Disease Control

Grouse are prone to two particular diseases, Louping Ill and Strongylosis. The latter occurs especially if numbers are high, partly accounting for the grouse's natural "boom-bust" population dynamics.

Louping Ill in Sheep and Grouse

Louping Ill is a particular problem encountered in certain moorland areas. Sheep ticks carry a virus that attacks the nervous system of sheep and red grouse. It has been proven to be 79% fatal in grouse chicks.

Control requires the cooperation of many people, and an initiative on the North York Moors has shown just how successful this can be. In 1995 Moorland Association members, The North York Moors National Park Authority, farmers and shooting tenants were successful in gaining financial assistance from MAFF and European Objective 5b funds to help control the disease through sheep dipping, vaccination for sheep and bracken control. A total of 4000 hectares of bracken within this 44,000 hectare SSSI site were treated and returned to heather. During the first four years of the programme, lamb deaths dropped by 7%, which equated to 2000 lambs saved, and the Game Conservancy Trust reported a substantial year-on-year reduction in ticks found on red grouse.

Trichostrongylus Tenuis

Trichostrongylus Tenuis is a nematode worm that can occur in the gut lining of an adult red grouse and cause strongylosis or "grouse disease". The digestive efficiency of the grouse is reduced and with a high infestation it will die, especially in early spring when food quality is at its worst and the bird is stressed by breeding activities. Grouse suffering from strongylosis also become easier targets for predators.

The eggs of the Trichostrongylus Tenuis worm are ejected into the heather in grouse faeces; there they hatch into larvae, which are subsequently ingested by grouse feeding on the heather. As the grouse population on a moor increases, so does the number of larvae in the heather and hence the number of worms in the grouse; as many as 40,000 have been counted in badly infected old birds. As the population peaks, grouse begin to die from strongylosis, and the 'crash' can be dramatic, with few surviving. The number of larvae in the heather now decreases; surviving grouse and their chicks become more healthy, and numbers begin to build again towards another inevitable 'crash' - such is nature's way. The moor manager can reduce the severity of this cycle by shooting hard when populations build towards a peak. He can also use medication to treat the disease.

For latest research and guidance on Trichostrongylosis Tenuis, the use of medicated grit and direct dosing in the treatment of worm can be found on the Game Conservancy Trust's website.