Mass mortalities associated with a virus disease in Japanese pearl oysters Pinctada fucata martensii

Abstract

ABSTRACT:The annual mortality of cultured Japanese pearl oysters Pinctada fucata martensii in all western regions of Japan was over 400 million in both 1996 and 1997. The main pathological signs of the diseased oysters were atrophy in the adductor muscle, the mantle lobe and the body accompanied by a yellowish to brown coloration. Histological studies revealed necrosis and degeneration of muscle fibers of the adductor, pallial and foot musculatures as well as the cardiac muscle. Electron microscopy revealed the presence of small round virions approximately 30 nm in diameter within intrasarcoplasmic inclusion bodies in necrotized muscle fibers of the adductor and pallial musculatures, and the heart. The causative virus was isolated and cultured in EK-1 (eel kidney) and EPC (epithelioma papilosum cyprini) fish cell lines. Marked mortalities occurred in pearl oysters that had been experimentally inoculated with the cultured virus; these oyster displayed the same pathological signs of the disease as oysters in natural infections. These results inbcate that a previously undescribed virus caused the mass mortalities in cultured pearl oysters. KEY WORDS:New virus disease -Japanese pearl oyster. Mass mortality . Virus in musc1.e fiber INTRODUCTIONresults of histopathological and electron microscopic studies, and report the isolation and culture of the Mass mortalities of the cultured Japanese pearl oyscausative virus. The results of infectivity experiments ter Pinctada fucata martensii (hereafter akoya oyster)

Cloning and expression of heat shock protein 70 gene in the haemocytes of pearl oyster (Pinctada fucata, Gould 1850) responding to bacterial challenge

“…Since the successful hatchery production in 1965, it has become an important asset to the economy. In recent years, however, mass mortalities of the cultured pearl oyster have occurred frequently in juvenile, mother and operated oysters [38][39][40]. The mortalities resulted in a severe curtailment in maricultured pearls and the destruction of available pearl oyster resources.…”

Clinical trial results on the use of a recombinant feline interferon-ω to protect Japanese pearl oysters Pinctada fucata martensii from akoya-virus infection

“…For comparison, an anti-viral interferon IFN-α (Serotec, England) which was produced by human lymphocytes was also injected in the same manner and concentration as rFeIFN-ω. Akoya-virus was cultured in EPC (epithelioma papilosum cyprini) cells from different diseased oysters and the primary isolates of akoyavirus were mixed and inoculated by a single injection into the mantle lobe of the oysters in accordance with to Miyazaki et al (1999). As shown by Miyazaki et al (1999), the virus never grew in a small volume of medium inside a small well of a 96-well plate (microtiter plate), so the virus titer of inocula was not measured in the present studies.…”

“…Akoya-virus was cultured in EPC (epithelioma papilosum cyprini) cells from different diseased oysters and the primary isolates of akoyavirus were mixed and inoculated by a single injection into the mantle lobe of the oysters in accordance with to Miyazaki et al (1999). As shown by Miyazaki et al (1999), the virus never grew in a small volume of medium inside a small well of a 96-well plate (microtiter plate), so the virus titer of inocula was not measured in the present studies. After the injections, all oysters were held without feeding in aquaria with a circulatory system using artificial seawater at 25°C for 20 to 30 d.…”

“…Infected akoya oysters die of a combination of physiological changes that affect feeding, respiration, glucose metabolism and cardiac function. Artificial infection with viral cultures (Miyazaki et al 1999) revealed the virus to be pathogenic to akoya oysters and replicated the pathological changes and high mortality that occurred in the natural outbreaks. Therefore, in the present study, we attempted to prevent the mortality of akoya oysters suffering from akoya-virus infection and introduced an anti-viral, recombinant feline interferon-ω (rFeIFN-ω) for clinical use.…”

“…The virus infects smooth muscle fibers in the adductor, pallial and peduncle musculatures as well as the cardiac muscle, causing atrophy, various kinds of degeneration and necrosis (Miyazaki et al 1999). Infected akoya oysters die of a combination of physiological changes that affect feeding, respiration, glucose metabolism and cardiac function.…”