Pet Health Library

Background

Anemia is a lower-than-normal number of red blood cells. The number of red blood cells can diminish due to loss (bleeding), destruction (hemolysis), or decreased production (bone marrow disorders). Red blood cells carry oxygen throughout the body, so anemia causes a decrease in oxygen delivery to cells.

There are three categories of anemia:

1. Blood Loss Anemia can occur from external and/or internal blood loss.

External blood loss from:

• Injuries like puncture wounds, getting hit by a car, or falling from a building (high-rise syndrome)
• Bleeding tumors such as mast cell, bladder, nasal, and intestinal tumors
• Nosebleeds or blood in stool or urine from low platelets (thrombocytopenia) or other bleeding disorders such as rodenticide poisoning
• Stomach ulcers

Internal blood loss from:

• Bleeding internal organ tumors such as hemangiosarcoma, liver, and kidney tumors
• Spontaneous bleeding from low platelets (thrombocytopenia) or other bleeding disorders such as rodenticide poisoning

2. Hemolytic Anemia occurs when red blood cells are destroyed at an abnormally high rate. Hemolysis is a normal process through which old red blood cells are removed so they can be replaced by new ones. However, if this removal process occurs faster than the replacement, the pet becomes anemic. This can happen from:

• Immune system disorder (immune mediated hemolytic anemia)
• Infections from organisms such as Babesia (parasites that cause babesiosis), Mycoplasma (bacteria), or Leptospira (bacteria that cause leptospirosis)
• Zinc poisoning from ingesting pennies or zinc screws
• Low phosphorus
• Red blood cell disorders resulting from pyruvate kinase and phosphofructokinase deficiencies
• Onion ingestion
• Acetaminophen ingestion in cats
• Exposure to skunk musk in dogs
• Cancer (the tumor(s) destroy red blood cells)

3. Decreased production of red blood cells in the bone marrow. Bone marrows, like any other organ in the body, can stop functioning properly. If the bone marrow cannot produce the necessary number of red blood cells, the pet will become anemic. This can happen from:

• Infections like FeLV or FIV
• Fungal infections
• Tick-borne illness
• Parvovirus
• Iron deficiency from a poor diet, intestinal parasites, intestinal disease or chronic blood loss. Iron is an important building block for red blood cells
• Lead poisoning
• Liver shunt
• Hepatic lipidosis (fatty liver syndrome)
• Kidney disease
• Systemic illness from pancreatitis
• Bone marrow disorders:
  • Myelophthesis (bone marrow tissue is replaced by cancerous tumors like leukemia, multiple myeloma, or lymphoma)
  • Myelodysplasia (bone marrow cannot produce enough red blood cells or produces abnormal cells)
  • Pure red cell aplasia (bone marrow stops making red blood cells)
  • Precursor immune mediated hemolytic anemia (red blood cells are getting inside the bone marrow)
  • Drug reactions: developing red blood cells are damaged in the bone marrow

Diagnosis

If the underlying cause of the anemia is not obvious, your veterinarian will ask for the complete medical history of your pet. These questions will assess any potential toxin exposures, previous illnesses, recent treatments and vaccinations, your pet’s travel history, and the duration of the current symptoms. Afterwards, your veterinarian may recommend further diagnostic tests such blood, urine, and stool tests. X-rays, ultrasound, and bone marrow evaluations are recommended in some cases.

Treatment

Treatment options for anemia depend on the underlying cause, meaning that the therapy will be different for each patient and tailored to your pet’s needs.

Prevention

Not all causes of anemia can be prevented. However, some can be prevented by protecting them against parasites, vaccinating against infectious disease, and avoiding accidental poisoning.