Equine Metabolic Syndrome and Human Diabetes Mellitus

Diabetes mellitus is a metabolic disease in which high levels of glucose are found in the blood and therefore in the urine.

In a normal situation the body’s insulin is in charge of regulating glucose levels by moving blood glucose into the tissues where it will be used to produce energy.

When diabetes mellitus is present, it can be due to a lack of production of insulin or a decreased sensitivity of the tissues to it, consequently there will be a failure in the transport of glucose outside the bloodstream. Two types of diabetes mellitus are described:

Diabetes mellitus type I: there is a decreased production of insulin by the cells of the pancreas, so there are low levels of insulin in the blood. This is associated with an immune-mediated cause. It is less common that type-2 diabetes.

Diabetes mellitus type 2: there is not enough production of insulin or the cells become resistant to it.  It appears to be more common in humans than type 1 diabetes.

Although diabetes mellitus is uncommon in horses, there is a condition called Equine Metabolic Syndrome (EMS) that has few similarities with diabetes mellitus type 2. 

The term EMS in horses defines a group of risk factors for the development of laminitis. Obesity is one risk factor. This can be generalised or focalised in certain areas of the horses bodies like around the base of the tail, over the eyes, behind the shoulders, on the crest of the neck. Other risk factors include being a ‘’good doer’’, difficulty in losing weight and abnormal insulin responses.

Obesity is defined by the World Health Organisation as abnormal or excessive fat accumulation that presents a risk to health. Like in human’s diabetes mellitus, obesity in horses plays a main role in the development of EMS. Fat tissue secrete hormones that have an adverse effect and it seems to be associated with the development of insulin resistance, inflammatory conditions and cardiovascular function.

Similarly to human diabetes mellitus type 2, in horses with EMS we find high insulin level in the blood. Insulin levels can be persistently high or have a high response to food consumption which is called post-prandial hyperinsulinemia. The situation where there is a failure of the tissues to respond to the hormone is called insulin resistance. Furthermore, in diabetes mellitus the body frequently fails to produce enough insulin to control glucose levels. Whereas high insulin levels in human associated with cardiovascular disease, in horses the severe complication linked to this condition is the development of laminitis.

The exact process in which laminitis is developed consequently to insulin resistance is not completely understood. However, it is likely to be a damage and constriction of the blood vessels cells that will affect blood support to the hoof as well as a direct damage to the horn cells.

EMS is more common in certain breeds like Shetland, Dartmoor, Welsh and Morgan ponies and donkeys. Like diabetes mellitus type 2 in humans, it is less common in younger ages and it is associated with low exercise lifestyles and high sugar diets.

In both conditions, a presumptive diagnosis can be made based in the presence of overweight and history of related condition like laminitis in the horse. However, final diagnosis of EMS can be made by different laboratory testing.

– Measurement of basal insulin levels. This is achieve by taking a single blood sample. However, it can be normal in some horses so further test will need to be used (as the one described below).

– Testing insulin level as response to feed (Oral glucose/karo test): The horses are fed with some glucose in form of syrup and two blood samples are taken between 60-90 min after. This test will show the presence of post-prandial hyperinsulinemia. There are other dynamics test similar to this that require intra-venous administration of glucose are available but they are less easy to do in the field.

– Other tests that can be helpful in the identification of EMS is the detection in the blood samples of certain hormones like adiponectin which is a hormone associated to fat.

Differently to diabetes mellitus, in EMS glucose levels are not as important in the diagnosis as insulin levels are. However, some of the tests are similar.

For both condition, the treatment and prevention will be directed to management of diet and exercise. Therefore, the goal is to reduce weight and increase insulin sensitivity in tissues and their associated complications. EMS dietary restrictions are based on low soluble sugar and starches. Also exercise schedules are very important. Medical treatment of horses with insulin resistance is currently based on the use of metformine with is one of the drugs used in the treatment of diabetes mellitus type 2. This drug acts at the intestinal level limiting the high postprandial insulin.

As diabetes mellitus, EMS is an important condition with potential severe complications that require prompt detection and management but we are here to help so if you think your horse might have one of the risks factor mentioned before please give us a ring and we will be more than happy to help you.

Laser Surgery As A Treatment For Sarcoids In Horses

What Are Sarcoids?
Equine sarcoids are the most common skin tumour in the horse, accounting for 40% of all equine cancers. They are locally invasive tumours which are variable in appearance, location and rate of growth. Sarcoids are caused by Bovine Papilloma Virus, which may be spread by flies. Not all horses that are exposed to the virus develop sarcoids but, it appears that some horses are more susceptible than others. This also explains why horses that have sarcoids will stay susceptible and are more likely to grow additional sarcoids. People are often concerned about whether sarcoids are contagious because of the viral cause. No proof has yet been found that shows horse to horse contact can cause horses to develop sarcoids.
Sarcoids mainly occur around the head and in the groin and axilla area.
They seldom affect a horse’s usefulness, unless they are in a position likely to be abraded by tack. They do not usually resolve on their own and most horses develop multiple sarcoids.

Types of Sarcoids
Nodular sarcoids–are firm spherical nodules found under normal looking skin. They can be variable in size and can become ulcerated.
Verrucous sarcoids–are slow growing, flat scaly tumours that look like warts. They can also look like ringworm or scars.
Fibroblastic sarcoids–are fleshy lumps which often ulcerate, because they grow rapidly. They often occur in clusters and have an irregular shape.
Occult sarcoids–are flat hairless patches that occur mostly around the eyes, mouth and neck.
Malignant sarcoids –highly aggressive and these spread via lymphatic vessels, which results in lines of sarcoids spreading from the original sarcoid.

Sarcoids can, in some occasions, be confused with other tumours. Although a biopsy can give more information into what kind of tumour your horse has, taking a small sample of a sarcoid can cause the lump to start growing rapidly. Because sarcoids are the most likely diagnosis for these lumps, your vet will most likely suggest complete removal and possible sending the tissue off to a lab for histopathology, which can determine if the lump was in fact a sarcoid.

Treatment or removal of sarcoids are not always necessary but, when treatment is required it can prove difficult and possibly expensive. Sarcoids can regrow after treatment and no treatment as of yet is 100 % successful. Success rates vary between types of treatment. It is important to note that every treatment failure , reduces the success rates of future attempts.

-Ligation; where the sarcoid blood supply is cut off, causing it to shrink and drop off over time. Recurrence rates are more then 50%.
-Creams; there are various types, some more irritant to the skin than others and some have to be applied by your vet. They have a success rate of 40-60%.
-Injections; A chemotherapy drug injected into nodular and fibroblastic sarcoids causing the lesions to regress but can cause local swelling and sometimes injections need repeating.
-Radiation therapy; Iridium wires are inserted into a sarcoid to destroy it. It is the most effective treatment method but is very expensive and not widely available
-Laser Removal; is a surgical instrument that cuts into and vaporizes soft tissue with minimal bleeding. The wound that the horse is left with heals very well on its own. This treatment has one of the highest success rates with 80-90 % of horses not re-growing the sarcoid that was treated and, 70% of horses did not develop new sarcoids.
On the rare occasion that sarcoids regress on their own, these horses seem to develop immunity and do not develop further sarcoids. Please talk to your vet for more information on treatment options.

Failure Of Passive Transfer

What is failure of passive transfer? 

Failure of passive transfer (FPT) occurs when a new-born foal does not consume enough of the mares’ colostrum in the first 24-48 hours of life. The colostrum contains immunoglobulin antibodies (IgG and IgM) that are required for the majority of their immunologic protection against the pathogens they encounter in the first few days of life. The intake of this vital colostrum must occur before 48 hours (ideally in the first 8 hours) after birth as the cells required to transport the antibodies into the bloodstream are lost by the foal.

How do I know if my foal has FPT?

It is almost impossible to tell in the first few days of life if your foal has not ingested enough colostrum. The consequences of this will be seen as various recurrent infections in the first few weeks of life. Therefore what we recommend is that you have a vet perform a blood test on your foal in the first 12-24 hours of life and check the level of the IgG antibody. A reading of less than 200mg/dL indicates complete lack of transfer. A reading in-between 200 and 800 mg/dL indicates partial lack of transfer. Both readings require treatment. A normal reading is one above 800mg/dL.

What to do if my foal is diagnosed with FPT?

In cases where FPT is diagnosed after 12 hours, your foal will require an intravenous plasma transfusion containing the IgG antibody. These commercial sources of plasma are very safe as all donors are free of infectious disease. The amount of plasma given to an FPT foal will depend on the degree of failed transfer and the size of the foal, but is usually in the 2-4L range. The vet will test the blood after treatment to ensure an adequate level of antibodies.

What causes my foal to ingest inadequate colostrum?

Problems with the mare and problems with the foal can cause FPT. Examples of problems with the mare are early production of colostrum so it is expelled before birth, no milk production, poor quality colostrum production, lack of maternal cooperation and unfortunately mare death. With foals, premature birth of the foal can lead to problems such as inability to feed, or inability of the intestine to absorb the antibodies. In cases where you the know foal will not receive colostrum, ie mare death or early production, you can feed the foal colostrum from a previous colostrum bank or commercial frozen colostrum in the first 8 hours of life.

Ways to prevent FPT

As the prognosis for untreated FPT can be very poor, having ideas of how to minimise the risk are very useful. Having a colostrum bank or an alternative source of colostrum is a must. A colostrum bank is achieved by milking 250ml of colostrum off a mare after their foal has had its first suckle. If this is done from multiple mares, you will have enough for one foal. This colostrum can be stored at -4°C for up to 1 year. Other management strategies to undertake are observing all foaling’s to ensure normal parturition and early suckling, and to ensure a clean environment for foaling.

OCD – Osteochondritis Dissecans

Osteochondritis dissecans (OCD) is a relatively common developmental disease that affects the cartilage and bone in the joints of horses. OCD can occur in all breeds, especially in big size horses, and can show clinical signs in up to 30% of them. Cartilage in joints with OCD doesn’t grow normally causing it and the bone underneath to become irregular in thickness and weaker until they develop into flaps that can either remain partially attached to the bone or break off and float around in the joint. These loose flaps cause inflammation in the joint and predispose it to arthritis.

What causes OCDs?

OCD is a multifactorial disease that can be caused by:

  • Rapid growth
  • Diets very high in energy or have an imbalance in trace minerals
  • Genetics
  • Hormonal imbalances
  • Trauma

How do you spot it?

The most common sign is swelling in the joint of a young horse between 4 months and 2 years of age but may not occur until they are brought into work. The grade of lameness varies with location and severity of the OCD. OCDs can occur in all joints but they occur most frequently in the hock, stifle and fetlock.

How do we diagnose it?

The vet will need to do a physical examination with lameness workup and radiographs. OCD is often bilateral and the vet would suggest taking radiographs of the opposite joint, even if there is little or no swelling in that joint. Sometimes older horses are diagnosed with OCD incidentally without apparent clinical signs. X-rays only show bone clearly and not cartilage so sometimes it is necessary to enter the joint surgically (through an arthroscopy) to assess the degree of damage under general anaesthesia.

How do you treat it?

The best treatment is surgical removal of the abnormal bone and cartilage is through arthroscopy under general anaesthesia. Arthroscopy is performed by making two or more small incisions into the joint through which a small camera called an arthroscope and other specially designed instruments are placed. Aftercare recommendations depends on the location and severity of the OCD but they always require a period of box rest followed by progressive exercise with full return to training in several months.

What’s the prognosis?

Prognosis for athletic function is good to excellent for most OCDs that are treated surgically but depends on the location and the severity of the OCD. In general, if the OCD lesion is not removed the prognosis for future soundness will be decreased.

Artificial Insemination

Artificial Insemination (A.I) is a technique used to transfer semen from a stallion into the uterus of a mare during the correct stage of her oestrus cycle. A.I has become very popular in stud medicine for the advantages that it offers compare to natural covering (though not allowed in racing thoroughbreds), but, as much as it’s exciting breeding from your own mare, it’s important to understand how it works and the pros and cons before deciding to take this route.

What are the advantages of A.I

  • You can choose a stallion that is competing without interrupting his schedule
  • Allows you to choose the best stallion for your mare from all around the world and too far away to make natural covering viable
  • You can choose a stallion of which semen was frozen before his death or castration
  • Improve bloodlines for a rare breed also encouraging its geographical spread
  • Reduce risk of breeding injuries to both the mare and the stallion
  • More disease control by preventing skin contact such as in natural service and also by checking the stallion with swabs for Contagious Equine Metritis (CEM) and blood test for Equine Viral Arteritis (EVA) and Equine Infectious Anaemia (EIA) every year before the semen collection
  • Permits use of valuable stallions and mare with breeding problems
  • Allows mares to be bred at the best time for conception
  • Permits evaluation of semen at each collection and immediate recognition of minor changes in seminal quality.

 What are the disadvantages of A.I

  • Cost
  • AI with chilled or frozen semen generally has a lower conception rate (chance of producing an embryo) than natural covering
  • Risk to the mare when performing rectal examinations
  • Like for natural covering, AI does not always result in a live foal the following year.

Semen presentation

Management of the mare and timing of insemination will be determined by which semen is chosen (fresh, chilled or frozen) but it is also very important to check in which of the three ways the semen is preserved best and travels best for the specific stallion.

Fresh semen

Fresh semen is usually used on studs and only lasts outside the horse for short periods of time. It always has the highest fertility but mares and stallions need to be at the same location for insemination. Also fresh semen is usually the least expensive method, because requires no processing and less frequent veterinary checks.

Chilled semen

The semen gets refrigerated immediately after collection and transported in chiller packs either by post or manual collection, staying viable for 2-3 days. The conception rates are greater than for frozen semen. With chilled semen it’s important to find out which days of the week the stud collects from the stallion and how much notice you will have to give for them to collect and send the semen.

Frozen semen

After collection the semen is separated and added to a preservative. It is then frozen and stored below freezing, usually in dry ice. The semen can then be transported great distances in liquid nitrogen container and last for many years as long as it is kept frozen. Once arriving at its destination it can be defrosted, re-awakening the sperm and inseminated into the mare. Compared to chilled semen, the freezing and handling process slightly reduces the viability of the sperm and conception rates, therefore requires mares to be inseminated immediately before or after ovulation. However advantages are that breeders can use stallions which are still competing and the semen can be sent well in advance of the mare being in oestrus, avoiding the last minute delivery of chilled semen, which may not arrive on time.

Pre-breeding check

Prior to embarking on an A.I. program it is important the mare is examined to ensure that she is fit to breed and asses for factors that may reduce fertility. The pre-breeding check, best if  performed safely in stocks, consist of a physical examination to evaluate vulval conformation, a rectal examination to check the cervix for any abnormalities and ultrasound scan to look for uterine cysts and to see at what stage of the cycle the mare is. At this time we will also be able to take clitoral swabs and, if required by the stud, to do blood tests to check your mare is free of venereal disease.

Timing the insemination

Mares cycle between February and October (cycles at the beginning and the end of the season can be very irregular) and have a 21-22 day cycle, with oestrus (the receptive period) lasting 3-6 days. To have a successful insemination resulting in pregnancy it’s important to place the semen in the uterus when the mare cycles regularly and at the correct stage of the cycle, so when she is in season and close to ovulation. Signs of oestrus in the mare include tail raising, opening and closing of the vulva (winking), frequent posturing and urination and some may, also, become anxious, aggressive, sensitive around their flanks and reluctant to work, though can be difficult to detect and irregularly shown. Ultrasound scans of the ovaries and uterus allows detection of the stage of the cycle and, measuring the size of follicle, we can predict when the mare is coming close to ovulation and inject her with drugs that induce it. The best time to inseminate varies with the type of semen used: for fresh and chilled, AI need to be done within 12-24 hours of ovulation whereas for frozen AI it needs to be done within 6 hours of ovulation, which means a greater number of scans are required both during day and night.

Pregnancy Diagnosis

The most appropriate time to determine the pregnancy is between days 14 and 16 following ovulation through a transrectal ultrasound. At this time it’s very important to check for multiple pregnancies and, if necessary, deal with it before the embryo becomes attached to the lining of the uterus and makes it difficult to “squash” the twin.

14-16 days embryonic vesicle

A further scan around 28 days to check the normal development by identification of the foal’s heartbeat is advised. This also reduces the risk of missing detection of a twin pregnancy. If the mare is not pregnant then she should go back in season again allowing the program to be repeated, hopefully, with a more favourable outcome.

2-3 month pregnancy scan

Glanders (Farcy)

Glanders is one of the oldest known diseases of the horse. It has now been eradicated in the United Kingdom and much of the world, although it is still reported in the Middle East, Pakistan, India, China, Brazil and Africa. The disease is caused by a bacterium called Burkholderia mallei and is a zoonosis, that is, infectious to people, with a 95% fatality rate, if untreated.

The disease is characterised by nodules or ulcers on the skin and in the respiratory tract, but is more often seen in a chronic or latent form. These chronically infected horses act as a reservoir of disease. Glanders is contracted by ingestion of food or water contaminated with nasal discharges of carrier animals or by ingestion of contaminated meat from infected horses. After an incubation period of 3 days to 2 weeks animals can develop acute or subacute respiratory symptoms or cutaneous symptoms.

Acute respiratory glanders is mainly seen in asses and mules,who are most severely affected. Symptoms include high fever, cough, nasal discharge and ulcers on the nasal mucosa. As the disease progresses respiratory signs develop and the animals often die.

The chronic disease is more often seen in horses and is commonly seen with both the cutaneous and respiratory forms, symptoms are slower to develop. In the respiratory form symptoms include; ulcers in the nasal passages, with nasal discharge, chronic pneumonia and scaring of the submandibular lymph nodes. In the cutaneous form (‘farcy’) nodules appear to course along the lymph nodes and degenerate to form ulcers that discharge a highly contagious sticky pus. The liver and spleen may also develop similar nodules.

Clinical signs develop when the disease is well advanced so diagnosis is best made by the use of diagnostic such as CFT antibody test or PCR test of infected skin tissue. Treatment of Glanders with antibiotics can be attempted in endemic countries, but often results in latent disease. In counties where Glanders has been eradicated, animals with confirmed disease are euthanased and  in contact animals are tested to monitor disease status.

Heart Murmurs

There are four valves in the heart, one between each atrium and its respective ventricle and one between each ventricle and the major vessel it supplies. A valve is a thin flap of tissue that opens and closes to let the heart fill and empty at the appropriate time. The opening and closing of the valves generate sounds and those are the heart sounds your veterinarian will be listening for with a stethoscope. A ‘heart murmur’ is an extra sound audible when listening to a horse’s heart, next to the normal heart beat.

Most murmurs that we find are ‘flow’ murmurs, which means that these murmurs can occur in completely healthy hearts which no significant abnormality but are caused by normal flow of blood. These flow murmurs happen in horses because they have a large heart compared to their body size, so there is a lot of turbulence in blood flow that can be audible as a murmur. These murmurs have no clinical significance.

However, some murmurs do indicate an abnormality in either blood flow or heart function. They can either mean a leaking heart valve, thickening or narrowing of a valve or large blood vessel or an abnormal hole between different heart chambers. A valve can start leaking for a variety of reasons. The most common cause is degeneration of the valve leaflets with age. They can become thickened and shortened. When this occurs, the valve leaflets cannot come together properly. Another reason for the occurrence of a murmur can be altered blood viscosity.

A thorough examination and listening to your horse’s heart will give us a better idea what kind of murmur your horse has. By determining the location of the murmur, the length, the volume and when the murmur is audible, the murmur will be graded. The grades run from 1, which is a very quiet murmur, to a grade 6 where the murmur can be heard without even touching your horse’s chest with the stethoscope.

Next to the murmur itself, the presence of any other clinical signs is important. Clinical signs of heart problems/failure could include exercise intolerance, weight loss, oedema and enlargement of blood vessels, mostly visible as a very clear visible pulsation in the jugular vein. If the murmur is severe or there are any other clinical signs, further investigation is required.

An ultrasound examination of the heart would be the first step. This allows for the heart to be imaged while it is beating. This is a specialised technique and your horse will have to be referred to a specialist. An ultrasound examination is also typically recommended for the evaluation of some murmurs detected at purchase examination, especially for horses intended for athletic use. The ultrasound will show the nature of the lesion causing the murmur to be identified, next to measuring the size of the chambers of the heart and the contractility of the heart. All these factors combined will give an indication of the severity of the murmur and the likely effect it will have on your horse. The examination will also provide a baseline; we may recommend a repeat examination in 6-12 months to note any progress of disease. Some lesions remain static for a number of years, and the horse can go on to work for several more years with no problems. However, if the problem appears to be progressing, it may be advisable to retire the horse.

Other tests that could be performed would be a blood test to tell if there is any damage to the heart muscle and an ECG or electrocardiogram to look for abnormalities in heart size and heart rhythm.

Much research has been conducted into the frequency of heart murmurs and they are a common finding and most do not seem to be clinically significant. With a thorough examination by your vet, decisions can be made if there are further investigations needed, or if the murmur is likely to be of no clinical significance.


A keratoma is a benign growth between the hoof wall and the pedal bone inside the foot. The growth starts from the horn producing cells, usually originating from the coronary band growing downwards to the toe.
The exact cause is unknown but some cases can be linked to chronic irritation or infection in the shape of slow abscesses or direct hoof injury. Injury to or inflammation of the coronary band is also thought to be a possible cause.

There may not be any visible signs of the keratoma on the outside of the hoof but a bulge on the hoof wall can be present.  There is often an inward deviation of the white line visible on the bottom of the foot. Lameness can develop, due to the pressure of the keratoma. Often this presents as an intermittent lameness. Other clinical signs may involve a foot abscess at the location of the keratoma and possible sensitivity to hoof testers.

Further investigation will include taking X-rays of the foot. This might show the location of the keratoma and how far it has advanced. The keratoma can sometimes be visible as a semicircular defect in the pedal bone. Other options for further diagnosis can be a biopsy of the keratoma to identify the growth and in difficult cases MRI can be a helpful tool.

Surgery is required to remove the keratoma. This can be done either standing or under general anaesthesia. The hoof wall is removed to gain access and the growth is excised. Complete removal is important because the keratoma can return if it is not completely removed. The wound is packed with gauze soaked in iodine and bandaged up completely to keep the wound clean with support of a special shoe. Your horse will require antibiotics and pain relief after the surgery. Further management will include box rest and regular bandage changes. The foot will be bandaged until a hard layer of horn has formed over the area. Following this the horse will have to remain in clean, dry conditions until the wound has completely healed over. The complete process can take many months because the hoof wall grows only about ½ cm each month. With patience and careful management the prognosis is usually good.

Photo source:  “Adams’ Lameness in Horses”, fifth edition, Ted S. Stashak, 2002, 720 – 722

Exporting/Travelling Horses Abroad

You will need to firstly go to the ‘Export Horses/ponies GOV.uk’ website – https://webgate.ec.europa.eu/sanco/traces/registration/open.do

You need to have a nominated veterinarian (such as Milbourn Equine) before continuing.

You will need to follow the links on this website to:

  1. Register with traces
  2. Then sign into traces
  3. Call Animal and Plant Health Agency APHA, to inform travel papers have been requested/created & the name of your signing veterinarian. (i.e. Milbourn Equine)

Your ITAHC (travel documents) are valid for 10 days after the veterinarian has signed them. There is no fee for the certificate but you will be charged for the veterinarian’s time.

If you decide to drive yourself, ensuring you have the correct documentation is vital, it may be a good idea to consult with your nominated vet.

You will need European vehicle insurance and, if you are a professional, you will need an International Operator’s Licence, which is obtained from the Driver and Vehicle Licensing Agency (DVLA).

You’ll also need a valid and up to date passport for your horse, an export licence to leave the UK and an in-date health certificate signed by a ministry vet.

Quarantine isn’t required when travelling within the EU.

Useful contacts
P&O Ferries: 0871 6642121, www.poferries.com
Defra: 0845 9335577, www.defra.gov.uk
John Parker International Horse Transport:
01303 266621, www.johnparkerinternational.com

Read more at http://www.horseandhound.co.uk/features/taking-your-horse-abroad-what-you-need-to-know-415477#EgrETa309DDAaeh2.99

Equine Exports from the Vets Perspective

Once the practice has been nominated an Official Veterinarian (OV) will have to inspect your horse and sign the certificate which will allow your horse to travel.

Upon inspection the vet will be looking to see if the horse is fit and well to travel. The passport and microchip will be checked to see if this matches the horse. The Official Veterinarian will examine the horses for any signs of discomfort/illness which are present alongside a general health check. If signs of infectious diseases are present or if the horse is not comfortable to travel the Veterinarian will not allow the horse to travel. If signs of parasites (such as lice) are present the horse will not be allowed to travel.

Once the OV has given the horse the all clear they will sign and stamp the certificate. Your horse is now declared fit to travel.


Small Redworms (Cyathostomes)

These are the most common worms in horses and they are infected from pasture contaminated by eggs passed out in faeces of infected horses. Although these worms are more prevalent in the summer they can be present all year round.

The eggs can develop into adults in the gut within 5 weeks, they can either attach to the gut wall or be absorbed into it and reduce the ability of the gut to absorb nutrients leading to weight loss, diarrhoea and general ill thrift. These worms can also encyst into the gut wall as larvae and delay their development to adults.  Emergence of these encysted larvae can cause major gut damage leading to severe diarrhoea, weight loss, colic and even death.

The adult stages are readily detected by faecal worm egg counts (WEC) and it is sensible to worm your horse based on the results of this. The encysted larvae will not be shown up by WECs so it is important to treat for these once a year (usually in the autumn).

You can reduce pasture contamination by avoiding overgrazing/overstocking of pasture, regular poo picking and cross grazing with sheep/cattle.

Encysted Small Redworm –  Owners Leaflet

Tapeworms (Anoplocephala spp.)

These worms tend to attach to the gut walls and can interfere with gut motility and cause irritation, they are a major cause of colic (research suggests up to 20% of spasmodic colic can be attributed to tapeworms). It is spread by an intermediate host (the forage mite) and infections occur all year round. Infection can be detected via a blood or saliva test but will not be shown on a WEC. Equisal Saliva test kits are available from Milbourn Equine which you can do yourself and your vet will analyse the results and advise you.


Pinworms are becoming increasingly common due to their location at the end of the digestive tract as ‘newer’ wormers tend to be absorbed before they reach this point. The female lays eggs around the anus and this can lead to perineal irritation and tail rubbing. They are generally not harmful and are more of a nuisance/ irritant to the horse. The adults are readily killed with a double dose of a ‘pyrantel’ based wormer but it is important to also disinfect any area the horse has rubbed on (fences/haynets/rugs etc)as otherwise the horse can become re-infected by ingesting the eggs.


Bots are actually flies that have part of their lifecycle within the horse. Eggs are laid on the hair by a fly, they are consumed by the horse and migrate to the stomach where they attach and can cause some inflammation/ulceration before being passed out in the dung. However they are not a major health concern unless present in very large quantities.


Lungworms are very rare in horses unless they are immune-compromised or are grazing alongside donkeys who are relatively commonly infected.

Large Redworms

Large redworms migrate to the blood vessels causing damage to major organs, historically they caused very serious illness but due to regular use of wormers nowadays they are less of a concern.

It is our advice to worm once yearly with a wormer containing moxidectin that kills encysted redworm larvae (ie Equest Pramox) which do not show up on worm egg counts.

In between times we recommend worm egg counts are performed and only to worm if these show a high level of adult redworms. This avoids unnecessary worming, reduces the risks of worms becoming resistant to wormers and is likely to reduce your costs!

We offer a worming programme for an annual fee which provides worm egg counts throughout the year. Please note tapeworm testing is at an additional cost.

Alternatively join our Equine Healthcare Plan, to help you save money on tapeworm testing and other additional preventative healthcare costs.