Worms are an inevitable fact of life for horses, and the vast majority of them have some level of infestation. Worm eggs, such a tapeworm, are usually ingested from infected pasture, they then develop into worms inside the horse’s gut or lungs before being passed out onto the pasture via faeces which can then infect other horses.
A low number of worms isn’t a problem; the horse’s immune system helps keep the worm burden (the intensity of infection) low and in fact a low worm burden can help the horse’s immune system develop. But if the horse’s immune system is compromised, or the worm burden becomes too high, it can lead to serious problems in the gut, including colic and diarrhoea. These can cause long-term damage, even after treatment so it’s important to monitor a horse’s worm burden.
But what are worms, and how do they get into the horse?
TYPES OF HORSE WORMS
1. Small Redworms
These are the most common internal horse parasite; they hibernate in the lining of the gut which can damage it.
Symptoms:
- Weight loss
- Colic
- Diarrhoea
- Fatalities in some cases
2. Large Redworms
These are more dangerous but luckily less common. They can spread to the blood vessels of the intestines, causing internal bleeding.
Symptoms:
- Weight loss
- Diarrhoea
- Fatalities in some cases
3. Roundworms
These are more dangerous to foals and young horses as their immune systems haven’t had as much time to develop. When ingested, the larvae are transferred through the lining of the gut to the lungs and liver where they can be coughed up and swallowed. Once in the intestine they mature and lay eggs.
Symptoms:
- Cough
- Nasal discharge
- Weight loss
- Diarrhoea
- A pot belly
4. Pin Worms
These lay their eggs around the anus, resulting in itchy, open sores which can become infected.
5. Threadworms
Horses usually develop immunity to threadworm at around 6 months of age. The worms can be transferred to young foals via the mare’s milk, which could make the foal more susceptible to diarrhoea and anaemia. It can also slow down their development so it’s important that they’re wormed against threadworm at around four weeks old; the mare could also be wormed while pregnant to reduce the risk.
6. Tapeworms
These can grow up to 20cm long and they can accumulate between the large and small intestines.
Symptoms:
- Respiratory problems
7. Botflies
These are a problem in the grazing season as they lay eggs on the horse’s coat that are then ingested when horses groom themselves or each other. Once swallowed they attach themselves to the stomach lining, before being passed out in the faeces.
SIGNS OF WORMS IN HORSES
- Weight loss
- Loose stools or diarrhoea
- Colic
- Pot belly
- Rough coat
- Developmental delay in young horses
- Cough/Nasal discharge
- Irritation around the tail area
HOW TO TEST
Regular testing can help monitor your horse’s worm count:
- FWEC – Faecal Worm Egg Counts detect the most common parasites. A sample of your horse’s faeces is sent to a lab to work out the number of worm eggs, and the results will determine whether or not you need to treat your horse, as well as what kind of wormer you should use.
- Saliva Test (EQUISAL) – This shows the level of tapeworm burden from a sample of your horse’s saliva. Moderate or high results will require a suitable wormer.
- Blood Test (ELISA) – A vet can assess your horse to see whether or not they should have this test, based on their age and earlier FWEC results. It can detect redworm larvae.
WHEN TO TEST
Worm counts should be done every eight to 12 weeks, but separate tests will be needed as a FWEC won’t pick up certain types and you need to work out which worms you need to target and which product to use. It’s recommended that all horses in the same paddock should be tested at the same time and remember to make a note of when you test your horse and the result, so you can track them.
THE BASICS OF WORMING YOUR HORSE
Your vet will tell you which product to use as there are different chemicals that target different parasites, your horse will also need to be weighed before any treatment to determine the dose. If your horse is new to worming, or is nervous, it might be a good idea to introduce a syringe slowly, before you have to give them their treatment. You could even put something they like in the syringe, like apple sauce, so that they associate it with something positive.
When giving them the wormer, hold your horse’s nose still while you slip the syringe into the corner of the mouth (you might need someone to help with this); you’re aiming for the back of the tongue. Try to make up for any spillages that don’t make it into the mouth as they need the full dose; the same stands for if you’re using tablets or liquid that can be mixed in with food.
Always clean up any spillages as chemical wormers can be dangerous for some animals and insects; e.g. certain dog breeds are at risk of ivermectin poisoning. It might help to keep your horse stabled for 48 hours after worming to prevent wildlife coming into contact with it via droppings, and to avoid contaminating other horses.
PREVENTION
Tips for preventing worm infestations:
- Clear away droppings regularly, ideally once a day, but at least twice a week. Worm eggs in droppings can turn into larvae in 5 days.
- Cross graze pastures with other animals to help break the cycle; equine worms can’t survive in sheep and cows.
- Rest and rotate paddocks – strong sunlight and hard frost help reduce to chances of eggs and larvae surviving.
WORMER RESISTANCE
Unfortunately, due to blanket worming practices, parasites are developing resistance to worming treatments, so they are becoming less effective. There are no new drugs in the pipeline but there are a few things we can do:
- A target-led programme – test your horses regularly and only worm according to the worm burden they have at that time.
- Make sure they have the right dose
- Good pasture management
Good pasture management and regular testing/worm counts can help manage and minimise the amount of worming your horse needs. Of course you want the best for your horse, but even the most well-looked after horses can become sick or injured and need veterinary care or treatment.
This is where horse insurance comes in; you start with one standard benefit of Death, Theft or Straying and then choose which of our optional benefits you want to add, including Vets Fees, Public Liability and Transportation, creating a bespoke policy that doesn’t leave you paying for what you don’t need. Take a look at our website, or give us a call for a free, no-strings quote today.
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