Parasites in horses: symptoms, treatment and prevention

What are parasites in horses?

Parasites in horses are defined as organisms that colonize on or in the horse's body and feed on their host (the horse). These parasites can include different types of worms, such as strongyles and roundworms, as well as other microorganisms such as lungworms and skin parasites such as mites and fly larvae. These parasites can cause a variety of health problems, from weight loss and dull coat to serious illness. It is therefore important to recognize and treat parasite infestations in horses at an early stage in order to maintain the animal's health and performance.

Types of parasites in horses

The list of parasites in horses is long, yet manageable. A distinction is made here between endoparasites and ectoparasites. The main difference between endoparasites and ectoparasites lies in their habitat inside or outside the host's body. Endoparasites live inside the horse's body, typically in the digestive tract or other organs, while ectoparasites live on the outer surface of the horse or in its immediate environment.

Both types of parasites can cause serious health problems in the horse, so it is important to take both preventative measures and appropriate treatments to minimize the risk of parasite infestation and protect the horse's health. Regular checks for parasite infestations and the use of appropriate preventative measures and treatments can help to maintain the horse's well-being and performance.

What are endoparasites in horses?

Endoparasites are organisms that reside within the body of their host and feed on its tissues or body fluids. In the context of horses, endoparasites mainly include different types of worms that live in the gastrointestinal tract of the horse. These worms include, for example, strongyles, roundworms and tapeworms.

Here you will find an overview of the types of worms that can infect your horse, how horses can become infected, what symptoms can occur and how these parasites are diagnosed:

These parasites can multiply in the horse's digestive system and become established there, which can lead to a number of health problems. If the population of endoparasites in the horse's body multiplies uncontrollably, they can damage the digestive tract, cause digestive disorders, impair nutrient absorption and even lead to serious illnesses.

Some endoparasites can also migrate to other organs of the horse and cause damage there. For example, lungworms can infect the horse's respiratory system and cause breathing problems.

‍3 Endoparasites in horses that you should know and what you can do about them

Small and large strongyles in horses

Small strongyles

As soon as the grazing season begins at the end of April or beginning of May, horses are increasingly exposed to small strongyles. These worms infect horses by ingesting infectious worm larvae in the pasture. The larvae pierce the intestinal mucosa in the large intestine and can migrate there for several months.

Encapsulation of the larvae: a survival mechanism

A special characteristic of the small strongyles is their ability to encapsulate themselves in the intestinal wall. This process is controlled by communication between adult worms and larvae:

• When enough egg-laying worms are present, they signal the larvae to encapsulate.
• The larvae can remain inactive in the capsule for up to three years.
• Only under favorable conditions do they continue their development into adult worms.

Symptoms of infection with small strongyles

An infestation with small strongyles can cause serious symptoms, including:

• Diarrhea
• Weight loss
• Colic
• Fever
• Edema (water retention in the lower abdomen and limbs)

Risk of larval cyathostominosis

Larval cyathostominosis occurs when encysted larvae are suddenly released from the intestinal wall. This disease causes massive damage to the intestinal mucosa and occurs particularly in spring.

• Main groups at risk:
  • Young horses up to 6 years of age are particularly affected.
  • This form of worm infestation can be fatal.

Diagnosis and treatment

Detection of the infestation

An infestation with small strongyles is detected by repeated fecal examinations according to the contemporary selective deworming strategy.

• Treatment is usually carried out from an infestation of 200 EpG (eggs per gram of feces).

Active ingredient moxidectin: the key to control

The treatment of encysted larvae is particularly challenging due to the resistance of active substances such as ivermectin.

• Moxidectin, a fat-soluble active ingredient, is the only approved agent that:
  • It penetrates the connective tissue capsule that surrounds the larvae.
  • Effectively kills the larvae in their dormant stage.
  • The main worm burden in the horse is sustainably reduced.

Limited effect of other preparations

Other approved preparations only combat the 10 % of larvae that are in the intestinal tube. They do not reliably prevent the outbreak of larval cyathostominosis and therefore do not offer comprehensive protection.

‍Thelarge strongyles

The large strongyles, also known as bloodworms (Strongylus vulgaris), pose a significant threat to the health of horses. Adult worms live in the cecum and large intestine, while their larvae migrate through the walls of the intestinal arteries. This migration can cause mucosal bleeding and inflammation, leading to colic and lameness. In severe cases, the larvae can cause vascular blockages or dilatations, which can be life-threatening if they rupture.

Infection route and development cycle

Infection occurs via the ingestion of larvae on contaminated pastures or in stables. Foals are particularly at risk during their first grazing period.

• Egg deposition: The females lay eggs in the intestine, which are excreted with the feces.
• Development into larvae: Within a few days, the eggs develop into infective larvae that are ingested by the horse.
• Larval migration: After ingestion, the larvae pass through various stages of development in the vascular walls before returning to the intestine, where they grow into sexually mature worms.

Symptoms of a bloodworm infestation

An infection with large strongyles can manifest itself through the following signs:

• Fever
• Loss of appetite
• Shaggy coat
• Colic

Prevention and treatment

• Diagnosis: A fecal examination can detect the infestation, although the migrating larvae are not directly detectable.
• Hygiene: Regular removal of droppings, keeping the stall walls dry and avoiding floor feeding are essential.
• Pasture management: Practices such as changing paddocks, intermediate mowing and draining swampy areas reduce the risk of infection.
• Worming: Regular worming is necessary to combat infections and prevent future infestations.

Whistletail (Oxyrius equi) 

The awl worm, also known as the anus worm, is a parasite that particularly affects stable horses. The adult worms live in the blind and large intestine and cause bleeding of the mucous membrane through their diet, which can lead to colic. Older horses are particularly susceptible to these parasites.

Development cycle

The female awl tails leave the intestine and lay their eggs in a viscous, sticky liquid - the so-called ice cords - in the anal region of the horse. These eggs fall into the bedding and are subsequently reabsorbed by the horse through feed or contact.

In the body, the larvae develop into sexually mature worms in several stages, starting the cycle all over again. This cycle quickly leads to the spread of the parasite if hygiene is poor.

Symptoms of an infestation

• Severe itching: The deposition of the ice cords causes severe itching in the anal area.
• Behavioral changes: Horses rub against objects more often, which can lead to skin injuries.
• Skin lesions: Chafing creates open areas that are susceptible to bacterial infections and can cause additional complications.

Diagnosis

Diagnosis is made by examining the anal region for the presence of egg strings. As eggs are often undetectable in the feces, a microscopic smear from the anal region is often taken to confirm the diagnosis.

Treatment and prevention

• Deworming agent:
  • Benzimidazoles such as fenbendazole and pyrantel have been shown to be effective. However, the effectiveness of pyrantel can vary.
• Hygiene:
  • Thorough washing of the anal region with soapy water removes the sticky ice cords and reduces their spread.
  • Regular changes of bedding and thorough cleaning of the hutch are essential to remove eggs from the environment.
• Prevention:
  • Avoid bottom feeding to reduce the intake of contaminated materials.
  • Ensure that the horses are regularly wormed and monitored.

Stomach fluke - The botfly

What are stomach bugs in horses?

Stomach flies, also known as stomach fl ies, are parasites that belong to the botfly genus. The species Gasterophilus intestinalis is most commonly found in horses. The females lay their eggs in the horse's coat, which are then ingested by the larvae and can cause damage in the horse's stomach.

What do stomach bugs do to horses?

The larvae of the stomach woodlouse can cause inflammation of the stomach lining in the horse's stomach, which can lead to symptoms such as listlessness, weight loss, dull coat and digestive disorders. A serious infestation can lead to severe damage to the stomach lining and even stomach ulcers.

Which active ingredient against stomach bugs in horses?

Worming treatments with active ingredients such as ivermectin or similar substances are used to treat stomach worms in horses . These active ingredients are effective against the larvae of the stomach worms and can help to reduce an infestation.

Which worming treatment for stomach worms in horses?

Choosing the right worming treatment for stomach worms in horses is crucial for effective treatment. Vets can help you choose the right product to suit your horse's individual needs.

When do you give worming treatment to a horse with stomach worms?

Deworming against stomach worms in horses is usually carried out in the fall-winter period, preferably between November and December. This is the time when parasite activity is at its highest and horses are at increased risk of infection. Some experts also recommend a second deworming in January to ensure that the last stomach lice are removed.

What are ectoparasites in horses?

Ectoparasites in horses are organisms that live outside the host's body and feed on its external tissues or body fluids. Unlike endoparasites, which reside inside the body, ectoparasites live on the surface of the horse's body or in its immediate environment. These ectoparasites can take various forms, including fleas, mites, ticks and certain types of fly larvae. They can settle in various parts of the horse's body, including the skin, coat, mane and tail. Some ectoparasites can also live in open wounds or skin lesions.

However, in addition to the typical symptoms by which we can recognize ectoparasites in horses, there are also serious secondary diseases that can be transmitted to the horse through the parasites' saliva, for example.

Which parasite transmits which secondary disease to our beloved horses?

Ectoparasites often cause a range of problems in horses. They can cause itching and skin irritation, leading to excessive scratching, rubbing or biting. This can lead to skin lesions, wounds and infections. In addition, some ectoparasites can transmit diseases, such as ticks, which can transmit Lyme disease.

4 common ectoparasites in horses: What you need to know!

Ticks, horseflies and co

Ticks, horseflies and other pests can also be a nuisance, especially in the summer months. A nice ride through woods, meadows or to the lake can quickly turn into an ordeal when the bloodsuckers are on the hunt. But you can quickly remedy this. Fly blankets and fly sprays can help you and your horse enormously to keep the horseflies and flies at bay. Fly repellent is available as a spray or as a gel, which is used especially for horses that are afraid of spray bottles.

➡️ Video tip: Don't be afraid of spray bottles! In this video, we show you practical tips on how to take away your horse's fear of spraying - for stress-free application of fly sprays and more serenity in summer!

The deer louse fly - a small parasite on horses

The deer louse fly (Lipoptena cervi) is an ectoparasite that can infest horses in particular. It is often referred to as a "flying tick" as it looks like a mixture of a fly and a tick. The deer louse fly is mainly active from July to October, i.e. during the warm season when there is a lot of vegetation. Rural areas with forests and tall grass are particularly affected, where the fly can easily find its hosts.

How does the deer louse fly infest the horse?

The deer louse fly can fall onto the horse during a ride or walk. It then moves specifically to typical infested areas, such as the mane crest or the anus region. Many horses react nervously when the flies are nearby, even before they land on the horse.

Symptoms of the deer louse fly in horses

• Painful bites: The bite of the deer louse fly can be painful for the horse and cause skin irritation.
• Allergic reactions: Some horses are allergic to the saliva of the deer louse fly, which can lead to severe itching and skin rashes.
• Restlessness and nervousness: Many horses show conspicuous behavior and discomfort because the parasites are extremely unpleasant.

Can the deer louse fly transmit diseases?

Although the deer louse fly carries bacteria such as Bartonella schoenbuchensis in horses, it has not yet been clarified whether these can actually be transmitted to horses or humans in the event of a bite. Nevertheless, caution is advised as the consequences of an infestation can be considerable.

What helps against the deer louse fly in horses?

Prevention against deer louse flies

• Insect repellents: Special products against deer lice flies in horses can help to prevent infestation.
• Fly rugs: These effectively protect the horse from bites.
• Natural household remedies: Products such as coconut oil are often used because their smell has a deterrent effect on flies.

Control of the deer louse fly in horses

• Spraying: If an infestation is suspected, it helps to spray the horse thoroughly with a hose to remove the flies from the coat.
• Thorough care: Regular brushing can help to remove flies and detect skin reactions.
• Hygiene in the barn: Cleanliness and regular maintenance of the environment can reduce the risk of infestation.

Which remedy helps against the deer louse fly in horses?

In addition to chemical insect repellents, there are also natural approaches such as coconut oil, which is popular as a home remedy against the deer louse fly in horses due to its deterrent effect. Both approaches can be combined to ensure comprehensive protection.

Mites in horses: sucking mite, burrowing mite & co

Scabies in horses? What is it and what do sucking mites, scaly mites and burrowing mites have to do with it? How can you tell if a horse is infested with these mites? Burrowing mites and other mite species are ectoparasites that can infest horses and belong to the mite family. These tiny, wingless parasites feed on dander and can live in the horse's coat or on its skin. The three most common types of mites in horses are Chorioptes equi (dandruff-eating mites), Sarcoptes scabiei (burrowing mites) and Psoroptes equi (sucking mites).

Mite infestation is a serious problem that can affect the health and well-being of our horses. To minimize this risk and provide a healthy environment for our beloved four-legged friends, cleanliness and hygiene in the stables are crucial.
Regular grooming and cleaning of the horses are essential to prevent mite infestation. This includes regular brushing and washing of horses to remove dirt and potential mites. Particular attention should be paid to the areas around the ears, under the mane and on the legs, as mites like to settle there.
As soon as a mite infestation is detected, quick action is required, as mites can multiply quickly. It is important to consult a vet to obtain the appropriate treatment. Various medications are available on the market that are effective against mites. In addition, some home remedies have also proven to be effective.
To prevent re-infestation with mites, it is important to treat the entire horse population, even if only one horse is affected. In addition, all equipment such as saddles, bridles and blankets should be thoroughly cleaned and disinfected to prevent the mites from spreading.

Hair lice in horses

What are hair lice and what do hair lice look like on horses?

Hair lice (Wereckiella equi) are ectoparasites that occur frequently in horses. Especially in warm and humid climates in fall and spring , they multiply rapidly and can infest entire herds of horses. It is normal for horses to carry a small amount of hair lice, but if there is severe itching and they are visible to the naked eye, this indicates an infestation that is too severe and needs to be treated. Hair lice are about 1.5 mm long, sometimes slightly larger, and have a rice grain shaped body with yellow and brown stripes.

The lifespan of a hair louse is around 40 to 60 days, during which it can produce up to 100 eggs. These eggs are laid in nests that form small, whitish piles, usually at the root of the hair. After about 10 days, young nymphs hatch from the eggs, which already look like adult hair lice, but are smaller. They are able to reproduce after a short time, which can lead to a rapid spread of the infection.

Hair lice feed on skin flakes and hair, which leads to hair loss that often looks particularly chewed up. They bite and chew off the hair just above the skin, resulting in a patchy coat. Hair lice can also be transmitted to humans through contact with infected horses, although this is rare. Infected horses can also transmit the hair lice to other stable animals such as dogs and cats, so it is important to contain an infestation as soon as possible.

Does my horse have hair lice?

Symptoms of a hair lice infestation in horses include severe itching and a patchy coat as well as restlessness and unhappiness. Some horses react aggressively under the rider , bucking or rubbing themselves bloody, which can lead to further skin problems, such as sores and moulting. Treating a hair lice infestation is therefore essential to ensure the horse's well-being and prevent the infection from spreading further.

What kills hair lice in horses?

To combat hair lice, you should make the parasites' habitat unpleasant. If the infestation is severe, it is necessary to shear the horse and cut off the legs. A vet should be consulted. Ivermectin can be effective, but the hygiene concept must also be adapted. Alternatively, spray or wash lotions can be used, but with caution due to substances that are toxic to water.

Home remedies for hair lice

The use of coconut oil, neem oil, tea tree oil and black cumin oil is possible, but irritating and without confirmed effect. Diatomaceous earth can attack hair lice, but should not be inhaled. Thorough cleaning of the stable environment and changing the bedding are important. Blankets, grooming materials and equipment should be removed and cleaned if infested. Repeated treatments are required every 14 days to prevent re-infestation.

Worming treatment: the panacea for all worms in horses?

To minimize the risk of endoparasite infestation in horses, regular deworming is crucial. Veterinarians can recommend deworming programs that are tailored to the individual needs of the horse. It is important to strictly adhere to these programs to ensure effective control of the endoparasite population and maintain the horse's health.

➡️ Video tip: Giving worming treatment stress-free! Learn how to make it easier to give your horse worming treatment or medication by mouth - as easy as scraping out hooves!

Deworming strategy 1: The flat-rate worming treatment

The flat-rate quarterly worming treatment was the standard practice for parasite control in horses for many years. This method was introduced to combat the large strongyles in particular, which were widespread at the time. Today, however, these parasites are hardly present in many herds and the method is increasingly viewed critically.

Procedure:

• All horses are wormed quarterly, without prior diagnosis as to whether there is actually a parasite infestation.
• A fixed deworming schedule made this strategy easy to implement and widely used.

Problems:

• Development of resistance:
  The regular and often unnecessary use of worming treatments has allowed parasites to become accustomed to the active ingredients and develop resistance. This resistance means that worming treatments lose their effectiveness and the parasites survive in the horse.
• No individual adaptation:
  As no diagnostics are carried out, no distinction is made as to whether a horse is actually infected or not. This leads to unnecessary drug exposure for the horses and their environment.

Conclusion:

‍The blanket worming treatment is considered outdated. If you want to protect your horse effectively, you should use targeted and diagnosis-based methods to avoid resistance and promote the horse's long-term health.

Deworming strategy 2: Strategic deworming

Strategic worming is a more modern alternative to the blanket method. It combines regular examinations with targeted, needs-based deworming. This strategy strikes a balance between blanket and selective deworming and therefore offers a more effective and sustainable solution.

Procedure:

• Regular fecal examinations:
  Fecal samples are analyzed at regular intervals to determine whether there is a parasite infestation.
• Targeted treatment:
  Targeted deworming with an active ingredient is only carried out if an infestation is proven and is changed in consultation with the vet to prevent resistance.

Advantages:

• Better control:
  The parasite load is monitored and treatments are only given when necessary. This protects the health of the horses and reduces the burden of unnecessary medication.
• Avoidance of resistance:
  The risk of resistance is significantly reduced by regularly changing the active ingredients.
• Sustainability:
  The targeted use of worm cures contributes to environmental protection, as less medication is released into the environment.

Challenges:

• The method is associated with higher costs, as fecal samples have to be analyzed.
• It requires more effort, as the treatment plans have to be individually adapted to the horses.

Conclusion:

‍Despitethe extra effort involved, the benefits of strategic worming clearly outweigh the disadvantages. It is a recommended method for horse owners who want to rely on sustainable and effective parasite control.

Deworming strategy 3: Selective deworming

Selective deworming is one of the most effective strategies, especially for controlling the small strongyles that horses often pick up on pasture. This method is mainly used for adult horses.

But how do you switch from blanket deworming to selective deworming and is this the best way for the horse?

‍Procedure:

• Fecal sample monitoring:
  • In the first year, fecal samples should be examined four times a year for parasites such as small strongyles, roundworms, tapeworms and awl tails.
  • This cycle starts in April/May and lasts until October/November.
• Deworming if necessary:
  Deworming is only carried out if the fecal sample result shows a value of over 200 eggs per gram (EPG) or other parasites are detected.

Advantages:

• Reduces the unnecessary use of worming treatments and prevents the development of resistance.
• The method provides clear information about the parasite load in the horse through regular fecal samples.
• However, annual deworming is recommended regardless of the fecal sample results in order to cover certain parasites such as tapeworms or awl tails.

Challenges:

• Inaccuracy: The number of worm eggs in the feces does not always correspond to the actual number of parasites in the intestine. A horse can still carry a considerable parasite load with just a few worm eggs in its feces.
• Costs: Fecal sample tests cost between €9 and €40 per test, depending on the provider.

Conclusion:‍

Selective worming is particularly suitable for adult horses and offers individual and effective parasite control. The regular effort pays off through the targeted use of worming treatments and the long-term health of the horses.

Deworming strategy 4: Modern selective deworming

The difference between selective deworming and modern selective deworming lies mainly in the diagnosis and treatment strategy.

Modern selective deworming is a further development of selective deworming and is based on more comprehensive diagnostics.

Procedure:

• In addition to the analysis of fecal samples, other factors are taken into account, such as the presence of specific parasite species in the herd.
• The treatment strategy is based not only on the fecal sample results, but also on an overall assessment of the individual circumstances.

Advantages:

• Holistic approach: This method combines scientific knowledge with practical experience and takes into account the specific needs of each horse.
• Effectiveness monitoring: Regular monitoring of the parasite load allows the effectiveness of the treatments to be accurately assessed.
• Sustainability: The targeted use of wormers reduces the burden of medication and contributes to environmental friendliness.

Conclusion:

‍Thisstrategy offers a modern and sustainable approach based on scientific principles. It ensures effective control of endoparasites and supports the long-term health of horses.

FAQ: Worms and parasites in horses

How long does a horse shed worms after worming?

After a successful worming treatment, it is important to know that your horse may shed more worms over the next three days. Deworming always takes place on a fixed date and it is crucial that the horses can excrete an increased amount of larvae, eggs and adult worms in the following days after treatment. It is therefore advisable not to let the horses out to pasture together after deworming and the stalls should be thoroughly cleaned to minimize the spread of parasites.

Are the worms killed after the worming treatment?

The effect of a worming treatment on all worms in the horse depends on various factors. As described in the section on worming treatment: the panacea for all worms in horses?

 resistant worms can survive deworming, while sensitive worms are killed. Complete eradication of all worms is therefore not guaranteed, especially if resistant worms are present.

To maximize the effectiveness of deworming and prevent the development of resistance, various measures are required. These include selective deworming based on fecal sample testing to treat only horses with a high worm infestation, as well as avoiding excessive deworming to maintain a refuge for non-resistant worms.

It is important to follow the vet's instructions carefully and to monitor the horse regularly for parasites in order to develop appropriate deworming strategies and avoid resistance.

Can worms cause itching in horses?

Yes, worms can cause itching in horses. When a horse is infested with worms, various symptoms can occur, including itching. This itching can be caused by the movement of worms in the gut, eggs in the anus area or allergic reactions to worm larvae or dying worms. It is important to carry out regular worming programs and have the horse's health checked regularly by a vet to prevent or treat worm infestations.

How do I know if my horse has worms?

There are several signs that can indicate that a horse is infested with worms. Here are some common symptoms:

• Weight loss or poor coat condition despite adequate feeding.
• Loss of appetite or sudden changes in eating behavior.
• Abdominal pain or colic.
• Diarrhea or altered consistency of the feces.
• Anemia can lead to fatigue and poor performance.
• Itching at the anus or base of the tail.
• Cough, especially in the case of infections with lungworms.

It is important to regularly examine your horse's feces and consult a veterinarian if worm infestation is suspected. Your veterinarian can perform a fecal examination to determine if and what type of worms are present and give you appropriate deworming recommendations.

What can you feed your horse for worms?

There are no specific foods that can directly help a horse against worm infestation. The best way to control worm infestations is regular worming and good management to reduce the likelihood of infection.

Here are some general management practices that can help reduce the risk of worm infestation:

• Regular deworming according to your vet's recommendations.
• ‍Pasture hygiene: Keep pastures clean and remove droppings regularly to reduce the spread of worm eggs.
• Rotational grazing: Avoid overgrazing by regularly rotating horses between different grazing areas.
• Remove horse droppings regularly, both in the pasture and in stables or paddocks.
• Avoid feeding hay or straw on a dirty floor to minimize contamination with worm eggs.
• Observe hygiene practices when handling and feeding horses to reduce the transmission of worm eggs.

However, a healthy diet rich in fiber and nutrients can help support the horse's overall health, which in turn can improve its ability to fight off worm infections. Talk to your vet about the best way to feed your horse to ensure it is getting all the nutrients it needs.

What helps against the deer louse fly?

It can be helpful to remove this annoying parasite with a fine-toothed comb. The most effective and quickest way, however, is to wash the horse or dog with water. The water causes the deer louse fly to lose its grip and is flushed out of the coat. It is also recommended that humans take a shower as quickly as possible, as the bite of the deer louse fly can also be very unpleasant or even painful for humans.

Why does a horse get mites?

A horse can get mites for various reasons. Mites are natural inhabitants of the horse's environment and are often omnipresent. They feed on the horse's dander and blood. However, under certain conditions, such as a weakened horse's immune system or humid, warm environments, mites can proliferate and lead to an infestation. Factors such as luxuriant coats and long manes, which offer ideal hiding places, as well as a lack of hygiene, immunodeficiency, infections or malnutrition can also increase the horse's susceptibility to mite infestation.