Towards sustainable and efficient therapeutic (antibacterial) strategies in Mediterranean

marine aquaculture

Andrea FabrisItalian Fish Farmers Association

George Rigos Hellenic Centre for Marine Research

INDUSTRY FORUM: SUSTAINABLE SOLUTIONS TO ADDRESS SEA BASS AND SEA BREAM FARMING CHALLENGES IN THE MEDITERRANEAN

➢Primary type is cage farming (small production is land-based or lagoons etc)

➢ large numbers of fish are kept together

➢There, fish subjected to several stressors for at least 12 months

➢Diseases are inevitable if management is problematic or not adequate

➢Parasites, viruses, bacteria and other pathogens

➢Infectious (bacterial) diseases in caged farming may become a substantial problem due to financial loss/mortalities, therapeutic costs, decrease of the performance of the fish and depreciation of product value

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1. OVERVIEW OF SEA BASS/BREAM PRODUCTION

Characteristics & concerns

V. anguillarum

V. alginolyticus

A. veroni

T. maritimumM. marinum

Epitheliocystis

➢Vibrio anguillarum, Photobacteriumdamselae subsp. piscicida, Aeromonas veroni, Tenacibaculum maritimum, V. harveyi, V. alginolyticus

➢Βacterial outbreaks in ESB account for 30-40% (but in endemic with A. veroni areas this can up to 70%) of total disease cases

➢Less bacterial infections in GSB (<15%)

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1. OVERVIEW OF SEA BASS/BREAM PRODUCTION

Overview of the main bacterial diseases

Use of antibacterials

Non use of commercial vaccines

2. ANTIBACTERIALS AND MANAGEMENT

Cases where antibacterial use may be necessary

Lack of any type of specific vaccines

New bacterial pathogens

Not adequate vaccination strategy

Improper management

Alteration of bacterial antigenicity

Low biosecurity measures

2. ANTIBACTERIALS AND MANAGEMENT

Antibacterial candidates for GSB & ESB

✓TETRACYCLINESOxytetracyclineChlortetracycline

✓(FLUORO)QUINOLONESOxolinic acidFlumequine

✓SULFONAMIDES Sulfadiazine Sulfamethazine

✓DIAMINOPYRIMIDINESTrimethoprim

✓PENICILLINS-B LACTAMAmoxycillin

✓PHENICOLSFlorfenicol

Registered for fish/animal use

✓(FLUORO)QUINOLONESSarafloxacinEnrofloxacinDanofloxacin

✓PHENICOLSThiamphenicol

Experimentally used/not registered

✓TETRACYCLINESDoxycycline

✓LINCOSAMIDESLincomycin

✓AMINOCYCLITOLSSpectinomycin

PFF antibacterials/not registered

(FLUORO)QUINOLONES are considered as antimicrobials critically important and with highest priority according WHO (2017), so probably their use forfarm animals will start to be reduced and eventually banned

*500 dd WT when used cascade principle

Antibacterial classPK/PD

interactionsOld PK/PD

models

Modern predictive indices of

PK/PD

Goal of therapy

Proposed values from

human medicine

Tetracyclines(codependent) conc. & time-

dependent killing

Cmax/MIC >4Cmax/MIC >8

AUC0-24/MICMax drug amount

>25

(fluoro)QuinolonesAminocyclitols

conc.-dependent killing

Cmax/MIC Max conc. >10

Sulfonamides & Diaminopyrimidines

PenicillinsPhenicols

Lincosamides

time-dependent killing

TC>MICMax duration of exposure

>50%

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2. ANTIBACTERIALS AND MANAGEMENT

Important aspects of antibacterials for GSB & ESB

OTC19%

OA19%

FLU17%

SDZ12%

THI10%

TRIM7%

AMO5%

ENR5%

SAR2%

DAN2%

FLO2%

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2. ANTIBACTERIALS AND MANAGEMENT

Number of published PK studies in ESB & GSB per drug

Drug MICs Kinetic profile Species

Proposed dosing

schedule based on PKs

WTs (h)-summer-

OTC

Low in V. anguillarum, big

variation in other

slow ESB, GSB1 meal/day-

sequential (winter)

<480

FLULow in almost all pathogens

fast ESB, GSB 1-2 meals/day >24

OA As above fast ESB, GSB 1-2 meals/day <24

SDZ Mixed fastGSB

PKs on ESB?>2 meals/day <144

AMO Mixed fast0.3% F in GSBPKs on ESB?

FLO Mixed fast ESB 2 meals/day 96

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3. PHARMACOKINETICS /PHARMACODYNAMICS OF ANTIBACTERIALS

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A. LINCOMYCINExp. Protocol PK

100 mg /kg fish for 5 days(23oC)5 ESB (93g) per time point3 samplings (D1,3,5)

Pathogen # strains MIC (μg/ml)

P. damselae piscicida 22 4-8

V. anguillarum 10 8-32

V. harveyi 10 32 -128

T. maritumum 7 0.12-0.5

•High plasma Linc levels•Drop fast during the 24h• 2 meals/day is suggested

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3. PHARMACOKINETICS /PHARMACODYNAMICS OF ANTIBACTERIALS

B. DOXYCYCLINE

Exp. Protocol PK

100 mg /kg fish for 5 days(22oC)5 ESB (79g) per time point3 samplings (D1,3,5)

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sma

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Time (h)

day 1

day 3

day 5

Pathogen # strains MIC (μg/ml)

P. damselae piscicida 22 0.125-0.5

V. anguillarum 10 0.125-0.5

V. harveyi 10 0.125-0.25

T. maritumum 7 0.25-0.5

•Low plasma Dox levels•Remain high during the 24h•1 meal /day or sequentialdosing is proposed

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3. PHARMACOKINETICS /PHARMACODYNAMICS OF ANTIBACTERIALS

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C. SPECTINOMYCINExp. Protocol PK

50 mg /kg fish for 5 days (26oC)5 ESB (152g) per time point3 samplings (D1,3,5)

Pathogen # strains MIC (μg/ml)P. damseale piscicida 22 8 - 32

V. anguillarum 10 8 -16V. harveyi 10 16-64

T. maritumum 7 16-32

•Low plasma Spe levels•Drop fast during the 24h•2 meals/day is suggested

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3. PHARMACOKINETICS /PHARMACODYNAMICS OF ANTIBACTERIALS

PKs:Cmax, AUC, TC

PDs:MIC / antibiogram

Data from clinical trials

Must be constantly updated

Ideal model for designing treatment schedule

•Consider evolution of the disease (proper early treatment)•Fish anorexia•Water temperature

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4. ANTIBACTERIAL SELECTION

Ideal : early administration strategy

Prodromic Acute Chronic Resolution

Low infection-lossesHigh-medium appetite

High infection-lossesVery low appetite

Decreased populationResistant survivorsLow infectionMedium appetite

Naturally survivorsReduced riskMedium-high appetite

Phase 1 (prodromic) is the key phase when antibiotic administration has much sense and efficacy: all the stock are still eating and can

become protected by the medication

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5. IMPLEMENTATION AND ESTIMATION OF MEDICATED DIET

Disease evolution phases

➢Most treatments in aquaculture are metaphylactic, in contrast to human and veterinary medicine; i) they are administered to particularly large population where a disease is being developed and thus include some infected and some uninfected animals ii) the main target in the metaphylactic treatments in aquaculture are not the affected or sick fish but those at considerable risk when an infectious agent cause an outbreak, iii) A metaphylactic treatment (control) should be clearly differentiated from therapeutic treatments (curative) and from prophylactic treatments (preventive)

➢Based on the above concept, when medicated diet is estimated, the whole population should not be included in the calculations. Periodical corrections should be implemented based on disease evolution phase and fish appetite. In some occasions, 50% of the initial estimation could be considered as overestimated

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5. IMPLEMENTATION AND ESTIMATION OF MEDICATED DIET

Correct estimation of medicated dietsThe concept of metaphylactic treatments

•Financial loss•Environmental pollution(uneaten feed & drug)

improper timing of therapy/false calculation

of medicated diet

Mainly related to coated-medicated diets

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6. ENVIRONMENTAL IMPACT

➢Rapid and proper diagnosis & selection of registered compound

➢Proper implementation of treatment; ideal to apply in prodromic phase not later; otherwise is it worthy to apply? Disease may be very progressive and most of the affected stock is anorectic or will eventually die

➢ Apply tailored Biosecurity measures and Vaccination strategies

➢Proper preparation of medicated diet. Consider unpalatable drugs. Use proper incorporation or coating techniques to enhance acceptance of medicated diets and reduce leaching. Masking also with attractants is advisable

➢Proper estimation of medicated diet. Adjustment/corrections based on metaphylactic concept; do not count all population in estimation of medicated diet

➢Accurate design of dosing schedule based on target species, target pathogen, environmental parameters (temperature etc). Use of published data when available from PKs on these species. Otherwise (not) extrapolate from other spp. Selection of single-double daily-sequential dosing. Completion of therapy

➢WTs should be considered when close to slaughtering

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7. CONCLUSIONS & RECOMMENDATIONS FOR BEST PRACTICES

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Contributors: HCMR: Kogiannou DimitraUAB-Francesc Padrós, Carles Cristòfol,UNIBO-Daniela Florio, Renato Giulio Zanoni, MarialetiziaFioravanti, SKRETTING-Carlos Zarza