Enterocytozoon hepatopenaei (EHP), one of t he etiologic agents of Hepatopancreatic Microsporidiosis (HPM), has emerged as one of the most problematic infectious diseases in shrimp aquaculture over the last ten years. As the disease continues to spread across the world, there has been a surge in the development of preventatives, treatments, and genetically resistant lines of shrimp.
EHP is an obligate parasite and currently there is no in vitro culture method to propagate the parasite in a robust and reproducible manner. The inability to rapidly produce a large quantity of inoculum to conduct experimental challenges has been an impediment when screening for EHP resistance in shrimp and in experiments in developing oral treatments.
We describe here a simple yet robust challenge method to generate large quantities of EHP inoculum which can be used to conduct in vivo EHP challenges with P. vannamei . The method involves injection of EHP inoculum directly into the hepatopancreas of Specific Pathogen Free shrimp (Penaeus vannamei). In less than 21 days following injection, an EHP infection can successfully be established in the injected animals as determined by both H&E histology and real-time PCR detection in the hepatopancreas samples. Hepatopancreata dissected from the EHP-injected animals can then serve as inoculum for challenging several replicate tanks of SPF shrimp. As this EHP challenge model has been repeated in experimental assays, both the limitations and the advantages of this challenge model have been illustrated. The data accumulated from studies in which SPF P. vannamei are fed tissue derived from EHP-injected animals demonstrates a reproducible challenge model with predictable results.
Key words: Penaeus vannamei , Enterocytozoon hepatopenaei, EHP challenge model