The standardisation and optimisation of a one step single tube reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) procedure is described for rapid diagnosis of white tail disease, a viral disease caused by Macrobrachium rosenbergii noda virus (MrNV) and extra small virus (XSV), in giant fresh water prawn, M. rosenbergii. Time, temperature and quantity of each reagent were optimised for the detection of the two viruses. This method was more sensitive than the conventional reverse transcriptase polymerase chain reaction (RT-PCR) for detecting the two viruses. The RT-LAMP reaction is highly suited for disease diagnosis in developing countries. Amplification of DNA can be detected without the use of agarose gel electrophoresis, by the production of a whitish precipitate of magnesium pyrophosphate as a by-product. The cost of RT-LAMP for one reaction is nearly 4 times less than that of RT-PCR.

Shrimp culture is the most lucrative aquaculture sector in Asia-Pacific region. Recently, shrimp farms in India have been affected by the microsporidian parasite, Enterocytozoon hepatopenaei (EHP) associated with retarded growth without other clinical signs, causing significant economic losses to the shrimp industry. The present study was carried out to investigate the incidence of EHP in Penaeus vannamei farms of Nellore district of Andhra Pradesh, and to identify the carriers of EHP and the role of management in reducing the incidence of EHP in ponds. PCR analysis by two sets of EHP specific primers indicated the incidence of EHP to be 92.50%. Histopathological studies of the hepatopancreas of affected shrimp showed sloughing of the epithelial cells of hepatopancreatic tubules, lifting and detachment of epithelial layers of hepatopancreatic tubules and heavy damage of hepatopancreas. PCR screening of aquatic macro fauna in the farms showed that samples of crabs, polychaetesand non-penaeids were positive for EHP, implying that they could act as carriers of EHP. On the other hand, fishes were found negative. Strict implementation of Best Management Practices (BMPs) in one selected farm which was confirmed to be infected by EHP clearly showed that practice of BMPs and avoidance of carriers can definitely reduce the incidence of EHP during the subsequent culture in shrimp farms. After implementation of BMPs, significant improvement in growth rate, and Feed Conversion Ratio (FCR) were also observed. In the control pond where BMPs were not implemented, EHP continued to be present, affecting growth and FCR adversely. This is the first report comparing the role of management in EHP infection and identifying carriers of EHP in P. vannamei culture in India. K e y w o r d sEnterocytozoon hepatopenaei,