Shooting estates in the region are predicting a poor grouse season this year as an infestation of worms threatens much of the country's population.

The resurgence of the deadly worm has meant many shoots across northern England and Scotland will be cancelled or severely restricted.

Estates in County Durham and North Yorkshire will reduce their number of shooting days after recent counts found the grouse figures "substantially down".

The Moorland Association has yet to complete a full game count across the country but a spokesman said it looked to be a ''very poor'' season.

The Association's Martin Gillibrand said: ''I haven't got the full figures yet but the message that is coming loud and clear from most of the Uplands is that it is going to be a very poor season.

''I know that in some parts they will not be shooting at all or else in a limited way.''

The problem began to emerge last autumn after a wet and mild shooting season - conditions in which the Strongyle worm thrives.

The worms are found on the heather eaten by grouse and thousands can infest a single bird at a time, leaving it very weak and in many cases killing it off completely.

Lindsay Waddell, head gamekeeper for Lord Barnard, said: "Next month's Glorious Twelfth will be anything but.

"The shooting season will be severely curtailed because of the numbers of birds, to the extent that a considerable number of grouse moors will not be shooting at all.

"I think it is unlikely that we will be doing very much, which is in keeping with most of our neighbours.

"It is a widespread problem and has affected the vast majority of the north Pennines, but I understand that the North Yorkshire moors is a little better off."

Many estates depend on the income from the shooting season, which contributes millions of pounds to the economy each year.