A novel Dicistro-like virus discovered in Procambarus clarkii with "Black May" disease

The peak period of morbidity and death in cultured Procambarus clarkii is around May each year and is called the "Black May" disease. The pathogen causing "Black May" disease is believed to be a white spot syndrome virus (WSSV). In 2018, a significant number of P. clarkii died in the pond culture of Xinglong Township, Xuyi County. Two sampling tests on the affected pond showed that, in addition to WSSV, a novel Dicistro-like virus (PcDV) was present. Genomic sequence analysis indicated that this new virus belongs to the Dicistroviridae family, Picornaviridaes order. A high number of spherical particles were detected in gill tissues of P. clarkii with "Black May" disease by electron microscopy, a finding consistent with viruses from the Picornaviridaes order. From October 2018 to September 2019, we took monthly samples from Hubei, Jiangsu and Anhui provinces, and tested for the presence of PcDV and WSSV in P. clarkii. The detection rates of PcDV in P. clarkii peaked from April to June, consistent with the onset of the "Black May" disease. In conclusion, we believe that the discovery of PcDV will provide new research directions for investigating the pathogens causing "Black May" disease in P. clarkii.