What do we know about EHP?
• Tissue specific for HP unlike most other microsporidians which affect muscle
• Transmitted orally between shrimp with no need for an intermediate vector very unusual and very worrisome
• Very difficult to visualize with normal histology
• Requires practice and patience
• Once spores are in ponds very difficult to eradicate
HP with EHP spores
Control of EHP
• Two fold approach to possible control
– Broodstock carriers shed spores in feces which contaminate egg and nauplii surfaces.
– Farmed animals shed spores into ponds which in turn are available to re-infect foraging shrimp feeding on dying shrimp and spreading spores.
– Reduce organic matter in ponds and use caustic treatments before stocking.
Flegel et al. Examined 200 Thai ponds at random for prevalence – GOAL 2014
Infected with the E. hepatopenaei (EHP): 72/148 = 49%
Infected with white spot syndrome virus (WSSV): 8/148 = 5%
Covert mortality nodavirus (CMNV): 64/148 = 43%
Early mortality with no HP lesions: 5/148 = 3%
Source: Stephen G. Newman Ph.D., Flegel et al.