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The enduring enigma of small dogs: they're loving, ideal for urban life and generally live longer but have health problems unique to them.

Small dogs have been bred for generations as loving companions alongside their owners. They're typically less than 20 pounds, cuddly and full of mischief just like their larger brethren. And to judge by one national measure, they're growing in popularity.

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In an analysis of medical records of 2.5 millions dogs at its 925 locations, Banfield Pet Hospital, which logs breed identification according to owners' descriptions, found small dogs now account for 45 percent of the dogs it sees. Specific increases over the past decade include Chihuahuas, 35 percent; Shih Tzus, 39 percent; Maltese, 87 percent; and Yorkshire Terriers, 95 percent.

Banfield acknowledges the increase may reflect the fact its hospitals tend to be in metropolitan areas and attract owners with small breeds who are convenient for urban living, but that's part of the dogs' appeal.

Multiple Advantages. "There are many advantages to having one of these small dogs. I think, especially for urban lifestyle, that a small dog is a great idea. He can be paper trained, he doesn't need quite as much exercise as a hunting breed dog, and he doesn't take quite as much food," says Katherine A. Houpt, VMD, Ph.D., ACVB, emeritus professor at Cornell University College of Veterinary Medicine.

Despite their attributes, small dogs remain one of nature's enigmas: they generally live longer than large dogs but have special health problems. "The speculation is that larger-type dogs have an exaggerated growth period that results in a more rapid aging deterioration," says Jerry Klein, DVM, chief veterinary officer at the American Kennel Club. "Some larger dogs may be prone to different health issues like developmental disorders, musculoskeletal and gastrointestinal diseases, and tumors, some of which can become fatal."

The difference in small dogs is that they may be prone to disc disorders and other ailments that can often be managed over longer period of time rather than being fatal conditions, Dr. Klein says.

Periodontal disease, retained baby teeth and dislocated kneecaps are problems particular to small breeds. Our Cornell experts explain some of the health challenges these small dogs face, their treatment, prognosis and, when possible, prevention.

Bred for Baby Faces, But Soft Tissues Stay the Same

Brachycephalic Airway Syndrome (BAS) refers to upper airway abnormalities. The dogs have a shortened, broad heads, which give their faces a pushed-in look resembling babies.

"BAS is a hereditary problem caused by selective breeding," says surgical specialist James A. Flanders, DVM, ACVS, associate professor at Cornell. "They have shortened bony features in their nose and jaws; however, the soft tissue structures within the nose and jaws--the soft palate, the nasal passages, the mucous membranes in the throat--have not been reduced in size."

The result can be respiratory distress. The soft structures crowded in a small space obstruct the passage of air through the nose and the mouth. "The characteristic snoring noise that brachycephalic dogs make when they breathe is caused by the movement of air through these narrowed air passages. The characteristic abnormalities are stenotic (narrowed) nares, elongated soft palate, everted laryngeal saccules, hypoplastic (narrow) trachea," Dr. Flanders says.

BAS can lead to exercise intolerance, collapse and death. "Severely affected brachycephalic puppies can develop fatal pneumonia because of airway--especially trachea--abnormalities," he says.

Signs vary from each dog and breed, and depend on the amount of airway obstruction. "Some brachycephalic breeds such as Pugs and Boston Terriers typically have minimal signs, mostly noisy breathing and occasional snoring, and these breeds rarely require surgical treatment. English Bulldogs can also have minimal signs, but some English Bulldogs can have severe airway obstruction, as can French Bulldogs," Dr. Flanders says.

Treatment: Plastic surgery may be performed to widen the nostrils of affected dogs to allow more air to enter the nasal passages, Dr. Flanders says. "We also shorten and sometimes thin the soft palate so that it does not obstruct the throat. Some dogs develop an additional obstruction to airway flow through the throat called everted saccules--the small mucous membranes within the throat that can be pulled into the throat due to the great pressure generated when affected dogs breathe."

Prognosis: Surgery greatly helps many dogs, yet many will still have residual noise. "The goal is to improve their ability to breathe and exercise," Dr. Flanders says. "They won't ever become racing Greyhounds!"

Possible prevention: "Keep brachycephalic dogs slim," he says. "The extra fat can cause them to breathe harder, and extra fat in the neck can add to the obstruction on the throat and trachea. Don't exercise brachycephalic dogs in the heat."

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Patellar luxation: A Hop and a Skip

Dislocated kneecaps are a common malady in small dogs. The kneecap can luxate to the inside (medial) more often in small dogs or to the outside (lateral), a condition more common to large dogs, says Rory J. Todhunter, BVSc, Ph.D., ACVS, professor of surgery at Cornell.

"No one knows the exact cause, but it relates to muscle imbalance and abnormal hip conformation. It's been postulated to be an autosomal recessive trait--two copies of an abnormal gene must be present for a condition to occur. I bet it's complex--multigenic," he says. The condition can result from injury just as in people.

Signs include skipping, carrying the affected leg up, intermittent to continuous limping and carrying the hind legs off the ground, with the weight on the front legs.

Treatment: "Challenges are the same for large dogs and include recurrence and lameness due to arthritis, and can occur with the rupture of the cranial cruciate ligament--the stabilizer inside the knee joint," says Dr. Todhunter.

Prognosis: Good for less severe cases but only fair for more serious ones, which may require surgically cutting bone to repair the disorder as well as aggressive soft tissue repair.

Possible prevention: Muscle strengthening through rehabilitation and exercise may be helpful. Better is to not interbreed dogs with the disorder.

A Mutation Can Cause Rear Limb Paralysis

Intervertebral Disc Disease (IVDD) is a spinal cord disease causing back pain, rear limb paralysis and the inability to walk or feel the back legs. The intervertebral disc is a jelly-doughnut like structure that acts as a cushion between spinal vertebrae.

"IVDD occurs due to conformation," Dr. Todhunter says. "A classic example is the Dachshund with short legs and long body, which is at least partly due to a mutation. It results in the degeneration of the intervertebral disc--especially the nucleus pulposus, the soft hydrated center of the disc--the jelly part of the doughnut. Mechanical overload, especially obesity, then adds insult to the genetic predisposition."

All small breeds are predisposed to IVDD, and Cocker Spaniels and large dogs can also develop it. "IVDD is a very serious condition and clinical signs include back pain, difficulty walking, wobbly gait, weakness and paralysis and loss of innervation to all sites below the problem," says Dr. Todhunter. "It can occur in the neck and back but most common is the junction of the chest and abdomen."

Treatment: Surgical decompression if the dog is down. Loss ot sensation and and motor function may be permanent.

Prognosis: Good if decompressed early. Poor if deep pain is not present and especially if a patient is deep pain negative for more than a few hours or days. It can take a long time to recover, and the dog may not regain full motor control.

Possible prevention: Fitness and ideal body weight to reduce mechanical load across the spine.

Anatomy's Role in Dental and Oral Health

Periodontal disease is an equal opportunity disease affecting most dogs, but small dogs seem to be more prone to severe periodontitis, says Kevin Ng, BSc, BVMS, a resident in dentistry and oral surgery at Cornell. "This appears to be partly due to their having tooth crowding due to their small skull size."

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Spaces between the teeth are then more prone to plaque accumulation that are harder to keep clean through normal chewing or dental home care. Other factors include breed, genetics, the bacteria involved and level of dental home care, Dr. Ng says.

Small teeth means it takes less bone destruction before the teeth become untreatable, and it's also what helps periodontal disease progress faster, Dr. Ng says. "If secondary nasal infection and pathological mandibular fractures are involved, then treatment will have to be more extensive. Periodontal treatment may have to be performed more frequently in small dogs."

Bacteria and their byproducts in dental plaque stimulate an inflammatory immune response seen as gingivitis, or inflammation of the gums. "While gingivitis is reversible," Dr. Ng says, "if left untreated, it frequently leads to the gradual destruction of the soft tissues and bone that support the tooth, or periodontitis. Unlike gingivitis, periodontitis is irreversible."

Bad breath and inflammation are the first signs. "In advanced cases, bleeding and/or receding gums, pus, loose teeth and facial swelling may be noticed," he says.

As with many conditions, the longer periodontal disease is left untreated, the greater the risk of developing severe consequences. Inflammation and infection of teeth in the upper jaw may spread to the nose in severe cases. One of the most devastating consequences of periodontal disease is pathological mandibular fracture. "In these cases, the bone of the lower jaw is so severely affected that it may break as a result light trauma or normal chewing behavior," Dr. Ng says.

Possible prevention: Control by removing plaque and calculus from the teeth. Additional treatments include root-planing, periodontal surgery and medications. In the most advanced cases, extraction of the teeth is frequently the only option, says Dr. Ng. "Prevention is definitely better than cure. Daily tooth brushing is the gold standard, and if performed properly, is the most effective choice."

AFFECTED BREEDS

Brachycephalic breeds will sound as though they're snoring when they breathe because of air moving through narrowed air passages, Among the breeds are:

* Bulldogs

* Boxers

* Boston Terriers

* Bull Mastiffs

* Chinese Pugs

* Lhasa Apsos

* Pekingese

* Shih Tzus

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Title Annotation:SPECIAL REPORT
Publication:Dog Watch
Date:Jun 1, 2017
Words:1647
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