Myasthenia Gravis, which can be encountered in dogs and rarely in cats; It is a neuromuscular disease. Neuromuscular diseases affect muscles, nerves, or both muscles and nerves. This disease, which occurs as a result of the deterioration of the impulse transmission from the nerves to the muscles, causes the dogs to weaken because it prevents the contraction of the muscles. Certain dog breeds are more affected by Myasthenia Gravis, including Jack Russel Terrier, English Springer Spaniel, Miniature Dachshunds. Myasthenia Gravis in dogs can be present at birth or acquired. Acquired Myasthenia Gravis can occur as a result of many different causes, such as other immune-mediated diseases. In this article, we will provide information about Myasthenia Gravis, which is less known but whose effects should not be ignored.
What Is Myasthenia Gravis in Dogs?
Each muscle in the body is controlled by its own nerve, but this nerve is not directly connected to the muscle. There is a small gap at the junction between the nerve and the muscle. The signals act like electrical currents, and when they reach the nerve end, they travel through the space and are transmitted to the muscles. The spaces in the parts where signals are transmitted to the muscles are normally filled by a chemical called Acetylcholine. Acetylcholine is secreted from the nerve ending, fills the space between the nerve and muscle and is fixed to its receptors in the muscles. When this fixation occurs, it triggers signals that cause the muscles to contract. In dogs with Myasthenia Gravis, messages, or signals, between nerves and muscles cannot be transported properly.
When this connection between nerves and muscles is not established correctly, muscles begin to weaken because they cannot respond to messages and contract. When muscle weakness progresses, dogs have trouble standing and doing their standard exercises. This problem in signal transmission to the muscles does not only affect the limb muscles. Esophageal muscles, swallowing muscles, and respiratory muscles can also be affected.
As we just mentioned, Myasthenia Gravis in dogs can develop congenitally or later. The incidence of the acquired form of the disease is higher. It is known that the risk of acquiring this disease is higher in breeds such as Golden Retriever, Akita Inu, and German Shepherd Dog compared to other breeds.
What Causes Myasthenia Gravis in Dogs?
The causes of Myasthenia Gravis in dogs may vary depending on whether the disease is congenital or acquired. The main reason for the presence of congenital Myasthenia Gravis is that dogs are born with very few Acetylcholine receptors. When Myasthenia Gravis occurs later in dogs, it is usually due to a fault in the immune system.
The main task of the immune system is to protect the body against infections or foreign invaders. Antibodies are produced for this task. Acquired Myasthenia Gravis occurs when the body produces antibodies that attack and destroy Acetylcholine chemicals. Unfortunately, it is not known why the immune system of dogs suddenly attacks Acetylcholine chemicals, which establish the connection between nerve and muscle, while such a structure did not exist for years. Although it is very rare, cancer formations can be observed behind this behavior of the immune system in both cats and dogs. At the same time, it is known that underactive thyroid glands and immune system diseases that affect the muscles or nerves can also be the cause of Myasthenia Gravis. Whatever the cause, altered immune system reactions reduce the number of receptors and cause muscle weakness.
Myasthenia Gravis Symptoms in Dogs
Dogs with Myasthenia Gravis usually experience weakness after a few minutes of exercise. This weakness can affect all legs or can only be observed in the hind legs. Muscle tremors are usually noticeable. Dogs experiencing this symptom recreate their former healthy impression when they rest for a short time and can be active without reappearing exercise-induced weakness. Although Myasthenia Gravis in dogs can cause complaints that occur after exercise, it can also feel its effect with different symptoms.
Complaints such as weakening of the muscles, sleeping with eyes open, difficulty in swallowing, change in barking sound, coughing, difficulty in breathing and excessive saliva production may also be experienced. There may be different problems behind the excessive salivation in dogs. Why Do Dogs Drooling? You can read our content here. We would like to explain the change in barking sound among these symptoms.
Myasthenia Gravis in dogs can affect muscle groups in different parts of the body. Behind the voice change, esophagus, pharynx and facial muscles may be affected. Symptoms can be mild or severe. Myasthenia gravis focal muscle weakness most commonly results in a condition called megaesophagus. This is perhaps the most common symptom of acquired myasthenia gravis and is actually a secondary condition. In a condition called megaesophagus, the esophagus becomes enlarged. When it expands, muscle tone may be lost and unable to function properly. Foods and liquids can cause blockages in the esophagus as well as cause vomiting in dogs. Another important thing to know about megaesophagus is that aspiration can result in pneumonia. This condition is characterized by the formation of infection as a result of filling the lungs with food and fluid. In addition to all these, it can be stated that some dogs may develop a type of tumor called ‘thymoma’ in the chest area due to acquired Myasthenia Gravis.
Myasthenia Gravis Treatment in Dogs
Veterinarians should be consulted immediately when symptoms of Myasthenia Gravis appear in dogs. Veterinarians listen to the history of the disease and perform a physical examination. As a result of the evaluations, imaging methods and blood tests may be used. It is possible to perform a specific blood test called the AChR antibody test to check whether the immune system is producing antibodies against acetylcholine receptors. With this test, myasthenia gravis in dogs will most likely be definitively diagnosed.
The subject of treatment is somewhat complicated. Myasthenia Gravis in dogs cannot be cured definitively. Unfortunately, some puppies are born with this disease and do not survive for long. In the case of acquired Myasthenia Gravis, it is possible to offer dogs a more comfortable life. It is critically important to establish an effective dialogue with veterinarians during the treatment process and not to disrupt the daily care of dogs. In this context, various treatment options can be used. Drug treatments, immunosuppressive treatments and supportive treatments are very important. Within the scope of Myasthenia Gravis treatment in dogs, veterinarians will inform the dog owners in detail and provide information about all the factors that need attention.