During late autumn and winter, there are several parasites all horse owners need to consider.

“The most important is encysted redworm, the larval stages of which have the ability to hibernate in the horse over winter, and which are a particularly dangerous threat to health,” says Claire Shand of Westgate Labs.

“Many thousands can burrow into the gut wall and lay dormant before staging a mass emergence in springtime. This can trigger colic that is very difficult to treat. To guard against this, we need to test or treat proactively.”

For horses that have had regular worm egg counts under 200epg through the previous year, a small redworm blood test by your vet is the best way to decide if worming is required.

“For others this is one of the only times when a proactive moxidectin treatment is recommended,” says Claire. “This is because out of the two chemicals licenced against larval small redworm, it is the one with least documented resistance, the alternative being fenbendazole as a five-day course.

“We aim to reserve moxidectin for this use in order to preserve its efficacy as a key medicine against encysted redworm.”

If you know you are going to treat then carrying out a redworm reduction test — a worm egg count before treatment and another 10 to 14 days afterwards — is advised to measure whether there is any resistance to the chemical used within the worms on your pasture.

“In addition, carry out a saliva test for tapeworm if this hasn’t been done in the previous six months, and consider bots if any of the small yellowish eggs of this fly have been seen on the horse’s coat over the summer months,” says Claire.

“Results from all of these tests will help to decide which, if any, treatment is needed and target this to help slow resistance. Do a worm egg count again eight to 12 weeks on.”

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