Granulocytes

Granulocytes are white blood cells that act as the first line of defence against bacteria, parasites, and fungi, in dogs just as in humans.

The name comes from the small granules (granula) in these cells. These contain enzymes that destroy pathogens. When you look at your dog’s blood count, you will usually find granulocytes listed under “Neutrophils”, “Eosinophils”, and “Basophils”.

What types of granulocytes are there in dogs?

Neutrophil granulocytes make up 60-75% of all white blood cells in dogs. They react within hours to bacterial infections, for example when a small wound becomes inflamed.

Eosinophilic granulocytes are the parasite specialists. Their levels rise in cases of worm infestation or flea problems. Normal values lie between 2-10% of leukocytes.

Basophilic granulocytes are the rarest, only 0-1% in healthy dog blood. They release histamine, which you may know from allergies.

What do elevated granulocytes mean in dogs?

If neutrophils rise above 11,000 cells per microlitre, this usually indicates a bacterial infection. An example: your dog has a bladder infection, and the immune system sends reinforcements.

Elevated eosinophils (above 1,000/µl) are often seen by vets in cases of worm infestation. But food allergies, for example to lamb, can also drive these values up.

Basophils rarely rise significantly. If they do, a parasitic infection or a severe allergic reaction may be the cause.

When are granulocytes too low?

If neutrophils fall below 3,000/µl, it becomes critical. The immune system is weakened, often by severe infections that use up all reserves. Some medications or bone marrow diseases can also suppress these values.

A dog with low neutrophils catches infections more easily. The vet will then probably carry out additional tests, such as a bone marrow examination.

What can you as a dog owner deduce from this?

Granulocyte values help the vet distinguish between viral and bacterial infections. Bacterial infections often require antibiotics, viral ones do not.

If eosinophils are elevated, your vet will probably examine a faecal sample. Parasites are common but well treatable. If values remain repeatedly elevated without finding parasites, a food allergy may be the cause.