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Last Updated: Thursday, 2 February 2006, 13:34 GMT
Toxic pill attacks zebra mussels
Zebra mussel
Colonies of Zebra mussels are clogging up waterways
University scientists have developed a sugar coated potassium chloride pill to help tackle one of the world's biggest and most expensive ecological pests.

Dr David Aldridge and his Cambridge University zoologists have devised a 'Bio Bullet' technique to get a toxic compound past zebra mussel defences.

The mussels have been spreading through rivers such as the Thames and Great Ouse flowing through Cambs and Norfolk.

The colonies block up pipes and bring water works to a standstill.

The animal also has devastating impacts on wildlife by killing some species and by changing the nature of lakes and rivers so that native species can no longer survive.

The annual cost of zebra mussels in North America is estimated to be $3bn, and Britain is catching up.

Causing boats to crash

Dr David Aldridge said: "We are really concerned. Zebra mussels are appearing everywhere, and are encrusting just about every solid surface available in rivers such as the Thames and Great Ouse. "What's more, they are smothering and killing some of our native mussels like the swan mussel.

"Last year zebra mussels caused a number of boats to crash in the Thames because the propellers and rudders were so fouled by them.

Zebra mussels can be controlled by chlorine, but the chemical has environmental drawbacks.

Mussels can also sense chlorine and other toxic substances and limit their exposure to the chemicals by closing their valves for as long as three weeks.

Researchers packed potassium chloride, deadly to zebra mussels but leaving most other organisms alone, into microscopic particles made of fats.

The mussels transfer the particles, or 'Bio Bullets', along their gills and into their mouths.

The particles rapidly dissolve in the animals' stomachs, releasing a lethal dose of potassium chloride.

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