First Detection of Infecting a Wild Population of Blue Mussels in the United Kingdom.

In the last decade, declines in the population of wild blue mussels in the Tamar estuary (United Kingdom) have been noted. In archived samples collected from 2013 to 2019, between 7% (in 2013) and 18% (in 2019) showed large granulocytoma and haemocytic infiltration in the interstitial tissue of the digestive gland. Four samples were selected for gene Nanopore sequencing. A consensus sequence of 1449 bp showed nucleotide similarities between 99.93-100% with published sequences of . In situ hybridisation (ISH) confirmed the presence of DNA within individual granulocytes of granulocytomas and also in prokaryotic-like inclusion bodies within the digestive epithelial cells. The design of diagnostic tests for surveillance of including more specific ISH probes and sequencing the genome of the isolates infecting mussels, will shed more light on the pathogenicity and spread of this pathogen.