Just like humans, dogs have white blood cells called monocytes. A monocyte is like a superhero — it protects your dog's body by fighting off infections caused by bacteria, viruses, or foreign materials. Your dog's level of monocytes is measured when your veterinarian performs a blood test called a complete blood count (CBC).
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What are monocytes in a dog blood test?
A CBC blood test measures your dog's levels of red blood cells, white blood cells, and platelets. It provides your veterinarian with important information about how your dog's body is functioning.
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For example, a high level of white blood cells, also known as leukocytes, could indicate infection or inflammation. High levels of red blood cells, which carry oxygen and carbon dioxide through your dog's body, could occur due to issues like dehydration or bone marrow disease. A low platelet count could be a sign of immune mediated disease.
Monocytes are one of the five types of white blood cells measured in a CBC's differential test, which shows the percentage of each type in your dog's body. Dogs generally have between 100 and 1,800 monocytes per microliter of blood, or from 1 to 9 percent as indicated in a differential blood test.
The other four types of white blood cells measured in a differential test are:
- Neutrophils: A high count may indicate inflammation, while a low count may indicate a bacterial infection.
- Eosinophils: High levels may indicate allergic reactions or a parasite infection; low levels may be a reaction to stress.
- Basophils: These may increase in dogs with allergies, fleas, ticks, and heartworm disease.
- Lymphocytes: High levels could be due to an infection, leukemia, or a chronic illness, such as arthritis, while low levels are often caused by prescribed corticosteroids.
What is a monocyte?
Monocytes are produced in your dog's bone marrow, the fatty tissue inside the bones. After these immature cells have circulated in your dog's bloodstream for about 24 to 36 hours, they enter tissues throughout your dog's body. There, they mature into macrophages, a type of white blood cell that "eats" antigens, which include unwelcome toxins, such as bacteria or viruses, as well as foreign substances.
Antigens can invade a dog's T-cells, the white blood cells that work with macrophages to protect the body from infection. Thanks to macrophages, the T-cells will be familiar with the offending antigens the next time they're encountered. This means your dog's body will be prepared to ward off any future antigen invasions.
Macrophages serve another important function: They also regulate the amount of iron in your dog's body, helping to prevent health conditions, like anemia.
Low monocyte levels in dogs
Although a dog may have a monocyte count as low as zero, this is rare and doesn't usually indicate an illness. Despite having a fancy name like monocytopenia, a low monocyte count in dogs is not considered a clinical problem
High monocyte levels in dogs
A high monocyte count could be due to a variety of causes, including something as simple as a stressful response to a visit to the veterinarian.
Other possible causes of an elevated monocyte level in dogs include:
- Corticosteroid medications
- Bacterial infections
- Inflammation
- Cushing's disease (hyperadrenocorticism)
- Tissue damage or trauma
- Protozoal infection
- Chronic renal failure
- Cancer
- Valley fever, a fungal infection in some areas of the Southwest
If your dog's monocyte level is above the normal range, your veterinarian may make a diagnosis by reviewing the other blood cell values in the CBC along with your dog's symptoms and medical history.
In summary
The level of white blood cells called monocytes in a blood test in part indicates how well your dog's immune system is able to fight off infections and inflammation. Low levels are rare, while high levels could mean anything from temporary stress to more serious health issues. A veterinarian can use this information to make a diagnosis and determine the best treatment plan.