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United States Department of Agriculture

Agricultural Research Service

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

Location: Harry K. Dupree Stuttgart National Aquaculture Research Center

2005 Annual Report


1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter?
Aquaculture has been a rapidly growing source of food production over the last few decades; total production value in the United States for 2000 was $973 million, of which total finfish production was $714 million. Fish pathogens continue to inflict significant economic losses to the U.S. aquaculture industry; extension personnel estimate that 10% of production ($71.4 million) is lost to parasites and infectious diseases. Current knowledge is inadequate for devising comprehensive management strategies for disease control. Many of the infectious diseases in fish (bacterial, fungal and parasitic) do not have effective vaccines; therefore, the need for safe and effective control measures to minimize losses due to outbreaks is pressing and critical.

Available Food and Drug Administration-approved therapeutants are very limited; the industry is frequently challenged with disease epizootics and no effective measures to curb losses. There are currently one parasiticide and three antibiotics (one is no longer manufactured) approved for use in U.S. aquaculture, with each therapeutant having a specific use. This is an inadequate arsenal against the plethora of diseases inflicting losses to the aquaculture industry. Approval of therapeutic compounds requires comprehensive studies to demonstrate human food safety, animal safety, environmental safety, and efficacy.

The development of effective strategies to control fish health problems is also hampered by the limited understanding of the biology, vectors, and epidemiology of fish pathogens plaguing the aquaculture industry. The need for disease control methods (chemical, biological, or environmental) not targeted at the pathogen, but at the intermediate host of these pathogens, is also immediate and critical.

The Project has two specific goals:.
1)develop data needed to demonstrate safety (animal, human, and environmental) and efficacy of compounds that are relevant to the needs of aquaculture, and.
2)determine the efficacy of compounds, biological control strategies, clearance rate and pathogenesis (understanding of the disease process) of parasites and fungi applicable to catfish, baitfish, and hybrid striped bass culture.

The research to be undertaken falls within the Integrated Aquatic Animal Health Management component of NP 106 - Aquaculture. The Project focuses primarily on the problems addressed in ‘Vaccines and Medicines’ goals to ‘Develop safe and effective vaccines and medicines for prevention and control of economically important pathogens of aquatic animals’ and to ‘Conduct research and development to support approval and licensing of safe and effective new drugs, vaccines and other biologics for aquaculture’. The Project includes elements of the problems addressed in ‘Mechanism of Disease’ goals to ‘Develop challenge models in the laboratory that reflect on farm conditions to assess pathogenesis of disease’ and to ‘Develop basic information on the sources of infection, modes of transmission, routes of entry, virulence mechanisms and host response to economically important infectious and non-infectious diseases’.

Attaining these objectives will provide benefits to farmers, fish health providers, scientists, and the public, which will result in increased economic growth by helping to overcome the impact of disease. Environmentally friendly, effective, and food-safe medicines to treat aquatic animal diseases and non-chemical methods to control diseases and disease vectors will become available not only to large commercial producers, but also to small, rural fish farmers. Research will provide the U.S. fish industry with the ability to identify important fish-pathogen hosts so the workforce can limit access of these hosts to ponds.

Anticipated products of the research will be additional fish health management strategies for fish diseases (bacteria and parasites) including FDA-approved compounds and the development of chemical and biological control methods to eliminate or reduce populations of non-fish hosts.

Fish farmers of cultured hybrid striped bass, catfish, tilapia, and baitfish species will benefit from this research. Scientists will benefit from the basic knowledge of efficacy and safety of fisheries chemicals used for therapy and vector reduction and the use of biological controls. Fisheries extension agents and veterinarians will have more disease control methodologies available for recommendation to their user groups. Consumers demanding safe and wholesome fish products will benefit.


2.List the milestones (indicators of progress) from your Project Plan.
Year 1 (FY2005)

Establish in vitro sensitivity of Flavobacterium columnare to florfenicol.

Establish safety of copper sulfate to channel catfish.

Optimize hydrated lime shoreline treatment for snail control.

Determine praziquantel toxicity to grass carp.

Year 2 (FY2006)

Establish infection model of external columnaris in channel catfish.

Establish efficacy of potassium permanganate against external columnaris in channel catfish.

Determine praziquantel toxicity to golden shiners.

Compare shoreline treatments for snail control.

Year 3 (FY2007)

Gain FDA-approval of copper sulfate for controlling Ich in channel catfish in earthen ponds.

Establish efficacy of florfenicol against Streptococcus iniae in hybrid striped bass.

Determine consumption of snails by sunfish.

Determine final hosts of specific trematodes.

Establish efficacy of Diquat® and copper sulfate for channel catfish eggs infected with fungus.

Year 4 (FY2008)

Establish efficacy of Diquat® against external columnaris in channel catfish.

Establish safety of potassium permanganate to channel catfish.

Establish efficacy of florfenicol against columnaris in channel catfish.

Complete shoreline treatment field tests to control snails.

Establish efficacy of praziquantel against Asian tapeworm in golden shiners or grass carp.

Establish efficacy of diflubenzuron against anchor parasite in goldfish.

Establish efficacy of hydrogen peroxide and formalin for channel catfish eggs infected with fungus.

Year 5 (FY2009)

Gain FDA-approval of potassium permanganate for external columnaris.

Establish safety of florfenicol on hybrid striped bass.

Determine snail consumption by other species.

Determine longevity of trematode in catfish.

Determine Diflubenzuron treatment for fish lice.

Compare all treatments to control egg fungi in channel catfish.


4a.What was the single most significant accomplishment this past year?
Copper Sulfate Animal Safety Study Accepted by FDA. A final study report entitled ‘Copper Sulfate Target Animal Safety for Channel Catfish’ was submitted by the HKD Stuttgart National Aquaculture Research Center through the sponsor company to the US FDA on 7/1/04. The study was accepted on 5/24/05. Additional information (the proposed label and a summary of previous submissions on file) was requested; this has been submitted and when accepted will complete the animal safety technical section for the future approval of copper sulfate as a therapeutant in aquaculture. This study was completed on-site following Good Laboratory Practice guidelines and determined the safety of copper sulfate to channel catfish at one-, three-, and five-times the recommended therapeutic dose when treated daily for 11 days. There was no mortality to the test animals and no histological changes due to copper toxicity at five-times the therapeutic dose. Upon completion of the final technical section (environmental assessment), the impact of this accomplishment will be to have a much-needed parasiticide as an FDA-approved aquaculture therapeutant.


4b.List other significant accomplishments, if any.
Optimizing Lime Treatments to Control Snails that Vector Disease in Catfish. An optimum pond-shoreline treatment for slurried hydrated lime to control snail populations was determined by scientists at the HKD Stuttgart National Aquaculture Research Center. Rams-horn snails are commonly found in production ponds and vector the catfish trematode that can cause significant losses to the channel catfish industry; few effective control methods for these snails exist. Trials were run at various treatment parameters to determine the best treatment for killing these snails along the shorelines of ponds; this was done as a subordinate project in conjunction with Mississippi State University, Stoneville, MS. The impact of this accomplishment is that a protocol is available to farmers that can greatly reduce the number of rams-horn snails vectoring disease to catfish in production ponds.

A Disinfectant to Control the Spread of the Red-Rim Melania Snail. An effective disinfectant for the snail that vectors a gill trematode known to kill wild and cultured fish species was found by scientists at the HKD Stuttgart National Aquaculture Research Center. The invasive snail, the red-rim melania, can be transported for several days on dried fisheries equipment, thereby contaminating environments previously free of the snail. A number of disinfectants at various concentrations and exposures periods were tested to find one that would kill 100% of the treated snails. The impact of this accomplishment is that an effective disinfectant is available for use on small fisheries equipment to control the spread of this snail.

Fathead Minnows can Carry the Catfish Trematode. The catfish trematode was thought only to infect members of the catfish family, but was definitively identified from the fathead minnow by scientists at the HKD Stuttgart National Aquaculture Research Center; this is the first report of this trematode in a species other than catfish. Fathead minnows can harbor the catfish trematode and indirectly serve as a source of infection for channel catfish; this trematode can cause significant losses to the channel catfish industry. Fathead minnows with trematodes found in the musculature were collected, the trematodes removed, processed and definitively identified; this was done as a subordinate project in conjunction with the University of Arkansas at Pine Bluff, Pine Bluff, AR, and North Carolina State University, Raleigh, NC. The impact of this accomplishment is that fathead minnows are now known to serve as a reservoir for the catfish trematode and appropriate measures can be used to control their population in catfish ponds.

Identification of Bird Vectors for Specific Trematodes. A survey conducted by scientists at the HKD Stuttgart National Aquaculture Research Center, elucidated 9 bird vectors for 3 species of trematode (catfish trematode, yellow grub and gill trematode). Understanding the life cycle of these trematodes and limiting bird access to fish ponds to control trematode populations can only be accomplished through identification of the parasite-host relationship (what trematodes infect what birds). Several bird species were collected and trematodes in their intestinal tracts were removed, processed and identified; this was done as a subordinate project in conjunction with North Carolina State University, Raleigh, NC. The impact of this accomplishment is that information is available for trematode control through limiting access of selected bird species to production ponds; further evaluation of more birds is needed.

DNA Sequence Method for Aquatic Epidemiology. Restriction fragment polymorphism (RFLP) and sequencing methods of the 16S rRNA gene and the 16-23S rDNA spacer were developed by scientists at the HKD Stuttgart National Aquaculture Research Center as an epidemiological tool for bacterial columnaris (Flavobacterium columnare) outbreaks in aquatic species. A technique does not exist to compare genotypes of this bacteria; this method has the advantage of being universal and capable of comparing the genotypes from different geographic locations. The method was used to show the correspondence between the genotypes of isolates in North America to those in Asia and Europe, and for the first time demonstrate the presence of genotype III in the US. The impact of this accomplishment is that with the global development of fish farming and the increased movement of fish between countries, this epidemiological tool will be indispensable in protecting the US from possible introduction of new genotypes of this pathogen.


4c.List any significant activities that support special target populations.
None.


5.Describe the major accomplishments over the life of the project, including their predicted or actual impact.
Copper Sulfate Animal Safety Study Accepted by FDA A final study report entitled ‘Copper Sulfate Target Animal Safety for Channel Catfish’ was submitted by scientists at the HKD Stuttgart National Aquaculture Research Center through the sponsor company to the US FDA on 7/1/04. This study was accepted in a letter dated 5/24/05. Additional information (the proposed label and a summary of previous submissions on file) was requested; this has been submitted and when accepted will complete the animal safety technical section for the future approval of copper sulfate as a therapeutant in aquaculture. This study was completed on-site following Good Laboratory Practice guidelines and determined the safety of copper sulfate to channel catfish at one-, three-, and five-times the recommended therapeutic dose when treated daily for 11 days. There was no mortality to the test animals and no histological changes due to copper toxicity at five-times the therapeutic dose. Upon completion of the final technical section (environmental assessment), the impact of this accomplishment will be to have a much-needed parasiticide as an FDA-approved aquaculture therapeutant. This accomplishment can be linked to Year 1 (FY2005) milestone of the Project Plan: Establish safety of copper sulfate to channel catfish. This accomplishment can be linked to the Integrated Aquatic Animal Health Management component of NP-106 addressed in ‘Vaccines and Medicines’ goals to ‘Develop safe and effective vaccines and medicines for prevention and control of economically important pathogens of aquatic animals’ and to ‘Conduct research and development to support approval and licensing of safe and effective new drugs, vaccines and other biologics for aquaculture’. This accomplishment can be linked to ARS Strategic Plan Objective 3.2 - Develop and Deliver Science-Based Information and Technologies to Reduce the Number and Severity of Agricultural Pest, Insect, Weed, and Disease Outbreaks and specifically Performance Measures 3.2.1 and 3.2.3.

Optimizing Lime Treatments to Control Snails that Vector Disease in Catfish An optimum pond-shoreline treatment for slurried hydrated lime to control rams-horn snail populations was determined by scientists at the HKD Stuttgart National Aquaculture Research Center. Rams-horn snails are commonly found in production ponds and vector the catfish trematode that can cause significant losses to the channel catfish industry; few effective control methods for these snails exist. Trials were run at various treatment parameters to determine the best treatment for killing rams-horn snails along the shorelines of ponds; this was done as a subordinate project in conjunction with Mississippi State University, Stoneville, MS. The impact of this accomplishment is that a protocol is available to farmers that can greatly reduce the number of rams-horn snails vectoring disease to catfish in production ponds. This accomplishment can be linked to Year 1 (FY2005) milestone of the Project Plan: Optimize hydrated lime shoreline treatment for snail control. This accomplishment can be linked to the Integrated Aquatic Animal Health Management component of NP-106 addressed in ‘Vaccines and Medicines’ goals to ‘Develop safe and effective vaccines and medicines for prevention and control of economically important pathogens of aquatic animals’. This accomplishment can be linked to ARS Strategic Plan Objective 3.2 - Develop and Deliver Science-Based Information and Technologies to Reduce the Number and Severity of Agricultural Pest, Insect, Weed, and Disease Outbreaks and specifically Performance Measures 3.2.1 and 3.2.3.

DNA Sequence Method for Aquatic Epidemiology Restriction fragment polymorphism (RFLP) and sequencing methods of the 16S rRNA gene and the 16-23S rDNA spacer were developed by scientists at the HKD Stuttgart National Aquaculture Research Center as an epidemiological tool for bacterial columnaris (Flavobacterium columnare) outbreaks in aquatic species. A technique does not exist to compare genotypes of this bacteria; this method has the advantage of being universal and capable of comparing the genotypes from different geographic locations. The method was used to show the correspondence between the genotypes of isolates in North America to those in Asia and Europe and for the first time demonstrate the presence of genotype III in the U.S. The impact of this accomplishment is that with the global development of fish farming and the increased movement of fish between countries, this epidemiological tool will be indispensable in protecting the U.S. from possible introduction of new genotypes of this pathogen. This accomplishment is not linked to a milestone of the current Project Plan; however, this accomplishment can be linked to the Integrated Aquatic Animal Health Management component of NP-106 addressed in ‘Epidemiology’ goals to ‘Develop methods to assess risk factors associated with the economically important pathogens of aquatic animals’ and to ‘Carry out basic epidemiology studies to identify disease prevalence, incidence, courses and origin of economically important aquatic animal pathogens. This accomplishment can be linked to ARS Strategic Plan Objective 3.2 - Develop and Deliver Science-Based Information and Technologies to Reduce the Number and Severity of Agricultural Pest, Insect, Weed, and Disease Outbreaks and specifically Performance Measures 3.2.1 and 3.2.3.

The potential customers of this 5-year Project are fish farmers of cultured hybrid striped bass, catfish, tilapia, and baitfish species. Scientists will benefit from the basic knowledge of efficacy and safety of fisheries chemicals used for therapy and vector reduction and the use of biological controls. Fisheries extension agents and veterinarians will have more disease control methodologies available for recommendation to their user groups. Consumers demanding safe and wholesome fish products will also benefit.

Attaining the objectives of this 5-year Project will provide benefits to farmers, fish health providers, scientists, and the public, which will result in increased economic growth by helping to overcome the impact of disease. Environmentally friendly, effective, and food-safe medicines to treat aquatic animal diseases and non-chemical methods to control diseases and disease vectors will become available not only to large commercial producers, but also to small, rural fish farmers. Research will provide the U.S. fish industry with the ability to identify important fish-pathogen hosts so the workforce can limit access of these hosts to ponds.

Potential impact of this 5-year Project will be additional fish health management strategies for fish diseases (bacteria and parasites) including FDA-approved compounds and the development of chemical and biological control methods to eliminate or reduce populations of non-fish hosts.


6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
Results of research studies and technologies developed were made available to customers and the general public through oral presentations (technical and non-technical), poster presentations at local, state, national and international meetings, and scientific publications.


7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
None.


Review Publications
Darwish, A.M., Ismaiel, A.A., Newton, J.C., Tang, J. 2004. Identification of Flavobacterium columnare by a species-specific polymerase chain reaction and renaming of atcc43622 strain to Flavobacterium johnsoniae. Molecular and Cellular Probes. 8(6):421-427.

Darwish, A.M., Straus, D.L., Griffin, B.R. 2005. Histologic evaluation of the safety of copper sulfate to channel catfish. North American Journal of Aquaculture. 67:122-128.

Darwish, A.M., Hobbs, M.S. 2005. Laboratory efficacy of amoxicillin for the control of Streptococcus iniae infection in blue tilapia. Journal of Aquatic Animal Health. 17:192-202.

Mitchell, A.J., Goodwin, A.E. 2004. Centrocestiasis (gill trematode disease). FHS Blue Book: Suggested Procedures for the Detection and Identification of Certain Finfish and Shellfish Pathogens. AFS-FHS (American Fisheries Society-Fish Health Section), Bethesda, Maryland. American Fisheries Society Book Series.

Mitchell, A.J., Brandt, T. 2005. Temperature tolerance of the red-rim melania Melanoides tuberculatus, an exotic aquatic snail established in the United States. American Fisheries Society Transaction. 134:126-131.

Mitchell, A.J. 2004. The effect of praziquantel bath treatments against Bothriocephalus acheilognathi in grass carp. Journal of Aquatic Animal Health. 16:130-136.

Green, C.C., Lochmann, S.E., Straus, D.L. 2005. Acute toxicity of isopropyl methylphosphonic acid, a breakdown product of sarin, to eggs and fry of golden shiner and channel catfish. Journal of Toxicology and Environmental Health. 68:141-149.

Darwish, A.M., Straus, D.L., Griffin, B.R. 2004. Copper sulfate target animal safety in channel catfish [abstract]. Annual Eastern Fish Health Workshop. p. 71.

Darwish, A.M., Straus, D.L., Griffin, B.R. 2004. Safety of therapeutic copper sulfate use on channel catfish [abstract]. Drug Approval Coordination Workshop Book of Abstracts. 10:132-137.

Mitchell, A.J. 2004. Bolbophorus infections in catfish: identification, impact and treatment [abstract]. Annual Eastern Fish Health Workshop. p. 58.

Mitchell, A.J. 2004. An unusual case: walleye lesions in the visceral cavity [abstract]. 29th Annual Eastern Fish Health Workshop. p. 12.

Straus, D.L. 2004. Status of research activities at SNARC [abstract]. Drug Approval Coordination Workshop Book of Abstracts. 10:21-22.

Mitchell, A.J., Overstreet, R.M., Goodwin, A.E., Brandt, T.M. 2005. Spread of an exotic fish-gill trematode: a far-reaching and complex problem [abstract]. Fisheries. 30(8):11-16.

Last Modified: 7/22/2014
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