Pathology and ultrastructure of an intranuclear bacilliform virus (IBV) infecting brown shrimp Crangon crangon (Decapoda: Crangonidae)

Abstract

The brown shrimp Crangon crangon supports an important fishery in Europe (over 25 000 t, valued at 80 million euros in 2000). Through the course of histopathological screening of crustaceans from the Clyde estuary, western Scotland, for the biological effect of contaminants, we have discovered a highly prevalent (up to 100%) non-occluded intranuclear bacilliform virus (IBV) infection in the hepatopancreatic tubule epithelia and midgut epithelia of wild C. crangon. This is the first report of an IBV in this family. We have termed this virus Crangon crangon bacilliform virus (CcBV). Histological and ultrastructural observations suggest that this virus is similar to other IBVs previously described from crabs and penaeid shrimps. The nuclei of virus-infected epithelial cells contained an eosinophilic, hypertrophied viroplasm that marginalised the chromatin of the host nucleus. Infected cells were often separated from their neighbouring cells and their nuclei appeared apoptotic. In heavily infected shrimp, apoptotic cells were expelled into the lumen of the hepatopancreatic tubule or the midgut. Following this stage, some hepatopancreatic tubules became degenerate, with remnants of the basement membrane and myoepithelial lining remaining. Transmission electron microscopy of hypertrophic nuclei revealed the presence of rod-shaped and cylindrical, envelope-bound virions. These virions did not form arrays and were not embedded within occlusion bodies, but did appear to be partially occluded in an amorphous matrix that corresponded to a granular viroplasm. The ultrastructure, morphology and size of the nucleocapsid and the complete virion aligns the virus most closely to the IBVs previously reported from other decapod crustaceans. Due to the pathological manifestation of IBV infection in C. crangon, it appears likely that it can act as a population modulator, particularly at sites where infection prevalence is high, such as that observed in the Clyde estuary.

Sex-ratio, seasonality and long-term variation in maturation and spawning of the brown shrimp Crangon crangon (L.) in the German Bight (North Sea)

“…While some bacilliform virus are found in C. crangon, particularly in the hepatopancreas or the midgut (Stentiford et al 2004), other pathological infections appear with gonad tissues. For several years in the early to late 1980s the fraction of shrimp in the North Sea showing ''black spot disease'' in the shell has been growing.…”

Disease will limit future food supply from the global crustacean fishery and aquaculture sectors

“…It is an oversimplification however to consider that pathogens with lower observed prevalence may be less damaging to wild populations than those occurring at higher prevalence. Cases of up to 100% prevalence of CcBV infection in Crangonid shrimps (Stentiford et al, 2004) may be less damaging for instance than a highly pathogenic viral infection such as PAV1 in P. argus (Shields and Behringer, 2004) which is detected at lower point prevalence in wild populations, but likely leads to death of juvenile hosts (Behringer, 2012).…”

“…In several cases, infection prevalence may reach 100% (e.g. C. crangon bacilliform virus in Crangonid shrimps; Stentiford et al, 2004, and Hematodinium sp. infection of blue crabs; Messick, 1994) without causing long term decline of the host population.…”

“…Dedicated field surveys have focussed on the prevalence of specific pathogens in fished populations of fisheries species such as European edible crab (Cancer pagurus) (Stentiford et al, 2002), Norway lobster (Nephrops norvegicus) (Stentiford et al, 2001), American lobster (Homarus americanus) (Stewart, 1975), brown shrimp (Crangon crangon) (Stentiford et al, 2004), spiny lobster (Panulirus argus) (Shields and Behringer, 2004), snow and tanner crabs (Chionoecetes spp.) (Meyers et al, 1996).…”

Cancer pagurus bacilliform virus (CpBV) infecting juvenile European edible crabs C. pagurus from UK waters

“…Despite their ubiquity, there are surprisingly few reports on their presence in wild marine animals. In this respect, crustaceans are no exception, with only limited examples of viral disease in species obtained from the wild (Johnson 1984, Shields & Behringer 2004, Stentiford et al 2004.…”