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

Abstract

Hepatopancreas necrosis disease (HPND) is a disease and serious impacts on the industry of Chinese mitten crabs (Eriocheir sinensis) culture, however the actual cause of this disease is still not known. In the present study, to explore the pathogenic changes and risk factors caused by HPND, ultrathin sections of different tissues from the diseased crabs were observed with transmission electron microscope. The hepatopancreatic cells, spermatogonium, gill tissues and muscle cells of the diseased crabs showed severe structural and morphological changes. To further investigate whether HPND was caused by pathogenic microorganism, the healthy crabs were fed/injected with diseased tissues, the symptoms of HPND were not found, suggesting that HPND was not caused by virus or microsporidian infections. In addition, the toxic effect of avermectin and high pH water were also examined in this study. 40% (p<0.01) crabs with HPND symptoms were found after breeding crabs in water with 9.5 pH to 10 pH for 14 days, but the crabs with no HPND symptoms were found when they were raised in water with different concentrations of avermectin. The results indicated that HPND was not caused by virus or microsporidian and might be induced by water of high pH value or other environmental factors.

Metatranscriptomic Analysis Reveals an Imbalance of Hepatopancreatic Flora of Chinese Mitten Crab Eriocheir sinensis with Hepatopancreatic Necrosis Disease

“…The Chinese mitten crab ( Eriocheir sinensis ) is one of the important crustaceans with great economic value [ 1 , 2 ]. Crab hepatopancreatic necrosis disease (HPND) had a high mortality rate of about 40–50%, which directly affects the crab farmers [ 1 ].…”

“…The typical clinical symptoms of crabs with HPND are hepatopancreas degeneration and atrophy, muscle atrophy, and a change in the color of the hepatopancreas from golden to pale yellow and white. The gastrointestinal tract is collapsed, and clear dropsy is observed in the inner cavity of the crab as the disease progresses [ 2 ]. Diseased crabs can survive for a long time, but have no commercial value because of the low content of lipids and proteins and the low growth rate.…”

“…However, typical symptoms of HPND were not generated in animal regression tests performed using Vibrio ; therefore, Vibrio is not thought to be associated with HPND of crab [ 5 , 6 , 7 ]. Moreover, HPND of crab was not generated by injecting bacteria-free supernatants from the hepatopancreas of crabs with HPND into healthy crabs, suggesting HPND was not caused by viral infections [ 2 , 8 ].…”

A Comparative Study on Growth and Metabolism of Eriocheir sinensis Juveniles Under Chronically Low and High pH Stress

“…In this study, there was no significant difference in growth performance parameters between any pH groups after 8 weeks, indicating the Chinese mitten crab can survive in pH 6.5-9.5. But there was also a study showing that 40% healthy crabs (about 50 g) died after exposure to pH 9.5 for 2 weeks (Pan et al, 2017). That is because smaller crabs have greater tolerance to environmental stress than bigger ones (Tood and Dehnel, 1960).…”

Transcriptome analysis of hepatopancreas of Eriocheir sinensis with hepatopancreatic necrosis disease (HPND)

“…Furthermore, HPND symptoms appeared when crabs were cultured in water with a pH of 9.5 to 10, but not when they were cultured in water with different concentrations of avermectin. Therefore, they concluded that HPND in the Chinese mitten crab was not caused by a virus or microsporidian, but caused by water at a high pH or other environmental factors [7]. Shen et al [8] constructed the meta-transcriptomic libraries of the hepatopancreas from crabs with and without HPND, and no significant differences in viral and microsporidial communities were detected.…”