J-R Bonami

Virus-like particles associated with brown muscle disease in Manila clam, Ruditapes philippinarum, in Arcachon Bay (France)

Recently, Manila clam, Ruditapes philippinarum, populations have suffered mortalities in Arcachon Bay (SW France). Mortality was associated with extensive lesions of the posterior adductor muscle, which become progressively brown and calcified. Ultrastructural observations by transmission electron microscopy revealed tissue degradation with necrotized muscle fibres and granulocytomas. Unenveloped virus-like particles (VLPs) were detected in muscle, granulocytic, epithelial and rectal cells. VLPs were abundant in the extracellular space, in the cytoplasm (free or enclosed in vesicles) and in the nucleoplasm of granulocytes. Nuclei and mitochondria of granulocytes displayed changes which suggested reactive oxygen species production and apoptosis induction. VLPs exhibited an icosahedral structure with a diameter of 25 to 35 nm. These observations suggest that the VLPs could belong to the family Picornaviridae or the Parvoviridae.

A roni‐like virus associated with mortalities of the freshwater crab, Eriocheir sinensis Milne Edwards, cultured in China, exhibiting ‘sighs disease’ and black gill syndrome

The freshwater Chinese mitten crab, Eriocheir sinensis Milne Edwards, is an economically important species cultured in China during the last 10 years. Culture areas have increased rapidly in inland provinces of China. However, with the development of intensive culture, various diseases have appeared and severely affected crab production. Among these, black gill syndrome (BGS) has caused important economic losses since 1996, particularly in the main culture provinces in China such as Jiangsu, Zhejiang, Anhui and Shanghai. Another major sign of the disease resembles a respiratory problem. Thus, the disease is often called sighs disease (SD) by farmers, because sounds reminiscent of sighs can be clearly heard from affected crabs, caused by slow extrusion of bubbles at night. Sluggishness and anorexia are other non-specific signs. During investigations on this disease we found a virus developing in connective tissue cells showing the general properties of the Roniviridae and designated it EsRNV for E. sinensis ronivirus . We report here histological investigations, viral ultrastructure and some genomic features of this new crab virus. Numerous viral diseases have been reported in crustaceans, since the first was noted by Vago (1966) in crabs. There were several reports of crab viral diseases during the 1970s and early 1980s, which included Reovirus (Bonami 1973, 1980; Johnson & Bodammer 1975; Johnson 1984; Mari & Bonami 1988a), Iridovirus (Montanié, Comps & Bonami 1993), Baculovirus (Pappalardo, Mari & Bonami 1986), Picornavirus (Johnson 1978), Herpesvirus (Johnson 1976; Payen & Bonami 1979; Sparks & Morado 1986), Parvoviridae (Mari & Bonami 1988b), Bunyaviridae (Bang 1971; Bonami, Veyrunes, Cousserans & Vago 1975; Hoover & Bang 1978; Corbel, Coste & Bonami 2003) and Rhabdoviridae (Chassard-Bouchaud, Hubert & Bonami 1976; Jahromi 1977; Yudin & Clark 1978, 1979; Johnson & Farley 1980). However, the rhabdo-like virus A (RhVA or EGV-2) of Callinectes sapidus (Yudin & Clark 1978, 1979) resembles a ronivirus rather than a rhabovirus on the basis of its size, shape and general structure. Diseased E. sinensis exhibiting typical BGS were collected from a farm in Hubei Province, China. Healthy animals with an average weight of 100 g were purchased from a local farm without a history of disease and maintained in the laboratory for 1 week before experimental infections. The water temperature was maintained at 24–30 C. Each crab was inoculated at the basal joint of the fifth pereiopod with 0.2 mL of haemolymph from a diseased animal, diluted 1/4 in TN buffer (0.04 m Tris, 0.4 m NaCl, pH7.4) and ultra-filtered Journal of Fish Diseases 2007, 30, 181–186