“How to define epidemiological areas for surveillance of notifiable mollusc diseases – an example from Denmark (7359)”

How to define epidemiological areas for surveillance of notifiable mollusc diseases – an example from Denmark

Introduction

The protozoan parasites Bonamia ostreae, Bonamia exitiosa and Marteilia refringens are causes of notifiable diseases in the EU. They infect bivalve molluscs and can cause considerable mortality. In Denmark, B. ostreae is present in the Limfjorden, in the Northern part of Jutland, but to date it has not been found anywhere else in the country. Neither of the other two parasites have been found in Denmark. A surveillance program for the three diseases was implemented in Limfjorden in 2000, as this is the major mollusc production area. After the finding of B. ostreae in the central part of Limfjorden in 2014, the surveillance program was restricted to only cover Nissum Bredning, the western part of Limfjorden. The surveillance was finally suspended in 2018, once B. ostreae was found in Nissum Bredning. Overall, the Danish waters (Limfjorden as well as other waters) cannot be considered one epidemiological unit for the three mollusc diseases, but mollusc treatment facilities receive mussels and other molluscs from several areas in the country. Further, restoration projects would like to move molluscs between areas. There is therefore a need to define epidemiological areas within the Danish waters.

Methodology

We have used available resources on the occurrence of suitable habitats for susceptible species in Denmark, based on maps of water depth. Information on hydrological and geographical properties of individual areas has been obtained from Sanitary Survey reports made for assessment of microbiological contamination of bivalve molluscs for human consumption. In addition, knowledge on prevalence of B. ostreae in Denmark and of the three diseases in other areas have been used.

Results

A map with proposed epidemiological areas for surveillance of the notifiable mollusc diseases will be presented.

Conclusions

Use of already available and easily accessible data and maps can be used for designing surveillance programs, when advanced epidemiological modelling is not an option -either due to capacity constraints or lack of data for input.

1. Bang Jensen, Britt, DTU AQUA, Presenter
2. Saurel, Camille, DTU AQUA, Author
3. Madsen, Lone, DTU AQUA, Author