trials are conducted by bath immersion with high levels of bacteria.  It has been argued that exposure to bath immersion with high bacterial levels is not realistic.  A longer low-level bacterial exposure may be more efficient.
University of Georgia Research and Extension - Gary Burtle
· Working on a program to educate county extension agents on assisting farms with fish problems to prevent farmers from having to drive as far to have fish checked.  There are 3 diagnostic fish laboratories in Georgia, but some farmers may be several hundred miles away from a diagnostic lab.  To aid in solving this problem all the county extension agents undergo training in their winter down time to identify parasites and other problems.  All are equipped with digital imaging technology and microscopes.  This enables farmers to only drive about 30 miles at the most to have their fish examined.  The agents send images and information to the diagnostic laboratory to determine if samples need to come for additional testing.  There are still some problems areas: recognition of smaller parasites and bacterial diagnosis, but with continued education and possible the addition of some videography these problems can be overcome.
Texas A & M University - Delbert M. Gatlin III
· Examining nutrition aspect requirements and manipulation for channel catfish and hybrid striped bass. 
· Looking at hybrid striped bass diets, particularly nucleotides in diet, to provide disease resistance.  Using commercially available nucleotides, increased resistance of hybrid striped bass to Streptococcus iniae has been demonstrated.
· Research indicated that the adenine nucleotide was the most beneficial nucleotide.
· Not sure when industry might adopt diet practices and the biggest drawback may be the cost.
· There is also research on yeast products to improve disease resistance.  Probiotics and brewers yeast have both been found to improve disease resistance in hybrid striped bass.
· There is additional work being conducted to more closely examine diets for red drum.
· Levamisole is an anthelminthic drug used in horses and cattle, but has found to be effective on Streptococcus iniae also.  There are adverse affects (reduced growth) at higher levels, but at low levels it enhances fish growth.
· Examining hybrid striped bass genetics in conjunction with KEO Fish Farm and examining cortisol levels in different crosses with Ken Davis of Stuttgart.
· Examining immune system of hybrid striped bass, extracellular superoxide anion production of head kidney macrophages, neutrophil oxidative radical production, and serum lysozyme were used as indicators.  Serum lysozyme was the easiest to perform but extracellular superoxide anion production of head kidney macrophages’ were the best indicator.
University of Arkansas at Pine Bluff - Kelly Winningham
· Completed a study on the no observable effect concentration of aerially applied cotton, soybean, and rice pesticides on fish and freshwater shrimp.
· Currently do research on ageing channel catfish from commercial catfish ponds that have been in continuous production for at least 10 years to determine the age structure in these ponds, whether there are fish that are remaining in the pond year after year due to poor growth and if the poor growing fish are serving as reservoirs of diseases, like ESC and channel catfish virus.
Dhirenda Nayak
· Virus research – The golden shiner virus is the grass carp reovirus
· Another reovirus, not the golden shiner virus, was found in golden shiners -- it has different cytopathic effects than golden shiner virus.
· Also working on identifying two other unknown viruses, even one that is possibly in the parvovirus family. 
· Also looking at the possibility that some shiners can serve as carriers of golden shiner virus.  Also have isolated GSV from fathead minnow.  Not all fish with GSV have symptoms, many will be assymptomatic and the farmer may only be seeing chronic mortality. Could the GSV be related to the loss of large shiners? If not what else could be causing the mysterious loss of larger shiners? Maybe a nutritional problem? Maybe a density related food distribution or genetic effect.

Bobban Subhadra
· Practical diet formulation for Largemouth Bass with particular emphasis on lipids and fatty acid concentrations.
Ignacio Masson
· Studying the development of hatchery techniques for fathead minnows.  Examining four different substrates for fathead minnows to attach eggs.  Some of the substrates are rough and some are smooth.  Fathead minnows deposit their eggs on the underside of substrates.  Will be determining if there is a statistical difference in one substrate over another.

 

March 9-11, 2003 Texas A&M University

Attendees:  Not available
Facilitator:  Not available

SESSION SUMMARY:
· Del Gatlin discussed the recent efforts in his lab to investigate nutritional influences on immune responses and disease resistance of hybrid striped bass. He indicated there were limited positive effects of vitamin C, vitamin E, and selenium when included above minimum requirement levels. However, positive effects on disease resistance had been consistently seen with brewers yeast supplementation to the diet.
· Ken Davis indicated the Stuttgart National Aquaculture Research Center (SNARC) would be de-emphasizing their program of data collection for drug approval. He also reported that Andy Goodwin is selecting for low-stress channel catfish.
· Jimmy Avery reported that field tests of the ESC vaccine have been promising although lab tests have been rather inconsistent. He also indicated smallmouth buffalo are being evaluated for the control of Dero worm associated with proliferative gill disease of catfish.
· Gary Burtle of the University of Georgia indicated there is a federal bill currently under consideration which would require veterinary approval to medicate any type of agricultural animal. This bill will be considered by each state.

 

March 29-30, 2000 Louisiana State University

Attendees: twenty five people
Facilitator: not available

SESSION SUMMARY:
· Approximately 25 people attended this information exchange group meeting.  John Hawke was asked to provide an overview of the Fish Diagnostician Workshop that was held the preceding two days at the LSU School of Veterinary Medicine.
· John commented on some of the disease problems of great concern at this time.  Several viral diseases were discussed including largemouth bass virus, koi plague and many of the different shrimp viruses.
· Several of the bacterial infections were mentioned including Yersinia ruckerii in warmwater fish, Streptococcus in tilapia and problems with Photobacteria in brackish/marine culture of striped bass and hybrid striped bass.
· A variety of parasites were mentioned including the catfish grub which has become a great  concern in the catfish industry.  Proliferative gill disease (hamburger gill) also continues to cause some problems in the catfish industry.
· John also mentioned some diseases which do not appear to be related to infectious agents such as toxic algal blooms and feed-related anemia which have sporadically appeared in some catfish production.  In addition, some comments about molecular diagnostic techniques and fish health inspections were made.

 

March 15-16, 1999 Kentucky State University

Attendees:  Six from six states
Facilitator:  not available

SESSION SUMMARY:
· The bulk of the discussion focused on vaccines and methods of delivery.  For both catfish and trout.
· Discussed issues surrounding fingerling disease avoidance vs exposure to reduce losses in growout operations.
· Research areas –  exploring different management techniques to try to keep fry free from disease exposure until they can be vaccinated.
· Management Techniques – Need to look into what to do after you do have a disease problem.
· Some discussion on hamburger gill  and oligocheate reduction techniques.

 

March 15-17, 1998 Clemson University

Attendees Not available
Facilitator:  David Wise

SESSION SUMMARY:

The main topic of discussion was the development and use of vaccines. An attenuated ESC vaccine has been developed by the USDA/ARS Fish Diseases and Parasites Research Laboratory and field trials are currently being conducted at the USDA/ARS laboratory and the National Warmwater Aquaculture Center (Stoneville, MS). Discussions concerning the development of a molecular columanaris vaccine focused on problems associated with the identification of virulence factors and efficacy testing. The emphasis of all the groups (Clemson University, Auburn University and the USDA/ARS laboratory) working with columnaris is identifying protective antigens and methods of grouping virulent and avirulent columnaris strains. The USDA/ARS laboratory is developing a PCR method to aid in bacterial identification and has identified a 58-60 kd protease produced by columnaris that appears to be associated with virulence.

An update on the study, An Epidemiological Study of Streptococcus iniae in Tilapia, Hybrid Striped Bass, and Channel Catfish was presented by the lead institute of the project (USDA/ARS). To date S. inae has not been isolated from commercially produced channel catfish sampled from Alabama, Arkansas, Louisiana, and Mississippi. Hybrid striped bass and tilapia cultured positive for S. iniae as previously reported. DNA profiles indicated a wide variation in isolates recovered from farms. These differences occurred nationwide with no regional pattern of distribution. To date none of the recovered isolates have had DNA patterns similar to the strain or clone of S. iniae associated with human infection. Other topics included the development of alternative methods for controlling infectious diseases in channel catfish production ponds (Mississippi State; USDA/ARS laboratory) and fee-fishing operations (Kentucky State), and work being conducted by Auburn University as part of an INAD evaluation the use of chlroamine-T to control Columnaris infections.

 

March 24-26, 1997 University of Tennessee

Attendees:  Skip Jack, LesterKhoo, Don Ourth, King-Thom Chung, Bob Durborow, Michael Jones, Gary Burtle, Jeff Hinshaw, Jaw-Kai Wang, Tom Hill, Stephen Smith
Facilitator: Stephen Smith

SESSION SUMMARY:

Each participant provided a brief overview of their respective aquaculture programs and major research activities (in order of presentation).  More specific details about each of the research projects can be found in the handouts of each institution or program.

Skip Jack
· Mississippi State University, Starkville. The University's research activities in the College of Veterinary Medicine continue to examine proliferative gill disease of catfish with the development and evaluation of molecular probes (L. Pote), evaluation of the immune basis of winter mortality syndrome in catfish (P. Waterstrat), and the use of molecular techniques applied to channel catfish virus (L. Hansen).  Additionally, a number of individuals are working on the INAD evaluation efficacy trials of Diuron, Amoxicillin and Sarafin as chemo-therapeutics in catfish, as well as the efficacy of Romet in catfish infected with enteric septicemia (ESC).  There was a group discussion on the development and use of vaccines/bacterins in catfish that included mentioning the work of Drs. Plumb, Klesius and Shotts.
Lester Khoo
· Mississippi State University, Stoneville. Research at the Delta Research and Extension Center has involved looking at the pathology of toxic algae blooms (Microcystis) and evaluating the effects of tapeworms in catfish.  In addition, several individuals are examining the differential evaluation of ascitic fluid from catfish infected with enteric septicemia of catfish (ESC) and channel catfish virus (CCV), and the efficacy of Romet against the bacteria causing enteric septicemia of catfish.  They are continuing their studies into the immune response of catfish, and are also trying to develop a Total Pond Management Program for catfish producers.
Don Ourth
· University of Memphis. Discussed his research on isolating various antibacterial agents from channel catfish neutrophils and his work on the immunology of catfish.  There was a group discussion of the effects of stress on the immune response in catfish.  It was noted that Specific Pathogen Free (SPF) catfish often have titers to enteric septicemia of catfish (ESC)
King-Thom Chung
· University of Memphis, reported on his work with the antimicrobia effects of tannins.
Jeff Hinshaw
· North Carolina State University, reviewed his work with enteric redmouth disease (ERM) of trout and the results of studies examining vaccination and management strategies in trout production facilities.
Bob Durborow
· Kentucky State University, reported the completion of two fish health extension videos: Parasites of Fish and Diseases of Trout.  He also described his clinical fish caseload and diagnostic findings.
Michael Jones
· University of Tennessee, an exotic animal veterinarian from the College of Veterinary Medicine expressed an interest in learning more about specific diseases of aquacultured fish.
Gary Burtle
· University of Georgia, Tifton, discussed his continuing work with hamburger gill disease in catfish and the role of the oligochete worm host, as well as the effect of fathead minnows for controlling the host worm in ponds.  He is also looking at diet-related anemias in catfish.
Stephen Smith
· Virginia Tech, research activities include looking at both the ontogeny of the immune response in hybrid striped bass and tilapia and the use of hematology and serum chemistries in clinical fish medicine.  Investigations are continuing on the examination of cultured and native trout populations for the presence of whirling disease (Myxobolus cerebralis), the evaluation of several chemotherapeutics in cultured fish, and the development of a diagnostic PCR assay for mycobacteriosis in fish.

Comment:  It was noteworthy that the major topic of discussion always seemed to return to the immune response of fish as it applied to the stress response in fish, vaccine usage and efficacy, and management strategies for fish health.  The overall impression was that research activities should continue to be focused on acquiring basic and applied information on the immune response of fish.

 

March 24-26, 1996 University of Arkansas, Pine Bluff

Attendees:  Representatives from eleven institutions
Facilitator:  Andrew J. Mitchell

SESSION SUMMARY:
· There were 12 studies on the use of chemicals to prevent or control disease. The chemicals involved in these studies included Bayluscide, calcium hypochlorite, chlorine, copper sulfate, hydrated lime, potassium permanganate, Romet, sodium chloride, and taic acid.
· There were nine studies on various diseases of catfish including; channel catfish virus, enteric septicemia of catfish, proliferative gill disease, no-blood disease, and a bacterial disease caused by Plesiomonas shiqelloides.
· There were nine studies on the immune systems of the fish, including two that dealt directly with the development of vaccines.
· Three studies were done on the relationship of nutrition and disease in fish and three on emerging diseases, including a report on a European eel nematode now found in Texas and an Iridovirus in gouramis.
· Two detection method studies, one for Edwardsiella tarda and one for the channel catfish virus, were reported.
· A single study was done on the epidemiologic analysis of diagnostic records, another on the effect of environmental contaminants on fish health, and one on determining the seasonal blood parameters of channel catfish.
There was no apparent duplication within the studies from the Southern Region. The greatest benefit from this meeting may be in establishing priorities for research and avoiding efforts that other research indicates might be a time wasting venture. This is probably most true for the field of immunology and vaccine research.

 

March 18-20, 1995 Auburn University

 Attendees:  Not available
Facilitator:  Tom Schwedler

SESSION SUMMARY:

Alabama (Auburn University).
· Crawfish and oyster diseases (Brady)
· INAD for HCG
· Striped bass calcium and sodium (Grizzle) 
· New species of parasitic copepod description (Rogers) 
· Vaccine ESC (Plumb)
· Salt and ESC 
· Pathogenesis of Columnaris and ESC 
· Pathogenesis of Pleisiomonas shigelloides
Marion Lab
· ELISA CCVD diagnosis 
· Aeromonas Splitting by virulence
· Salt and ESC 
· Cell mediated immunity (macrophages)
· No blood and Bacillus therengensis
USDA (Auburn Lab) 
· ESC ELISA antibody 30 min. test available
· Antigen 30 min test field testing 
· Looking for immunodominant antigen for E. ictaluri 
· Evaluated vaccines for ESC and found (no effect)
· Looked for passive maternal immunity in Channel catfish (none found) 
· Looking for immunodominant antigen in ICH (possible vaccine)
· Effect of iron and zinc on non specific immunity 
Arkansas (Stuttgart Lab) 
· Yellow Grub treatment (doncit) (Drew Mitchell) 
· Copper sulfate and potassium permangenate NAD registration 
Kentucky
· Two fish disease tapes have been produced, Warmwater (available now), Coldwater (soon)
Tennessee (University of Memphis)
· Red swamp crawfish antibiotic

 

March 13-15, 1994 Texas A&M University

Attendees:  Representatives from Georgia, Mississippi, North Carolina, Tennessee, South Carolina, Texas and Arkansas were present.
Facilitator:  Tom Schwedler

SESSION SUMMARY:
· Ken Johnson (TAMU) reported on the Joint Subcommittee for Aquaculture fish disease group activities. The most important issue before the Subcommittee was who should be involved in fish health management. TAMU also reported on strep infections in intensive culture and an intercellular parasite of shrimp. 
· Clemson University reported on work on immune function in catfish related to stress and therapeutants, stress physiology, ESC pathogenesis, and drug and vaccine evaluations. 
· The University of Georgia reported on the work that they are doing on Proliferative Gill Disease, the work is focused on transmission and terminal host detection. 
· The University of Arkansas at Pine Bluff reported on work on "no blood", indicating a pathogen may be involved, their effect of pantothenic acid on Winter Kill, and drug clearance work concentrating on copper sulfate. 
· North Carolina State University reported on their work with immunological indicators of ERM epizootics, vaccine efficacy and diet, and a toxic dinoflagelate. 
· Mississippi State University reported on a recombinate vaccine for Channel Catfish Virus, rapid diagnostic procedure for Listeria, and drug clearance trials. 
· The University of Tennessee reported on differential nitrite effects on blue catfish, channel catfish and their hybrids, and temperature effects on methemoglobin formation.
· There were several very active fish health laboratories that were not at the meeting, which would have added greatly to the information exchange group.