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United States Department of Agriculture

Agricultural Research Service

Research Project: EVALUATION OF COMPOUNDS AND STRATEGIES FOR CONTROLLING AQUATIC ANIMAL DISEASE
2009 Annual Report


1a.Objectives (from AD-416)
Develop data needed to demonstrate safety (animal, human, and environmental) and efficacy of compounds that are relevant to the needs of aquaculture. Determine the efficacy of compounds, biological control strategies, clearance rate and pathogenesis of parasites and fungi applicable to catfish, baitfish, and Morone sp. culture.

Conduct production efficiency trials with Channel x Blue catfish hybrids at multiple densities. Evaluate pond management using water circulators to improve production. Develop disease challenge models for catfish.


1b.Approach (from AD-416)
Submit the FDA-required Efficacy data for control of Ichthyophthiriasis by Potassium Permanganate. Submit the environmental assessment data for potassium permanganate and copper sulfate on channel catfish in earthen ponds. Submit the target animal safety data for potassium permanganate in channel catfish. Use in vivo challenge models and in vitro assays to investigate the efficacy of florofenicol against streptococcus infection in hybrid striped bass and tilapia. Evaluate the safety of florofenicol use in hybrid striped bass and tilapia. Evaluate praziquantel for control of asisan tapeworm in grass carp and golden shiners. Evaluate the biological control of trematode vectoring mollusks by determining comparative consumption and preference by snail-eating fishes. Determine the clearance rate of the catfish trematode (bobophorus) in channel catfish and the gil trematode in hybrid striped bass, golden shiners, and channel catfish. Determine the prevalence of trematodes in black and yellow crown night herons, little blue herons, snowy egrets, cattle egrets, and belted kingfishers. Determine efficacy of dimilin for the control of anchor parasites and fish lice in morone sp., golden shiners, and gold fish. Evaluate copper sulfate treatments to control snails under commercial farm conditions. Use the DNA sequence of F. columnare and F. psychrophilum or F. Branchiophilum to detect and "fingerprint" strains of pathogens by molecular techniques as restriction fragment length polymorphism (RELP) using polymerase chain reaction, or pulse field gel electrophoresis (PEGE).

Pond evaluations of channel/blue hybrids will be initiated. Simultaneously, channel/blue hybrids will be challenged by Flavobacterium columnare and Edwardsiella ictaluri to evaluate hybrid disease resistance. Coupled with the pond and disease challenge studies, engineering principles will be applied to develop improved methods for efficient, reduced-stress production, harvesting and transport of standard and hybrid catfish.


3.Progress Report
The project ends on 11/07/2009. Research under the project clearly showed the safety of copper sulfate (CuSO4) to catfish and catfish eggs, the safety of the antibiotic florfenicol to sunshine bass, and the effectiveness of CuSO4 for fungus on catfish eggs in flow-through hatching troughs; all of these are required components of the FDA drug approval process. Hydrogen peroxide, diquat, and formalin were evaluated for fungus control on catfish egg masses, and the optimal doses of these therapeutants, along with CuSO4, were compared to determine that CuSO4 and formalin performed best. A study using peracetic acid to control free-swimming Ich was conducted. An abrasion method to produce an acute columnaris infection in catfish and a system to produce a natural columnaris infection without abrasion were developed; the latter method demonstrates the typical disease progression. The abrasion method was used to demonstrate the effectiveness of potassium permanganate and diquat against very early stages of columnaris. Great blue herons and great egrets are the main avian vectors of yellow grubs in commercial fish ponds; green herons vector the majority of gill trematodes; and white pelicans vector the majority of catfish trematodes. This is important information for farmers to control specific birds causing trematode problems. Longevity studies showed that the catfish trematode can remain in the fish for more than 1.75 years; negative effects include reduced feeding and slow growth. The effectiveness of praziquantel against the Asian tapeworm in grass carp and the toxicity to grass carp and golden shiners was established. The effectiveness of florfenicol against an acute streptococcosis infection in blue tilapia and the effectiveness of carvacrol and caprylic acid against the causative bacteria were evaluated. Conducted pond studies to examine the impact of paddlefish on channel catfish production, to compare production of channel catfish and hybrid catfish (female channel x male blue catfish) when fed full or restricted rations, to determine growth and yield of channel and hybrid catfish from a common maternal strain, and to determine the impact of minimum dissolved oxygen concentration on growth and yield of channel catfish and hybrid catfish from a common maternal strain. Conducted a study on the stocking density of NWAC 103 strain channel catfish on production characteristics and water quality in HDPE-lined raceways and a follow-up study with a diffuser grid in raceways to improve water quality and increase production rates. Showed that channel catfish yield increased linearly when stocked into a suspended-growth (biofloc) production system at various densities. Initiated research to determine the effect of three different initial sizes of channel catfish stocked at a common stocking rate on yield and water quality characteristics in a suspended-growth (biofloc) production system. Evaluated the effects of hauling density on golden shiners, tested a custom grader for use in concrete holding vats, and developed a method for estimating oxygen needs of catfish during transport.


4.Accomplishments
1. Method to simulate the natural disease progression of columnaris: Typical columnaris infections are hard to reproduce but are needed for effectiveness evaluations. Scientists at the HKD Stuttgart National Aquaculture Research Center developed an ultra low-water flow system which helps produce natural columnaris infections in catfish by increasing the fish's contact time with the organism. This system allows for realistic studies with various therapeutants to determine their ability to control columnaris. Effectiveness studies developed with this method will benefit the drug approval process by delivering a more realistic and treatable disease outbreak.

2. Microbial pathogens extremely sensitive to digestive tract fluids of fish-eating birds: Development of biosecurity and disease eradication programs for commercial fish farms depend upon determination of the viability of important pathogens of farm-raised fish after passing through the gastrointestinal systems of fish-eating birds. In cooperative research conducted by the University of Arkansas at Pine Bluff, DNA extraction and culture methods for bird, crawfish, and turtle samples have been optimized and samples collected and cultured. Work with viral and bacterial pathogens has been completed using a recognized in vitro model that replicates the gastric and intestinal systems of birds, reptiles, and crawfish. Data show that microbial pathogens, especially the viruses, are extremely sensitive to digestive tract fluids, especially at warm temperatures. This shows that birds are highly unlikely to serve as significant vectors of these fish pathogens.

3. FDA-required study on the safety of florfenicol to sunshine bass: The margin of safety for using the antibiotic florfenicol to treat streptococcosis in sunshine bass is required as a major component of the FDA-approval process. In collaboration with researchers at the US Fish & Wildlife Service in Bozeman, MT, scientists at the HKD Stuttgart National Aquaculture Research Center completed a Target Animal Safety study to demonstrate that the drug manufacturer's proposed recommended daily treatment was safe for treating sunshine bass. Approval will benefit the industry economically by providing a legal means to increase survival rates in sunshine bass culture.

4. Peracetiv acid (PAA) as a novel therapeutant for Ich: Treatment options for Ichthyophthirius multifiliis (Ich) are limited, and the novel therapeutant PAA has recently been introduced as a possible alternative by international scientists. In collaboration with a scientist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin, Germany, scientists at the HKD Stuttgart National Aquaculture Research Center completed acute toxicity studies of PAA-containing formulations to free-swimming Ich from two geographically separate isolates in ground water. The impact of this accomplishment is an increased scientific understanding of strain differences when related to toxicity and may lead to more specific therapeutic treatments for Ich control in different environments.

5. Florfenicol is effective against strep infections in blue tilapia: Streptococcosis costs the tilapia industry in the US more than $10 million in annual losses, and the disease has closed many tilapia operations worldwide. Scientists from the HKD Stuttgart National Aquaculture Research Center tested the effectiveness of florfenicol against streptococcosis in blue tilapia, and the results clearly demonstrate its ability to control mortalities. Tilapia treated with florfenicol for 10 days had less than or equal to 6% mortality compared to 81% mortality in the infected, non-treated group. The tilapia industry will be able to use this information, and ongoing drug-approval efforts could make this the first antibiotic to control mortalities caused by streptococcosis.

6. Best fungus treatment for hatchery-reared catfish eggs is hydrogen peroxide: Fungus can destroy entire catfish egg masses in commercial hatching troughs and potentially cause fish shortages. An experiment was designed by scientists from the HKD Stuttgart National Aquaculture Research Center to compare four therapeutants (hydrogen peroxide, formalin, copper sulfate, and diquat) for their ability to control fungus and increase egg survival. All treatments were effective, but the highest survival and lowest incidence of fungus was achieved using hydrogen peroxide. The use of hydrogen peroxide (an FDA-approved product) will allow catfish producers to raise more catfish and realize greater economic benefits.

7. Hybrid catfish produce more because they eat more: There is increasing demand by farmers for the hybrid catfish (female channel x male blue catfish), but its superior performance has yet to be demonstrated broadly. Scientists at the HKD Stuttgart National Aquaculture Research Center conducted an intensive study in earthen ponds to compare production characteristics of hybrid catfish to channel catfish; both groups of fish shared a common maternal strain. This study clearly demonstrated that the yield of the hybrid catfish was greater because the hybrid consumed more feed at each feeding. Identifying a superior performing fish is an important factor in ensuring sustainable catfish production in the US.

8. More frequent feeding of channel catfish improves survival and yield over the winter: In cooperative research at the University of Arkansas at Pine Bluff, winter feeding studies demonstrated a need to refine winter feeding recommendations. New feeding schedules developed from previous winter feeding studies were evaluated in earthen ponds stocked in multiple-batch production of channel catfish. Survival and yield increased with more frequent feeding, but mean weight at the end of the winter was not different among feeding levels. More frequent feeding over the winter reduced winter mortality by 4 to 6%.

9. Cost of hybrid striped bass fingerling production in ponds vs. tanks: Technology to produce hybrid striped bass fingerlings in tanks has been developed that allows for year-round production, but the cost of fish production in indoor tanks frequently is several times higher than that in ponds. In cooperative research at the University of Arkansas at Pine Bluff, 15 enterprise budgets were developed for hybrid striped bass fingerling production in ponds and 17 for tank production. Overall, pond production of hybrid striped bass was less expensive in ponds than in indoor tanks for the higher annual production levels analyzed that ranged from 250,000 to 2,000,000 fingerlings. However, tank production was less expensive at lower levels of production (50,000 to 100,000 fingerlings a year) if multiple cycles a year are possible. Tank production of hybrid striped bass fingerlings appears to be a technology appropriate for small-scale production of hybrid striped bass fingerlings.


Review Publications
Straus, D.L. 2008. Comparison of copper sulfate concentrations to control ichthyophthiriasis in fingerling channel catfish. Journal of Applied Aquaculture. 20(4):272-284.

Mitchell, A.J., Cole, R. 2008. Survival of the faucet snail Bithynia tentaculata after chemical disinfection, pH extremes, and heated water bath treatments. North American Journal of Fisheries Management. 28:1597-1600.

Mitchell, A.J., Darwish, A.M. 2009. Efficacy of 6-, 12-, and 24-h praziquantel bath treatments against Asian tapeworm Bothriocephalus acheilognathi in grass carp. North American Journal of Aquaculture. 71:30-34.

Darwish, A.M., Mitchell, A.J., Straus, D.L. 2009. Evaluation of potassium permanganate against an experimental subacute infection of Flavobacterium columnare in channel catfish, Icatlurus punctatus. Journal of Fish Diseases. 32:193-199.

Mitchell, A.J., Darwish, A.M., Fuller, S.A. 2008. Comparison of tank treatments with copper sulfate and potassium permanganate for sunshine bass with ichthyobodosis. Journal of Aquatic Animal Health. 20:202-206.

Green, B.W., Perschbaucher, P., Ludwig, G.M. 2009. Effect of threadfin shad as forage for channel catfish fed daily or every third day. North American Journal of Aquaculture. 71:46-51.

Beecham, R.V., Labarre, S.B., Pearson, P.R., Minchew, D.C. 2009. Swimming performance and metabolism of cultured golden shiners. North American Journal of Aquaculture. 71:59-63.

Pearson, P.R., Small, B.C., Beecham, R.V., Sink, T.D., Labarre, S.B., Minchew, D.C. 2009. Effects of loading density on golden shiner survival during and after hauling. North American Journal of Aquaculture. 71:24-29.

Straus, D.L., Hossain, M.M., Clark, T.G. 2009. Copper sulfate toxicity to two isolates of Ichthyophthirius multifiliis relative to alkalinity. Diseases of Aquatic Organisms. 81(1):31-36.

Min, B., Chen, M., Green, B.W. 2009. Antioxidant activities of purple rice bran extract and its effect on the quality of low NaCl, phosphate-free patties made from channel catfish (Ictalurus punctatus) belly flap meat. Journal of Food Science. 74(3):C268-C277.

Straus, D.L., Meinelt, T. 2009. Acute toxicity of peracetic acid (PAA) formulations to Ichthyophthirius multifiliis theronts. Parasitology Research. 104:1237-1241.

Darwish, A.M., Farmer, B.D., Hawke, J.P. 2008. Improved methodology for determining antibiotic susceptibility of Flavobacterium columnare isolates by broth microdilution. Journal of Aquatic Animal Health. 20:185-191.

Straus, D.L., Mitchell, A.J., Carter, R.R., Steeby, J.A. 2009. Optimizing CuSO4 treatments for fungus control on channel catfish eggs. Journal of Aquatic Animal Health. 21(2):91-97.

Darwish, A.M., Mitchell, A.J. 2009. Evaluation of Diquat against an acute experimental infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus. Journal of Fish Diseases. 32:401-408.

Mitchell, A.J., Brandt, T. 2009. Use of ice water and salt treatments to eliminate an exotic snail, red-rim melania Melanoides tuberculatus, from small immersible fisheries equipment. North American Journal of Fisheries Management. 29:823-828.

Mitchell, A.J., Radomski, A.A., Straus, D.L., Carter, R.R. 2009. The effect of hydrogen peroxide on the hatch rate and Saprolegnia spp. infestation of channel catfish eggs. North American Journal of Aquaculture. 71:276-280.

Straus, D.L., Mitchell, A.J., Radomski, A.A., Carter, R.R., Steeby, J.A. 2009. Laboratory dose confirmation of copper sulfate for treating fungus on channel catfish eggs. North American Journal of Aquaculture. 71(4):333-338.

Mitchell, A.J., Overstreet, R., Goodwin, A. 2009. Eustrongylides ignotus infecting commercial bass (Morone chrysops female X Morone saxatilis male) and other fishes in the southeastern USA. Journal of Fish Diseases. 32:795-799.

Last Modified: 10/23/2014
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