Monodon baculovirus (MBV) affects the cultured shrimp and results in production and economic losses in the shrimp hatcheries and farms. Microscopic observation of the malachite green stained wet mount squashes from the hepatopancreas for the presence of MBV occlusion bodies is the widely followed method to diagnose MBV. This method was compared with a sensitive nested PCR assay to grade the level of MBV infection in shrimp seeds (postlarvae). Out of 100 shrimp seed samples screened for MBV, 20% of the seed samples were found to be positive for MBV by both microscopic observation and I step PCR whereas 30% of the shrimp seeds samples were found to be positive for MBV by II step or nested PCR only, The opimum concentration of DNA to be used for nested PCR assay for diagnosis of MBV was also standardized in this study.
