PCR‐based prevalence of a fatal reovirus of the blue crab, Callinectes sapidus (Rathbun) along the northern Atlantic coast of the USA

Abstract

There is a need for more information on the relationship between diseases and fluctuations of wild populations of marine animals. In the case of Callinectes sapidus reovirus 1 (CsRV1, also known as RLV), there is a lack of baseline information on range, prevalence and outbreaks, from which to develop an understanding of population‐level impacts. An RT‐qPCR assay was developed that is capable of detecting 10 copies of the CsRV1 genome. In collaboration with state, federal and academic partners, blue crabs were collected from sites throughout the north‐eastern United States to assess the northern range of this pathogen. In addition, archived crab samples from the Chesapeake Bay were assessed for CsRV1 by RT‐qPCR and histology. PCR‐based assessments indicate that CsRV1 was present at all but one site. Prevalence of CsRV1 as assessed by RT‐qPCR was highly variable between locations, and CsRV1 prevalence varied between years at a given location. Mean CsRV1 prevalence as assessed by RT‐qPCR was >15% each year, and peak prevalence was 79%. The wide geographic range and highly variable prevalence of CsRV1 indicate that more study is needed to understand CsRV1 dynamics and the role the virus plays in blue crab natural mortality.

Systems and techniques used in the culture of soft‐shell swimming crabs

“…In addition to the operational advantages of the closed system, recent studies have reported the occurrence of acute mortality in companies producing soft crab caused by a crab-specific reovirus (CsRV1) (Bowers et al 2010;Flowers et al 2016) and that the pathogenicity of this virus is related to high temperatures (Chung et al 2015). These findings would reinforce an additional advantage of closed production systems over open systems, due to greater possibility of control of environmental variables, including temperature, in this kind of system.…”

“…; Flowers et al . ) and that the pathogenicity of this virus is related to high temperatures (Chung et al . ).…”

Elevated water temperature increases the levels of reo-like virus and selected innate immunity genes in hemocytes and hepatopancreas of adult female blue crab, Callinectes sapidus

“…The quality and quantity of RNA was estimated on a Nanodrop spectrometer (FisherSci). The levels of CsRLV RNA present in the total RNA (=equivalent of 2.5 % of hemolymph) were assayed in triplicate using a one-step RT-qPCR assay with TaqMan® Fast Virus 1-Step Master Mix (Life Technologies) using the primers listed in Table 1 [11]. Standards for the CsRLV qPCR assay were prepared as described [12] ranging from 10 to 10 6 copies.…”

“…In the blue crab, a reo-like virus (CsRLV) has been described that infects mesodermallyand ectodermally-derived tissues, especially hemocytes and epidermal tissues [10,11]. CsRLV is associated with the majority of mortality in captive molting crabs from shedding facilities, and CsRLV prevalence in wild intermolt crabs is reported to average 20% [12].…”

Parasites affect hemocyte functionality in the hemolymph of the invasive Atlantic blue crab Callinectes sapidus from a coastal habitat of the Salento Peninsula (SE Italy)

“…In native habitats, C. sapidus is subjected to a wide spectrum of parasitic pathogens, including viral, bacterial, and micro algal agents (Flowers et al, 2016;Shields, 2015 and literature cited). In invaded Mediterranean habitats, the occurrence of parasites in the species is to date virtually unexplored, even though it is an appreciat-ed shellfish product, in particular in Greece and Turkey (Mancinelli et al 2017c).…”