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Epidemic and pathogens

Learn more about mass mortality

In the beginning, the Balearic Islands were considered the primary and only infected zone, but in less than a year, this parasite killed natural noble pen shell populations in Spain, France, Italy and Tunisia. In 2018, it killed noble pen shells in Libya, Egypt, Israel, Cyprus, Turkey and Greece. The year after that, the parasite continued its dispersal to the north, destroying populations in Albania and Montenegro. By the middle of the year, parasite presence was detected in the southern Adriatic. The parasite continued to spread from the Elaphiti Islands to the mid-Adriatic. In April 2019, the first positive result of the H. pinnae presence in the tissue of a noble pen shell from Mljet National Park was obtained.

Learn more about the pathogen effect on the noble pen shell

The parasite affects the noble pen shell by inhabiting the digestive gland and causing an infection of epithelial cells, decreasing the filtration activity of the bivalve. The mantle of the starved individual reduces, and the noble pen shell loses its ability to close properly. The final result of the infection is death. Parasite reproduction begins at temperatures above 13.5°C and salinity between 36.5 and 39.7 ppm. Under these conditions, it can spread up to 300 kilometres in a single season. In synergy with the bacteria Mycobacterium sherrisii, Haplosporidium pinnae is considered the main cause of the noble pen shell mass mortality event.