Yellow head viruses and disease

Abstract

Yellow head disease (YHD) is caused by yellow head virus genotype 1 (YHV-1), which is a positive-sense (+) ssRNA virus that belongs to the genus Okavirus, family Roniviridae, order Nidovirales. There are currently eight recognized genotypes. The virions are rod-shaped (bacilliform) and approximately 35–60nm×140–200nm with rounded ends. YHD was first recognized in Thailand where outbreaks of YHD caused substantial economic losses in the 1990s, but losses decreased after the widespread introduction of specific pathogen-free (SPF) seedstocks of Penaeus vannamei around 2002. YHV genotype 8 (YHV-8), recently described from China also appears to have high virulence. The infection of YHV can be transmitted vertically and horizontally. Control of YHD is focused on the use of SPF stocks in biosecure culture settings.