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Overactive immune response pneumonia in dogs

Overactive immune response pneumonia in dogs

Animal diseases

Overactive immune response pneumonia in dogs

Dogs can develop lung disease following an overactive immune response to an antigen present in the body. This is called allergic or hypersensitivity pneumonia.

It is typically characterized by a significant infiltration of eosinophils in the lungs. Eosinophils are a type of white blood cell that play an important role in the body’s response to allergic reactions and parasite infections. Eosinophils can attack and destroy specific antigens, therefore they move to areas of the body at risk of infection. In this specific case, however, the immune response is excessive and eosinophils can infiltrate and limit lung function rather than directly counteracting the infection.

Previously, this condition was known as eosinophilic lung infiltration (pulmonary infiltration with eosinophils – PIE), but is currently referred to as eosinophilic bronchopneumopathy (eosinophilic bronchopneumopathy – EBP).

Dogs usually develop chronic cough, breathing difficulties and exercise intolerance. A heartworm infection (known by the common term heartworm) is one of the best known causes of eosinophilic bronchopneumopathy (EBP). In this case, the allergic reaction is caused by the presence of microfilariae (immature worms) in the lungs. Other parasites or bacterial infections may also be the main cause of the overactive immune response that occurs in the case of EBP, but more commonly the condition is idiopathic, related to an unknown allergen or a self-perpetuating autoimmune response.

The symptoms of eosinophilic bronchopneumopathy can vary in severity, from chronic bronchitis to a form of pneumonia with rales to small, audible bubbles over the entire surface of the lung fields and difficulty in breathing. A very serious infection (usually related to heartworm disease) can develop nodules on the lungs and compromise the functionality of some of the alveoli, causing a drastic reduction in oxygen absorption.

Most types of hypersensitivity pneumonia respond to steroid treatment, so eosinophilic bronchopneumopathy is a treatable condition.


It is advisable to consult the veterinarian immediately if the dog should experience any of the following symptoms:

  • Cough persistent chronic
  • Vomiting
  • Greenish or yellow secretions
  • Weight loss
  • Temperature
  • Wheezing
  • Shortness of breath
  • Abnormal lung sounds
  • Exercise intolerance
  • Bluish coloring of mucous membranes


  • Eosinophilic bronchopneumopathy (EBP). It is a vaguely defined group of pathologies characterized by eosinophilia and eosinophilic infiltrates in the lungs.
  • Pulmonary nodular eosinophilic granulomatosis it is a very severe form of EBP in which eosinophilic infiltrates cause inflammatory nodules in the lungs.


These are some of the conditions that could trigger eosinophilic bronchopneumopathy in dogs:

  • Parasites (especially Dirofilaria)
  • Bacterial infection
  • Fungal infection
  • Virus
  • External antigen
  • Dusty, smoky or contaminated with mold environment
  • Idiopathic
  • Higher incidence in the Siberian husky

Overactive immune response pneumonia in dogs


The vet examines the symptoms and auscultates the heart and lungs. The presence of rattles and abnormal breathing, in fact, will be even more evident through the use of a stethoscope. Blood and urine tests may not show abnormalities. Following a blood test, about 50% -60% of dogs show eosinophilia, but EBP can also be present in the absence of high levels of eosinophils in the blood.

One pulmonary radiographic study usually shows some degree of infiltration depending on the severity of the problem. Liquids in the lungs and nodules are visible only if actually present. Furthermore, the X-ray helps to identify a possible different condition that could cause the disease from which the dog suffers, such as cancer, foreign body or a different type of lung disease.

The execution of further tests is aimed at identifying the cause of the EBP. The heartworm test and thestool exam for the search for parasites they are very important, since these are commonly present in case of EBP. A liquid sample is taken from the dog’s lungs or bronchial tubes for evaluation of other infections or cytological changes. This can help the vet to determine if the person responsible for EBP is a known antigen.


Preliminary treatment is aimed at treating the symptoms. Severely ill dogs require oxygen therapy (oxygen administration). Typically, a glucocorticoid like the prednisolone for several weeks in order to promote the reduction of lung inflammation. If the airways are severely restricted, the use of a bronchodilator may be necessary.

There melarsomine dihydrochloride is usually used to treat theheartworm infection. This active ingredient belongs to the category of arsenic compounds and, if taken in high doses, it can be toxic. Typically, the dog is given two injections 24 hours apart or 3 injections over the course of a month. As a rule, before proceeding with the treatment, the veterinarian waits for the dog’s respiratory symptoms to stabilize making sure that the dog’s health is good enough.

Antibiotic and antifungal drugs will be prescribed if these infections are part of the problem. The appropriate antibiotics can be identified based on a laboratory analysis or the level of resistance of the bacteria. Antibiotic treatment may be necessary before prescribing glucocorticoid drugs, as steroids limit the function of the antibiotic.

In the absence of another cause, glucocorticoid treatment can be continued for several months in order to eliminate the symptoms. The vet usually adjusts the dosage down to 25% -50% as soon as improvement is observed. Administration of can also be recommended inhaled glucocorticoids, as this type of treatment has fewer negative side effects. Many dogs with unknown allergies need to be treated with glucocorticoids for the rest of their lives to keep the problem under control.


If the cause of EBP is treatable, the dog often recovers completely.

Very serious heartworm infections can be fatal, but if they are discovered in time they are generally treatable. Monthly prophylaxis for heartworm disease is also available and is recommended for dogs that live in areas where heartworm is common.

Unidentified immune responses often require the administration of medications throughout the dog’s lifespan.

Steroid treatment usually reduces the dog’s symptoms to a manageable level, but there are potentially long-term side effects associated with the use of this type of drug. We recommend that you discuss the risks with your veterinarian and make sure your dog takes the lowest effective dose.

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