Virus linked to carp deaths

[Spiel]

Virus linked to carp deaths

 

May 9, 2008

JAMES NEELEY / thepeterboroughexaminer.com

 

 

A fish virus new to Ontario has been identified as one cause of the carp die-off that littered area lakes with 12,000 to 24,000 fish last summer.

 

John Cooper, of the Lake Erie fisheries management unit for the Ministry of Natural Resources (MNR), said extensive testing by the University of Guelph and the federal fish health labs confirmed finding a new fish virus to Ontario - the koi herpesvirus.

 

The MNR previously identified a bacteria, columnaris, as the cause of the fish kill, but now say the new virus also killed fish.

 

The koi herpesvirus, first found in North America in 1999, was discovered in two fish collected from Scugog and Pigeon lakes last year, Cooper said.

 

It only affects carp, goldfish and koi, he said, and is not a danger to humans "because it can't live in a body as warm as a human."

 

Carp infected with koi herpesvirus are safe to eat and handle, he said.

 

Last year's die-off also will not threaten carp counts for this season, Cooper said. "Carp are a prolific fish that can quickly bounce back from a die-off," he said.

 

There is no evidence the 2007 carp die-off was caused by a contaminant spill, Cooper said.

 

Trying to determine what caused last summer's carp kill took extensive testing, he said, noting one of the difficulties was, unlike humans, autopsies don't work on fish.

 

"Once they are dead the natural process may mask the cause," Cooper said. "We have to get the fish alive and transport to the lab as quickly as possible."

 

The MNR released a new formalized protocol yesterday to better handle fish kills in the future.

 

To speed the research to determine causes of die-offs, Cooper said the MNR will collect fish themselves instead of taking samples from the public.

 

 

Cause of a koi herpesvirus disease outbreak:

 

- The koi herpesvirus virus causes disease and death when water temperatures are between 18 to 28 C. Disease outbreaks are rare when water temperatures are lower than 13 C.

 

- Fish are most susceptible when stressed as a result of fluctuating high water temperatures, crowding and spawning.

 

- The virus is highly contagious and has been linked to large mortalities of carp and koi.

 

- The virus is most likely passed from fish to fish in close contact, entering the body through the gills or possibly through the intestine.

 

- The virus lives in fish, in water for short periods of time (possibly for at least four hours, probably less than a day), in feces, and possibly in the mud bottoms of lakes and rivers.

 

- Fish infected with koi herpesvirus may survive a disease outbreak and become carriers of the virus, passing the virus to other fish.