Autumn is traditionally a time for proactive parasite control in horses. We hear the mantra ‘tapeworm time’, are primed to give our annual dose for encysted redworm and there may be bots to treat as well. But wait! Do you know if there are parasites present and is now the best time to reach for the wormer?
As responsible horse owners our job is to keep parasite levels in check so that our horses remain healthy and to use the drugs we have responsibly to minimise the build-up of resistance to worming chemicals.
This means being aware of which parasites to target seasonally or in specific conditions. Those we specifically need to be aware of through autumn and winter are encysted redworm, tapeworm and bots.
A mature, healthy horse can follow a very simple pattern of testing and dosing with additional tests or treatment added in as required. If all is well then no need to worm. Foals, youngsters, neglected or older horses will require more attention.
Redworm (large and small strongyles)
Small redworm or Cyathostomins are the most common and dangerous parasite, accounting for around 95% of intestinal horse worms. They have a remarkably quick lifecycle, completing to maturity in as little as 5-6 weeks. For this reason they should be monitored with worm egg counts at least every three months, worming if the test indicates.
Encysted small redworm
Through the autumn/winter redworm larvae can delay their development and hibernate in the gut lining to emerge en-masse in spring and cause life-threatening colitis known as larval cyathostominosis. These encysted stages of redworm are not mature so don’t lay eggs to be detected by a worm egg count.
Treatment for the possibility of encysted redworm is advised once a year. This is now thought to be most effective given in the winter, rather than autumn, due to milder weather over the last few years which has led to increased parasite activity later into the year.
Two drugs are licensed for treatment: a single dose of moxidectin or a five-day course of fenbendazole, take care with the latter due to widespread resistance to this chemical.
Testing of horses in the UK estimates that between 20-25% of horses are infected with tapeworm. This is fewer than once thought but we still need to be vigilant.
The simple and reliable ‘EquiSal’ saliva test is available that can be taken by the horse owner to measure tapeworm infection levels and give a reading of low, borderline and moderate/high and whether treatment is required. Doing this in spring and autumn can prove a useful aide memoir but as long as the gap is six months apart it does not matter in the year when the tests are taken.
Two drugs are licensed for treatment: double dose of pyrantel or a single dose of praziquantel, sold as a single product or in combination with ivermectin or moxidectin if worming for other parasites is required at the same time.
Bots are not worms but the maggot stage of a large fly which is active during the summer months. It lays eggs on the hairs of the horse’s coat seen as tiny cream or yellow flecks.
These eggs can be ingested by the horse and hatch in the mouth, slowly migrating to the stomach where they can cause mild discomfort. Treat with ivermectin or moxidectin after the first frost has killed off fly activity. You could combine this with your encysted redworm dose.
What to do now
This autumn plan a worm count for redworm and roundworm, EquiSal test for tapeworm and keep an eye out for bots and pinworm activity. This will help you to decide which wormer to treat with for your winter dose.
All tests and free veterinary approved advice is available from your friendly team of SQPs at Westgate Labs.