Koi Herpes Virus – Disease Course

It’s not ‘all the time’ that someone documents a KHV outbreak this thoroughly. I’m moticing things like the onset of disease, the source of the fish, the commencement of heating the fish to 82+ DF and the cessation of mass mortality after that.

Koi Herpes Virus – Disease Course

Written by Dr Erik Johnson and

May 24, 2003 – Purchased beni kumonryu from Bill Jones at Louisville koi show. The fish had been purchased 1 hour before from Ray Abell (And had been in quarantine for 7 weeks.) This fish had been in pond with Bill’s infected fish for that 1 hr. – then the beni kumonryu was bagged and floated in that pond water for rest of day until 7:00pm when it was introduced directly into my 10,000 gal. Koi pond @ 71-72 degrees.
May 30, 2003 – Still eating, but not swimming with other fish.
June 1, 2003 – (8 days later) Kumonryo staying at top of pond – quit eating.
June 7, 2003 – Put kumonryo in quarantine.
June 9, 2003 – Main pond: 4 koi gulping air and forcing out gills.
June 10, 2003 – Large kohaku (22”) had red blotches, a scraping showed costia.

Koi Herpes Virus - Disease Course
Koi Herpes Virus – Disease Course

– Started Proform C treatment
June 11, 2003 – 30% water change, 2nd Proform C.
June 12, 2003 – 30% water change, ProformC + Prazi.
June 13, 2003 – Kumonryu died in quarantine. We had to leave for business trip, returned late Sunday night, June 15.
June 16, 2003 – First view of fish – they looked terrible. We thought it was some sort of chemical burn from the Proform C. We did a 40-45% water change. The fish had no slime coat.
June 17, 2003 – 35% water change. – Salt at .18%. First of our fish died – 17” showa. I called Bill Jones and he reluctantly told me that a batch of his fish had been diagnosed with KHV.
June 18, 2003 – Sent 2nd dead fish to Georgia (KHV Positive), started raising temperature from 71 degrees, reached 75 degrees. (Why?) Added extra aeration.
June 19, 2003 – Temperature at 82 degrees, salt at .3%, two more fish died.
June 20, 2003 – Four more fish died.

June 21, 2003 – Our annual club auction. Thank goodness I knew what I had. Started using KoiZyme twice a week instead of once a week. Ordered antibiotic food from Pond RX. Lost 9th fish.
June 24, 2003 – Started on antibiotic food for 11 days, but they ate very little, for 3 weeks. Four required further treatment with Baytril, but all remaining fish survived (29 out of 38 + 2 small 6”fish & kumonryo) – Heated to 83 degrees for 11 days, starting the 19th.

Now Aug.12, 2003 – 9 weeks after outbreak, all are eating well and acting normal. Several lost some color and several still have sunken eyes. No more infections.

I should mention that I did a scraping of two fish 7 or 10 days before introducing the new fish just to be cautious – I didn’t see any parasites. However, the very first indications I got of the problem was the obvious presence of costia and the scraping showed them to be heavily infested. This was before any “disease-like” symptoms, but 16 days after I introduced the KHV fish.
June 17 (24 days after introducing fish and 18 days after it appeared ill) was when a friend called me and told me about three other ponds already wiped out from the same purchases at Louisville. It really appears as if treating for costia, either before or during the heating process might make a big difference in survival rates. My first mortality, other than the initially infected fish was not until this date. And Proform C does seem ideal as it is so quick.
Linda: Something I really want to know and forgot to ask, do the sunken eyes come back to normal?
Doc: Answer: Yes, they do as the fish recover their strength. heat seems to make a big difference in how fast this recovery is.
Linda Kinney

President, Dayton Koi Club

Dr Erik Johnson is a Marietta, Georgia Veterinarian with a practice in small animal medicine. He graduated from University of Georgia with his Doctorate in 1991. Dr Johnson is the author of several texts on Koi and Pond Fish Health and Disease as well as numerous articles on dog and cat health topics.