Nihad Fejzić International consultant

Fresh water fish raised in tanks Farms with 2 to 20 tanks Each tank 1000 to 5000 fish Disease Present in the country Low infectivity During winter months Adult fish Draft surveillance design - farm accreditation -

One stage survey 95% confidence that disease will be detected if present Free status + maintenance of biosecurity OIE standards α= 5% probability of rejecting true Ho Ho – disease is present on farm with prevalence 5% Draft surveillance design - farm accreditation -

Target population - all fish on a farm Clustering of disease minimal Stratification by tank proportional to population of tank Sampling of fish for antigen based ELISA (Se=98% 95%CI 96,7% -99,2%, Sp=99,4% 95%CI 99,2%-99,6%) Confirmatory test for (possibly false) positive result – culture Se=90%, Sp=100% Draft surveillance design - farm accreditation -

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Sample size using ELISA – 410 fish per farm Sample size using two tests – 169 fish per farm Adjustment to population size: Draft surveillance design - farm accreditation - Population sizeSample size Sample size calculation done by FreeCalc

Draft surveillance design - farm accreditation -

Selection of samples – as much random as possible i.e. 4 tanks with 1850, 4250, 4270 and 4880 fish = ,13% 27,87% 28% 32% =100% =169 Harvesting – systematic sample 1850/21 – every 88th fish (first chosen randomly) Dip net – different location of the tank Draft surveillance design - farm accreditation -

Fresh water fish raised in cages Small number of farms/importers – 2302 registered Farms with 3 to 60 cages Disease Absent from the country Highly contagious No clinical signs, high mortality Common in late summer, but appears all year round Growing faze Draft surveillance design - national accreditation -

Two stage survey OIE standards α= 5% probability of rejecting true Ho Ho1 – disease is present in the cage with prevalence 50% (of cages within the farm ) 95% confidence that disease will be detected if present Ho2- disease is present on the farm with prevalence 1% (of farms within the country) 80% confidence that disease will be detected if present Draft surveillance design - national accreditation -

Target population - all cages with susceptible species in the country Two stage sampling Establishments breeder farms /importers cages Three tests Owner observation of mortality (Se=87%, Sp=68% - determined by special study) PCR for cages with mortality (up to 20 fish) Se=98,6, Sp=99% Transmission test for PCR positive cages Se=95%, Sp=100% Draft surveillance design - national accreditation -

 Sample size calculation done by FreeCalc

OIE Aquatic animal health cone standard-setting/aquatic-code/access- online/ Principles for the Design and Conduct of Surveys to show Presence or Absence of Infectious Disease in Aquatic Animals _file/0004/146713/surveillance.pdf Surveillance and zooning for aquatic animal diseases 325e0b.htm Aquatic animal disease surveillance in developing countries pdf Recomended resources