How to worm your horse

ArticleHow To - HealthThursday 22 December 2011
By Jessica Surrey Dane and Sue Messenger

It is worth first asking why attention to worming is so important. A horse or pony heavily infested with worms will lack condition and find it hard to keep on weight. Even an apparently healthy horse, however, can have a worm burden bad enough to cause colic and other health problems.

Not so long ago owners used one of a limited number of wormers regularly for a year and then changed the next year to another make. In recent years as horse ownership has grown, so has the choice available and it is possible to buy, without advice, online.
However, concerns are now arising that some worms are becoming resilient to some wormers and there are concerns about the amount of chemicals being used unnecessarily on horses and also subsequently going into the ground.
Responsible owners are now being urged to use targeted programmes throughout the year and to use worm counts as a way of achieving this. By doing this the horse will only receive what it needs (and it can save money as well).
So how does this work? There are some circumstances where you should always give a broad spectrum wormer immediately and these include when a new horse is going into a yard. Preferably, though not always possible, you would have a worm count done before worming and then 2 weeks afterwards. Otherwise you can start your programme at any time of the year.
The company doing the worm count will give you a reading and comprehensive advice on which wormer you need to use. Some worms do not always show in the counts, so even if the worm count is so low that you do not need to worm, you are still advised to worm for encysted redworm in December and tapeworm in September each year and you can use wormers targeted for these .
The process of taking a worm count is very easy, everything you need is sent to you through the post, even some plastic gloves! Westgate will even set up a database for you so you can keep track of your results and they will email you reminders too.
There are other things you can do to keep your horse or pony with a low count, but not all are possible if you keep your horse at livery. Picking up the droppings regularly, keeping the horse with the same companions, resting the grazing and ensuring all the animals follow the same programme at the same time will all go a long way to helping.
There are potentially a bewildering number of products on the market and they are not cheap. It really does make sense not to just guess but to use a worm count service, talk to their experts and if still unsure check with your vet.
Types of worms and how to treat them
Redworms – these worms are the most likely to cause disease and owners need to be on guard while their horses are on grass as they thrive in pasture. Redworms come in two forms – large and small. 
The former travel through the blood vessels and create blood clots, which can lead to colic as the blood vessels supplying the gut are obstructed. 
The latter, which are the most common type of worm in horses, lie inactive in the gut wall where they are unaffected by most wormers. Once they emerge in the gut in spring they need to be treated with Telim or Equest, which are effective on almost all types of redworm, as they can damage the intestines, leading to diarrhoea and weight loss.
Tapeworm – these are thought to be the cause of up to 20% of colic surgeries as they attach themselves to the junction between the small and large intestines, causing rupturing, twisting and blood vessel blockages. 
They usually measure 8cm long, and need to be treated every six months as they’re not seasonal – the mites, which are eventually consumed by horses, survive in pasture, forage and bedding all year round. A praziquantel-based product like Equitape will do the job.
Roundworms – also known as ascarids, these are ingested by horses as eggs, they hatch and are carried by the bloodstream into the lungs and liver.  Here, and also in the bloodstream, they can cause coughing, fever, bleeding lungs and pneumonia.
As egg-laying adults they live in the intestine where they can cause colic, ruptures and blockages. These are especially dangerous in large numbers in foals, but horses build up immunity to them with age. Strongid P is effective against roundworms.
Lungworms – these are most commonly encountered in horses in contact with donkeys, which carry can carry large numbers without showing any medical signs. In horses they’re found in the lungs as adults where they lay eggs, which are then coughed up, swallowed and leave the horse via its droppings. If a horse is coughing and losing weight, use an ivermectin or moxidectin-based product such as Eqvalan or Equest to treat lungworm.
Bots – though these are not actually worms, these flies are still treated in the worming cycle. Eggs, laid by the fly on the horse’s body, most commonly the legs, are licked off by the horse and then hatch, embedding themselves into its gums. 
After about a month they migrate to the stomach and, after a further 10 months, are passed out in the droppings. They can live in the stomach throughout the winter, causing it to become inflamed and ulcerated so it’s important to treat all horses with Equest or Equimax around New Year.
Top tips for avoiding worm problems
  • Adopt an organised worming routine. And stick to it
  • Take dropping samples and send them to the vet for a count
  • Rotate grazing after worming so horses can have a fresh, worm-free pasture
  • Clear droppings regularly
  • Avoid chopping and changing multiple horses between field
  • Keep feed and water buckets clean
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