Sunday, October 02, 2011

Chiari is a malformation of the back for some spaniels

Paws & Claws

Jill Bowen has practiced veterinary medicine in England and Texas. She lives in Blacksburg now, and answers local pet owners' questions every week in The Roanoke Times and roanoke.com.

Recent columns

Q. As I was looking for a suitable Cavalier King Charles spaniel puppy online, I was surprised to see that one breeder declared that her dogs were Chiari free. What is this condition?

A. Chiari-like malformation has been recognized in this breed for many years, and in Britain it is thought that it affects 95 percent of the breed.

This condition is a congenital malformation of the back of the skull, where the opening at the base is too small, causing pressure on the back of the cerebellum and the brain stem. There is disturbed function of the brain and spinal cord at this point. In people this malformation causes headaches, neck pain, dizziness and clumsiness, and there is every reason to suppose that canine Chiari-like affected animals have the same symptoms.

In time syringomelia may develop in an older dog. That is an accumulation of cerebrospinal fluid in the spinal canal causing damage to the spinal cord. This buildup of fluid causes weakness, impaired balance, pain in the neck and forelegs, and in severe cases, incontinence.

It is believed that the condition is inherited, although the gene or genes responsible have yet to be identified. Puppies do not usually show any of the typical signs of Chiari malformation. This only becomes apparent in the adult dog; indeed some dogs that are shown to have the malformation diagnosed by Magnetic Resonance Imaging never show any obvious clinical symptoms.

Obviously any dog diagnosed with this condition should not be used for breeding.

Q. Is there anything new on the Lyme disease front? I am sure that my dog and I both have Lyme disease, although the blood tests came back negative. My vet has prescribed a course of antibiotics for the dog and wants me to give them for at least 2 months. This seems very costly. Is it necessary?

A. Research at both Cornell University and the University of California-Davis veterinary schools this year has produced some interesting new information.

Workers at Cornell developed a new test for Lyme disease that can be used in both horses and dogs. This not only speeds diagnosis, but it also pinpoints when the animal was infected. The bacteria (Borrelia burgdorferi is actually a spirochaete) that cause Lyme disease hide in the joints, nervous tissue and organs of the host. By the time clinical signs appear, the bacteria have left the blood stream and thus blood samples appear to be negative.

Cal-Davis scientists found that the bacteria responsible for Lyme disease also infect the animal's lymph nodes. This stimulates a significant immune response, but unfortunately the response is not strong enough to eliminate the infection. This could explain why some people and animals experience repeated clinical signs of Lyme disease -- and why your dog has been prescribed a prolonged treatment of antibiotics.

The vector of Lyme disease is a tick, the most commonly found vector is the blacklegged tick (Ixodes scapularis), formally known as the deer tick (Ixodes dammini).

It is still important to be vigilant in checking your pet and yourself for ticks on a daily basis, as well as being consistent with the monthly topical application of flea and tick medicine.

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