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Sweet Itch

Technically called culicoides hypersensitivity sweet itch refers to a skin condition caused by an allergy to midge saliva.

Symptoms

Itching which can be all over the body but is mainly centred on the mane and tail and is seasonal with the horse mainly affected over the summer grazing season from March-October. Often the mane and tail hairs are broken, and the underlying skin is thickened and can become ridged in appearance. The itching can be severe with horses taking every opportunity to rub on fence posts or stable door frames that they can. The skin can become broken with the development of open sores, and it can be a debilitating condition.

Diagnosis

A diagnosis can be made from clinical examination and history taking in a lot of cases due to the classic appearance and pattern of disease. The diagnosis can be confirmed via intradermal skin testing.

Treatment

The mainstay of treatment is management. The itch is caused by an allergy to midge saliva so if we can prevent the midge from biting the horse we can prevent the allergic reaction in the first place. Management strategies include:

• Physical covering – an affected horse must be covered in insect proof material all over 24 hours a day during the whole midge season – generally from March to October but assess each year on its own. This can be achieved using a fly rug with neck, belly and tail covers, ‘bug rugs’ or sweet itch rugs as well as a full face fly mask with ear covers. It can be overwhelming to commit to but it really is the key, on a rainy day either use a waterproof fly rug or a rain sheet over the top of the fly sheet.
• Insect repellent – regular use of a permethrin-based repellent such as Switch or Deosect is the most effective fly and midge repellent. It is also important to apply fly repellent cream or gel to areas of the body not covered by rugs such as the sheath or teats.
• Regular bathing – to relieve symptoms, prevent scurf build up and keep the coat shiny and slippery which reduces the midges ability to grip to the horse to bite them.
• Keeping away from water – there will be more midges in areas near to water courses so affected horses should be kept away from these areas.

During a flare up or in more severely affected horses some veterinary treatments are indicated on top of the management strategies such as:

• Steroids – a course of steroids can be useful to reduce inflammation and itchiness.
• Medicated creams – prescription creams containing steroids and antibiotics can be used on targeted areas where the skin is worse affected or broken.
• Immunotherapy – targeted vaccinations against the midge saliva injected under the skin in a series of injections which can reduce the horse’s symptoms.
• Insol – a vaccination originally made for ringworm has been found to improve sweet itch symptoms in some horses when given just ahead of the midge season.

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Strangles

An infection of the upper respiratory tract caused by streptococcus equi equi bacteria. The infection is in the guttural pouches which are blind ended pockets within the horse’s head which communicate with the pharynx. It is a contagious disease which can be spread by direct and indirect contact with infected horses, i.e. nose to nose horse contact as well as being transferred by humans and fomites between horses. Horses can become silent carriers of the disease meaning that it can be very difficult to identify where the disease came from and keep a strict lid on an outbreak without in depth diagnostic tests.

Symptoms

An infected horse can demonstrate one or more of the following symptoms:

• Nasal discharge – yellow and thick, one or both nostrils.
• Cough.
• Breathing difficulties.
• High temperature (>38.5 C) – this may present as the horse being lethargic, not right and inappetant.
• Swelling under the chin.
• Abscesses burst from under chin or side of face.
• Difficulty eating and swallowing.
• Altered ‘voice’ – neigh sounds different.
• A ‘pyrexia of unknown origin’ – these are cases of poorly horses with a high temperature but the underlying cause is not immediately obvious (if early in disease before nasal discharge starts).
• No symptoms if a silent carrier.

Diagnosis

Identification of the bacteria itself confirms diagnosis. The most accurate way of doing this is via a PCR test which tests for the bacteria DNA. It can be difficult to culture the bacteria sometimes so a PCR is more often used as will have much less false negatives and it is much quicker (within 24 hours vs 3-7 days for culture).

The samples sent for PCR can be a nasopharyngeal wash, nasopharyngeal swab, pus from an abscess or guttural pouch wash. A nasopharyngeal wash is where sterile fluid is squirted up the horse’s nose to wash the nasal passages and pharynx and the returned fluid is captured in a bag to be sent off to the lab. This does not require any further equipment, can be done in the acute phase even if horses are quite sick and is inexpensive compared to the guttural pouch wash. It is also more accurate than a swab on comparison tests as it washes the whole area. A swab takes a sample of the nasal discharge from the nasal passage for analysis. A guttural pouch wash is more involved but is by far the most accurate test. It involves the horse being sedated, an endoscope camera being passed up the nasal passage and then into the guttural pouch itself, fluid is then washed into the pouch and then captured for sending to the lab. Because this washes the exact area where the infection starts it is the most accurate test but is more invasive and has higher cost associated with it.

Often on the day of presentation we would opt for a nasopharyngeal wash, and we can run strangles PCR tests ourselves in our on-site lab so results can be obtained within hours.

There is a blood test for strangles which measures antibodies (immune response). A one-off sample of this is often not very helpful but repeated blood tests 14 days apart can show an increasing immune response confirming active current exposure. The one-off sample which was positive could reflect current exposure or previous exposure which has left the horse with an immunity against strangles therefore is not helpful in identifying a currently affected horse.

Treatment

Treatment varies depending on the severity of the disease observed. All affected horses will need nursing with constant access to fresh water, wet feeds for easy swallowing and rest alongside biosecurity measures to reduce spread.

In mildly affected horses anti-inflammatories alone may be sufficient to control the fever and improve welfare whilst the immune system deals with the infection.

In moderately affected horses antibiotics may be indicated, the most appropriate choice being penicillin injections twice daily. These would be alongside anti-inflammatories.

In severely affected horses anti-inflammatories and penicillin may be combined with fluid therapy if the horse is not eating and drinking as well as active flushing of the infection from inside the guttural pouches via endoscopy. Sometimes indwelling catheters are placed and left in the pouches to allow daily flushing of the pouches. If the horse has abscesses bursting on the outside of the head then these need cleaning and caring for.

Biosecurity

A horse with strangles needs to be isolated away from other horses to minimise the risk of spread. This can be achieved in a stable or a small double fenced paddock where there is no ability for the horse to have direct contact with other horses or share a water source with other horses. When dealing with the affected horse you should wear overalls and gloves and scrub boots and hands afterwards. Strangles is not airborne and is an easy bacterium to kill, it requires direct spread of the snot itself to spread so with good hygiene it can be well contained with ease. It is sensible to restrict movement of horses on and off the yard as well to minimise spread and let all professionals know about the situation such as vets, EDTs, physios and farriers so they can either rearrange or use biosecurity measures.

Managing an outbreak

The best results are achieved when a yard works together in an outbreak. Firstly, a horse map should be drawn up to ascertain which other horses the affected horse could have possibly had contact with. A traffic light system can be useful – red = clinical signs, amber = potentially been in contact with infected horses but no signs yet, green = not been in contact with infected horses. Red horses will be isolated and treated, amber horses should be kept separate to green horses. All amber and green horses on the yard should have their noses checked for discharge and listened to for coughing and have their temperature taken twice daily and recorded in a book (tip – check green horses before amber). Any increase to over 38.5C or constant increasing each time should flag the horse as potentially early infected and prompt isolation (move from amber to red). This is the quickest way of stamping out the infection to isolate the horses before they start shedding via a snotty nose.

Confirming resolution

It is important to get a negative test result before ceasing biosecurity measures and stopping treatment. This is done with a guttural pouch wash and re-testing for strangles DNA via PCR. Approximately 1/3rd of horses infected with strangles will become a carrier of the disease. This happens by the disease outwardly looking like it has resolved but there is in fact some infection trapped in the guttural pouch which sits there dormant for up to many years. The immune system keeps it at bay and usually prevents obvious repeat infection in this horse, but the horse continues to be infectious to other horses intermittently.

Screening Tests

Due to the carrier status, it is sensible to screen horses prior to them moving onto a new yard or prior to purchase. The only way to do this accurately is the guttural pouch wash with PCR. Yards regularly request the blood test but this has been shown to be ineffective at identifying carrier horses so is difficult to recommend in this scenario.

Vaccination

There is a vaccination for strangles available, it is not a requirement and not routinely performed due to its short-lasting action although it is effective. Immunity is achieved 2 weeks after the second vaccination, which is 4 weeks after the first. Immunity lasts for 2 months after it is initiated. The main indication for its use would be in the event of an outbreak nearby, there being a lot of cases in the area or in advance of a known higher risk activity to provide as much prevention as is possible for that short period.

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Sarcoids

Sarcoids are growths on the skin of horses and are a form of tumour. Thankfully they do not spread to other organs but they are locally invasive and can spread to other parts of the body. There are a few different types of sarcoid including verrucose, nodular, occult, fibroblastic, mixed and malignant. A horse can have multiple different types of sarcoid in one region or in different regions over the body.

Symptoms

A sarcoid can look like a lump or bald patch which may be scaly and could be mistaken for ringworm or other skin conditions. Occasionally sarcoids grow in wounds and can be mistaken for proud flesh. Sarcoids can grow anywhere on the body but are most commonly found in the axillae (armpits), inner thighs, on the belly and on the face.

Causes

Sarcoids are an area of interest in equine research and yet we still do not fully understand them. There is some evidence of a genetic link which is an important consideration when breeding. Bovine papilloma virus has also been associated with sarcoids and there is a theory that this may be transmitted by flies although it has not been proven.

Diagnosis

Physical examination alone is often sufficient due to the classic nature of most sarcoids. However, some lumps may not look classic and require a biopsy to confirm the diagnosis.

Treatment

There are a few options, and the right treatment will depend on the type and location of the sarcoid as well as individual circumstances of the owner and horse. The options include:

• AW5 cream – this is a prescription only chemotherapy cream which must be applied by a vet and sometimes needs to be applied under sedation. There are different strengths, and an individual protocol is made for the horse based on the type of sarcoid under guidance of a specialist.
• Laser surgery – removal of the sarcoids via surgery using a laser.
• Injections of products into the sarcoids – BCG, Cysplatin or Mitomycin C are some examples.
• Banding – application of a tight band or suture around the base of the sarcoid to cut off the blood supply until it drops off.
• Non-prescription creams – blood root ointment for example can be purchased and applied by the owner.

Prognosis

Most sarcoids respond well to treatment but they can fail to respond, recur, or new lesions can develop in new sites in the future. We know that every failed attempt at treatment reduces the long-term prognosis so it is worth seeking specialist help to make the best plan from the start for the best results.

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Kissing Spines

The term kissing spines is used to describe a condition called over-riding dorsal spinous processes (ODSP). It is when the dorsal spinous processes (bony processes which stick up on top of the vertebrae) are close together, touching or overlapping in the horse’s back. This can happen in the thoracic or lumbar regions or both.

Symptoms

ODSP causes back pain which may present as obvious back pain picked up by an owner or therapist or more subtly as poor performance when ridden. Poor performance due to ODSP can include tension, resentment to work in a contact, inconsistency of contact, reluctance to bend, canter issues, refusing at fences, shooting off after jumping, bucking, rearing or mounting issues.

Diagnosis

ODSP is diagnosed by x-rays of the back. It is important however to have the horse assessed for concurrent issues such as hind limb lameness, neck issues or sacroiliac disease. This is because ODSP is often seen as part of a wider problem and in some cases the ODSP is actually not clinically significant or only a part of the issue.

Treatment

Surgery

There are two main surgical techniques used for treating ODSP which are both performed standing under sedation and local anaesthetic. The ligament snip is the least invasive and involves cutting the ligaments between the dorsal spinous processes to remove the damaged soft tissue and nerves and allow movement between the bones. The ligament snip plus ostectomy is the same plus some shaving of small portions of the bone of the DSPs as well to create a physical gap between them. Surgery is the most permanent solution but is of course more invasive and costly.

Steroid injections

Steroids can be infiltrated around the ODSPs via sterile injection technique. This provides targeted pain relief and anti-inflammatory action to the area to allow effective rehabilitation. This is more temporary but in milder cases where the owner can commit to excellent rehabilitation this can be very successful in helping ODSP horses.

Rehabilitation

Rehab is essential as part of any treatment plan for any horse with ODSP. The aims are to improve the core strength and posture to support the back, increase lift in the back and therefore open the DSPs from each other. This involves physiotherapy, farriery, saddle fitting, acupuncture, water treadmill work, stretches, targeted exercises, long reining, pole work, hill work, careful schooling and hacking.

Systemic pain relief

In some cases the use of systemic pain relief may be sufficient to keep the horse comfortable in combination with careful rehabilitation.

Change of use

In some circumstances it may be decided that the best way forward is a change in use of the horse. This may involve being limited to straight line only work such as hacking and pleasure riding or retirement. Some horses with ODSP only struggle with certain types of work and so adjusting the workload, if possible, may be all that is required.

It is also essential to treat any concurrent issues at the same time as if the horse is compensating for another source of discomfort the back treatment is unlikely to be successful.

Prognosis

The majority of horses with ODSP respond very well to a thorough approach which has been designed for their individual needs making it a rewarding condition to treat in most cases.