Microbiological and Histological Analysis for the Evaluation of Farmed Mussels (Mytilus galloprovincialis) Health Status, in Coastal Areas of Italy

Roberta Battistini,Elena Bozzetta,Katia Varello,Michela Zambon,Danila Raffaella Francese,Giuseppe Arcangeli,Valeria Listorti,Laura Serracca,Carlo Ercolini

doi:10.3390/pathogens9050395

Abstract

Shellfish farming is a relevant economic activity in Italy. The Gulf of La Spezia is one of the major production areas for mussels: the area is characterized by the presence of numerous human activities that could harm the quality of seawater. Additionally, the presence of potentially pathogenic microorganisms may influence the health status of animals, which must be constantly monitored. To have a clear view of the health conditions of the mussels (Mytilus galloprovincialis) farmed in this area, microbiological, parasitological, and histological analyses were performed. The study was conducted from November 2016 to October 2017. Overall, despite the presence of potentially pathogenic microorganisms for mussels, abnormal mortality rates were not reported during the monitoring period and the histological examination revealed no significant lesions. Our study confirms that studying different aspects together is a useful tool for assessing the health conditions of mussels and points out the importance of adverse environmental conditions for the expression of the pathogenicity of microorganisms.

Highlights

Mussel farms are usually located in highly anthropized areas, these guarantee a good supply of nutrients for mussels breeding, could represent a problem for the introduction of polluting agents that can weaken the immune system of the mussels
To continue the surveillance undertaken by these previous studies in the area and prevent economic losses to a regionally important traditional sector, we reported the results relating to the presence of the potential pathogenic microorganisms mentioned above and the health status of the farmed bivalves. this was achieved through a monitoring program that includes pathophysiological, microbiological, molecular, and parasitological analyses on mussels sampled in four sites in the Gulf of La Spezia
V. splendidus clade was found in 9/12 months in Internal East Site (IES), in 7/12 months in the Internal West Site (IWS), in 6/12 months in the External West Site (EWS), and only in 2/12 months in the Portovenere (PV)

Summary

Introduction

Mussel farms are usually located in highly anthropized areas, these guarantee a good supply of nutrients for mussels breeding, could represent a problem for the introduction of polluting agents that can weaken the immune system of the mussels. Several environmental contaminants can cause oxidative stress, being strongly pro-oxidant [1]. The presence of abiotic environmental stressors (variations of environmental parameters and presence of pollutants) and biological variables (variations of the physiological state in particular phases of the reproductive cycle, presence of potentially pathogenic microorganisms) can lead to particular criticalities depending on the seasonality or the performance of human activities in particular sites. Among the pathogenic microorganisms, members of the genus Vibrio can cause mortality and economic losses. Vibrio spp. are ubiquitous in marine environments and can be found in large quantities within bivalve mollusks. These microorganisms are normal components of mussel microflora without any pathological

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Discussion

Conclusion