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Oyster Outbreak Investigated in Ctes dArmor

FRANCE - Following the notification of nine hepatitis A cases clustered in the Ctes dArmor district in northwestern France, epidemiological, environmental and microbiological investigations were set up in order to identify the source and vehicle of contamination and implement control measures.

In total, 111 cases were identified in the outbreak, all of whom lived or had stayed as tourists in the Côtes d’Armor district. Of the cases, 87% had eaten raw shellfish, and 81% specifically oysters, said figures from Eurosurveillance.

Traceback investigations carried out on raw shellfish consumed by the cases showed that the raw shellfish originated from a single shellfish farm. The shellfish were probably contaminated either in the submersible tanks or in a depuration land-based tank where they were stored. The source of contamination was not identified but shellfish could have been tainted by sewage overflows or by wastewater releases from a polluted storm sewer close to the shellfish farm or from on-site sanitation facilities.

To prevent future hepatitis A outbreaks due to shellfish consumption from this area, hazards specific to each farm should be analysed, advised Eurosurveillance. Timely information on sewage overflows should also be part of communities’ efforts regarding sewage collection and treatment.

"The monitoring of these facilities should also be used to timely alert shellfish farmers, district health and veterinary services about sewage overflows. We also recommend assessing specific risks on each farm of the bay to identify specific hazards and possible control measures. These recommendations may contribute to preventing not only hepatitis A [15] but also other food-borne infections."

Eurosurveillance results highlight the fact that in a country with low HAV endemicity, such as France, consumption of raw shellfish can cause a large community outbreak. Increasing susceptibility of the European general population either from low endemic countries or from countries in transition (from moderate to low) is an important public health issue as illustrated in 2008 by reported outbreaks in several European countries.

the Fish Site Editor

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