Birmingham-based pharmaceutical company Henderson Morley is coming to the aid of some of the most expensive fish in the world.

The Moseley firm is to start field trials of a vaccine to treat herpes in koi carp.

It is in collaboration with the Hagerman Aquaculture Research Institute in the United States.

The company has been working for the last ten months on a vaccine for the virus, which is found in at least 28 countries and is a problem for koi breeders. It said no treatment or vaccine is currently licensed in the UK.

Henderson Morley said the market for ornamental fish is estimated at 3.5 million homes in the UK and 13 million in the US.

There are some 139 million koi in the States alone.

Many are worth very little but top fish can cost thousands of pounds.

The company said: "In 1998, widespread outbreaks of death occurred in both fish farms and ornamental ponds - when some 85 per cent to 100 per cent of infected fish died within a few days.

"It was subsequently discovered that this disease was caused by a newly isolated virus - koi herpes virus. This virus has now been isolated in at least 28 countries including the US, Japan and the UK, and it has become a very significant problem for koi breeders and enthusiasts.

"Once infected, a pond will lose the majority of its fish within days."

Andrew Knight, chairman, said: "We believe that animal health is an important area of development for Henderson Morley." The firm added that products targeted at animal health may offer nearer term revenue opportunities, as the time taken to commercialise human ones can be significant.