Reading a CBC, Eosinophils

Eosinophils may be counted by machines or by a technician doing a manual differential or "manual diff".  This involves taking a drop of blood and making a smear on a slide.  It is allowed to dry, then stained with Diff Quick stain.  Once the stain has dried the slide is viewed under a microscope and evaluated for red and white blood cell morphology as well as a count of 100 white blood cells to determine what percent of cells are of each WBC type including eosinophils.

The number of eosinophilss may be expressed as a percent or as an absolute number which is expressed as some number per microliter.  If you have a choice it is best to work with the absolute number since, with abnormal WBC counts, the number expressed as a percent can be misleading.

Below is a photo of a normal eosinophil although the size of the red granules differ with species, especially the can in which they are more pale and rod-shaped:

Eosinophils are responsible for allergic responses and also play a part in systemic parasite infestations.

Increases in eosinophils or "eosinophilia" occurs as a result of:-Worms: systemic parasites such as heartworm or hookworms.
-Weases: allergic reactions or hypersensitivity reactions including flea bite dermatitis.
-Weird diseases:  feline hypereosinophilic syndromes and some poorly characterized gastroenteritis cases.

Decreases in eosinophils or "eosinopenia" occurs as a result of:-Stress:  due to increased natural or administered steroids.