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Control of Aquatic Diseases. http://www.flsart.org/library/index.htm. Various Methodolgies Allowing Control. Test and Slaughter Quarantine and Restriction of Movement Immunization and Disease Resistance Destruction or Reduction of Intermediate Hosts Drug Therapy External Treatments

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control of aquatic diseases

Control of Aquatic Diseases

http://www.flsart.org/library/index.htm

various methodolgies allowing control
Various Methodolgies Allowing Control
  • Test and Slaughter
  • Quarantine and Restriction of Movement
  • Immunization and Disease Resistance
  • Destruction or Reduction of Intermediate Hosts
  • Drug Therapy
  • External Treatments
  • Systemic Treatments
  • Hatchery Sanitation
1 test and slaughter
1) Test and Slaughter
  • Requires testing population for pathogen
  • If found, entire group is destroyed
  • Carcasses buried or burned
  • Effective when absolute control is needed:
    • agent has no known treatment
    • agent is exotic
    • fish have high levels of pathogen
  • Often requires legislation to be effective
    • which agents require mandatory slaughter?
    • must include all policies
    • requires indemnification or won’t work
2 quarantine and restriction of movement
2) Quarantine and Restriction of Movement
  • Restricts all movements of fish between drainage systems and between hatcheries -or-
  • Fish transport requires “Q” of fish in “suspected” area
  • No disease = fish moved
  • Disease = rejected.
2 q r cont
2) Q/R cont.
  • Applies to whole animal, parts, or products
  • Good on paper, hard to implement
  • Why? How can you practically hold fish outside your facility for the incubation period? Spoilage?? Death? Latent carriers?
  • Q/R also applies to all fish/shrimp imports:
  • Need certified inspectors
  • Sampling assumes 5% prevalence, or 95% chance of recovering one infected individual
  • Infected? Who knows?
2 q r
2) Q/R
  • Programs not typically effective because farmers won’t pay for inspections if not required by law
  • Interstate transport laws are fairly “loose” (Idaho has no regulations)
  • True inspections programs are best handled by large institutions (e.g., public aquaria)
  • For permitting import of shrimp in Texas, you can only have one species (L. vannamei) and it must be SPF for TSV, white spot, IHHNV and Vibrio sp.
3 immunization and disease resistance
3) Immunization and Disease Resistance
  • Vaccines—good for terrestrials, not as much for fish
  • Fish not very immunocompetent at low temps
  • Time, $$$, limited methodologies
  • Breeding/genetics can increase disease resistance: rainbows (furunculosisr), brown trout (whirlingr), L. vannamei (WSSVr)
  • Common problem: breeding in resistance usually means breeding out growth...oops!
4 destruction reduction of other hosts in life cycle
4) Destruction/Reduction of Other Hosts in Life Cycle
  • Can be effective against most metazoan parasites
  • You can try to eliminate some snails, keep birds out (Problems with permits?)
  • Difficult to eradicate vertebrates: most are “protected”
  • Herons, egrets, etc.
5 drug therapy cure crutch or wheelchair
5) Drug Therapy: Cure, Crutch or Wheelchair??
  • Tried-and-true-method for fish/shrimp, but…
  • Resistance, cost, approval issues?
  • $$$$: limited potential volume of sales prohibits most companies from doing the R&D required to bring drugs to market
  • “Registration of a single compound for one type of use costs about $1.5 million and 1.5-3 years elapsed time”
federal food drug and cosmetic act 1915
Federal Food, Drug and Cosmetic Act (1915)
  • Revised in 1956
  • limited use of many substances until safety to animals established
  • all compounds used must be registered as safe for use by FDA
  • GRAS = generally recognized as safe
  • testing: efficacy, toxicity, tissue residence time (food implications)
federal food drug and cosmetic act revised 1956
Federal Food, Drug and Cosmetic Act (Revised, 1956)
  • Applied to previous, but also included section on food additives
  • really targeting feeds
  • feed additives require additional registration:
    • dosage (what is effective?)
    • withdrawal time (last dose ---> market) (OTC=30 days)
    • information on dose must appear on tags
  • real limitation on use, originally intended to curb only indiscriminate use
6 external treatments
6) External Treatments
  • Controls pathogenic agents of fish/water
  • Requires immersion
  • Chemical effective but at lower-than-lethal level (e.g., chlorine not good for this use)
  • Miscible in water
  • Resist absorption by fish
  • Usable for multiple treatments
  • Cheap

What fits THIS category?

types of external treatments dips
Types of External Treatments: dips
  • Characterized as high concentration for short time
  • Used on small #’s of fish, often prophylactic
  • Advantages: concentration easily established, requires small amount
  • Disadvantages: have to handle all fish, can create situation where effective dose is higher than lethal dose
external treatments dip on the run splash and go
External Treatments: dip on the run, “Splash and go!”
  • Strong chemical concentration via inflow water
  • chemical rapidly enters water
  • applicable to troughs, tanks, raceways
  • advantage: don’t have to turn off water
  • disadvantage: uneven distribution
external treatments bath
External Treatments:bath
  • Actually just a prolonged dip
  • lower concentration, determined accurately by volume of tank, amount of chemical
  • no water exchange
  • advantage: concentration known, no fish handling
  • disadvantage: oxygen can decrease, NH3 can increase, hot-spots, must quickly remove chemical at end of treatment (this last one can be a real problem for large volume recirculation systems)
external treatment flow through
External Treatment:flow through
  • Designed to maintain constant concentraton flowing into tank
  • chemical dripped-in or siphoned
  • advantages: no water shut-off, no handling
  • disadvantages: must have even flow for even treatment, costly
external treatment indefinite
External Treatment:indefinite
  • Simple to treatment of most ponds
  • very low concentration of chemical applied
  • broken-down naturally or dissipates into air
  • must break-down quickly (problem: few do)
  • advantages: no handling of fish
  • disadvantages: lot of chemical ($), adverse affects on pond (kills phytos), even application difficult
7 systematic treatment of diseases
7) Systematic Treatment of Diseases
  • Compounds introduced orally thru feed
  • problem: sick fish go off feed!
  • drug must 1) control pathogen under internal conditions, 2) effective dose < lethal dose,

and 3) be cost-effective

  • Applied during manufacturing process, can be integrated into gelatin binder on pellet surface
  • problem: even distribution difficult,

pellets must be prepped daily

  • Why not often used? Apathy, $$, FDA regs
8 hatchery sanitation
8) Hatchery Sanitation
  • Purpose 1: prevention of any foreign disease agents from getting into hatchery
  • Purpose 2: limits disease spread to tank of origin
preventive guidelines
Preventive Guidelines
  • Reduces vertically-transmitted pathogens:
  • 1) import only eggs, never juveniles/adults
  • 2) eggs should be from SPF/high health facilities
  • 3) wild individuals should be prohibited or all water, etc. needs to be disinfected
  • 4) disinfect all eggs prior to stocking hatching containers (also disinfect/destroy all shipping containers)
  • chemicals: iodophores (Argentyne) 100 ppm for 10-15 min
guidelines for limiting spread
Guidelines for Limiting Spread
  • Disinfect all hatchery and personal equipment after or between use (equipment must be clean prior to disinfection)
  • sports fishermen or farmers should never be allowed near facility (political issue)
  • transfer/shipping equipment, vehicles must all be disinfected whenever leaving grounds
  • do not overlook any possible source of contamination
  • proper hatchery design limits spread
part 2 biosecurity
Part 2. Biosecurity
  • Recently, shrimp disease agents and associated problems have spread from foreign countries to the U.S.
  • Major efforts established defense against disease
  • Due to severity of issue, parallel efforts were undertaken to design production systems to exclude diseases
  • Such systems are called “biosecure”
  • Key issue: zero water exchange
biosecurity general issues
Biosecurity: General Issues
  • Definition: the sum of all procedures in place to protect fish/shrimp from contracting, carrying and spreading diseases
  • Critical to identify all known and potential vectors
  • critical: use only seed from SPF or high-health facilities
  • stocks monitored periodically for disease using rapid methodologies
  • infection of facility = shut-down, complete disinfection (chlorine gas, formaldehyde, etc.)
biosecurity general issues1
Biosecurity: General Issues
  • Other potential disease sources: incoming water
  • facility should be isolated from other farms, processing plants, capture fisheries
  • water should be recycled
  • replacement water disinfected by chlorine, ozone, ultraviolet light
  • avoid vectors: gulls, dogs, crabs, etc.
  • feeds ( prepared vs. raw)
slide26

Biosecurity will reduce the likelihood that potential pathogens will be transferred from workers to the fish.

Footbaths & hand disinfection required before entering any fish rearing area.

human biosecurity
Human Biosecurity
  • Don’t be afraid to keep

folks out…

  • Your research or data is

your livelihood!

  • You don’t want to be liable

for someone’s injury either.

human biosecurity1
Human Biosecurity
  • Monitoring systems add redundancy to

trained personnel.

  • Always good to have an extra set of eyes!
  • Walk-throughs before going home should be routine.
human biosecurity2
Human Biosecurity
  • Don’t assume folks will take precautions on their own.
  • You must establish a record

and atmosphere of safety

and maintain it.

approval requirements for new drugs
Approval Requirements for New Drugs
  • Approval from EPA or the FDA
  • requires research/admin. tasks
  • scientific research entails learning:
    • efficacy of treatment (does the compound achieve the desired results?)
    • can results be obtained w/out further jeopardizing health?
    • Does its use pose danger to humans?
    • Does the therapeutant harm the environment?
efficacy or effectiveness
Efficacy or Effectiveness
  • First step is to test the drug against potential pathogens (Are they sensitive to the drugs?)
  • usually performed in vitro Minimum Inhibitory Concentrations (MIC’s)
  • develop a standardized test battery of isolates
  • isolates are representative bacterial strains + two references
  • acceptable MIC’s are less than 2 ppm
efficacy continued
Efficacy (continued)
  • Second Step: assuming drug is determined safe, it must be effective in vivo
  • a series of dose-titration studies
  • disease intentionally induced (w/pathogen)
  • followed by administration of drug at various levels
  • if effective: dose response
safety when used on test animal
Safety when used on Test Animal
  • Lowest dose toxic to the test animal must be established
  • toxicity is more than just the lowest level causing mortality
  • death + any other deleterious effect (e.g., lethargy, poor growth, aesthetic considerations, etc.)
  • levels established by: lethal concentration (LC), lethal dose (LD), effective concentration (EC), effective dose (ED)
standardized procedure
Standardized Procedure??
  • Toxicity testing procedures for cattle are not that applicable to fish or shrimp
  • Proposed method (Williams et al., 1992)
  • Uses therapeutic index (TI)
  • TI = (highest inhibitory level of drug/lowest level toxic to shrimp)
  • if animals show a TI value (therapeutic index) of greater than 4, go on to more detailed studies in other stages
human safety issues
Human Safety Issues
  • If the drug is shown to be effective against the pathogen, it is assumed that some is incorporated into tissue
  • greatest concern: how long are effective levels in tissue maintained?
  • Must establish withdrawal period
  • definition: the amount of time a given drug persists in the edible flesh of treated fish/shrimp at detectable levels
human safety issues continued
Human Safety Issues (continued)
  • Studies used to establish withdrawal period are referred to as “residue” or “depletion” studies
  • time consuming, expensive, required detailed lab analyses, equip, etc.
  • procedures must follow GLP: good laboratory practices (very rigid)
  • requires FDA certified GLP lab (few in the U.S.)
  • typical lab is owned by pharmaceutical company
environmental safety
Environmental Safety
  • The FDA is primarily responsible for reviewing information to support the premise that the prospective drug does not harm the environment
  • they like to see data indicating that the drug breaks down rapidly:
    • short half-life in the system
    • low effluent volume
    • effluent that is highly diluted
    • further dilution in the environment
environmental safety1
Environmental Safety
  • The FDA is really only concerned with the prospective drug harming the environment as a direct toxicant
  • other factors should be of concern:
    • direct/indirect effects on microflora in and outside the culture facility
    • antimicrobials can shift things towards resistant species...oops!
    • each successive use could increase proportion of drug-resistant microbes
administrative procedures
Administrative Procedures
  • Unfortunately, the previous scientific concerns are the only ones addressed for acceptance of newtherapeutic drugs
  • administrative tasks are more difficult than the scientific ones
  • myriad types of FDA applications and procedures that must be followed
what does the fda want
What does the FDA Want?
  • review your protocol for testing
  • follow up with a visit
  • must respond to your application within a certain time limit (sometimes up to 1/2 year)
  • then they tell you that you forgot something!!
  • Keep bugging them...
investigational new animal drug inad applications
Investigational New Animal Drug (INAD) Applications
  • If INAD’s approved, you can use an unapproved aquaculture drug
  • INAD’s are, however, used for specific purposes, many restrictions:
    • meaningful data
    • only under INAD protocol
    • virtually no hazard to humans (rapid degradation in test animals)
    • minimum impact on the environment
    • really restricted to certain user groups
inad applications
INAD Applications
  • INAD’s lead to NAD’s
  • NAD’s provide for the submission of required data in support of a request to gain the approval of a new drug for use with animals.
  • This process is very expensive
  • Usually, NAD’s are submitted by pharmaceutical companies manufacturing the drug
key resources
Key Resources
  • USDA-APHIS fact sheets for various animal diseases

http://www.aphis.usda.gov/lpa/pubs/fsheet_faq_notice/fsfaqnot_animalhealth.html

  • APHIS’s Center for Emerging Issues (CEI) has various worksheets available on animal health and diseases of concern

http://www.aphis.usda.gov/vs/ceah/cei/worksheets.htm

  • Aquatext.com -- a free, online aquaculture dictionary

http://www.pisces-aqua.co.uk/aquatext/dicframe.htm

State Agricultural Response Team

34

key resources1
Key Resources
  • Florida Department of Community Affairs, Division of Emergency Management

http://www.floridadisaster.org

  • United States Department of Agriculture (USDA)

http://www.usda.gov

  • Florida Department of Agriculture and Consumer Services (FDACS)

http://www.doacs.state.fl.us

State Agricultural Response Team

35

key resources2
Key Resources
  • Florida Division of Aquaculture home page

http://www.floridaaquaculture.com

  • Aquaculture Best Management Practices manual can be accessed directly at

http://www.floridaaquaculture.com/BAD/BMP%20Rule%20-%20Manual%206-9-04.pdf

  • Aquaculture Network Information Center

http://aquanic.org

State Agricultural Response Team

36

key resources3
Key Resources
  • USDA Animal and Plant Health Inspection Service (APHIS)

http://www.aphis.usda.gov

  • World Organisation for Animal Health (OIE)

http://www.oie.int

  • Safety for Fish Farm Workers video on the National Ag Safety Database (NASD), English and Spanish versions available from the following link

http://www.cdc.gov/nasd/videos/v001401-v001500/v001433.html

State Agricultural Response Team

37

key resources4
Key Resources
  • Spawn, Spat, and Sprains book produced by the Alaska Sea Grant College Program. The entire book can be downloaded from the following link

http://www.uaf.edu/seagrant/Pubs_Videos/pubs/AN-17.pdf

  • University of Florida Institute of Food and Agricultural Sciences Electronic Data Information Source (EDIS) fact sheets for aquaculture, including diseases, can be found at the following links

http://edis.ifas.ufl.edu/DEPARTMENT_VETERINARY_MEDICINE

http://edis.ifas.ufl.edu/DEPARTMENT_FISHERIES_AND_AQUATIC_SCIENCES

State Agricultural Response Team

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