If late-autumn worms counts are still not sufficiently high to merit using medication, then we recommend further sampling. Larval pick-up in the intervening period will be strongly influenced by winter weather mild and wet weather being good for worm larval survival and subsequent pick-up by foraging grouse. The relationship between autumn worm counts and those in the following spring can however be highly variable and difficult to accurately predict. Mean infestations above 500-750 worms per adult bird in early autumn may require the use of medicated grit through the winter before the next breeding season. Importantly, these count results should be discussed with your vet when asking for a medicate grit prescription. It is the spread of individual worm values across the measured sample, guided by the average, that will help steer decisions on whether medicated grit is required to control worm parasites. As a rough guide, we know from previous research that more than an average of 2,000 worms per adult grouse can severely impact on productivity and survival. Worm counts can either be done by estate staff, once trained by the GWCT, or the guts from those grouse selected can be delivered (or posted using a bio-bottle) to GWCT offices and we will do them for you. Strongyle worms should be counted from a sample of 20 adult grouse randomly selected from those shot, preferably in August and again at the end of the shooting season.

Before commencing parasite management, it is important to know what levels of worms are present in grouse.

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