Canine Masticatory Infections

The canine masticatory muscles give the dog the ability to chew and bite. They control the opening and closing of the mouth. The masticatory muscles comprise the jaw and temple muscles. The muscles often suffer inflammation and infection when they are attacked by the immune system, which renders the dog unable to close its mouth. The canine's lower jaw will hang open. The condition is referred to as masticatory myositis

  1. Occurance

    • Masticatory myositis occurs when the dog is around 3 years of age. Certain breeds, such as German Shepherds, Dobermans, King Charles Cavalier Spaniels, Labrador Retrievers and Golden Retrievers appear to have a genetic predisposition, according to Mar Vista Animal Medical Center. The condition does not appear to be gender-based and appears in male and female dogs equally.

    Symptoms

    • The masticatory muscles in the temple region of the dog's head become inflamed, which causes the dog's eyes to bulge from its head. As the inflammation and infection advances, the dog's lymph nodes feel enlarged when palpitated. The dog will also run a fever and suffer lack of appetite and lethargy. When the condition becomes advanced the dog will suffer rigid muscles, which makes closing the dog's mouth and chewing difficult.

    Diagnosis

    • Diagnosis of masticatory myositis is made using a blood test known as the 2M antibody test, discovered by Dr G. Diane Shelton at the University of California at San Diego. The test has never rendered a false-positive, so it is considered to be highly accurate.

    Treatment

    • Once a diagnosis of masticatory myositis is made, the dog will be placed on high doses of prednisone and dexamethasone. The drugs are used to suppress the body's immune system so it ceases attacking the masticatory muscles. A chemotherapy drug known as azathioprine also works to suppress the immune response, but it requires close monitoring.

    Long Term Outlook

    • When the condition is caught early, the long-term outlook is good. Treatment must be ongoing or the disorder will return. Relapse is common when the medications are discontinued, according to the Michigan Veterinary Specialist. If masticatory myositis has been ongoing for a long time the muscles often sustain widespread scarring, which is difficult or impossible to treat. The dog may require a liquid diet. Providing chew toys helps to loosen the jaw muscles up.