IN-DEPTH: GERIATRIC MEDICINE/METABOLICS


hospital study. Of the horses presenting for lame- ness, 37.5% had laminitis (mostly in conjunction with PPID), and 55% had lameness classified as degenerative disease. Older horses were signifi- cantly more likely to be given long-term medications than were younger horses. The most prevalent medication given to older horses fell in the non- steroidal anti-inflammatory drug (NSAID) and chondroprotective categories. One can assume that this is an indication of chronic musculoskeletal pain.1 It is hypothesized that earlier injury to joints, muscles, tendons, and ligaments set up the geriatric horse for progressive degenerative changes in the musculoskeletal system. Loss of shock absorption is caused by chronic inflammatory changes in the synovial fluid, cartilage defects, and sclerosis of sub- chondral bone. Osteophytes are a hallmark of os- teoarthritis. Cartilage research in old horses demonstrated that glycosaminoglycan (GAG) levels remain constant throughout life, but there are age- related decreases in proteoglycan size though the loss of GAG chains.13 Older horses also have greater pentosidine crosslinks, which may predis- pose older horses to osteochondral disease caused by stiffer and more brittle cartilage.14 A progressive degeneration of the suspensory ligaments in the hind limb is seen in some geriatric horses (particu- larly older broodmares). Clinically, these horses have straight hock conformation and progressive sinking of the fetlocks. Management of osteoarthritis in the older horses involves judicious use of NSAID drugs and increas- ing mobility. Increasing the mobility of the animal plays a role in decreasing pain. One should avoid stall rest in these animals. Unlimited turnout is preferred. If the older horse is still in work, modi- fications to the training program may need to be implemented. Older horses will probably take lon- ger to become physically fit. Older horses fatigue quicker than younger horses. Continuous low-level work will be better for the older horse than a “week- end warrior” session. The addition of nutraceuti- cals such as glucosamine-chondroitin sulfate has been shown to improve lameness grade, flexion test grade, and stride length in horses with osteoarthri- tis. Acupuncture, chiropractic treatment, and mas- sage therapy may be helpful in the older horse that has multiple problems.


7. Respiratory Problems in the Older Horse


Respiratory tract disease was the third most com- mon body system affected among the geriatric horses in the Brosnahan study. Although RAO or heaves is not restricted to old horses, age has also been determined to be a risk factor for RAO. It was the most common specific respiratory tract disease diagnosed in our study population. In the survey study, 19% of the older horses that were receiving medication were receiving drugs that were compat- ible with the treatment of heaves.5 RAO is an in-


flammatory airway disease similar to asthma in humans. Inflammation of the airway plus broncho- constriction leads to severe obstruction. Clinical signs of RAO include increased respira-


tory rate and effort, cough, the development of hy- pertrophied muscle along the ventral rib cage, exercise intolerance, and increase crackles and wheezes on auscultation of the lung fields. Treatment of RAO is aimed at decreasing inflam-


mation and bronchoconstriction. Environmental reduction of allergens is a main objective in the treatment of this disease. Providing 24-hour turn- out, eliminating hay from the diet, improving venti- lation, and decreasing dust in the environment are important elements of the treatment. For a more rapid reduction in lung inflammation, oral or in- haled steroids are the primary anti-inflammatory drug of choice. Dexamethasone and prednisolone are the system drugs of choice, and beclomethasone is the most commonly inhaled steroid. Bronchodilation can be achieved with several dif-


ferent drugs, including the following: albuterol (in- haled), clenbuterol (oral), and aminophyline (oral). Inhaled albuterol is probably the most effective.


8. Ophthalmology in the Older Horse


Although not commonly reported by owners, 94% of horses more than 15 years of age had at least one abnormality identified by external ocular and oph- thalmologic examination by a veterinary investiga- tor. Degeneration of the vitreous was the most common lesion seen in the aging horse.15,16 In ag- ing humans, the vitreous liquefies and creates “float- ers.” This may be seen in horses as a consequence of recurrent uveitis. Senile retinopathy is the sec- ond most common ophthalmologic problem seen in geriatric horses. The findings consist of irregular linear hyperpigmentation in the non-tapetal fundus and depletion of pigment in the adjacent areas.15 Ireland at al15 reported that the median age for senile retinopathy was 24 years. In the same study, 58% of the geriatric horses examined had evidence of cataracts. The median age for affected animals was 23 years; for bilateral cataracts, the median age was 25 years.15


9. Neoplasia


Squamous cell carcinoma and melanomas are the two tumor types that increase in incidence with age. Squamous cell carcinoma is the most prevalent. It is most commonly seen on the eye and equine penis and prepuce.17 Masses may be single or mul- tiple. In one study, affected animals had a mean age of 16.5 years of age.17 The lighter, non-pig- mented skin is more susceptible to development of squamous cell tumors. It spreads by metastasis to local lymph nodes. Preputial lesions metastasize to the corpus cavernosum penis and inguinal lymph nodes.


Approximately 80% of older gray horses have ev-


idence of external melanomas. These rarely metas- AAEP PROCEEDINGS  Vol. 59  2013 323


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