Five suspected crab carriers of yellow head virus (YHV) were commonly found in shrimp farming areas in Prasamutjedi District, Samutprakarn Province. These were Varuna literata, Sesarma mederi, Sesarma moeschii, Sesarma polita and Sesarma bocourti. Two possible routes of infection were investigated test with YHV infected haemolymph from Penaeus monodon and feeding with YHV infected muscle from Penaeus monodon. Three days after the infection, the crabs were monitored by immunohistochemistry using monoclonal antibodies specific to 135, 67 and 22 kDa proteins of YHV and then were confirmed results by one step RT-PCR. Natural infection with YHV in wild crabs was also investigated. Evidences of YHV infection was not observed in both detection methods in all crab species. By contrast, YHV-injected Penaeus monodon in control experiments were clearly detected with both methods after infection for 3 days. The antibodies specific to the 22 kDa protein gave the best immunohistochemistry results in terms of intensity. The results indicated that these five species of Grapsidae were not carrier of yellow head virus as previous expectation. The application of these monoclonal antibodies were efficiently use for development of detection test for YHV carriers.
