A study published on 5 May 2026 in Scientific Reports compared six real-time PCR assays for EHP head to head. A new assay targeting the spore wall protein gene (SWP) was both sensitive and specific to EHP.
Why testing matters
EHP causes long-running growth retardation and cumulative losses rather than acute mortality. Histology can miss light or patchy infections, which makes PCR the main tool for screening post-larvae and monitoring ponds.
Several PCR assays target different EHP genes, but until this study nobody had compared them directly. The World Organisation for Animal Health (WOAH) lists EHP as an emerging pathogen.
What the team did
The Aquaculture Pathology Laboratory at the University of Arizona (USA) evaluated six TaqMan assays within the WOAH validation framework: three published assays (SSU rDNA, β-tubulin, NFS1), two in-house assays (DNA polymerase, ATP/ADP translocase) and one newly designed assay (SWP).
The assays were tested on specific-pathogen-free (SPF) whiteleg shrimp infected with EHP through feed. Samples were taken on days 15, 30 and 45 after exposure, 10 shrimp each, plus 10 controls, 40 samples in all. The team also checked for cross-reaction with other pathogens such as white spot (WSSV), IHHNV, acute hepatopancreatic necrosis (AHPND) and NHP.
Results
| Assay (target gene) | Diagnostic sensitivity | Notes |
|---|---|---|
| SWP (new) | 100% | EHP only; most sensitive at low infection levels |
| SSU rDNA | 100% | Sensitive at low levels, but also amplified a different Enterocytozoon species |
| NFS1 | 100% | PCR efficiency less stable between run days |
| DNA polymerase | 100% | Stable |
| β-tubulin | 90% (27/30) | Missed some positives; PCR efficiency out of range |
| ATP/ADP translocase | 80% (24/30) | Missed the most positives; PCR efficiency out of range |
All six assays reached 100% specificity on 10 SPF shrimp and detected EHP at 10 gene copies per microlitre. None cross-reacted with the common shrimp pathogens tested, except that SSU rDNA also picked up a related microsporidian. The authors therefore conclude that the SWP assay currently gives the most specific result and can make EHP surveillance more accurate.
What it means for farmers
PCR results are not the same everywhere. A weak assay can report negative when shrimp are already infected. When sending post-larvae or shrimp for testing, choose a reputable laboratory that uses validated methods. Testing post-larvae before stocking remains the first and most important step against EHP.
Sources
- Dinh-Hung N., Mai H.N., Dhar A.K. Development and comparative evaluation of TaqMan real-time PCR assays for detecting Enterocytozoon hepatopenaei (EHP) in penaeid shrimp. Scientific Reports 2026;16:20648 (published 5 May 2026). DOI 10.1038/s41598-026-52052-2. Open access, CC BY-NC-ND 4.0: this article reports the results only and does not translate or adapt the paper.
This article is a synthesis and interpretation by Than Vuong, not a translation. Numbers come from the original articles; product promotion in the originals has been left out. Charts were redrawn by Than Vuong from the numbers and the 3D models were built by Than Vuong; the originals’ own figures and tables are not reproduced.
