Avian Anemia

Anemia is evidenced by a decrease in the erythrocyte count and packed cell volume. Deficiency anemias are not recognized in exotic birds. Due to the presence of iron in many dietary products fed to pet birds, it unlikely iron deficiency anemia would occur except with blood loss. For the purpose of this discussion, anemias are classified as non-regenerative/regenerative, hemolytic, and blood loss related. Juvenile pet birds will often run somewhat lower RBC counts and hematocrits. As a general rule of thumb, these values should be within normal adult ranges at weaned sales age.

Non-regenerative anemia
Non-regenerative anemias (NRA) are the most common type observed in avian patients. Factors which reduce erythropoesis will cause non-regenerative anemia. These include infectious disease, cachexia, neoplasia, and certain toxins. The most common etiologies of non-regenerative anemias in pet birds are of infectious origin.
Chronic active and acute active chlamydial infections represent a common cause of NRA. Bacterial infections, including degenerative gram-negative septic states, and chronic granulomatous (mycobacteria, coliforms, Salmonella) infections can cause NRA. Granulomatous fungal infections (aspergillosis) occasionally cause anemia. Mycoplasma infections in pet birds are not well-documented as a cause of anemia. Viral infections can also cause non-regenerative anemia. Cessation of NRA is characterized by increasing RBC count, increased PCV, increase in immature erythrocytes, increase in anisocytosis, and increased polychromasia. When the clinician manages treatable infectious etiologies, cessation of NRA gives an improving prognosis.
Wasting diseases and neoplasia often result in anemia, due to catabolic influences. Renal failure anemia is not frequently noted. This may be partly due to difficulties in early clinical and biochemical recognition of renal dysfunction. In addition, it is likely that uric acid metabolites don't have the same inhibitory effect on erythropoesis as urea in mammals.
Toxins can result in non-regenerative anemia.

Hemolytic anemia
While it is likely that autoimmune hemolytic anemia occurs in birds, this type of anemia is not well-documented. Lead toxicosis damages the hemoglobin and results in premature lysis and removal of the damaged cells. Affected cells will be seen in the peripheral blood showing hypochromatic cytoplasm and erythrocytic ballooning. One hallmark of lead toxicosis is the vigorous regenerative response occuring within hours of the toxic insult. Basophilic stippling is not a typical finding with avian lead toxicosis.
Oil-ingestion is well-documented as causing hemolytic anemia and is one of the adverse effects suffered by birds residing in oil spill disaster zones.

Blood Loss Anemia
Acute blood loss greatly concerns many pet bird owners. In reality, the highly effective avian clotting system, coupled with adequate exogenous Vitamin K, prevents many bleeding episodes from becoming terminal events. Severe trauma, organ rupture, aneurysms, and iatrogenic causes can result in severe blood loss. In an otherwise healthy bird, post-shock recovery from blood loss is rapid and effect. No significant storage pool exists in birds, but erythropoesis will increase dramatically within hours. As with cessation of non-regenerative anemia, recovery from blood loss anemia is characterized by increasing RBC count, increased PCV, an increase in immature erythrocytes, an increase in anisocytosis, and increased polychromasia. Mitotic figures will occur in the peripheral blood of birds experiencing a dramatic response to blood loss anemia.
Conure Bleeding Syndrome (CBS) appears in conure species with rapid onset of weakness and somnolence. The patient may be bleeding from the mouth or cloaca. In some cases, the hemogram suggests responsive anemia with no visible bleeding, consistent with internal hemorrhage. Cytologically, CBS appears similar to changes seen with lead toxicosis. This syndrome may be due to a calcium deficiency, which is supported by a finding of hypocalcemia in a historically calcium/Vitamin D3-deficient bird. Clinical response to parenteral calcium strengthens this hypothesis.

Erythrocyte Artifacts
Errors in collecting, handling, and preparing avian blood samples can result in artifacts affecting erythrocyte appearances. The blood film should be made immediately during the blood collection or soon after from mixed anti-coagulated blood. Failure to make an adequate blood film may result in ruptured and distorted cells. EDTA can cause distortion of erythrocyte shape, when the whole blood remains in contact for several hours. Blood films which are shipped in packages containing formalin can be damaged by the fumes, resulting in staining artifacts. Stains containing excess sediment can create the appearance of erythrocytic inclusion bodies or parasites.