First Description of a Natural Infection with Shrimp Hemocyte Iridescent Virus in Farmed Giant Freshwater Prawn, <em>Macrobrachium Rosenbergii</em>

Abstract

Macrobrachium rosenbergii is a valuable freshwater prawn in Asian aquaculture. In recent years, a new symptom that was generally called as &amp;lsquo;white head&amp;rsquo; caused high mortality in M. rosenbergii farms in China. Samples of M. rosenbergii, M. nipponense, Procambarus clarkii, M. superbum, Penaeus vannamei, and Cladocera from a farm suffering from &amp;lsquo;white head&amp;rsquo; in Jiangsu Province were collected and analyzed in this study. Pathogen detection showed that all samples were positive for Shrimp hemocyte iridescent virus (SHIV). Histopathological examination revealed dark eosinophilic inclusions and pyknosis in hematopoietic tissue, hepatopancreas and gills of M. rosenbergii and M. nipponense. Blue signals of in situ DIG-labeled LAMP (ISDL) appeared in hematopoietic tissue, hemocytes, hepatopancreatic sinus, and antennal gland. TEM of ultrathin sections showed a large number of SHIV particles with a mean diameter about 157.9 nm. The virogenic stromata and budding virions were observed in hematopoietic cells. Quantitative detection by TaqMan probe based real-time PCR of different tissues in natural infected M. rosenbergii showed that hematopoietic tissue contained the highest SHIV load with a relative abundance of (25.4&amp;plusmn;16.9)%. Hepatopancreas and muscle contained the lowest SHIV load with a relative abundance at (2.44&amp;plusmn;1.24)% and (2.44&amp;plusmn;2.16)%, respectively. Above results verified that SHIV is the pathogen causing &amp;lsquo;white head&amp;rsquo; in M. rosenbergii, and M. nipponense and Pr. clarkii are also the susceptible species of SHIV.