Why Is My Dog Or Cat’s Basophil Count High Or Low?

Ron Hines DVM PhD

See What Normal Blood & Urine Values Are

Causes Of Most Abnormal Blood & Urine Tests

See How Tests Are Grouped

The Number Of Basophils In Your Pet’s Blood “Basos”

The basophil is one of your dog or cat’s white blood cell types. It is a very uncommon cell, rare in most pets and humans. Often none are seen when your pet’s blood is examined microscopically. Basophils form in your pet’s bone marrow from progenitor cells that can also produce mast cells. Mast cells are the basophil’s closest relative. Of all the white blood cell types, we know the least about what basophils functions are in health or disease. (read here)  

An over-abundance of basophils (= basophilia) is quite rare. When your dog or cat’s basophil numbers are above normal, it is often in conjunction with an increased number of eosinophils, another of your pet’s white blood cells that is associated with allergies and parasitic worms. Like their cousins, the mast cells that are found scattered stationary throughout your pet’s body tissues, basophils contain histamine, a compound always involved in allergic and inflammatory reactions. There are probably many more basophils scattered as residents in tissues throughout your pet’s body than there are in its blood stream. Since they contain histamine, a compound associated with inflammation, basophils most likely perform positive and negative policing activities as yet to be discovered. 

Why Might My Dog Or Cat’s Basophil Count Be High? (=basophilia)

In the very rare cases where too many basophils are present in your dog or cat’s blood and its eosinophil count remains normal, bone marrow problems involving the cells that give rise to basophils (hematopoietic stem cells) are generally the cause. Those problems are often cancerous (leukemias). Generally, when that is the case, findings regarding other bone marrow stem cells will be abnormal as well. That includes their number, their shape, their maturity and their location. 

I mentioned that increased basophil numbers are often found in association with higher than normal eosinophils numbers being present in your pet’s blood or the presence of internal parasites or allergiesFlea infestations might also be a cause. Basophil numbers occasionally go up in liver disease. An excess number of basophils has also been reported when persistently high triglyceride levels were also present.

Why Might My Dog Or Cat’s Basophil Count Be Low? (=basopenia)

It is not unusual for a veterinary laboratory to report that no basophils were present in the blood samples of healthy dog and cat’s. In humans, low basophil counts are associated with sudden, severe allergic reactions (anaphylaxis), severe bacterial infections, hyperthyroidism, prolonged corticosteroid administration or stress. No information I know of exists for dogs or cats. 

Complementary tests:

WBC differential count and blood chemistry values, M:E ratio,    bone marrow biopsy. When accompanied by elevated eosinophil numbers – an examination for parasites of all kinds – preferably including PCR tests.  Read more about the PCR test here


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