The main ailments affecting the older horse

Focus on Cushing’s disease (PPID)

Cushing’s disease represents a dominant ailment in equine geriatrics : around 20 % of horses over the age of 15, and 40% of those over 30 could be affected, against 0,5 % of the total equine population. This disease also induces a decrease in immunity.

Therefore old horses with PPID are more sensitive to :
•    Infections
•    Auto immune afflictons[1], and tumoral afflictions
When given a vaccination booster jab, these horses have a much lower immune response than younger horses.
Age related immune deficiency does not appear to pay a part in the parasitic load, unlike Cushing’s disease where a higher intestinal parasitic load is common.

In practice

• Increase the frequency of vaccine booster jabs.
• Monitor the horse’s parasitic status by carrying out egg-counts so as to adapt the frequency of a de-worming programme. Horses affected by Cushing’s disease appear to require more frequent de-worming.
• At the onset of the PPID, clinical signs are discrete, therefore it is important, with the older horse, to have your veterinarian carry out frequent check-ups, so as to establish a diagnosis as early on as possible and subsequently manage the disease.

[1] auto immune afflictions: afflictions where the horse’s immune system secretes antibodies directed aginst his own antigens which the system considers as foreign.

Dental abnormalities and their consequences

Older horses’ teeth tend to lose their enamel[2] and the cementum[3] coating, causing the formation of sharp peripheral edges and ridges.
Excessive angulation, and hypercementum cause deviations and loosening, which in turn cause pain when seizing food and when chewing.  Periodontitis[4], tooth decay, and sometimes even fractured teeth can be observed. Even when there are no signs of dental problems, the efficiency of mastication decreases due to worn teeth.
Any of theses abnormalities can lead to the following :

• Obstuctions of the oesophagus, and intestinal impaction due to poorly chewed hay.
• Weight loss due to pain and lessening of speed of ingestion.

In practice

• Regularly watch the horse eating to detect any abnormalities in the way he seizes his food, or in the way he chews : Does the horse tend to drop balls of hay ? Does he eat more slowly ?
• Have the horse’s mouth examined by a veterinarian or a dentist once or twice a year
• Regularly monitor the horse’s body weight condition
• Adapt his fodder : prefer hay with short blades or fibre cubes for example

Colic

With older horses the incidence of bouts of colic increases due to :

• Small intestine strangulation due to the presence of lipomas. Thses are benign fatty tumors with a long stalk. The stalk can wrap itself around the intestine due to the weight of the lipoma. This type of colic is a medical emergency.
• Large colon impactions often related to dental problems, a deficiency in absorbtion by the colon and/or by a decrease in excercise of the older horse..
• Tumors of the intestine, which apart from lipomas are fairly rare.

In practice

With older horses, the tolerance to pain is somewhat greater than their younger counterparts. It is therefore important to call out the vet quickly as soon as there are signs of colic, even moderate, since intestinal strangulation is frequent and is very serious. Rapid intervention and dealing with this type of colic greatly improves the prognosis.

[2]Tooth enamel: visible part of the tooth which protects the different internal layers such as the dentin and pulp tissue
[3]Cementum : tissue covering the dentin at the root of the tooth
[4]Periodontitis : inflammation of the tissues surrounding and supporting the teeth.

With senior horses, muscuoskeletal problems are the most frequent reason for calling the vet.
The joints are subject to cartilage deterioration associated to chronic inflammation causing osteoarthritis.  The pain incurred due to osteoarthritic afflictions leads to difficulties in moving which can in turn cause weight loss and muscle shrinkage.
Laminitis is also a frequent affliction in older horses living out, especially those affected by Cushing’s disease.

In practice

• It is of utmost importance to manage pain in the older horse, so as to ensure proper quality of life.
• A bout of laminitis in the senior horse should be followed by a diagnosis test to detect whether or not the horse is affected by Cushing’s disease.

• Difficulty on expiration (the horse has to strongly contract his abdominal muscles during expration, which leads to the appearance of the « heaves line »)
• Faster breathing frequency
• Dilated nostrils

Treatment is mainly reducing the horse’s exposure to dust, and administering steroid anti-inflammatory drugs associated to broncho-dilating medication. This treatment is not a cure, but improves the horse’s comfort and reduces subsequent changes to the lung structure

In practice

• Prefer accomodation outside in fields,
• Prefer haylage to hay.

Aorta failure

Degenerative valvular conditions, especially concerning the aorta valve, are more frequent in the older horse. The aortic valve takes part in circulating the blood between the heart and the aorta. This condition is characterised by an alteration in the structureof the valve, which causes it to disfunction (this is known as aortic failure) and it disrupts the circulation of blood between the heart and the aorta.

This condition evolves very slowly with very slight clinical signs for several years. It is usually discovered by chance during a check up, and is heard as a heart murmur. There is no cure

Congestive heart disease

This is the inability of the heart to pump sufficient blood for the needs of the body. In the senior horse this congestive heart condition, is mainly due to aortic deficiency.
Clinical signs include coughing and increased breathing frequency. Sometimes there is a frothy nasal discharge from the nostrils.

Treatment can only alleviate the clinical signs and improve the horse’s comfort. It is rarely effective in the long term

In practice

Have the horse’s heart monitored every year to detect a potential heart murmur. This condition will need to be taken into account by the veterinarian when sedating or anaethesising the horse.

Excepting lipomas of the intestine (see above), there are two types of tumor which are more frequently encountered in senior horses : melanomas (of the skin) and squamous cell carcinomas.

Melanomas

There is a certain predisposition to developing melanomas in grey horses : 80 % of grey horses could be affected. These tumors can be benign or malignant (they will spread to other internal organs). Typically these melanomas are located on the underside of the tail, the perineal region, and external genital organs, even if there are many other possible locations. They can cause functional discomfort such as problems defecating.

Squamous cell carcinomas

These tumors are very aggressive locally. They mainly affect the skin (around the eyes, external genitalia), the eye structure, and the stomach. Horses with non-pigmented skin (as well as paint horses and appaloosas) are more often affected when subjected to exposure to UV radiation.

In practice

Regularly monitor horses’ skin to detect the presence of tumors early on. Surgically removing melanomas, often small when they first appear, is preferable.

With horses, ageing is not necessarily associated to a decrease in liver and kidney functions. However, tumors of the bladder and external genitalia are fairly frequent in older horses. In the same way urinary incontinence (involuntary loss of urine through the urethra) is more frequently diagnosed with age :

• In brood mares, this is often a secondary ailment due to bad conformation of the vulva, or damaged bladder or urethra after foalings or when covered naturally.
• With entire or gelded horses, incontinence is usually associated to sabulous cystitis (inflammation of the bladder). Sediment accumulates in the bladder when it does not empty entirely. This causes irritation of the bladder and leads to complications when infection sets in.

In practice

Observe the horse urinating on a regular basis to detect any pain or an abnormal position. When incontinence is noticed, it should be followed by a clinical examination by the vet : for males, the prognosis depends on the duration of the condition.