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%

Mortality

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.