Good aquaculture and biosecurity
practices to minimize AMRLarry A. Hanson
Aquatic AMR Workshop 1: 10-11 April 2017, Mangalore, India
FMM/RAS/298: Strengthening capacities, policies and national action plans on
prudent and responsible use of antimicrobials in fisheries
ANTIMICROBIAL RESISTANCE MANAGMENT
o AVOID DEVELOPMENT-
• Biosecurity
• Disease prevention
• Alternative treatments
• Judicious use
o REDUCE PERSISTANCE
• Crop rotation/complete harvest
• Monitoring and disinfection?
• Antibiotic use restriction or rotation
o AMR experience in channel catfish production
Biosecurity-Avoiding obligate pathogens and AMR strains
o Fish source- critical factor
• Indiscriminant use of antibiotics during early stages can result in build up in system
• Fry and eggs sometimes given prophylactic bath treatments during handling- these
may be critical during establishment of microbial flora and allow establishment of
AMR.
• Know how fish produced and antibiotic usage- hatchery GAP
• Due to economics of hatchery systems and susceptibility of young- improper use of
antibiotics at this stage is more common (also opportunity to spread pathogens and
antibiotic resistance through industry
• Disinfection of tanks and ponds between batches.
• Separation of eggs from brooders and disinfection of egg surface (iodine, formalin,
potassium permanganate)
Biosecurity- avoid obligate pathogens and introduction of AMR
o Surveillance, quarantine and monitoring
o Used of certified free stocks
o Use pathogen free water, and processed feeds or SPF live/fresh feeds
o Between farm security-
• On farm equipment, nets
• Limited access
• Cleaning/disinfecting trucks, trailers, boats entering facility
o Within farm security
• Avoid water movement between ponds
• Disinfect nets and equipment
• Predator and scavenger control- mammals, birds and reptiles can shed fish pathogens
Disease prevention- reduces need
for antibiotics
o If you don’t correct underlying cause
disease will reoccur after treatmentPathogen Host
Environment
Disease
Disease prevention
o Manage the environment to minimize stress and physical injury
• Water quality
• Handling
• Environment
• Manage predators
• Prevent aggression and cannibalism- remove dead
o Minimize viral, water mold and parasite diseases (Predispose fish to
bacterial disease and suppress feeding- resulting in subtherapeutic
treatments)
o Vaccines-if effective for bacterial pathogens and viruses
o Good quality feed, freshness and amount
Non-antibiotic alternatives
o Management to reduce pathogen load or transmission dose
• Fecal oral transmission- Allow time for gut to clear before feeding- reduces defecation
where feeding- ESC every-other day feeding during peak disease season
(feed restriction may help with others by reducing close contact)
o Chemical treatments that interrupt transmission or stimulate resistant state in
host
• Copper sulfate makes catfish less susceptible to columnaris disease
• Salt 1-5 ppt reduces F. columnare’s ability to adhere to fish (Used during hauling)
• Potassium permanganate oxidizer kills surface bacteria and free bacteria in the water
Judicious Use of Antibiotics-medicated feeds- minimizes selective
pressure
o Use when needed and effective
• Must be diseased- no prophylactic use, no use for growth promotion
• must be susceptible bacteria pathogen- susceptibility testing
• Fish must feed well enough to get a therapeutic dose
o Give for full treatment duration- antibiotic must persist long enough to kill
pathogen
o Use fresh good quality medicated feed- reliable licensed feed producer
o Careful feeding practices- avoid wastage- AMR can develop in bacteria that
grow in wasted feed
Judicious Use-
Antibiotics-medicated feeds- regulation
o Prescription- Licensed or certified health professional-requires VCPR
• Must know disease treated (has done the primary diagnosis- should follow up with AMR
testing)
• population activity (feeding well enough for treatment)
• Must assure that producer is understands proper safe application, rate, duration and
withdrawal time before slaughter and agrees to use it in that way
o approved antibiotics from licensed source, licensed feed manufacturer
• Approval for species, pathogen, rate of application and withdrawal time- drug company
must show efficacy, safety to user and fish and human food safety
o Record keeping- producer, veterinarian/ licensed fish health professional,
feed manufacturer
Judicious Use- Enforcement
o must be consequences for improper use
• Illegal drugs human food chain- serious repercussions- human health and product
• Government agency – in US FDA
• Enforcement branch- actively seeks out any illegal drug usage and presence on
facility- results in condemnation of fish, large fines and imprisonment
• Monitors and traces prescription use drugs- through feed manufacturer
• Fillet (human food) monitored for residue if any found condemn lot, recall any on
market and trace back to farm source
• Licensing (drug company, feed mill, fish health professional) - assigns legal
responsibility and can inappropriate activity can result in revocation
• Can be industry driven through contracts or cooperatives
REDUCE PERSISTANCE
o Minimize use-AMR is a natural process. There is cost to the bacteria to
maintain this state, minimal antibiotic use will minimize selective pressure
and result in lower numbers of AMR pathogens.
o Complete harvest and disinfection of production system prevents build up in
system.
o Crop rotation if practical- breaks pathogen cycle
o Voluntary antibiotic use restriction or rotation on a facility for 2-3 production
cycles.
Experience in Channel catfish production
o Major pathogens
• Flavobacterium columnare
• Edwardsiella ictaluri (Enteric septicemia of catfish) and E piscicida
• Aeromonas hydrophila
o Approved antibiotics- All medicated feeds all by Veterinary prescription in
2017 (Terramycin and Romet OTC in 2016).
Terramycin-Oxytetracycline 10 days- 21 day withdrawal (rarely used- has been in past)
Romet- Sulfadimethoxine-Ormetoprim 5 days- 3 day withdrawal (occasionally used)
Aquaflor- Florfenicol 10 days- 15 day withdrawal (commonly used)
o Cost $800 per ton vs. $390 for non-medicated
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
growthJun 29
Brood pond
Hatchery
Grow out
Harvest
stocking
Fingerling pond
Vaccinate and stock fry
7-8 days post hatch
H
GO
Catfish production Stock fingerlings
Continuous production allows pathogen and AMR build up
Routine stress management
o Dissolved oxygen intensely managed over summer months
o Chlorides maintained above 100ppm to reduce nitrite toxicity
o Use fresh, well formulated feeds
o Stock fish in cool months to reduce handling stress
Columnaris- Management
o Avoid damaging mucus layer-
• Handle during cool weather
• Use smooth surfaces or water cushion when handling
• Treat hauling tanks with 1-3 ppt salt
• Avoid damage to gills- particulates, ammonia, parasites
o Manage ESC, Winter mortality, CCV
o Vaccinate (effectiveness in fry not great, likely better in older fish)
o Treatment with copper sulfate has been shown to help
o Antibiotic medicated feed- Aquaflor labelled, Terramycin not labelled effective
but not used, Romet not labelled and may not be effective
Enteric Septicemia of catfish-management
o Avoid stress (DO and Nitrite)
o While in 22-27 C window feed on alternate days
• This reduces transmission- enteric pathogen. Gut clearance before feeding reduces
bacterial shedding when fish concentrated for feeding.
Wise, D.J., Johnson, M.R., 1998. Effect of feeding frequency and Romet-medicated feed on survival, antibody
response and weight gain of fingerling channel catfish (Ictalurus punctatus) after natural exposure to
Edwardsiella ictaluri. Journal of the World Aquaculture Society 29, 170-176.
o Vaccination- helps in fingerlings but losses still occur
o Antibiotic treatment- Aquaflor (labelled), Romet (labelled), Terramycin (not
labelled)
New Disease: Virulent Aeromonas hydrophila (VAH)
Courtesy of William Hemstreet
High losses over a short time in
warm months.
First seen in 2009
Most important cause of disease
in larger catfish
Distinct strain
Biosecurity: limiting VAH Spread
o Moving infected fish?-not
common
o Contaminated equipment
& Water (correlation with
seining frequency-
Bebak et al. 2015. Prev.
Vet. Med. 118, 161-168)
o Predators and Scavengers. Experimentally
shown to survive through gut of Egrets,
pelicans, wood storks and cormorants
Human Natural
Management
o Hold off feed at first signs of disease
o Antibiotic medicated feed- aquaflor (Working on label, extra label use),
Romet (not labelled), Terramycin (labelled)
o Often re-occurs after treatment period finished. Suspect environmental
factor(s) involved.
Observed antimicrobial resistance 2016 MSU-CVM DL
Number
evaluated
percent
Florfenicol
percent
Romet
percent
Terramycin
percent
MDR
Aeromonas hydrophila 97 1.03 0 1.03 0
Aeromonas sobria 71 12.6 1.41 49.3 2.82
Aeromonas caviae 4 0 0 0 0
Edwardsiella ictaluri 41 14.6 0 12.2 12.2
Edwardsiella piscicida 18 5.55 0 0 0
Plesiomonas shigelloides 7 71.4 14.3 85.7 71.4
Streptococcus 4 0 0 0 0
Total 242 9.09 0.826 19.4 4.96
67 of A. sobria were with F. columnare, 7 were with E. ictaluri, 3 parasites, I saprolegina
AMR in catfish pathogens- Observations
o Highest resistance seen in Aeromonas sobria
• This is a secondary pathogen, not usually the target of antibiotic treatment but often
present during columnaris disease
• Also highest resistance to terramycin which is rarely used now
o Second highest level of resistance seen in E. ictaluri
• Most are resistant to both Aquaflor and Terramycin
• Early research by Cooper et al. 1993 demonstrated a Romet and Terramycin resistance
mediated by an R plasmid that was very similar to a R plasmid isolates from an E. coli.
o Industry has seen increasing levels of Aquaflor resistance. May seriously
impact treatment options.
o Romet resistance subsided rapidly when it was used less often
Summary
o Disease management is the most important component for AMR management
o Antibiotic resistance will develop and may occur in non-target pathogens
o Industry needs to be proactive to minimize the impact