THE most important parasites we need to address going into the autumn/winter are encysted small redworm larvae and, if necessary, tapeworm. It may come as a surprise to some to know encysted larvae are not killed by most wormers.

Tapeworms can cause digestive disturbances, loss of condition and colic if a horse develops a large burden of worms. Small redworm larvae can encyst within your horse’s gut wall throughout the year, especially in the autumn and winter. If the larvae are not treated, a sudden mass emergence of larvae can occur in the spring, damaging the gut, which can cause diarrhoea, colic and may be fatal.

A targeted worming programme is vital for our horses because of the increasing resistance to the active ingredients used in wormers. It is recommended that you carry out a tapeworm saliva test to determine whether or not your horse needs to be treated for tapeworm.

Encysted redworm larvae are treated using a wormer containing moxidectin, which also treats redworm and bots, which is why it’s not necessary to carry out a faecal worm egg count at this time of year.

The wormer should be administered late in the grazing season (people often use the first frost as a reminder) so that reinfection on the pasture is minimised. If the result of the tapeworm saliva test suggests that you need to treat your horse for tapeworm, it is possible for this to be done at the same time that your treat your horse for encysted redworm. This can be done using a wormer containing both moxidectin (to treat the encysted larvae) and praziquantel (to treat the tapeworm). Next week Dr Joe Collins takes a closer look at parasites as we come to the end of the grazing season.

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