First case of hepatopancreatic necrosis disease in pond‐reared Chinese mitten crab, Eriocheir sinensis, associated with microsporidian

Abstract

An epidemic of hepatopancreatic necrosis disease (HPND) with a high mortality rate (40%-50%) recently occurred in the cultured Chinese mitten crab, Eriocheir sinensis, which is a very important economic crustacean species in China. Histology revealed infection by a microsporidian parasite within the cytoplasm of the epithelial cells of the hepatopancreas. Numerous discrete inclusions in the infected cells and presumably free parasite spores were also observed. By negative staining using electron microscopy, a typical morphology of spores was observed with a protuberant front of the anchoring disc. Infection was confined to the epithelial cells of the hepatopancreas, with no other organ implicated. By sequencing the PCR products using specific primers based on conserved regions of microsporidian small subunit (18S) ribosomal DNA, it was revealed that the parasite from HPND ponds had 99% sequence identity to that of Hepatospora eriocheir. Phylogentic analysis also placed the microsporidian in the same lineage as H. eriocheir. This study reported the first case of widespread infections of H. eriocheir associated with HPND found in the pond-reared Chinese mitten crab, E. sinensis. The description of microsporidian in this important commercial host is fundamental for future consideration of factors affecting stock health and sustainability.

A Meta-Transcriptomics Survey Reveals Changes in the Microbiota of the Chinese Mitten Crab Eriocheir sinensis Infected with Hepatopancreatic Necrosis Disease

“…This approach is powerful, because it simultaneously evaluates both viral and bacterial communities, and even suspected pathogens from the Eukaryota domain. Considering that RNA viruses can associate with certain diseases in E. sinensis (Zhang et al, 2004; Zhang and Bonami, 2007, 2012; Shen et al, 2015), and microsporidia were found in crabs infected with HPND (Ding et al, 2016), we analyzed the meta-transcriptomes of hepatopancreata from crabs with and without HPND to identify potential pathogens from viruses, bacteria, and eukaryotes.…”

“…However, these crabs are of little/no economic value, and they eventually die. A previous study reported that microsporidia were detected in the hepatopancreata of crabs infected with HPND (Ding et al, 2016). In addition, hepatopancreatic injury caused by environmental toxicants is believed to be one of the main causes of HPND.…”

“…For example, hepatopancreatic necrosis disease (HPND, “shuibiezi” in Chinese), which affects E. sinensis , has been a major problem in the crab-cultivated area of Jiangsu Province since 2015. Crabs with HPND exhibit multiple clinical symptoms, including hepatopancreata that are lighter in color (turning from golden yellow and light yellow to gray–white) and soft shells that are darker in color than usual, as well as muscle atrophy and edema (Ding et al, 2016). Furthermore, the stomachs and intestines are empty in many diseased crabs.…”

Pathological Changes and Risk Factors of Hepatopancreas Necrosis Disease of Mitten Crab, Eriocheir Sinensis

“…Ding et al [3] reported that infection of microsporidian Hepatospora eriocheir was associated with HPND, but animal regression test was not carried out. Meta-transcriptomes of the hepatopancreata from crabs with and without HPND were used to explore the etiology of HPND, and found that there were no striking differences in viral and microsporidial communities in the hepatopancreata of diseased and healthy crabs, however there were significant changes in the bacterial community of diseased and healthy crabs, increase of bacteria belonging to Tenericutes and Actinobacteria phyla and decrease of bacteria belonging to the Bacteroidetes phylum in crabs with HPND was suggested to associate with HPND [4].…”

Single and multi-gene phylogeny ofHepatospora(Microsporidia) – a generalist pathogen of farmed and wild crustacean hosts

“…In both studies, the spores were described as ellipsoid, measuring ∼1·8 × 0·9 µm and containing seven to eight polar filaments. Recently, Ding et al (2016) have shown that not only is the pathogen infecting the Asian population of Chinese mitten crabs H. eriocheir, but also the infection is associated with an emerging disease condition causing significant proportions in aquaculture production of this species in China. In their original taxonomic paper, Stentiford et al (2011) also highlighted an unassigned microsporidian infecting the hepatopancreas of edible crabs, C. pagurus, and suggested at the time that this was also likely a member of the genus Hepatospora based upon high similarity with the partial SSU gene sequence from H. eriocheir.…”