Yellow Head Virus Infection in the Giant Tiger Prawn Penaeus monodon Cultured in Taiwan.

Abstract

ABSTRACT-In the course of experimental infection of Penaeus monodon with white spot syn drome virus (WSSV) for virus isolation and purification, one unexpected virus was found to be domi nant in purified virus samples prepared from shrimp hemolymph. Under electron microscopical virions with a density of 1.154-1.162 g/mL in sucrose gradient were obtained and at least three viral structural proteins of 20, 63 and 110 kDa were observed when analyzed by SDS-PAGE. Injection of P. monodon with this purified virus demonstrated rapid and mass mortality. By ordinary histo logical studies, the cells with densely basophilic inclusions were found in the lymphoid organ, gill, stomach, hepatopancreas and heart. By electron microscopy, ultrathin sections of lymphoid organs from infected shrimp showed that numerous enveloped virions and nucleocapsids scattered or enclosed in the vesicles within the cytoplasm. The morphology, histopathology and structural proteins of this virus closely resemble those of the yellow head virus (YHV) from Thailand. More over, the results of RT-PCR diagnosis using primers specific to the 135 bp of YHV also suggest that this virus is closely related to YHV. PCR diagnosis of YHV and WSSV in P. monodon sampled from culture farms in Taiwan between 1996 and 1999 demonstrated that YHV has been present in P. monodon for at least 3 years and that all of the samples, which were diagnosed as YHV positive, were also co-infected with WSSV.

Vertical transmission of gill-associated virus (GAV) in the black tiger prawn Penaeus monodon

“…Morphologically, GAV is indistinguishable from yellow head virus (YHV), which is a major pathogen in south-east Asia. GAV and YHV induce similar cytopathology , Wongteerasupaya et al 1995, Wang & Chang 2000, and sequence comparisons indicate that they represent closely related but distinct genotypes (Cowley et al 1999).…”

Genomic Similarity of Taura Syndrome Virus (TSV) between Taiwan and Western Hemisphere Isolates.

“…A highly TSV-susceptible species particularly P. chinensis (Overstreet et al, 1997) had been introduced and cultured in Taiwan prior to known outbreaks but no Taura or similar syndrome was reported. Besides, based on the previous documents the diseased shrimp sampled before 1998 showed viral particles with bacilliform instead of icosahedral shape (Chen et al, 1989;Wang et al, 1995;Wang et al, 1997;Zhan and Wang, 1998;Wang and Chang, 2000). Fur thermore, the timing of outbreak of Taura sydrome in Taiwan coincided with the large-scale importation of post-larvae, brooders, and frozen products of white shrimp.…”

Differences in the susceptibility of some penaeid prawn species to gill-associated virus (GAV) infection

“…Although GAV has not been reported in stocks of M. japonicus cultured in Australia, a yellow head-like virus was identified in 1 to 3 g M. japonicus from Taiwan which were co-infected with white spot syndrome virus (WSSV; Wang et al 1996). P. monodon stocks from Taiwan have also been shown to be co-infected with YHV and WSSV (Wang & Chang 2000). F. merguiensis from Thailand has been infected experimentally with YHV, and has been implicated as a carrier of latent YHV infection in prawn culture ponds (Flegel et al 1996).…”