Small Redworm

Small Redworm (small strongles/cyathostomes) are the most common parasite to effect your horse with horses under 6 years of age being most at risk. The Small Redworm grows up to 2.5cm long, are thin and can range in colour from white to red.  Small Redworm larvae are picked up by horses whilst grazing. Historically the key period of risk was spring and summer, however recent climatic changes mean that Spring and Autumn have now become the periods of greatest risk. Worryingly recent studies involving monitoring pasture infectivity have shown high levels of infective larvae present on turnout paddocks even in January after snow, highlighting the importance of winter worming.

Small redworm larvae can develop into adults within a period of five weeks, however in the autumn their development is prolonged remaining in cysts as tiny inhibited larvae within the gut wall, broadly termed encysted larvae. In the late winter or spring an unknown trigger causes these larvae to resume their development, simultaneous emergence of large numbers of 4th-stage larvae include colic, weight loss and diarrhoea causing devastating damage to the large intestine with potentially fatal results. Even before emergence large numbers of encysted larvae can cause fatal illnesses accounting for over 90% of the total Small Redworm burden.

Horses that are subject to effective worming procedures and where good pasture management is practised throughout the year will pass fewer small Redworm eggs in their manure so the levels of worm burden will be less and therefore the risk of encysted larvae will be reduced. Only 2 types of wormers have claims of efficacy against encysted Small Redworms they are Febendazole (5 day course) and Moxidectin (single dose)