Eosinophilia

Eosinophilia refers to an increased proportion of eosinophils in a dog’s blood. Eosinophils are white blood cells that belong to the immune system and play a central role in defending against parasites and in allergic reactions. If their numbers rise above normal levels, this usually indicates an underlying disease.

Causes of Eosinophilia in Dogs

Parasitic infections:

• Worms such as roundworms, hookworms and tapeworms trigger a strong immune response that leads to eosinophilia.
• Heartworms are another parasitic cause of elevated eosinophils, particularly in areas where these parasites are common.
• Protozoan infections such as giardia or other parasitic diseases of the gastrointestinal tract.

Allergic reactions:

• Dogs can react to environmental allergens such as pollen, dust or mould, which causes the number of eosinophils in the blood to rise.
• Food allergies or intolerances can also trigger eosinophilia.

Inflammatory diseases:

• Eosinophilic gastroenteritis is a rare form of gastrointestinal inflammation in which eosinophils enter the gastrointestinal tract and cause inflammation there.
• Autoimmune diseases or chronic inflammatory processes can also lead to elevated eosinophils.

Cancer:

• Certain tumours such as mast cell tumours or lymphomas can cause eosinophilia, especially when the immune system reacts to the tumour.

Skin diseases:

• Eosinophilic granulomas, a skin disease with nodules and ulcers, are considered a sign of an eosinophilic reaction and are often associated with allergic diseases.

Symptoms of Eosinophilia

Symptoms depend on the underlying cause. Some dogs show no obvious complaints, while others exhibit signs of infection or an allergic reaction:

• Itching and skin changes: Especially with allergic reactions or skin diseases, itching, redness and swelling can occur.
• Digestive problems: Vomiting, diarrhoea or loss of appetite can occur with parasitic infections or inflammatory gastrointestinal diseases.
• Breathing problems: In severe cases of allergic reactions or heartworm infections, breathing difficulties can occur.
• Fatigue and lethargy: Due to the immune response or physical strain, dogs may appear weak and tired.
• Weight loss: With chronic infections or gastrointestinal problems, the dog may lose weight.

Diagnosis of Eosinophilia

The diagnostic process begins with a blood analysis, which determines the proportion of eosinophils in the blood:

1. Blood test: A complete blood count shows the eosinophil level and reveals an increase. The normal range is usually between 0–1.2 × 10⁹ cells per litre of blood, depending on the laboratory.
2. Faecal examination: A faecal analysis can be carried out to look for parasites as a possible cause.
3. Allergy tests: If an allergic reaction is suspected, specific allergy tests can identify the triggering allergen.
4. Ultrasound and X-ray: Imaging techniques such as ultrasound or X-rays help detect internal inflammation, tumours or parasites (e.g. heartworms).
5. Biopsies: In cases of skin diseases or tumours, a tissue sample (biopsy) can be taken to narrow down the cause of eosinophilia more precisely.

Treatment of Eosinophilia

Treatment depends on the underlying cause:

1. Parasites: If a parasitic cause is present, antiparasitic therapy is used, with deworming agents or specific medications against heartworms.
2. Allergies: In cases of allergic reactions, antihistamines, corticosteroids or special diets can alleviate symptoms. Desensitisation therapy can help with severe allergies by gradually accustoming the dog to the allergen.
3. Inflammatory diseases: Inflammatory diseases that trigger eosinophilia are often treated with anti-inflammatory medications and a special diet.
4. Tumours: If a tumour is the cause, surgical removal, radiotherapy or chemotherapy may be required.
5. Supportive measures: In some cases, fluid therapy or further supportive measures may be necessary to stabilise the dog and relieve its immune system.

Prognosis

The prognosis depends heavily on the cause. In the case of a parasitic infection or allergic reaction that is treated specifically, it is generally good. For chronic or serious conditions such as tumours or autoimmune diseases, treatment success depends on the progression of the disease.