An overview of PCR techniques for shrimp disease diagnosis in Asia, with emphasis on Thailand

Abstract

Asia leads the world in cultivated shrimp production with export earnings in the order of billions of US dollars per year. In spite of this success, annual production decreased in the late nineties because of widespread epizootics caused by new viral pathogens. Although, these viruses were no cause for alarm to human health authorities, they were economically crippling for Asian shrimp farmers. In Thailand, shrimp production trends have mirrored those in the rest of Asia, except that recovery from the viral epizootics has been somewhat better than it has for most of its close neighbors. Our work in Thailand has focused on the characterization of the causative viruses and on the development of rapid diagnostic probes for them. Similar work has been done elsewhere. The aim of the work has been to develop effective control measures to help shrimp farmers. We are engaged in similar work on bacteria and parasites. The major viruses of concern (in our estimated order of economic impact for Thailand) are white-spot syndrome virus (WSSV), yellow-head virus (YHV), hepatopancreatic parvovirus (HPV), monodon baculovirus (MBV) and infectious hypodermal and haematopoeitic virus (IHHNV). We have also prepared probes for Vibrio parahaemolyticus and for a microsporidian parasite, Agmasoma penaei. These highly specific and sensitive tools for detection are already helping shrimp farmers and we hope that new technological advances will make them practicable in the field. At the moment, however, the most rapid test is the polymerase chain reaction (PCR) test, which takes approximately 3 hours to complete. This review covers important Asian shrimp diseases for which PCR tests are currently available.