1. Equine Influenza

Equine flu (influenza) is similar in appearance to flu in humans. Clinical signs are caused by infection of the respiratory tract and include a dry, hacking cough, runny nose, watery eyes and fever. It is caused by a highly contagious virus and, while it does not normally cause long term illness, it will lead to your horse requiring time off from work and it can lead to serious complications in very young or old horses.

Typically, equine influenza occurs in sporadic outbreaks of horses after the introduction of a carrier animal. Carrier animals shed the virus but do not otherwise show clinical signs.

Although the virus is very infectious it only infrequently results in mortality. In severe cases the virus affects other areas of the body including the lungs, heart and gastrointestinal tract. Secondary infection by bacteria can result in more severe respiratory signs and sinusitis. In rare cases the virus can cause neurological disease.

There is no specific treatment for equine influenza and although antibiotics may be useful to control a secondary bacterial involvement they will not treat the virus itself. The only method of active control of the virus is by ensuring routine vaccination.

2. Tetanus

Tetanus is caused by a bacterium (Clostridium tetani) that is present in soil everywhere. Horses become seriously ill and in many cases the disease is fatal despite all attempts at treatment. The bacteria enter the body through cuts in the skin and puncture wounds in the foot, and then cause disease by producing toxins that affect the nervous system, ultimately paralysing the victim. Fully vaccinated horses are able to neutralize the toxin before it can cause any ill effects and disease is completely prevented.

All horses should be vaccinated against tetanus whether they are retired, companion or competition animals.

3. Herpesvirus

Equine Herpes Virus (EHV) is a virus that can cause mild respiratory disease in young horses. As with the flu virus this can then lead to further complications such as pneumonia. EHV can also cause the more serious problem of abortion in pregnant mares and it is therefore recommended that breeding animals (stallions and broodmares) should be vaccinated against EHV. Rarely, EHV can also cause paralysis in horses and can be fatal. Vaccination against EHV reduces the chance of becoming infected, and reduces the concentration of virus in the local environment, making infection of other horses less likely.

4. Strangles

This highly contagious bacterial infection (Streptococcus equi) is now common in many areas of the UK and causes major economic problems on big yards. Unlike other infections, strangles tends to localise itself at the back of the throat, rather than spreading around the whole body. Infected animals show a wide variety of clinical signs - classically they develop a high temperature, nasal discharge and get large, hot and painful lymph-node swellings around the neck and jaw area. These swellings can eventually burst out as abscesses. In rare cases horses can go on to develop 'bastard' strangles, where abscesses form elsewhere in the body. Bastard strangles is usually fatal.

Infected horses should be isolated and kept confined until they have recovered and been declared free from disease (this is achieved by 3 clear swabs taken from the nose or 1 clear wash taken from the guttural pouches at the back of the head). The disease is spread very quickly by contacting discharges from the nose or draining abscesses, so it is essential that different equipment is used for infected horses and that anybody handling infected horses wears protective clothing and properly disinfects themselves before coming into contact with healthy horses.

5. Colic

The term 'colic' is a symptom or sign and is not a diagnosis of a disease. It means there is pain in the abdomen or belly. This could be associated with the gut (gastro-intestinal tract), but equally, the kidneys, liver or another condition such as pneumonia, fractured ribs or 'tying up' may be responsible.

Why is colic so common in horses?
Horses were designed to be 'trickle feeders', meaning they eat very little amounts often and typically would graze in excess of 20 hours a day. They would get their exercise by foraging around for food and mixing grasses, grains, and other roughages. They have very fragile and finely balanced gastro-intestinal systems that are easily disrupted by even the slightest changes. Through domestication, man has interfered with this delicate balance by introducing concentrated feeds, stabling, small paddock confinement and changes in exercise to suit the seasons.

What are the signs of colic?
In the early stages it can be very difficult to distinguish between a mild problem that can resolve on its own and a more severe condition that is potentially fatal. This is why ALL cases of horses with colic symptoms should be taken seriously from the start and veterinary advice sought immediately.

Colic signs may present mildly or be so severe that they are life threatening to the horse and to those trying to help it. The following are a few examples of what to expect:

• Scraping the ground either mildly and occasionally, or vigorously and constantly striking out
• Lying down more than usual, often completely on its side
• Getting up and down repeatedly
• Standing with hind legs stretched out behind it
• Frequently posturing to urinate
• Flank watching, stretching head and neck around to look at abdomen
• Repeatedly curling the upper lip
• Kicking at the under belly
• Lying on its back, perhaps getting cast up against a wall
• Rolling
• Manic uncontrolled thrashing

What can you do while waiting for the vet to arrive?

• Bring the horse in from the paddock and put it in a clean, well bedded box.
• Do not offer feed, hay or water.
• Remove items from the box that the horse could potentially injure itself on, e.g. hanging buckets, hay nets, etc.
• If it helps relieve pain, the horse can be walked out around the stable yard until the vet arrives.
• Pay close attention to times and details of when the colic started and how the horse has been managed so the vet can get a clear history. Write everything down.
• Your vet may ask: when was the horse last fed? Any changes in eating habits? When was the horse last wormed? When was it last exercised? Could your horse be pregnant? When was the last time he/she passed faeces? etc.
• Do not put yourself in danger by trying to stop a thrashing, violently painful horse!

Your vet may do some or all of the following when they arrive:
1. Observe the horse's behaviour while left alone in its box. Look for faeces and note the character and consistency of them. They can then assess the severity of the pain.
2. Ask you if there have been any changes in management; anything from change of paddocks or feeding regime to increase in box rest.
3. Do a clinical examination:
a. Including checking the horse's heart rate, respiration (breathing) rate, and temperature b. Looking at the colour of the mucous membranes (gums) c. Listening for gut sounds and look for abdominal distention 4. Relieve pressure in the stomach. A small intestinal blockage may cause the stomach to bloat. This is potentially serious because horses can't vomit. Relieving pressure involves passing a tube into the stomach and releasing any gas and fluid. With the stomach decompressed, the horse may feel immediately more comfortable. 5. Take a blood sample to check for dehydration. Very sick colicky horses rapidly become dehydrated and this is simple to diagnose by performing a blood concentration test (haematocrit).
6. Take a sample of peritoneal fluid; this is the fluid that normally bathes the guts in the abdominal cavity. Changes in its colour and clarity can indicate a problem with the intestines. This can be quite difficult to do unless the horse is adequately restrained and there are good levels of light. The procedure involves putting a needle into the abdominal cavity of the horse from underneath. Fluid is collected in a tube and evaluated.
7. Perform a rectal exam. This could also be difficult if the horse is not adequately restrained. Drugs used to sedate the horse are frequently used to help relax it for this examination. The examination aims to detect any abnormal swellings and blockages that may be present in the intestines. Due to the size of the horse and the length of the human arm this test is not always conclusive.
8. Give the horse pain relief and/or sedation.

Your vet may decide to refer your horse to a hospital for further investigation or surgery.

90% of horses with colic do not require surgery and respond to medical treatment. The decision to send a horse for surgery will depend on the results collected from various examinations and tests. These results are then pieced together to form an overall picture of what may be happening and how it may need to be treated. Deciding to take a horse to surgery is not an easy decision or one that should be taken lightly.

Preparing for the journey to a specialist hospital:

• Have clear written directions and contact numbers on how to get to the hospital
• Take a detailed report of the history and treatments given by your vet.
• Take a friend along, especially at night, in case you run into trouble on the way.
• Take a mobile phone with you
• DO NOT ride in the back of the horse box or trailer with the horse. You could incur serious injury if you are caught in a confined space with a colicking horse.

How can I prevent colic?

• Feed your horse small amounts often
• Feed at regular intervals the same time each day
• Feed hay and water before hard feeds (grains)
• Allow free access to clean water
• Turnout as often as possible
• Remove all traces of mouldy hay and hard feeds
• Do not over feed
• Keep weight within normal limits
• 60% of energy intake should be from forage
• Do not overgraze paddocks
• Do not graze on sandy paddocks
• Worm regularly according to veterinary advice and preferably check for efficacy with worm egg counts
• Make sure the horse is fully cooled down before feeding and offering water
• Provide access to good quality forage as much as possible when stabled
• Maintain a consistent exercise programme
• Most importantly, make all changes to diet, exercise and management slowly

6. Laminitis

The term laminitis refers to the swelling of the 'laminae' within the hoof capsule. The laminae bond the hoof wall to the pedal bone in the foot thus transmitting the entire weight of the horse from the hoof to the skeleton. The weight of the horse tries to shear the hoof wall from the pedal bone which, in the normal horse, is resisted by the laminar attachments in between the two. In a healthy foot, the laminae are more than strong enough to cope with this.

When laminitis occurs, the intertwining laminar attachments become weakened, resulting in a partial or complete failure (depending on severity) to oppose this shearing force, damage is caused and this results in pain for the horse. In severe, long standing (chronic) cases, the laminae may not be able to support the pedal bone sufficiently and it can rotate away from the hoof wall and break through the sole of the foot.

What causes laminitis?
Unfortunately, there are many factors which can cause laminitis. Much research into the exact mechanisms is ongoing but the most common identified causes of laminar swelling are stated below:

• Obesity - Increased weight is thought to cause mechanical damage to the laminae by an increased downward force on the pedal bone putting more strain on the laminae. Simply put, the horse is too heavy for its own laminae.
• Grass associated - Usually associated with turnout on to a fresh lush pasture or when a horse eats lots of first flush spring grass, the exact reason for this is yet to be determined but it has been linked to the high level of a specific sugar being ingested. One theory suggests that bacteria within the gut multiply rapidly in the abundance of sugar. These bacteria release waste products which are toxic to the laminae. Normally, low levels of toxin are kept within the gut and excreted in the faeces but when the numbers of bacteria increase rapidly these waste products leak from the gut into the circulation.
• Endotoxaemia (internal toxins) - Circulating endotoxins (internal blood poisons) result in changes in blood flow to the laminae causing swelling and damage to the laminar attachments. Endotoxaemia can result from grain overload, uterine infections and severe colic episodes.
• Steroids – High levels of substances in the horse called steroids are known to cause laminitis.

Types of Laminitis

• Acute onset - the horse with acute or rapid onset laminitis will be depressed and often will not eat. They are reluctant to move and stand awkwardly with their weight shifted to the hind legs. There can be an increase in heart and respiratory rates, with bounding pulses at the back of the pasterns (digital pulses). Usually both forelimbs are involved, though all limbs can be affected in cases of endotoxaemia. One limb may be affected in cases of mechanical laminitis where the opposite limb is injured or non-weight bearing. Horses with acute laminitis should be seen by your vet as soon as possible so that further changes within the hoof can be minimised.
• Sub acute - This tends to be a less dramatic onset with less severe signs; usually the first sign is shifting weight lameness or stiffness in gait.
• Chronic (long standing) -This usually occurs after an episode of one of the above.There are usually visible changes noted in the hooves, which can be mis-shapen, with a seedy toe (wide and weakened white line is visible) and a history of chronic recurring foot abscesses. The horse/pony often has a longstanding history of lameness.

How can I prevent laminitis?
Prevention of laminitis is complicated due to the varied inciting causes. However, by preventing horses susceptible to developing laminitis from over eating lush pasture and not overfeeding with concentrates, it can be controlled. Also, in such individuals, extra vigilance should be employed when feeding and with hoof care so any episode can be detected early and thus treated more effectively. Your veterinary surgeon will be able to offer further advice on all aspects of laminitis.

Why does my vet want to take X-rays (radiographs)?
In some chronic cases of laminitis the laminae will have degenerated to the extent that the pedal bone has rotated away from the hoof wall. Taking radiographs is not a treatment for laminitis but it enables the veterinary surgeon to visualise any long-term changes that may affect his/her treatment decisions in the future. Unfortunately, where significant rotation has occurred, it may be unrealistic to expect the pony to fully recover its previous quality of life and, in such circumstances, euthanasia may be advised.

7. Conditions of the Eye

Injuries to the eye and surrounding tissues are common and should always be treated as potentially serious. Injury can result from direct trauma, i.e. kicks or blows, grass seeds or thorns which can abrade or puncture the surface of the eye, or from infection by parasites, bacteria or viruses. Owners should not be tempted to leave an eye condition to 'self-resolve'. Some diseases are not an emergency but may be indistinguishable from potentially dangerous conditions, or can progress over time to become much more serious if not appropriately treated. Veterinary attention should always be sought. An accurate diagnosis is critical to the successful management of eye disease. High Bandwith : WMV 1.48 MB Low Bandwith : WMV 74 KB

NB Eye drops prescribed for one horse may not be appropriate for another horse showing similar signs.

Corneal ulceration
Corneal ulcers are defects in the surface of the eye (cornea) often caused by infection; they cause inflammation, pain and irritation. Initial presentation is a closed, swollen eye, often running with tears. Your vet will diagnose corneal ulceration by putting a fluorescent dye into the horse's eye. Affected areas will take up the dye and appear green. Infection may have started by a piece of grit entering the eye, or by direct injury to the eye, e.g. from a thorn.

Moon Blindness (Equine Recurrent Uveitis)
Moon Blindness is characterised by periodic bouts of acute pain and inflammation of the eye. When fluorescent dye is placed in the eye, there is no area of corneal ulceration even though the presenting signs may be very similar to corneal ulceration. Treatment with anti-inflammatory eye drops brings about apparent complete recovery but the condition may reoccur in the same or opposite eye in a few weeks or a few years.

There is no one particular cause of Moon Blindness. It is thought that there may be some inherited component to its occurrence but mild infection or allergy may also play a part.

Cataract
Any change in the clarity of the lens is termed a cataract. Any opacity will interfere with the passage of light through the lens to the retina. Therefore, a horse with a cataract may experience anything from slightly impaired eyesight to complete blindness in that eye.

Cataracts can occur at an early age, known as developmental cataracts, or in older horses, known as degenerative cataracts. Developmental cataracts occur due to defects in the lens in young animals and do not tend to get worse with time. Degenerative cataracts are a result of disease and tend to result, ultimately, in total blindness in that eye.

There is no treatment for cataracts in horses.

Conjunctivitis
The conjunctiva is the outermost covering of the eye and inflammation can be caused by infection or direct injury. Typically, with conjunctivitis, the eye is swollen, painful and the surface looks red and sore. The eye may be running tears or, occasionally, pus. Presenting signs are similar to moon blindness or corneal ulceration. It is very important that an inciting cause be properly looked for and this must be done by a veterinary surgeon, who may have to sedate the horse in order to conduct a full and thorough examination of the eye.

Entropion
Entropion is seen in newborn foals and describes a condition where the eyelid and eyelashes turn in on the eyeball and cause irritation and sometimes ulceration. Treatment of the ulcer is by routine antibiotic eye-drops but the eyelid may need to be stapled in position or its shape corrected by surgery. Sometimes, simply correcting the abnormal position of the eyelid is sufficient to stop it reoccurring.

Blindness
The ability to see relies on the proper functioning of multiple organs in the pathway to the brain. Any injury or malfunction of any of these steps may result in blindness. For example, cataracts prevent light reaching the retina, the retina may detach from the back of the eyeball or the optic nerve may be damaged or diseased. Only a veterinary specialist with the appropriate equipment may be able to diagnose the exact cause.
If you suspect that your horse may be blind, you can gauge its eyesight practically in a number of ways:

• Menace response: When a hand is brought up sharply towards the eye the normal horse should flinch or display a blink response.
• Obstacle course: animals can adapt to a loss of sight remarkably well and a horse that spends all of its time in the same surroundings may not show overt signs of blindness immediately. By leading the horse through a number of strange obstacles, defective eyesight will become obvious.
• General behaviour will change. As the horse's eyesight deteriorates, it will become less confident during exercise and may trip or fall more frequently.

8. Skin Problems

Melanomas
Melanomas are tumours of the skin, which are derived from the pigment producing cells. They therefore have a heavily pigmented or darkened appearance. They are reasonably common and have a reported incidence of between 4 and 15%. They occur anywhere on the body but are more common in older horses with lighter coats. In fact in old, grey horses the incidence has been recorded as high as 80%!

These tumours are initially benign (unlikely to spread) but they may develop into malignant tumours and spread. The commonest sites for the development of these tumours is around the anus and vulva.

Squamous cell carcinomas
Squamous cell carcinomas are a type of skin tumour and are reportedly the second most common skin tumour of horses. They most frequently occur in horses between the age of 8 and 14 years but have been found in horses from 1 years to 29 years! They are more common in lighter coloured horses, as sunlight has been implicated as a cause of them.

They can occur anywhere on the skin of a horse but are more commonly found on the hairless areas such as eyelids, lips, nose, vulva, penis and prepuce. Early diagnosis is essential and your veterinary surgeon may even recommend removal of them to prevent further spread.

Sarcoids
The most commonly diagnosed skin tumours found on horses are sarcoids, and they have been reported to account for nearly 90% of all skin tumours in horses. Luckily, the majority are non-malignant (unlikely to spread) but they can invade local tissue and cause irritation to the horse. Also, if they are knocked and bleed, they will attract flies and increase the irritation.

Sarcoids can appear in a number of different forms and can look similar to other skin tumours. It is essential that any lumps are discussed with your veterinary surgeon as soon as they are noticed.

Rain Scald
Rain scald is a bacterial infection of the skin of horses, which causes scabs to form on the back, rump and lower limbs. These scabs can be easily removed to reveal patches of moist raw skin. This condition is caused by prolonged wetting of the skin which allows the bacteria to invade.

It is important that you contact your veterinary surgeon for advice on rain scald as there are a few other conditions which can appear similar. Rain scald can be avoided by ensuring the skin remains dry, so stabling the horse or applying a weather proof rug can reduce the risk of this condition developing.

Sweet Itch
This is a skin condition caused by an allergy to the saliva of certain biting flies or midges. The severity depends on the degree of allergy or reaction to the insect bites. The allergy causes the horse to be itchy and thus rub the skin; in fact they can actually rub the hair off the affected areas (upper neck, back, tail base and ventral abdomen). This problem is usually encountered in the warmer months when these insects are more active.

Reducing the exposure of horses to the flies is the best form of control of this condition. Therefore stabling the animals at high risk times, rugging the horse, reducing the number of insects present, and fly and insect repellents can all help to reduce a horse’s exposure. Your veterinary surgeon will be able to offer advice on forms of reducing the exposure as well as appropriate treatments that are available to control the itching.

Mud Fever
Mud fever is caused by the same organism as rain scald and is associated with damp, muddy conditions. However, any damage to the skin surface can allow the bacteria to invade the skin and cause problems. Signs of the disease are matted, crusty scabs on the legs and these tend to be around the coronet, heels and pastern. White legs tend to be more commonly affected than coloured legs.

For mud fever, by far and away, prevention is better than cure and hence muddy areas of the paddock should be avoided. If legs do get muddy this should be allowed to dry and then brushed off and any scabs should be observed for signs for problems. Your veterinary surgeon will be able to provide further advice on the treatment of this condition.

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Chorioptic Mange
Although Scabies or Sarcoptic mange has been eradicated from the UK, mange due to the mite Chorioptes equi is still relatively common. The mite lives on the surface of the skin and its burrowing activities are what causes irritation to infected horses. This irritation causes the horse to nibble at the affected areas (hind limbs, belly forelimbs and groin).

Chorioptic mange, as with other types of mange, is associated with close contact of horses where the mite is able to easily pass between them. Treatment for mites involves adopting good hygiene practices as well as certain parasiticides of which your veterinary surgeon will provide advice on the most suitable for your horse.

Ringworm
Ringworm is not, as its name suggests, caused by a worm but it is actually due to infection of the skin by one or two types of fungi – Trichophyton or Microsporum. These fungi live in the environment (e.g. dirt, wooden fences etc) and horses pick them up when in contact (e.g. rubbing themselves on a fence). Horses may also be infected by other horses or animals (e.g. cattle) or infected tack or grooming utensils. Young horses are at greater risk than older horses as immunity to the fungi develops with age.

Signs of ringworm are small 1-2cm circular tufted areas from which the hair will eventually fall out revealing scaly skin. Ringworm generally occurs on areas of the body in contact with tack, clothing and riding boots. Treatment is aimed at both the horses and removing any possible sources of contamination. Your veterinary surgeon will be able to provide you with further advice on appropriate treatments and prevention measures.

Warts
Warts are caused by a virus similar to that which causes warts in humans. It is generally passed from the mare to the foal during suckling and so warts are sometimes termed "milk warts". The warts tend therefore to develop on the head, i.e. muzzle, and eyelids, but can also be found down the forelimbs. Once a horse is older than 18 months, warts are very rarely seen as the horse develops immunity against them. Transmission of the wart virus between young horses is common.

Warts usually regress by themselves but can cause trouble if they become infected. Your veterinary surgeon will be able to offer advice if you are at all concerned.

9. Parasitic Worms

Three main groups of parasitic worms (Helminths) affect horses,
1. Roundworms (Nematodes)
2. Tapeworms (Cestodes)
3. Flukes (Trematodes).

Many of the species of parasitic worms within these groups have evolved to live specifically in the gut of the horse. Many horses will have some worms but, as long as the overall burden is low, the horse will suffer no ill effects. However, domesticated horses are kept on much smaller areas of concentrated grazing in close proximity to other horses. This change in husbandry has increased the individual horse's exposure to worms and increased the chances of the development of large infections.

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The principles of parasitic control focus on both management and pharmaceutical means.

Tapeworms (Cestodes)
Tapeworms generally live in the small intestine. Their head is attached to the intestine wall by suckers and their flat, ribbon-like body extends along the bowel. Tapeworms do not have an alimentary tract but absorb nutrients across their body wall. The body itself is formed from a large number of segments; one by one the segments become mature and break off from the end of the worm. These segments contain eggs which they now release and which are ultimately shed in the faeces. These eggs, once on the ground, can then be eaten by other horses and are immediately infective to other animals.

The horse tapeworm (Anoplocephala perfoliata) grows to up to 8 cm in length and 1.5cm in width; it is shorter and wider than tapeworms of dogs, cats and humans. It lives at the point of the intestine called the ileo-caecal junction, where the small intestine notionally joins the large intestine.

Diagnosing tapeworm infection by testing the faeces of the horse is very difficult. The tapeworm segments are shed sporadically, and in small numbers, so the likelihood of finding eggs is remote. Consequently, results are inconsistent and do not necessarily give an accurate representation of the scale of infection. Fortunately, a blood test to detect tapeworm infection has recently become available. It relies on detecting the level of immune system response (antibody) to tapeworms. The full benefit of this test is derived from the fact that high levels of antibody correlate to a high level of infection and vice versa. The test is also consistent.

Roundworms (Nematodes)
The term 'roundworm' describes many different zoological groups of worms. Most roundworms are free-living, (non- parasitic), others can become parasitic if conditions dictate. The roundworms that affect the horse are purely parasitic.

Small Redworms (Cyathostomes)
Infection is by ingestion of an infectious larva. The larva passes into the intestine and penetrates the lining of the small bowel. The larvae may remain within the mucosa of the intestine for long periods of time before emerging to complete the life cycle. Potentially, large numbers of encysted larvae can build up over time and, if a significant proportion emerges at the same time, severe damage can be caused to the gut wall. Once reactivated, the larvae develop into adults and lay eggs that are passed in the faeces.

Large Redworms (Stongylus vulgaris & edentatus)
The beginning lifecycle of the large redworms is similar to that of the small redworms, apart from where the infective larvae encyst (lie dormant). Large migratory redworm larvae penetrate the lining of the intestine and, depending on the species, migrate to different areas within the body. One species of redworm larvae rest within the intestinal arteries and the other type migrates through the liver before returning to the intestine as adults. The developing larvae may become dormant within the body over winter; they are described as being 'encysted'. Once they have become encysted they will not emerge as adults until the spring. When they do reactivate they will all do so at the same time, causing severe damage to the tissues where they are at the time. The encysted redworm larvae in the mesenteric arteries may cause thrombosis, embolism, colic and death.

Large Roundworms (Parascaris equorum)
Roundworm eggs are ingested by grazing horses from the field where they can remain infectious for many years. The eggs hatch inside the intestine and the larvae penetrate the small intestine and migrate within the mesenteric veins. They are transported within the blood circulation to the lungs where they pass from the circulation into the lungs. The horse coughs up the larvae and swallows them. Once back in the small intestine, they mature into adults and lay eggs that are shed in the faeces.

Bots (Gasterophilus intestinalis)
Bots are the larvae of the bot fly. The adult insect lays eggs on the horse's coat, typically on the chest and front legs. The horse ingests the eggs during grooming. Once in the stomach the eggs hatch and the larvae attach to the lining of the stomach. Ultimately they are passed through the intestines and are expelled in the faeces. Once outside the horse the larvae develop into adult flies and the cycle starts again.

Pinworms (Oxyuris equi)
The most serious complication of Pinworm infection is thought to be irritation around the tail base and perineum. Female worms deposit their eggs around the anus using a sticky material; this is irritating to the horse. The eggs are dropped onto the pasture when the horse rubs or passes droppings where they are potentially infective for other horses.

Other worms that infect horses
Strongyloides Westeri
Habronema
Dictyocaulus Arnfieldi

10. Grass Sickness (Equine dysautonomia)

Grass sickness is so called because it only affects horses and ponies at grass. The exact cause of this disease is unknown but has been linked to free living bacteria called Clostridium botulinum. The bacteria release botulism toxin once inside the horse's intestines. The toxin damages the sympathetic nervous system that innervates the gut and paralyses it. Grass sickness is diagnosed all over the UK and, invariably, horses affected ultimately die or are euthanased.

Clinical signs may be very variable, depending on the form of the disease that the horse is suffering, but can include patchy sweating, swallowing difficulties, recurrent impaction colic, dullness, lethargy, weight loss and depression.

There are four forms of the disease
1. Per-acute. The horse is found dead in the field. There was no previous warning as to the fact that the horse was ill. Post mortem reveals substantial fluid accumulation within the stomach and the intestines.
2. Acute. Principal symptom is severe, sudden onset colic. The horse may have patchy sweating, high heart rate and skin/ muscle tremors. Many horses have, in addition, a green nasal discharge that is associated with a difficulty in swallowing and regurgitation of stomach contents, which is particularly noticeable since horses cannot normally vomit. Horses will normally die or be euthanased because of the uncontrollable recurrent colic bouts.
3. Sub-acute. Symptoms include low-grade colic, usually caused by mild impaction of the large colon, which is induced by lack of intestinal motility. Typically these animals will have a high heart rate and patchy sweating, sometimes with some muscle tremors. Owners may notice some dribbling and inability to swallow properly. Faeces tend to be dry, small and scant in number.
4. Chronic. The appearance of a horse with chronic grass sickness is akin to that of a greyhound. They develop a thin and tucked-up appearance from long periods of inappetance, swallowing difficulties and, therefore, weight loss.

Whether or not a horse survives Grass Sickness depends on the degree of damage suffered by the intestine and nervous system. Invariably, horses with the first three forms of Grass Sickness are euthanased or die. Rarely, horses with chronic Grass Sickness may survive with intensive supportive care. These animals tend to be forever prone to choke and impaction colic and require special attention and feeding.

Diagnosis
Diagnosing Grass Sickness is not straightforward. The range of clinical signs that individuals can display is not consistent and varies according to the extent that the nervous system has been damaged. Frequently, severe colic cases are taken to surgery to discount other factors (such as a twisted gut or small intestinal blockage). Definitive diagnosis involves sampling a portion of small intestine (an ileal biopsy) during surgery, and examining it under a microscope. Grass sickness causes very specific damage that can only be identified microscopically.

One method of assessing sympathetic tone is to administer phenylephrine into one of the horse's eyes. In a horse suffering Grass Sickness, the eye that received the drops will open slightly and the eyelashes will assume a different angle to that of the other eye. This test may be an interesting adjunct to other clinical signs but does not rule Grass Sickness in or out since results can be variable

11. Heart Murmurs

Heart murmurs are abnormal noises that can be heard amongst the normal heart sounds of your horse. Although they can sometimes indicate a problem with your horse's heart, fortunately, in most instances these murmurs are harmless. In fact in a study involving racing thoroughbreds it was found that only 1 in 10 did not have an audible murmur.

What causes heart murmurs?
The normal sounds (beats) of the heart are caused by the closure of the valves in the heart as the heart pumps blood around the body. Heart murmurs are simply any noise other than the normal beats and are usually due to the valves become defective. Many murmurs are considered not to be related to a problem. Due to the anatomy of a horse (e.g.thin skin, low heart rate) these non-problematic noises are simply heard more frequently than in other animals and humans. These sounds are also more noticeable if the horse is excited or stressed.

A heart murmur indicates problems when its nature signals that the ability of the heart to pump blood is compromised. Your veterinary surgeon will be able to identify whether a murmur is serious or not by the time and character of its occurrence within the normal heart cycle. Such murmurs may indicate a variety of problems including leakage of blood through the heart valves, thickening or narrowing of a blood vessel or even a hole in the heart wall. Generally, the severity of the murmur depends on the extent of the defect, i.e. the bigger the defect the more significant the murmur will be, but more exact diagnosis is available by ultrasonography available at a few veterinary clinics and all referral centres. In the most severe cases a murmur may be heard or felt without a stethoscope.

What might be the clinical signs of a horse with a murmur?
Most murmurs do not signify a problem with the horse's heart. In the rare case that your horse does have a heart problem however, the clinical signs are related to disturbance in the blood flow through the heart and therefore the inability of the heart to pump blood efficiently to the body. Therefore if the defect is only small there may be no noticeable signs; a larger defect, however, may cause a decrease in the horse's performance and willingness to exercise. If severe enough, your horse may even refuse to exercise at all.

If you suspect your horse may have a heart problem, contact your veterinary surgeon.

12. Cushings Disease

Cushing's disease occurs in horses when the pituitary gland in their brain becomes overactive. The gland produces excessive amounts of hormone which, in turn, leads to excessive production of steroids by the adrenal glands which it controls.

What causes Cushing's Disease?
There is currently no known reason why any given horse may develop this condition, although some consider that it is a natural result, in some ponies, of old age.

What are the signs of Cushing's disease?
The average age of horses affected by this condition is 20 years. The clinical signs of the disease are related to the over-production of the adrenal gland hormones. This excessive production of steroids causes the horse to drink excessively and produce large amounts of urine which is called polydipsia and polyuria respectively. The horse may also become lethargic and unwilling to exercise.

Another quite striking sign of disease is that some animals stop naturally shedding their coats and become excessively hairy; this is known as hirsutism. As the hormones that are produced inhibit the horse's immune system, affected animals become more prone to developing other diseases such as liver disease and pneumonia. Horses affected chronically are also much more prone to developing laminitis and do not respond to normal treatment.

Can Cushing's disease be prevented?
There is no known inciting cause of Cushing's and therefore it is impossible to actively prevent this condition from developing. However, early diagnosis and treatment can ensure that the horse lives a relatively normal life for many years after the initial diagnosis. It is important therefore that if you suspect your horse may have Cushing's disease you contact your vet to discuss any concerns with them.

13. Gastric Ulceration

Gastric ulceration in horses is identical in its form to ulceration in humans. Erosions of the stomach wall occur when the stomach acid literally eats it away. It has only recently become clear as to how many horses are affected by this condition. Recent studies have shown that between 70-100% of horses can be affected; this includes mainly sport horses and race horses in training.

What causes gastric ulceration?
The normal equine stomach has high levels of acids and enzymes present that would normally destroy and breakdown the lining of the stomach. To prevent this happening the stomach wall has protective mechanisms. Ulceration occurs when the levels of acids and enzymes overcome the protective mechanisms and therefore damage to the stomach lining occurs.

What are the signs of gastric ulceration?
The signs can be quite subtle and affected horses may be lethargic, have poor performance, decreased appetite, weight loss and recurrent bouts of colic. In foals, however, the signs are more severe as they have bouts of colic and may also develop diarrhoea. Due to the discomfort, foals tend to grind their teeth and salivate excessively.

How can I prevent gastric ulceration?
Stress, diet, exercise and certain drugs can all increase the risks of your horse developing gastric ulcers. Your veterinary surgeon will be able to give you specific advice on each aspect.

14. Choke

Unlike the term in human medicine, the trachea or windpipe is not affected in equine choke. Choke occurs when the oesophagus, the pipe between the mouth and the stomach, becomes obstructed by food or a foreign body. Typically this may occur in horses that eat dry food too rapidly. Sugar beet often causes problems because, unless it is thoroughly soaked beforehand, it tends to swell rapidly when mixed with saliva as it is being chewed. As the food bolus increases in volume, its passage down the oesophagus slows and eventually it becomes lodged.

The first sign in some horses may be panic as they make repeated unsuccessful attempts to swallow the food. Subsequently the horse tends to tense all their neck muscles. Further signs may be a nasal discharge of food and saliva, depression and inappetance and repeated coughing or swallowing attempts.

Choke is a common condition and, although at the time it may look very dramatic, the obstruction usually clears by the time a vet arrives. It is important to notify your veterinary surgeon as soon as you suspect that your horse may be choking; they can then give you suitable advice and organise a visit.

15. Ragwort Poisoning

Ragwort (Senecio jacobea) is often found in pasture throughout the UK and contains a poisonous substance (toxin). This toxin (Pyrillozidine) causes damage to the liver of a number of animals including horses and donkeys. Most animals tend to avoid eating Ragwort as it is not very palatable. Poisoning generally occurs when horses ingest Ragwort in dried hay, which has been contaminated with the plant. Although, if food is scarce or there are a large number of plants present within the pasture, horses may be forced to eat it.

What are the signs of ragwort poisoning?
There are two types of poisoning with Ragwort – acute (immediate) and chronic (long term). The acute form is rarely seen as large quantities need to be eaten but when it occurs it is manifested as sudden death.

Chronic poisoning is the most common. The signs of poisoning are usually not seen until 4 weeks to 6 months after eating the plants. Small doses of the poison gradually accumulate in the horse's liver where it causes damage to the liver cells and scarring. Eventually the liver shrinks in size. The liver has large functional reserves and so it is only once these reserves have been exhausted that signs of poisoning develop. These signs can often come on suddenly although, in some horses and ponies, mild illness can precede more severe symptoms. Signs of chronic disease include loss of appetite, depression, diarrhoea, weight loss, sensitivity to sunlight and jaundice (yellow colour to skin or eyes). The liver is responsible for filtering the blood of many of the body’s waste substances so when it stops functioning correctly these compounds can affect the brain. Animals can develop neurological symptoms such as weakness, circling, head pressing and even seizures.

How can I prevent ragwort poisoning?
Ragwort is a biennial plant, which in its first year forms flat rosettes. In the second year it becomes much taller and produces yellow flowers. The only reliable method of prevention is to remove the weed from pasture. The plants should be pulled up by their roots and disposed of away from livestock, preferably by burning. It is important to ensure that animals have no access whatsoever to any plants even dried as they can still be poisonous. The poison can also be absorbed through the skin of humans so it is important that impervious gloves are worn. Plants on adjacent land should be removed to avoid the spreading of seed back into your paddocks. Always ensure that there is adequate grazing or alternative food sources such as hay, so that your horse or pony is not tempted to eat any ragwort, which may have been missed. Sprays are available for the control of ragwort and advice can be sort from your local farm merchant on appropriate ones for you.

There is a DEFRA Code of Practice to prevent the spread of ragwort. Those who disregard the need for the weed's control may face prosecution by the government (Ragwort Control Act 2004): http://www.defra.gov.uk/environ/weedsact/cop_ragwort.pdf

16. Whistling and Roaring

Horses that make an abnormal inspiratory (breathing in) noise during exercise are termed either "whistlers" or "roarers". This noise is only heard during the inspiratory phase and can sound like anything between a high pitched whistle to a loud roaring sound.

What causes whistling and roaring?
Anything that interferes with the normal flow of air from the nostrils to the lungs can cause a noise. The most common cause of horses developing these noises is a condition called laryngeal hemiplegia. This condition is caused by one of the two vocal chords in the larynx (voice box or adams apple) becoming paralysed; the left vocal cord is most commonly affected. This is thought to be due to injury to a nerve called the recurrent laryngeal nerve which runs up the neck of the horse.

Another condition called epiglottic entrapment can cause whistling and roaring and occurs when the epiglottis (a piece of tissue in the throat) becomes trapped and cannot be moved. Other causes of whistling and roaring include tumours, cysts in the larynx, infection and congenital problems (birth defects) of the larynx.

What are the signs of whistling and roaring?
The main sign is, of course, an abnormal noise on inspiration. When the condition is mild, noise may only be heard when the horse is exercising strenuously. However, as the condition develops, the noise may become evident even during the trot.

What can I do to prevent whistling and roaring?
Nothing can be done to prevent this condition but early diagnosis and treatment can prevent further complications from developing. Surgical treatment (known as a 'tie back') usually results in a complete resolution. It is also believed that this condition is hereditary. Do contact your veterinary surgeon for further advice if you suspect your horse may be suffering from this condition.

17. Azoturia

Azoturia is known by a number of different names including rhabdomyolysis, tying-up, exertional myopathy and setfast. It is a disease which is fairly commonly seen in horses and typically affects their hindquarters and back. The condition is seen most commonly in horses in training and occurs after a rest day on full rations followed by severe exertion. For this reason it has also been called "Monday morning disease" from when carriage horses were worked after a rest day on Sunday. It is known, however, to occur in any horse regardless of rest.

What causes azoturia?
Damage to the muscles and tendons of the hindquarters and back gives rise to inflammation and pain in these regions. The actual reasons why horses develop this condition is not known. It appears that the disease can be related to excess energy intake with a low amount of exercise or to excess levels of certain salts in the blood.

What are the signs of azoturia?
In mild cases, the first signs are of general stiffening or cramping of the hindquarters and back. Both hindlimbs are affected equally so the horse is unlikely to appear specifically lame. However, in more severe cases the horse may be unable to move and can even collapse; this may occur during exercise. Other signs may also be evident, with affected horses showing colic signs such as "sweating up" and pawing at the ground. In very severe cases, the horse’s urine may be dark brown in colour.

How can I prevent azoturia?
Azoturia can be controlled by finding a balance between diet and exercise. Too much high energy feed with too little exercise can spell trouble. Your veterinary surgeon will be able to give you advice on appropriate regimes for both feeding and exercise, as well as what to do if your horse has recurrent episodes.

What to do if I think my animal has azoturia?
In the most severe cases a horse may develop signs during exercise. On no account should the horse be forced to complete the exercise regime or hack. Transport back to the yard by vehicle should be considered if access is possible. If you are at all unsure what to do, contact your veterinary surgeon immediately.