A study on the susceptibility of Helice tientsinensis to infectious hypodermal and hematopoietic necrosis virus
Meifeng Wang1, Xiuhua Wang2, Jie Huang2
1State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong 266071, China; Key Laboratory of Mariculture Epidemiology and Biosecurity, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong 266071, China; Shanghai Ocean University, Shanghai 201306, China.
Abstract:
Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is a widely distributed and highly pathogenic virus affecting shrimp. Helice tientsinensis, a key benthic crab commonly found in shrimp ponds in northern China, has unknown susceptibility to IHHNV and a potential role in viral transmission. In this study, healthy H. tientsinensis individuals were experimentally infected with IHHNV through non-invasive oral way to mimic natural exposure pathways in shrimp aquaculture systems. By day 15 post-infection, some individuals developed small black lesions on the carapace, which mostly resolved after molting. IHHNV-challenged crabs exhibited no mortality. Histopathological examination revealed the presence of Cowdry type A eosinophilic inclusion bodies in hemal sinuses and hepatopancreatic tubules of challenged crabs. In situ hybridization detected strong IHHNV-specific signals in the hepatopancreas, confirming viral infection. Quantitative PCR analysis showed relatively high IHHNV loads in the gills, hepatopancreas, and stomach, with the hepatopancreas exhibiting the highest viral load. Furthermore, this study confirmed cross-species transmission of IHHNV from infected H. tientsinensis to juvenile Penaeus vannamei by qPCR detection and histopathological analysis. These findings meet the WOAH criteria for confirming susceptibility as outlined in Chapter 1.5 of the Aquatic Animal Health Code, supporting the conclusion that H. tientsinensis is a susceptible host of IHHNV. Additionally, a survey conducted from the year 2021 to 2023 revealed the persistent presence of IHHNV in H. tientsinensis populations across various shrimp farming periods along China's coastal regions, with notably high viral loads detected within pond environments. This study highlights the overlooked risk of cross-species pathogen transmission by wild crab species. The foraging behavior of H. tientsinensis may facilitate the spread of IHHNV within aquaculture systems, posing a potential threat to the health management of shrimp pond farming.
