In this article
🐟 Fish Herpesvirus Infections: Vet Guide 2025 🩺
By Dr Duncan Houston BVSc – Herpesviruses cause serious diseases in koi, goldfish, catfish, and trout—presenting as gill necrosis, skin lesions, mortality, and lifelong carriers. With no cure available, 2025 care emphasizes early detection, biosecurity, supportive therapy, and telehealth veterinary guidance to protect fish health.
📌 Major Fish Herpesviruses & Affected Species
- Cyprinid herpesvirus-3 (KHV): Highly contagious virus causing koi herpesvirus disease; mortality can reach 80–100% between 16–25 °C :contentReference[oaicite:3]{index=3}. Symptoms include gill necrosis, hyperemia, mucous, lethargy, sunken eyes, scale sloughing :contentReference[oaicite:4]{index=4}.
- Cyprinid herpesvirus-2 (CyHV‑2)
- Cyprinid herpesvirus‑1 (Carp pox virus): Leads to benign skin growths on koi/carp; cosmetic concern, may predispose to secondary infections :contentReference[oaicite:6]{index=6}.
- Salmonid herpesvirus 3: Affects trout/lake trout; causes skin lesions, gill pallor, mortality in hatcheries :contentReference[oaicite:7]{index=7}.
- Channel catfish virus (IcHV‑1): Infects young catfish with hemorrhages, erratic swimming; no cure :contentReference[oaicite:8]{index=8}.
🔍 Clinical Signs to Watch For
Koi & Carp (KHV)
- Severe gill necrosis, mottled/pale gills, hyperemic base of fins :contentReference[oaicite:9]{index=9}.
- Excess mucus, lethargy, loss of appetite, sunken eyes, scale loss, rapid death post-symptom onset (within ~24 h) :contentReference[oaicite:10]{index=10}.
Goldfish (CyHV‑2)
- Gill pallor, anemia, enlarged hematopoietic organs, anorexia, lethargy :contentReference[oaicite:11]{index=11}.
Carp pox
- Raised, milky-looking skin lesions/papillomas; aesthetic impact; may lead to infections :contentReference[oaicite:12]{index=12}.
Salmonids & Catfish
- Skin ulcers, epidermal shedding in trout; hemorrhage, swim issues and mortality in catfish :contentReference[oaicite:13]{index=13}.
🧪 Diagnosis & Carrier Detection
- PCR: test gill/tissue swabs for active infection; OIE-validated for KHV :contentReference[oaicite:14]{index=14}.
- ELISA: identifies antibodies—useful to detect carriers post-infection :contentReference[oaicite:15]{index=15}.
- Histopathology: lesions consistent with viral necrosis and gill damage :contentReference[oaicite:16]{index=16}.
- Telehealth evaluation: Submit photos & parameter logs via Ask A Vet for case assessment and next steps.
⚠️ Treatment & Supportive Care
- No curative treatment; focus is on supportive management and recovery :contentReference[oaicite:17]{index=17}.
- For KHV: Raise pond/tank temperatures above 25–27 °C for several days—may reduce mortality—but fish become lifelong carriers :contentReference[oaicite:18]{index=18}.
- Enhance aeration, salinity (0.5–3‰), oxygenation; maintain water quality; treat secondary infections if present :contentReference[oaicite:19]{index=19}.
- For carp pox: No treatment; culling best in quarantine to avoid spread :contentReference[oaicite:20]{index=20}.
- Catfish and trout herpes: Environmental control and strict hygiene are critical :contentReference[oaicite:21]{index=21}.
🛡 Prevention & Biosecurity Measures
- Quarantine new fish for ≥6 weeks; include PCR screening before integration :contentReference[oaicite:22]{index=22}.
- Strict disinfection of nets, boots, equipment between ponds or tanks :contentReference[oaicite:23]{index=23}.
- Control stocking density and stressors; maintain optimal water parameters and stable temperatures.
- Monitor carrier populations—surviving fish may shed virus under stress.
- No KHV vaccine currently in the U.S.; limited vaccine use elsewhere :contentReference[oaicite:24]{index=24}.
🩺 Vet-Supported Protocol with Ask A Vet
- Early recognition: Upload photos/video of clinical signs and share water logs for evaluation.
- Sample collection & PCR/ELISA testing ordered via telehealth to confirm infection or carrier status.
- Implement supportive measures—temperature, aeration, salinity, water hygiene—under expert guidance.
- Follow quarantine timelines; repeat PCR before reintroducing fish.
- Periodic carrier screening and ongoing biosecurity checks with vet oversight.
✅ 2025 Management Checklist
| Step | Action |
|---|---|
| 1. Vigilant monitoring | Watch for rapid gill damage, mucus, lesions, lethargy. |
| 2. Immediate isolation | Separate sick fish and test via Ask A Vet. |
| 3. Diagnosis | Perform PCR/ELISA and histopathology if needed. |
| 4. Supportive care | Manage temp, oxygen, salinity; treat secondary infections. |
| 5. Quarantine control | Maintain 6+ weeks and disinfect equipment. |
| 6. Carrier surveillance | Screen survivors periodically; record test results. |
🔗 About Ask A Vet & AquaCare Support
The Ask A Vet app offers 24/7 telehealth access to aquatic vets skilled in managing viral diseases. Share images, PCR results, water logs, and receive tailored advice on recovery protocols, sampling schedules, biosecurity, and follow-up monitoring. AquaCare’s line includes diagnostic kits, immune-boost supplements, quarantine system supplies, and hypo-salinity packs for herpesvirus management. Download now to protect your fish health and water ecosystems in 2025 and beyond! 🐠📱💙
