Protection against white spot syndrome virus (WSSV) infection in kuruma shrimp orally vaccinated with WSSV rVP26 and rVP28

White spot syndrome virus (WSSV) is the causative agent of white spot disease (WSD), one of the most serious diseases affecting global shrimp farming. We compared WSSV infection induction in kuruma shrimp Marsupenaeus japonicus by oral, immersion, and intramuscular injection (IM) exposure methods and evaluated the oral vaccine prepared from the recombinant WSSV proteins rVP26 and rVP28. The 50 % lethal doses (LD50) of WSSV by oral, immersion, and IM challenges were 10(-0.4), 10(-4.4), and 10(-7.7) g shrimp(-1), respectively, indicating that WSSV infection efficiency by oral challenge was significantly less than the other 2 challenge routes. However, in shrimp farms it is believed that WSSV infection is easily and commonly established by the oral route as a result of cannibalization of WSSV-infected shrimp. Kuruma shrimp vaccinated orally with WSSV rVP26 or rVP28 were challenged with WSSV by oral, immersion, and IM routes to compare protection efficacy. The relative percent survival values were 100% for oral challenge, 70 to 71 % for immersion, and 34 to 61 % for IM. Thus, the protection against WSSV-infection that was induced in kuruma shrimp by oral vaccination with rVP26 or rVP28 seemed equivalent to that obtained through IM vaccination.