Detection of major penaeid shrimp viruses in Asia, a historical perspective with emphasis on Thailand

Asia leads the world in cultivated shrimp production with export earnings in the order of billions of US dollars per year. Despite this success, annual production decreased in the latter nineties because of widespread epidemics (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 epidemics has been somewhat better than it has been for most of its close neighbors. Initially, Penaeus monodon was the main cultivated species but this has changed markedly since 2002 when Penaeus vannamei (also called Litopenaeus vannamei) started to be cultivated in many Asian countries. Since 2004, it has been the dominant cultivated species in the world. Research in Thailand has focused on the characterization of shrimp viruses and on the development of rapid diagnostic probes for them. The major viruses of concern (in estimated order of past economic impact for Thailand) are white-spot syndrome virus (WSSV), yellow-head virus (YHV), hepatopancreatic parvovirus (HPV) and monodon baculovirus (MBV). However, with the introduction of P. vannamei, Taura syndrome virus (TSV) and infectious hypodermal and hematopoeitic virus (IHHNV) have now become important. Presently, the most rapid and sensitive tests employ polymerase chain reaction (PCR) technology and take approximately 3 h to complete. However, lateral flow chromatographic tests based on nanogold-labeled monoclonal antibodies have recently been introduced. Although they tend to be less sensitive than PCR-based methods, they are highly specific, very inexpensive and so user-friendly that they can be used pond-side by farmers themselves to verify disease outbreaks. This review covers the main Asian shrimp viruses for which PCR tests and some antibody tests are currently available and it emphasizes work that has been done in Thailand. (c) 2006 Elsevier B.V. All rights reserved.