Susceptibility of Neohelice granulata (Decapoda, Varunidae) to white spot syndrome virus (WSSV)

Abstract

White spot syndrome virus (WSSV) continues to be the most severe viral pathogen to the shrimp industry worldwide. Pacific white shrimp Litopenaeus vannamei is particularly affected by WSSV, and this virus has been detected in a wide range of wild crustaceans, including penaeid and non-penaeid shrimp and crayfish, as well as crabs. Crabs have been considered as a dangerous threat to shrimp farms because they are generally believed to be highly tolerant to WSSV and to remain infected for long periods without signs of disease. The burrowing crab Neohelice (= Chasmagnathus) granulata can be commonly found in the surroundings of the shrimp farms in southern Brazil. Here, we investigated the susceptibility of N. granulata to WSSV infection in comparison to L. vannamei. WSSV infectability and host susceptibility were investigated by viral challenge (intramuscular injection) in both species. Viral load in challenged animals was quantified by qPCR in both hemolymph and gills. Furthermore, the transcript levels of sixteen target genes related to the molecular defense status were assessed. The results revealed that N. granulata experimentally infected by WSSV, as well as those naturally infected, showed lethargy, lack of appetite, and later gross signs of the disease. Moreover, N. granulata showed to be less susceptible to WSSV when compared to L. vannamei. While no death was observed in crabs before a post-challenge interval of 120 h, shrimp death was seen as early as 48 h post-infection. Comparative viral load was also assessed by qPCR in gills of captured wild crabs and farmed shrimp naturally infected by WSSV. Transcript levels of target genes were also investigated after WS challenge between 24 and 48 hpi in shrimp and between 96 and 120 hpi in crab. Differences in gene transcripts were particularly noteworthy with the increase of viral copies at 106 copies µl−1. These results indicated that WSSV infection modulated genes related of important cellular responses, such as apoptosis, chaperone function, and ion storage, in both shrimp and crab.Graphical Abstract