Koi Herpes Virus Prevention Management Guide: KHV Quarantine
Koi herpes virus (KHV, also called CyHV-3) is the disease that ends collections. The koi herpes virus kills 80-100 per cent of infected populations within 7-21 days at temperatures of 22-28°C — exactly the range Singapore ponds operate in year round. There is no treatment, no cure, and no vaccine widely available outside Israel and Indonesia. Prevention through rigorous quarantine, biosecurity, and import vetting is the only viable defence. This guide from Gensou Aquascaping at 5 Everton Park covers KHV biology, symptoms, the 30-day quarantine protocol, and the AVS reporting requirements for Singapore outbreaks.
KHV Biology and Transmission
KHV is a double-stranded DNA virus from the Alloherpesviridae family. It infects only common carp and koi (Cyprinus rubrofuscus) and replicates aggressively at 22-28°C. Above 30°C and below 18°C the virus stays dormant in latently infected carriers — but those carriers can shed virus when temperatures swing back into range. Transmission routes: water contact, fomites (nets, hands, equipment), bird vectors. The virus survives 4 hours in pond water and up to 3 days on damp surfaces.
KHV Symptoms in Acute Infection
Day 1-3: lethargy, surface gulping, slight fin clamp. Day 3-7: gill necrosis (the diagnostic hallmark — pale, mottled, eroded gill filaments visible under operculum), excess mucus production, sunken eyes. Day 7-14: secondary bacterial infections on damaged gill tissue, mortality begins. By day 14-21, mortality reaches 80-100 per cent in unprotected populations. Surviving fish become latent carriers and can re-shed virus during temperature triggers years later.
Why There Is No Treatment
KHV is viral, so antibiotics do nothing. Antiviral compounds tested in research settings (acyclovir derivatives) are not available for veterinary aquaculture use. The Israeli vaccine (KV3) requires controlled application and is not registered in Singapore. Once symptoms appear, supportive care (water quality, oxygen, salt at 0.3 per cent) only marginally extends life. The protocol is containment, not treatment.
The 30-Day Quarantine Protocol
Quarantine all incoming koi for a minimum of 30 days at 22-28°C — the temperature range that triggers KHV expression. A separate 500-litre tub with sponge-baffled filtration, dedicated nets and equipment, and zero water sharing with the main pond. Day 1-7: observation. Day 7: skin scrape and gill biopsy for parasites. Day 14: temperature challenge — if pond water is naturally cooler, raise to 25°C to force any latent KHV to express. Day 21-30: continued observation. Only after a complete 30-day clean window does the fish enter the main pond. Equipment from the aquarium equipment range.
Biosecurity at the Pond
Use dedicated nets, buckets, and equipment for quarantine versus main pond. Disinfect all equipment between uses with iodine solution (Vanodine V18) or a 10 per cent bleach soak followed by full drying. Wash hands between handling fish from different ponds. Restrict pond access for visitors who keep koi elsewhere. Stock from the water care and treatment shelf includes biosecurity disinfectants.
All-In/All-Out Stocking
Once a koi pond is established with virus-clean stock, treat it as a closed system. Each new fish goes through full quarantine. If KHV ever appears in the pond, all surviving fish become latent carriers and the pond is permanently compromised. Some serious keepers fully drain, disinfect (sodium hypochlorite at 200 ppm for 24 hours), and re-establish from clean stock after a confirmed outbreak.
AVS Reporting in Singapore
The Animal and Veterinary Service (AVS) under National Parks Board treats KHV as a notifiable disease. Confirmed or suspected outbreaks must be reported to AVS via their hotline. AVS may request samples for laboratory PCR confirmation, conduct on-site assessment, and impose movement restrictions on the affected pond. Importing dealers face stricter consequences than hobbyists. Maintain documentation of all imports and any disease events.
Sourcing Clean Stock
Buy from Singapore importers handling reputable Japanese bloodlines (Sakai Fish Farm, Dainichi, Marudo, Marusei) where breeding facilities run KHV-screened stock with PCR documentation. Yamamatsu Singapore and Shintaro Carp distributors provide breeder paperwork that includes health declarations. Avoid mixed-source ponds at low-cost retailers where stock provenance is unclear. Quality feed from the fish food and feeding range supports immunity that may help latent carriers stay symptom-free.
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5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
