Chapter 30 Hematologic and Immunologic Diseases
Hematology is an important part of the diagnostic workup in the ill bird. With a little practice and a minimum amount of equipment, a technician can perform a complete blood cell count (CBC) as for the mammalian patient. Blood collection is practical even for small birds. Up to 1% of the bird’s body weight can be collected safely unless the bird is anemic or hypovolemic (Box 30-1). The preferred collection site for samples is the jugular vein (accessed from the right side of the neck), but the basilic (wing vein) vein and the medial metatarsal veins also can be used. Hematoma formation from venipuncture of the basilic or metatarsal veins can become a serious problem in small birds if not addressed promptly. A toenail clip is the least desirable method for blood collection because it is painful for the bird and the site is usually contaminated with feces and other debris.
Evaluating blood smears for the avian patient takes a bit of practice because the cells are slightly different from those of the mammal. They are more fragile and tend to be damaged when preparing the blood smear. The use of glass coverslips for the preparation of the smear will decrease the amount of cell damage. (The technician should refer to a hematology text for the exact description of each cell type found in the avian sample [see Color Plates 15 and 23].)
Causes of anemia in birds include blood loss caused by trauma, toxicosis resulting in coagulopathy, parasites, and organic disease. Chronic diseases such as chlamydiosis, mycobacteriosis, nephritis, aspergillosis, and others can also result in a decrease blood cell production and anemia. Most anemias in birds are nonregenerative.
Although not actually a disease of the heme system, hemochromatosis does involve blood. The disease results from an excessive amount of iron stored in various tissues of the body, especially the liver. It is an inherited metabolic defect common in toucans and mynahs but rarely is seen in psittacines.