A mycobacterial disease is associated with the silent mass mortality of the pen shell Pinna nobilis along the Tyrrhenian coastline of Italy

Abstract

Disease is an increasing threat for marine bivalves worldwide. Recently, a mass mortality event (MME) impacting the bivalve Pinna nobilis was detected across a wide geographical area of the Spanish Mediterranean Sea and linked to a haplosporidian parasite. In 2017–2018, mass mortality events affecting the pen shell Pinna nobilis were recorded in two different regions of Italy, Campania and Sicily, in the Tyrrhenian Sea (Mediterranean Sea). Histopathological and molecular examinations of specimens showed the presence of Haplosporidium sp. in only one specimen in one area. Conversely, in all of the surveyed moribund animals, strong inflammatory lesions at the level of connective tissue surrounding the digestive system and gonads and linked to the presence of intracellular Zhiel-Neelsen-positive bacteria were observed. Molecular analysis of all of the diseased specimens (13) confirmed the presence of a Mycobacterium . Blast analysis of the sequences from all of the areas revealed that they were grouped together with the human mycobacterium M. sherrisii close to the group including M. shigaense , M. lentiflavum and M. simiae . Based on pathological and molecular findings, it is proposed that a mycobacterial disease is associated with the mortality episodes of Pinna nobilis , indicating that, at this time, Haplosporidium sp. is not responsible for these events in Campanian and Sicilian waters.

In the Wake of the Ongoing Mass Mortality Events: Co-occurrence of Mycobacterium, Haplosporidium and Other Pathogens in Pinna nobilis Collected in Italy and Spain (Mediterranean Sea)

“…Mycobacterium species have been documented as an important source of morbidity and mortality in fish aquaculture, as well as in wild animals (Gauthier and Rhodes, 2009), but few descriptions exist in bivalves (Grimm et al, 2016;Carella et al, 2019). Showing to be present at the level of phagocytes as intracellular pathogens (Carella et al, 2019).…”

“…Since 2016, numerous mortality events of P. nobilis have been reported in the Mediterranean Sea reaching up to 100% of the population in many areas like Italy, Greece and Spain (Catanese et al, 2018;Carella et al, 2019;Katsanevakis et al, 2019). At first, an Haplosporidian parasite, named Haplosporidium pinnae, was designated as the solely responsible for the mortality (Catanese et al, 2018).…”

“…At first, an Haplosporidian parasite, named Haplosporidium pinnae, was designated as the solely responsible for the mortality (Catanese et al, 2018). After that, a mycobacterial infection has been also associated to the disease outcome (Carella et al, 2019), while Vibrio mediterranei appears to cause major mortality among stabled individuals in Spain, possibly associated to animal stress in captivity (Prado et al, 2019). Mycobacteriosis is a chronic, systemic, progressive and frequently lethal disease affects a wide range of terrestrial and aquatic teleost fishes (Ross, 1970;Gauthier and Rhodes, 2009).…”

“…This phylum contains 52 described species and several unnamed species reported in the four genera (Burreson and Ford, 2004). After a recent study reporting mortality episodes of P. nobilis in the Campania region associated to a mycobacterial disease (Carella et al, 2019), the aim of this work is to evaluate the geographic spreading of the mycobacteriosis and its cooccurrence with H. pinnae and other pathogens in other parts of Mediterranean Sea, in particular in different regions of Italy (Campania, Tuscany, Apulia, and Sardinia), and one region in Spain (Ebro Delta, Catalunya).…”

Nocardiosis and mycobacteriosis of bivalves: “Yet‐to‐emerge” zoonoses of public concern?

“…The first isolations of this mycobacterium in wild animals were recorded in Africa by Botha, Gey van Pittius, and Helden (2013) and again in Africa in 2017, there was the first isolation from a sick lion with tuberculous-like lesions (Gcebe & Hiokwe, 2017). Finally, very recently, M. sherrisii has been involved in mass mortality events affecting the bivalve Pen shell Pinna nobilis, recorded in two different regions of Italy, Campania and Sicily, in the Mediterranean Sea (Carella et al, 2019). The origins of disease caused by M. sherrisii remains an area of investigation.…”