Whole blood and component transfusion medicine is still an evolving science in many exotic species. Only recently has the practice become more widely used and researched as to its efficacy in avian species. Often the practical aspects of obtaining appropriate donors, expense, and owner willingness are limiting factors in avian transfusion medicine. This chapter will focus on our current knowledge of avian transfusion medicine derived from an extensive literature review, methods translated from mammalian transfusion practices, and the authors’ experiences.

Anemia is a common finding in birds presenting for illness and can be a result of numerous acute and chronic disease processes. Documented and speculated causes can be classified as RBC loss (e.g., hemorrhage, coagulopathies, parasitism), increased RBC destruction (e.g., hemoparasites, certain bacterial infections, autoimmune disease), or decreased RBC production (e.g., nutritional deficiencies, chronic infection/inflammation, chronic kidney disease, toxicosis) (Samour 2006; Johnston et al. 2007). A common cause of non-regenerative anemia in birds is anemia of infection or inflammation.

To date, the majority of the published work regarding avian blood groups has been performed in chickens, with 28 blood groups described in the species (Hohenhaus 2004), along with the major histocompatibility complex (MHC) B and Y (Gilmour 1962; Briles and Briles 1982; Miller et al. 2004). MHC class IIB gene sequences have also been classified in quail (Shimizu et al. 2004). Early studies of 94 species of passerine birds used antisera to human RBC antigens ABO, Rh, Kell, Duffy, Kidd, and others to test for agglutination. Based on these tests, A, B, AB, and O-“like” reactions were observed, but it was uncertain if they were identical to the same groups in humans (Ferrell 1966). Similar research has been performed attempting to classify the variation in those blood reaction frequencies in song sparrows in the San Francisco Bay area (Ferrell 1966). Further research is needed to classify avian blood groups and determine how they might differ among species and individual birds.

The ideal avian donor is healthy and in good weight, with no history of recent illness. In an emergency situation, it might not be practical to attempt to screen donors for all diseases that might endanger the recipients. For this reason, the ideal donor might be a bird of the same species from the same household. If time allows, collect a single drop of blood from the donor to evaluate PCV, RBC, and white blood cell (WBC) morphology, as well as an estimated WBC count.

Whenever possible, donor birds should be of homologous species (e.g., cockatiel to cockatiel). Select post-transfusion RBC survival time studies indicate that heterologous transfusions result in considerably shorter RBC lifespans. For example, pigeon RBCs administered to raptors result in an estimated survival time of 0.51 ± 0.19 days, while previous studies show that the RBC lifespan after homologous transfusions from pigeons to pigeons is 7.1 days (Sandmeier et al. 1994). Investigations of post-transfusion RBC survival between homologous species (i.e., sun conure to sun conure) and closely related species (i.e., white-eyed conure to sun conure) show similar RBC lifespans of 8.5 and 4.5 days, respectively (Degernes 1999a). These results suggest that while homologous transfusions are ideal, closely related or heterologous transfusions can be considered when a homologous donor is not available.

While homologous (of the same species, e.g. cockatiel to cockatiel) transfusions are considered safest, successful heterologous (between different bird species) transfusions have been performed in multiple avian species. Autologous (transfusion of blood from a donor back to itself), homologous, and heterologous transfusions were studied in cockatiels (Nymphicus hollandicus) and conures of the genus Aratinga (Degernes 1999b). In cockatiels, transfused heterologous RBCs from either Amazon parrots or pigeons had significantly shorter half-lives than both autologous and homologous transfusions. Importantly, the half-lives of the heterologous RBCs decreased significantly with repeated transfusions. However, heterologous transfusions between conures of the genus Aratinga did not result in shorter RBCs half-lives after a single transfusion, therefore in the absence of a homologous donor, a single heterologous transfusion between birds of the same taxonomic genus might be efficacious. Ultimately, many experienced avian practitioners have regularly transfused heterologous species with good to excellent results. While RBC longevity is questionable, the benefits noted might be due to the short-term oxygen-carrying capacity of transfused RBCs and correction of hypovolemia during emergent or critical clinical situations.

Avian total blood volume is variable among species, but is approximately 6–8% of total body weight. Therefore, collecting no more than 1% of the body weight (approximately 7–10% of total blood volume) is the accepted collection guideline for donor birds (Shaw et al. 2009). Crystalloid fluid replacement for the donor bird is recommended, minimally equaling the total amount of blood collected.

Processing of blood components such as packed red blood cells or plasma is feasible but impractical in most pet bird hospital settings. Larger institutions such as aviaries or zoos can theoretically process larger volumes of blood such as that collected from an ostrich or penguin for heterologous transfusions in emergency situations. Cryopreservation of whole blood or blood components is also impractical in most situations when they might not be utilized before significant degradation of the product occurs.

Birds requiring blood transfusions are usually in a critical condition. Low-dose sedation often allows safe handling of critically ill birds for placement of a catheter. One of several sedation protocols uses low-dose midazolam (0.25–0.5 mg/kg) and butorphanol (1–2 mg/kg) combined into one syringe and quickly administered intramuscularly (IM) while minimizing handling and stress. Administration of higher dosages of intranasal midazolam with or without IM butorphanol is also efficacious for reduced stress and handling (Mans et al. 2012).