Infectious inflammatory myopathies or myositis in dogs are a group of diseases that generate inflammation of the different muscular tissues of the animal. The word myositis comes from “mine” which means muscle, and “itis” which means inflammation, which is why it is defined as an inflammatory disease of the muscles.

Types of myopathies in dogs

There are two pathologies that cause myositis in dogs: polymyositis and myositis of the chewing muscles.
Polymyositis is a type of inflammatory myopathy that is shown as a more generalized aspect of muscle involvement. First, it damages the muscles of the extremities, especially in adult races. Generally, it is discovered through exercise when the dog shows weakness, fever or the beginning of muscular atrophy.
For its part, the myositis of the chewing muscles, also called eosinophilic myositis, is an inflammatory disease that damages the animal’s chewing muscles, that is, the temporal muscles (masseter and pterygoid), causing immobility in them.
There are two types of these pathologies, chronic and acute. In the chronicle, muscle atrophy predominates; In the acute, its most common symptoms are pain and fever.

Causes of inflammatory myopathies in dogs

The main cause of an inflammatory myopathy has not been discovered, however, a possible cause that generates myositis could be viruses, since the animal’s immune system turns against its own muscles, causing weakness and other complications.
Also, a bacterial infection can produce a local myopathy after the condition, if the animal is exposed to a wound or distant external agent. Within these inflammatory diseases are microorganisms such as Toxoplasma gondii and Neospora caninum, which aggravate the symptoms of these pathologies, especially in young and depressed dogs.
Toxoplasma gondii is a parasite that integrates the group Coccidia and Phyllum Apicomplexa. Generally, it is found in warm-blooded animals, but in the case of dogs, this bacterium is only a host in the canine organism.
This germ is formed as an inoffensive cyst that, when broken in the dog’s organism, can cause abortions as it crosses the placenta and infects the fetus. Toxoplasma gondii is lodged in the myocardial fibers that, when split, can cause lymphohistiocytic focal myocarditis with partial hyalinization of the fibers, hemorrhage and other serious injuries.
Neospora caninum, on the other hand, is a parasite that was originally associated with Toxoplasma gondii due to its similarities. This causes neuromuscular alterations in dogs, especially those found in fields or stables. In general, the dogs infected with this parasite had some kind of contact with another infected animal or access to infected placentas and fetuses of cattle. To become infected, the dog’s age is not relevant, it should only have contact with the bacteria.

Symptoms of inflammatory myopathies in dogs

Among the main symptoms associated with inflammatory myopathies in dogs, we find:

  • Fever
  • Pain with lameness
  • Rigidity in the extremities
  • Loss of muscle mass (atrophy
  • Inflammation in the affected area
  • Progressive paralysis of the hind legs
  • There may be alterations in the nervous system

In case of an inflammation of the chewing muscles, eosinophils rise and creatine kinase (CK) increases.

Diagnosis and treatment by the veterinarian

The diagnosis of these diseases is made by the veterinarian through a blood test, where it is evaluated whether an enzyme is elevated or not; This ferment is called creatine kinase.
Creatine kinase or kinase (ck) is that enzyme that allows muscle contraction. When muscle damage occurs in the dog, the activity of the CK reaches its maximum level of 6 to 12 hours. This time must wait and if the damage does not persist, the muscle can return to normal in about 2 days.
When the blood test is done to the dog, you can see in the results those muscles that were affected; This can also be diagnosed by means of a biopsy.
Once proven to be an infectious myopathy, immunosuppressants and medications such as clindamycin, pyrimethamine and trimethoprim-sulfadiazine can be given.
In the case of Clindamycin, this antibiotic belongs to the group of Lincosamides. It acts on positive bacteria streptococci, anaerobic bacteria and staphylococci. Dogs that have Toxoplasma gondii should give orally 1 tablet every 10 kg of weight, twice a day, approximately between 14 and 21 days.
This medicine can not be used in puppies or newborns, it can not be consumed by pregnant or lactating females, nor should it be administered with other antibiotics. In addition, it should be stored at a temperature between 15 and 30 degrees and should only be supplied under veterinary medical supervision.
Its excessive use can generate vomiting and diarrhea. In case you have to opt for a prolonged use, the animal should be given probiotics since they protect the intestinal flora and reinforce the immune system of the same.