Veterinary products and aquatic
Peter Smith
Chair OIE ad hoc Group on the responsible use of
antimicrobials in aquatic animals
Veterinary products
FAO Definition
‘a drug of natural or synthetic origin, with the
capacity to inhibit the growth of or to kill
microorganisms. Antibiotics that are
sufficiently non-toxic to the host are used as
chemotherapeutic agents in the treatment of
infectious diseases of man, animals and
Reasons for antibiotic use in aquaculture
Prevention (good husbandry and correct use of vaccines)
is the best way of reducing disease risks
When bacterial infections occurs in farmed animals
antibiotics are the only therapy that will
reduce loses
Reasons why antibiotic use must be
Antibiotics are powerful chemicals - biologically active at low
Aquacultural use involves the deliberate introduction of these
chemicals into the food chain and the environment
Use of antibiotics lead to the emergence of resistant bacteria and
resistance compromises their value as therapeutic agents
Presence of residues may affect consumers of aquaculture products
Public perception of a “drug-based” industry and results in reduced
market acceptability of aquaculture products
Resistance to antibiotics
Resistance and aquatic animal health
There is clear evidence that resistance to antibiotics has
emerged when these agents are used in aquaculture
The more we use (and misuse) these agents the smaller is
the chance that antibiotics will be effective therapeutically
We run the risk of entering the ‘pre-antibiotic’ era
Resistance to antibiotics
Resistance and human health
Resistance to antibiotics is global
There is a risk that antibiotic resistance selected
by aquacultural use will compromise therapy of
human infections
Pressure from human medicine (WHO) may
reduce availability of antibiotics to aquaculture
Presence of unacceptable residues
Presence of any residues of banned antibiotics
Presence of levels of other antibiotics above
maximum allowed limit
Will have major trade implications
Overall strategy to ensure prudent use
A new draft chapter of the
OIE Aquatic Animal Code
is being prepared
It will primarily address issues of
the regulation and the monitoring/surveillance of
the use of antibiotics in aquaculture
This talk is an introduction to some of these issues
Current global status
There is huge variety in the extent and the
style of regulation and
monitoring/surveillance of antibiotic use in
Some authorities have very sophisticated
procedures but the majority, including many
responsible for large production volumes,
have not
Current global status
Central to regulation
is the licensing of antibiotic containing products
by the granting of
Marketing Authorizations
Current global status
Very few antibiotics are licensed for aquaculture
Many countries have licensed no antibiotics
Some have only licensed a few (2-4)
Some large industries (shrimp) have
no licensed antibiotics
Current global status
We have little (quality) information on the
consequence (target bacteria resistance) of
antibiotic use in aquaculture
We have no accurate estimates of the amount
of antibiotics used in aquaculture
The way forward
The way forward - Regulation
To ensure that antibiotics used in aquaculture are safe to
the animals treated and to the consumers
To ensure that antibiotics are used in a way that is likely to
be efficacious (cost/effective)
To ensure all stakeholders are informed of their
duties and responsibilities
The way forward - Regulation
Regulations based on Marketing
Only products for which MA have been granted should be
used in aquaculture
MA will facilitate
correct product labeling
and definition of
the responsibilities and duties of all stakeholders
The way forward - Regulation
Marketing authorizations
(treated animals, users and to consumers)
The way forward - Regulation
Safety to consumers
Maximum residue level (MRL)
independent of species and rearing conditions - internationally set
Withdrawal time
time after therapy when residue is below MRL
dependent on species and rearing conditions – locally set
The way forward - Regulation
Establish that
a specified dose regimen delivered
using a specified antibiotic containing product
will control loses resulting from
a specified bacterial infection
of a specified species
under specified environmental conditions
The way forward - Regulation
Problems with basing regulation on MA
MA are expensive and time-consuming
to produce
(who pays?)
MA are specific but disease conditions
encountered in aquaculture are diverse
The way forward - Regulation
Problems with basing regulation on MA
There will always be a need for
extra/off label
use of antibiotics in aquaculture
The way forward – Monitoring resistance
Information on resistance in target bacteria is
to ensure individual therapies are rational and
to understand emerging patterns of resistance
nationally, regionally and globally
to inform risk assessment
The way forward – Monitoring resistance
We are in the process of
standardizing and harmonizing laboratory methods
for measuring susceptibility in aquatic bacteria
We possess no quality information on resistance in
bacteria that infect fish
Embarrasing fact
After 50 years of research
we have no clear procedures for establishing if a
bacterium isolated from an aquatic animal will be
resistant or sensitive
to an antibiotic therapy
The way forward – Monitoring resistance
Determining resistance involves 2 stages
Development of appropriate standardized
laboratory protocols
Developing interpretive criteria that allow
meaning (sensitive/resistant)
to be given to the results of these laboratory tests
The way forward – Monitoring resistance
Test protocols
There is general agreement that the test
protocols outlined in the CLSI documents
M42-A and M49 -A should be adopted
Current status of CLSI resistance methods
Test protocol
Interpretive criteria
Aeromonas salmonicida
Aeromonas spp
Edwardsiella spp
Flavobacterium spp
Photobacterium spp.
Streptococcus spp.
Photobacterium spp
Vibrio spp
Piscirickettsia salmonis
Vibrio salmonicida
Tenacibaculum maritimum
Francisella spp
We know how to do the tests
We don’t know what the results mean
Current status of CLSI methods
Interpretive criteria
There is an urgent need for progress
Progress can be made on a species by species
Not all species are relevant to all industries or all
regulatory authorities
The work required to set criteria for one species is
not expensive or time-consuming
The way forward – Monitoring use
Data on how much antibiotics are being used is
to understand emerging patterns of resistance
to inform and monitor strategic planning
to perform risk analysis
The way forward – Monitoring use
Use data requirements
Absolute amount (kg active drug) used
Animals treated (species, number, weight)
Rationale for use (diagnosis, therapy/prophylaxis)
Mode of administration, type of husbandry
system, environmental conditions etc
Risk analysis
What are the risks that use of antibiotics in
aquaculture will select for resistances that will
have a negative impact on human therapies?
A very difficult question to answer
Risk analysis
Risks associated with aquacultural use much less
than those associated with use in
land-based agriculture
Risk primarily associated with selection of
transferable resistance factors in
environmental bacteria
Risks associated with resistant bacteria in
aquaculture products less important
Antimicrobial Resistance (AMR) Risk
Analysis in Aquaculture
Discussion on the applicability of risk analysis principles for AMR in aquaculture
Thursday, 30 June 2011 8:30 am
Speakers Room/Salon Republicco
To receive a copy of a white paper describing the topic drafted by the OIE ad hoc
Group on antimicrobial resistance in aquatic animals send a message to
[email protected]
Prudent use of antibiotics
Farmers buy and use antibiotics because they
think/hope that it will increase their profits
Much use by farmers is inappropriate and
The greatest gain in prudent use and economic
efficiency will be achieved by providing
farmers with quality advice
Prudent use of antibiotics - education
Education programmes to train
farmers and their on-farm advisors in the
correct use of antibiotics
the provision of adequate and local
diagnostic and antibiotic susceptibility testing
Will greatly reduce imprudent use

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