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Sampling design for biotoxins monitoring in bivalve molluscs crops of the Santa Catarina coast, Brazil

Isabella Fontana1*, Pedro M. Sesterhenn2, Marina C. Delphino3, Vitor Salvador P. Gonçalves4 and Fernando Ferreira1
  • 1 Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, Brazil
  • 2 Companhia Integrada de Desenvolvimento Agrícola de Santa Catarina, Defesa Sanitária Animal, Brazil
  • 3 Ministério da Agricultura, Pecuária e Abastecimento, Coordenação de Animais Aquáticos, Brazil
  • 4 Universidade de Brasília, Faculdade de Agronomia e Medicina Veterinária, Brazil

Purpose: Bivalve molluscs are filtering organisms capable to concentrate biotoxins produced by toxic microalgae. When highly contaminated, they may cause severe symptoms in consumers. Where the occurrence of these microalgae is frequent, monitoring programs are necessary to prevent unsafe products from being commercialized. In the Santa Catarina state, the biggest bivalve molluscs producer in Brazil, the toxins that cause diarrheic (DSP), amnesic (ASP), and paralyzing (PSP) shellfish poisoning syndromes have been monitored in 39 official sampling points. For the statistical significance of the monitoring results and for its incorporation into a future surveillance system, it is primordial to stablish a sampling design. The goal of this work was to determine the sample size and suggest sampling strategies to detect biotoxins in the bivalve molluscs crops from the Santa Catarina coast. The sampling efforts are costly and intensive laboring due to long distances and amount of shellfish to be weekly sampled. Farmers are reimbursed for the molluscs collected in their properties. Methods: Sampling units were stablished according to the farms proximity, quantity of aquaculture sites, and its arrangement related to the hydrographic units (Fig. 1). The tests sensitivities were estimated by the comparison between the minimal detectable concentration of each toxin and the maximum acceptable concentration according to legislation. Scenarios with different estimated prevalences and sensitivities were developed to simulate the variation of sample sizes. An online calculator of EpiTools® was used for pooled sample size calculation to detect each biotoxins groups. Results: A total of 24 sampling areas were designed. For the scenarios with high estimated prevalence, one to two pools of 10 to 30 individuals would be enough for detection. But for scenarios with low estimated prevalence, up to 12 pools or two pools of 100 individuals would be necessary to detect each biotoxin. Conclusions: Considering a high prevalence and high tests sensitivities in the official monitoring points, we can suggest two pools to detect Lipophilic Toxins (2x30), two to detect PSP (2x15), and one to detect ASP (1x20). If the test of Liquid Chromatography with Mass Spectrometry (LC-MS/MS) becomes validated for all biotoxins, only one pool would be enough (1x15) for each of the 24 established areas. The use of autonomous equipment for water samples collection and satellites for phytoplankton monitoring should be incorporated to amplify the sensitivity of the system. Relevance: This sampling design can be suggested as a strategy to be incorporated into a future bivalve molluscs surveillance system of the Santa Catarina coast.

Figure 1
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Acknowledgements

We thank the Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA) and the Integrated Agricultural Development Company of Santa Catarina (CIDASC) for providing databases and support for field visitings. This study was conducted at the Laboratories of Epidemiology and Biostatistics (University of São Paulo), and of Epidemiology and Animal Health Planning (University of Brasília), and funded by the Coordination for the Improvement of Higher Education Personnel (CAPES).

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Keywords: Pooled sample size, Marine biotoxins, Bivalve molluscs, surveillance, Shellfish Poisoning

Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016.

Presentation Type: Poster

Topic: Aquatic Animal Epidemiology

Citation: Fontana I, Sesterhenn PM, Delphino MC, Gonçalves VP and Ferreira F (2016). Sampling design for biotoxins monitoring in bivalve molluscs crops of the Santa Catarina coast, Brazil. Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00014

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Received: 30 May 2016; Published Online: 14 Sep 2016.

* Correspondence: DVM. Isabella Fontana, Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, São Paulo, SP, 05508 270, Brazil, isabellavet@yahoo.com.br