At the center of the circulatory system is the all-important heart, a muscle that pumps blood to the rest of the body. Diseases that affect the canine heart include birth defects, aging, infectious disease, and heartworm. Heart-worm is a condition that can be deadly but is easily avoided by giving regular preventive heartworm medication, as discussed in Chapter 18.

All activity in the nervous system generates from the brain, the spinal cord, and the peripheral nerves. Spinal cord diseases, seizures, head injuries, and paralysis are some of the problems that can result from injury or disease of this system.

A seizure is caused by a sudden burst of electrical activity in the brain, affecting the entire body by causing uncontrolled convulsions: foaming at the mouth, jerking of the limbs, snapping of the jaws, or rolling of the eyes. Depending on the severity, the dog may collapse and slip into unconsciousness. Seizures can be caused by trauma to the brain or the healing associated with it, or by a hereditary condition.

Epilepsy is a state of recurrent and similar seizures that typically happen in three phases: sudden restlessness accompanied by champing or foaming at the mouth; falling to the ground with head thrown back and pupils dilated, slobbering and drooling; and a recovery phase in which the dog is disoriented. The more violent phases, one and two, happen in just a few minutes; the recovery phase may last hours. You must consult with your veterinarian and your puppy's breeder if your puppy has epilepsy.

Complete paralysis is the result of permanent damage to the spinal cord. But a dog can experience partial paralysis due to a spinal cord disease or infection. Lyme disease is a form of tick paralysis in which the effects of the tick bite come on slowly, impairing movement to the point of paralysis. A speedy diagnosis is key to recovery. Normally the paralysis resolves with treatment by antibiotics.

Problems of the Musculoskeletal System

Bones and muscles support the body and protect the internal organs. All dogs, regardless of size, have an average of 319 different bones in their bodies. The bones are connected by ligaments and surrounded by muscles.

If your puppy is limping or is favoring a particular leg (lame), chances are he's got a bone or joint disease, a strained muscle or tendon, or possibly a broken bone. The causes range from something as severe as a congenital disorder like hip or elbow dysplasia, to something as ordinary as a strained muscle or age-related as arthritis. Your veterinarian should give you a professional diagnosis.

Canine hip dysplasia (often referred to as CHD or just HD) is a disorder of the hip socket. In a healthy hip, the head of the thigh bone (femur) should fit snugly in the hip socket (acetabulum). If the ligaments around the socket are loose, the head of the femur will start to slip from the socket. This causes gradual hind end lameness and pain. Treatment varies depending on the age of the dog, the severity of the condition, and the options available to dog and owner. Rapid advances are being made in the treatment of hip dysplasia.

While a specific cause of CHD has not been identified, it is suspected to be an inherited disorder, and breeders are encouraged to x-ray their dogs before breeding and to only breed dogs that have been certified free of the disease. It has happened, however, that CHD-free parents have produced pups that develop hip dysplasia. Weight, nutrition, and environment have all been implicated in the possible exaggeration or development of CHD, which normally manifests at an age of rapid growth.

Another common occurrence in dogs — particularly larger, active dogs — is a rupture of the cruciate ligament. These ligaments support the knee, where the femur, tibia, and patella connect. A sudden movement or a trauma to the area can result in tearing, or rupturing, of one of these critical ligaments. Obesity can also contribute to injury to these ligaments. An ACL injury is one to the anterior cruciate ligament in the front of the knee; a PCL is one to the posterior cruciate ligament behind the knee. A dog with a CL injury will pull up lame, usually unable to put weight on the foot of the affected leg. An immediate trip to the veterinarian is in order, and from there, if the diagnosis is ACL or PCL, treatment is typically surgery.