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• First aid check list
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Worming

Worms are parasites that live in the gut and intestines of host animals. Most grazing animals, including horses, naturally have a very low level of worms in their bodies but sometimes the level becomes excessive causing serious damage. Worms attach themselves to the lining of the intestines, sucking blood and burrowing through the lining of the gut.

The consequences can include damage to the digestive system, inflammation of the gut, diarrhoea, colic, anaemia, loss of appetite, loss of condition and even death.

There are many different types of worms as shown in the table below:

Paddock Management and the Worm Cycle

In the wild, horses roam over thousands of acres of pasture and are constantly on the move. This means that after they pass droppings they then move on to new pastures. By keeping horses confined in paddocks, they are unable to get away from their droppings and the 'worm cycle' can become established.

Worms start their life as eggs and in most common species, such as cyathostomes, eggs are deposited onto the grass through the droppings of an infected horse. These eggs then hatch into larvae, which are ingested by horses grazing on the pasture. Inside the horse, the larvae develop further and then mature into adults, which go on to lay eggs. The eggs are passed out in the droppings and the cycle starts again.

The most effective way to reduce the risk of worm infestation is to keep paddocks as free from droppings as possible. Yearly paddock maintenance can involve harrowing, resting and re-seeding which ensures the eggs are destroyed and the grass is given a chance to rest and recuperate free from worms. Rotating grazing with other species such as sheep and cattle can also reduce worm contamination of pasture.

Worming regime

Your horse should be wormed regularly. No one brand of wormer kills all types of worms and over time worms can develop a resistance to one kind of wormer making it ineffective. To combat this problem the type of wormer used should be rotated on an annual basis. Contact your veterinary surgeon for further information on the best worming protocol for your horse.

Wormers generally come in either a paste form or as granules, and the amount given varies according to the weight of the horse. It is important that horses receive the correct dose and if unsure you can measure your horse's weight using a weigh tape. The interval between doses is advised by the manufacturer and varies from six to thirteen weeks.

Top Tips

• Worm all new horses and ponies that come onto the yard as soon as possible, ideally before mixing with the others or turning out.
• Use a paste wormer rather than in feed granules if your horse is a fussy eater.
• Horses and ponies in poor condition are more prone to worm infestation than those in good condition.
• Keeping horses stabled for 48 hours after worming will minimise contamination of the paddock as not all worms are killed and some may be passed out and ingested by other horses.
• Try not to keep too many horses in the same field. Overgrazing the field means there is less grass to go round and horses end up eating rough patches of grass where they do their droppings.
• Keeping other grazing animals such as goats, sheep and cows, helps to minimise worms as they ingest and kill off some of the larvae.
• Feed concentrates from a bucket rather than off the ground to reduce the intake of eggs.
• Watch out for bot eggs, particularly on horses and ponies at grass. They usually appear on the legs as little yellow eggs, and if not removed are ingested by the horse if he licks them. They are most prevalent during April and May.
• Your horse's worm count can be measured by collecting a small sample of dung and sending it off to a laboratory or to your veterinary surgeon.