This is aimed at worming horses at specific times of year to disrupt the seasonal cycle of transmission Theoretically a rational approach based on the seasonality of the life cycle of small redworms, (cyathostomes), the main target for control. Strategic dosing in the first half of the grazing season aims to limit worm egg output from the horse and so prevent a build up of infective larvae on pasture. It may still be necessary to treat again in the Autumn, depending on weather and husbandry factors. Worm egg counts on faecal samples can help determine the need. Problems can arise if abnormal weather patterns lead to early or late peak larval burdens on pasture Susceptible to breakdown if infected horses are added to the population without testing and treatment if necessary This method may not be so successful with larger groups of horses because within a population certain individuals will shed more eggs than others. Younger animals also tend to acquire heavier worm burdens and will therefore be a potential source of infection for older animals grazing with them. Modification of the strategic dosing system Also aims to suppress pasture contamination at critical times of the year but all horses are sampled for a faecal egg count (FEC) prior to dosing Treatment is then targeted at animals with adult parasites (as indicated by a worm egg count of over 200 eggs/gram) Eggs counts are a useful indicator but do not correlate well with the total parasite burdens Egg counts will not identify the presence of immature or encysted small redworm larvae within the gut wall (mucosal stages), so worm burdens for small redworms can be grossly underestimated Worm egg counts are best performed in the Summer months when mucosal numbers are likely to be lowest Egg counts may not detect presence of tapeworms. Anti-tapeworm treatments can be targeted by identification of infected animals using the tapeworm antibody ELISA. This test is performed on a blood sample and results indicate either a low, moderate or high infection intensity.