Hemorrhagic (Blood Loss) Anemia
Sudden and severe loss of blood can result in shock and even death, if over 30 to 40% of the total blood volume is lost. This is aggravated if the condition is not dealt with swiftly with intravenous fluids or blood transfusions, or both. Severe loss of blood could be due to major injury or surgery. In cases where the blood loss cannot be easily identified, your veterinarian will search for other causes, e.g. conditions influencing the blood’s clotting ability, bleeding tumors, stomach ulcers, or parasites. Hookworms in dogs are a classic example of parasites that cause severe blood loss in puppies. Iron-deficiency anemia is also caused by extensive and low-grade blood loss, leading to unusually tiny red blood cells and a lack of haemoglobin. In young animals, parasites are the unusual cause, but in older animals, stomach ulcers or tumors are the common cause.
Haemolytic anemia’s result from destruction of red blood cells, and are typically regenerative. It is also a result of toxins, red blood cell trauma, infections, immune system defects, and red blood cell membrane defects.
Immune-mediated Haemolytic Anemia
This type of anemia results from tumors, infection, drugs, or vaccinations. The body develops antibodies that attack its own red blood cells, leading to their destruction.
Dogs suffering from immune-mediated haemolytic anemia show signs of jaundice, fever, and an enlarged spleen. They can display mild, slow–developing signs and may not seem to be in pain at first, but can unexpectedly feel extreme agony. Your veterinarian will modify treatment according to the animal’s signs. Any deep-seated infections will be cured and needless drug therapy stopped. Fluid treatment may be combined with blood transfusions if needed. Medication is also prescribed to repress the immune system so as to prevent the destruction of red blood cells.
Dogs with immune-mediated haemolytic anemia suffer the risk of their blood vessels being obstructed by pieces of blood clots (known as pulmonary thromboembolism). Though the underlying cause is not known, the risks could be minimized using fluids and blood transfusions. Fluids help to maintain the proper functioning of kidneys and protect them from the excessive concentrations of circulating bilirubin (reddish-yellow blood pigments that cause jaundice). If the danger of blood clot formation is high, anticoagulant medication may be used.
Alloimmune haemolysis is the generation of antibodies meant to destroy the red blood cells of another individual of the same species. A rare example of such a condition in dogs is neonatal isoerythrolysis. It is experienced by puppies that nurse from a mother whose colostrums contain antibodies to the newborn’s red blood cells. These antibodies are created in the mother during blood transfusions that are unmatched. Puppies with neonatal isoerythrolysis are born normal but develop extreme haemolytic anemia within 2 to 3 days, resulting in jaundice and malaise. Test can be conducted by a veterinarian to confirm a diagnosis, with treatment involving cessation of suckling while providing supportive care with transfusions. Neonatal isoerythrolysis can also be controlled by withholding colostrum from the mother herself and providing colostrum that is devoid of the antibodies. A test for alloimmune haemolysis should be conducted prior to allowing the puppy to receive maternal colostrum.
Microangiopathic haemolysis occurs when there is unstable flow of blood via abnormal blood vessels, resulting in damage to red blood cells. It manifests in dogs with severe heartworm infection, blood vessel tumours (hemangiosarcoma), and twisting of the spleen. Disseminated intravascular coagulation also occurs, a condition where minute blood clots in the bloodstream block small blood vessels, thus using up all the platelets and clotting factors required to manage bleeding. Correcting the underlying disease is the only solution.
Metabolic Causes of Haemolysis
Dogs suffering from diabetes, hepatic lipidosis (a fat-metabolism disorder in the liver), and re-feeding syndrome (chemical and fluid abnormalities that occur during recovery from fasting or starvation) are susceptible to phosphorous deficiency, which culminates in destruction of red blood cells. The recommended treatment involves provision of additional phosphorus, either orally or by injection, depending on the severity of the disease.
Toxins (Drugs, Plants, Chemicals)
There are numerous types of medication that can result in anemia if they are swallowed by mistake or if their approved use is not tracked closely. These include familiar drugs such as acetaminophen, aspirin, naproxen, penicillin, and a lot of other antibiotic and anti-parasitic agents. Other anemia-creating toxins include plants like oak, red maple, and bracken fern; foods like onions and fava beans; chemicals; and heavy metals such as copper, lead, and zinc. A total medical history has to be provided to the veterinarian when anemia is suspected. This will help to pin down the cause.
Most bacterial, parasitic, and viral infections can cause anemia, by directly destroying the red blood cells or by harming the components that generate red blood cells within the bone marrow. In dogs, such infections involve particular organisms in the genus Ehrlichia and Babesia.
There are certain genetic red blood cell disorders that cause anemia. Deficiencies of the enzyme pyruvate kinase are common in Basenjis, Beagles, West Highland White Terriers, Cairn Terriers, and other breeds. Deficiencies of the enzyme phosphofructokinase occur in English Springer Spaniels. These deficiencies cause brief red blood cell life spans and a regenerative anemia. Dogs with phosphofructokinase deficiency experience abrupt destruction of red blood cells, due to high blood pH produced after extreme exhilaration or exercise. If such situations are reduced, dogs experience an ordinary life expectancy. Unfortunately, pyruvate kinase deficiency has no cure, so affected dogs have shortened life spans caused by irregularities of the bone marrow.