The detection of White Spot Syndrome Virus (WSSV) and Yellow Head Virus (YHV) in imported commodity shrimp

Transmission of exotic pathogens occurs through a variety of means, including migration with humans and animals, rapid transit by land, sea or air or through the shipment of infected frozen food products. White Spot Syndrome Virus (WSSV) and Yellow Head Virus (YHV) have caused mass mortalities of cultured shrimp in Asia beginning in 1992. In 1995, these viruses appeared for the first time in the Western Hemisphere causing high mortalities in farm reared shrimp in Texas, USA. The purpose of this study was to determine if WSSV and YHV are present in frozen shrimp products imported into the United States from Asia. Infectivity assays, transmission electron microscopy (TEM), and polymerase chain reaction (PCR) showed these viruses were detectable and infectious in frozen shrimp imports. Frozen shrimp were used to infect indicator shrimp ( Penaeus stylirostris) which resulted in mortalities. The cause of these mortalities was determined by histology and TEM to be by YHV. PCR confirmed the presence of WSSV in the frozen, purchased products. The results from this study indicate that exotic shrimp pathogens can be transmitted via imported frozen products.