Horses regularly get infected with worms – this is completely normal. But to prevent worm infestation from getting out of control and your four-legged friend from suffering, there are a few things you can do. In our guide, you will learn how horses get infected, what the possible symptoms of worm infestation look like, what deworming methods are available and how you can best protect your horse.
Infection: How does my horse get infected with worms?
In most cases, horses ingest the parasites through their feed. The foal can also become infected with worm larvae through its mother’s milk – this is known as lactogenic ingestion. These then develop further in the intestine. Another transmission route is percutaneous infection – i.e. infection through the skin.
If a horse is infected within a herd, it can pass the parasites on to the other animals. If a horse comes into contact with the horse droppings of its infected conspecific, this is often enough for it to become infected. Even if the animals groom each other’s coats, they can transmit the pathogens.
Horses are permanently infected
As a horse owner, you should know that there is no such thing as a completely worm-free horse. Horses are permanently infected with worms. This cannot be prevented. In principle, a certain infestation of parasites is actually a positive thing, because it boosts the horse’s immune system and keeps defense mechanisms going. So with a low parasite infestation, horses usually have no problems.
Eradicating worms completely is therefore not the goal in parasite control. The infestation should only be reduced to a tolerable level. Parasites are so well adapted to horses and their habitats that complete eradication is not possible. You should be prepared for the fact that your horse will become infected again. Only a new deworming will help. However, you can also do a few things to keep the infestation as low as possible.
What are the most common types of worms in horses?
A variety of worms can occur in horses. But don’t worry – almost all worm species can be treated well. The primary place where parasites spread is the intestine. However, there are also a few types of worms that lodge in the lungs and cause symptoms there.
These are the most common worms:
Tapeworm in horses: Tapeworms become a problem especially during the second half of the grazing season. Infection of horses often occurs via moss mites. Roundworms: Roundworms are among the most common worms in foals. Roundworm eggs are shed in large masses and can survive in the environment for years.
Greater strongylids: Also known as large pallisad worms, these parasites are considered one of the greatest parasitic threats to horses within Europe. If affected animals are not treated, they can die.
Small Strongylids: This type of worm is also called lesser pallisaden worms. They are among the most common worms in horses. During the cold season, the larvae rest encapsulated in the intestinal wall of affected animals, and in the spring, the larvae can migrate en masse.
Dwarf threadworms: Newborn horses in particular become infected with this worm species while drinking from their mothers. The consequences are, for example, eczema or irritation of the skin.
Awl tails: Infection with awl tails often occurs in the stable. Affected horses suffer from severe itching in the region around the anus, often leaving the tail rump scoured bare.
Stomachworms: The small, whitish stomach worms cause disturbances in the gastrointestinal tract. For example, the stomach lining may become inflamed.
Lungworms: Lungworms infest the horse’s respiratory tract, which can cause breathing discomfort, coughing and weight loss.
Botflies: There are, for example, the stomach borers, which lay their eggs in the horse’s coat. When the horse licks these areas during its grooming and the eggs come into contact with saliva, the larvae hatch. They enter the oral cavity and from here to the stomach and intestines.
Symptoms: How do I recognize worm infestation in my horse?
It is difficult to tell with the naked eye if a horse is infested with worms. In most cases, the infestation only becomes apparent when the parasites have already spread to a great extent. Accordingly, a worm infestation can go unnoticed for a long period of time.
Depending on which organs and which sections of the organs are infested, the horses show different symptoms. Often, the general condition is impaired.
The following symptoms may occur when a horse is infested with worms:
Dull, lackluster coat
Loss of appetite and weight
Bare chafed tail rump
Diagnosis: How are worms detected in horses?
If you suspect that your horse may be infested with worms, you must have this clarified by a veterinarian. The vet will ask you questions about your horse’s attitude, feeding, herd and worm prophylaxis, and will examine your horse thoroughly. Since the majority of worm species are not visible to the naked eye, the veterinarian will take a fecal sample and examine it under a microscope.
Some worms are not permanently excreted by the horse, so it is sometimes necessary to examine several fecal samples. In some cases, a blood sample is also taken. With the help of the blood, the veterinarian determines inflammation levels in the body. A certain percentage of inflammatory cells may be elevated due to the worms.
Deworming: What to do in case of worm infestation of the horse?
In general, there are two ways to combat worm infestation in horses and thus limit the health consequences for the animals:
Application of so-called anthelmintics (dewormers). Consistent implementation of hygiene measures.
Medication: What are the treatment options?
The veterinarian can prescribe dewormers as medications to effectively treat the worms. There are several preparations available for deworming with different active ingredients. However, these are only effective against certain worms and do not cover the entire worm spectrum.
Active ingredients commonly used for deworming in horses:
Regular deworming prophylaxis with changing active ingredients is often recommended because worms develop resistance to certain active ingredients and dewormers become ineffective. Therefore, it is important not to always use the same worming agent for deworming. Unfortunately, there are now also reports that horse worms have become resistant to several active substances. Further down in the text, we will go into more detail on how to combat resistance.
Resistance: Worms in horses despite worming treatment?
For some time now, it has been observed that worms are becoming increasingly insensitive (resistant) to deworming agents. They manage to survive despite the medication. This means that horses get sick even though they are treated, and the parasites can continue to spread in the equine environment.
Deworming frequency: How often should you deworm your horse?
To prevent further resistance, it is recommended to deworm only as often as absolutely necessary. For this, especially the “high excretors” of a herd should be treated. Especially small strongylids in adult horses should be controlled with this “selective deworming”. For this purpose, fecal samples must be examined from all horses.
Strategic control”, on the other hand, is based on an age-group-specific concept for deworming in order to avoid resistant worms. Foals and young animals in particular should be treated less frequently. Regular fecal examinations also help here.
Discuss with your veterinarian which approach to deworming is right for your horse in its specific husbandry. He will select a suitable active ingredient individually.
Prevention: What hygiene measures should you pay attention to when keeping horses?
To reduce the development of resistance to anthelmintics, prophylactic measures are becoming increasingly important.
To reduce the infection pressure with worms, carry out the following measures:
Hygiene in the stable: – Muck out daily! – Clean the horse stalls, drinkers, grids etc. regularly! – Disinfect at least once a year with a disinfectant! – Put the feed in feeding troughs if possible! This prevents contact between feed and excrement that may be contaminated with eggs or larvae. TIP: In our guidebook “Mucking out horse stalls properly – all not so much manure!” you will learn interesting facts about the proper mucking out of horse stalls.
Hygiene in the pasture: – Remove horse droppings daily if possible, at least once a week! – Use spring pruning to reduce overwintered larvae! – Remove horny spots! – Let the pastures be grazed alternately! – Adjust the stocking density to the grazing conditions! – It is better not to fertilize with horse manure! – Apply calcium cyanamide to the pasture in spring! This promotes the growth of the grass and reduces the number of parasites in the soil as well as on the green fodder.
Horse hygiene: – Rub the horse’s chest and legs with a warm, damp cloth about twice a week during the summer and fall to remove botfly eggs. – Clean the anus area daily if your horse suffers from warble fly infestations. This will remove the ice strings from the weevil tails.
What else can you look out for?
For foals, the first deworming against the dwarf nematode can be done one week after birth. If your mare is pregnant, she will need to be treated for Dwarf Nematodes at the end of pregnancy or shortly after foaling to prevent the newborn from becoming infected with the parasites. If a new horse is to be integrated into your herd, it must be examined for worms and treated with a worming treatment if necessary. Separate the horse for a few days.
Then you remove the bedding from the stall, clean and disinfect it. You should also consider the timing of deworming. A good time for deworming is, for example, in the spring, a few days before grazing begins. In this way you prevent the horse pastures from being loaded with worms and the horses in the herd from infecting each other.
Homeopathy: Can worms in horses be treated homeopathically?
If you want to worm your horse successfully, worming with the active ingredients listed above remains the remedy of choice. However, you can support your four-legged friend with homeopathic remedies that strengthen the mucous membrane of the intestine and the immune system.
If you are looking for a veterinarian who can advise you accordingly, you can contact the Association for Veterinary Naturopathy. Here you can find a veterinarian in your area who knows homeopathy.
My name is Mark and the senior editor
I take great pride in being the best possible author and giving you the knowledge that i have on all different types of animals!
I have spent a lifetime learning about pets and animals, and have worked in the pet and vet industry for over 20 years now!
The website will draw have authors who are vets, pet owners, and local pet breeders. All who will contribute their fantastic knowledge which in turn will be able to help you i hope.
There is a lot of information on the internet so it may be hard to know where exactly is the best place to start learning. But we will write articles that get straight to the point, and give you all the information that you need with no fluff!
If you have any questions please leave a comment on the article, and i will reply to you!