What are Hemochromatosis?
Hemochromatosis is a potentially fatal condition caused by the over-storage of iron in the liver and other major organs of captive birds. Accordingly known as “iron storage disease,” the manner of causation, or etiology, behind the disease is not fully understood, though research suggests it may have some basis in genetics and nutritional imbalance. Two forms of the iron storage disease exist, though the differences between them are negligible. Variations occur mainly in the degree of damage caused to the bird’s primary organs, as well as the stage or level in the progression of the disease. Hemosiderosis, the second type of the disease, appears to be less lethal than the primary form, hemochromatosis. Like hemochromatosis, the supplemental iron (known as hemosiderin) accumulates in the tissues, but somehow circulates without inflicting damage on any of the key organs. While it’s neither proven, nor specified, many veterinary researchers believe that hemosiderosis is simply the precursor to hemochromatosis, and variations depend only upon the current stage of the disease’s progress.
When at the proper level, iron (Hb or Hgb) serves a range of purposes in the bodies of vertebrates, but functions primarily as a contributor to the production of hemoglobin. Hemoglobin is the protein in red blood cells that serves as an oxygen delivery system, transporting life-sustaining oxygen molecules from the bird’s respiratory system throughout the rest of the body’s tissues. In the case of hemochromatosis, the concentration of iron exceeds what is necessary to produce hemoglobin, forcing the surplus iron to find a “home” in major organs such as the liver, heart, and lungs. When iron is stored in excess, toxicosis occurs. Within a brief period, the organs become too damaged to function normally, and potentially lead to the sudden death of the bird. Even if the bird were to survive the initial poisoning, the iron imbalance leads to a deadly accumulation of fluids in the body. Breathing becomes labored, and the heart is unable to effectively pump blood. Diseases and conditions such as anemia and cancer arise, leading to the bird’s early death.
Hemochromatosis, or “iron overload disease,” is a high-risk condition that is increasingly being seen in captive birds around the world. Avian species that seem particularly vulnerable include toucans, birds of paradise (Sturnidae), quetzals (Caprimulgiformes), tanagers and starlings (Passeriformes), and some parrots (Psittaciformes). Primary iron overload is largely considered a genetic aberration; however, other causes are being explored.
Excessive iron in the diet (in fortified bird seeds and pellets) is currently noted as a plausible causation of hemochromatosis, primarily because the condition is not replicated in wild bird populations. Other potential causes include immune-related stress, heavy metal toxicosis, metabolic defects, starvation, and comorbidity to other diseases.
Hemochromatosis is a potentially fatal condition caused by the over-storage of iron in the liver and other major organs of captive birds.
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Symptoms of Hemochromatosis in Birds
- Loss of balance
- Distension of coelomic cavity (due to ascites and weakness)
- Dyspnea (shortness of breath)
- Lack of appetite
- Sudden death
The condition is divided into two types. Hemosiderosis is considered the less lethal form of the disease. In this case, the iron accumulates in the liver, but major damage to the organs does not occur. Hemosiderosis is considered by some researchers to be a precursor to the original form, and not a distinct disease.
Causes of Hemochromatosis in Birds
Hemochromatosis is largely believed to be a hereditary disease, though many species of birds have not yet been studied for possible inclusion or exclusion. Recently, at least two genes have been isolated as possible contributors to its development. Other links include over-supplementation of iron in the diet. Some veterinary nutritionists believe that a low iron diet could help reduce the number of cases. Also, immune-related conditions, bacterial infections, periods of starvation, and stress (such as poor living conditions) are all considerations.
Diagnosis of Hemochromatosis in Birds
Many birds succumb quickly to the disease, so a living diagnosis is usually not possible. Necropsy is the only definitive way to do a full examination and biopsy of the liver.
In some cases, however, symptoms pre-date death, and a diagnosis is attempted. Diagnosis depends upon history, symptoms, a physical examination, radiography and evaluation of accumulated fluid. In such a case, medical treatment may be attempted, but has not proven to be effective. Many birds are unable to recover, and eventually succumb to the disease within a matter of days or weeks from first symptoms.
Treatment of Hemochromatosis in Birds
Hemochromatosis is not usually survivable, but treatment attempts have included aspiration of accumulated fluid, a low iron diet, phlebotomy, and careful watch of the hematocrit, weight, and administration of sub-Q Deferoxamine.
Recovery of Hemochromatosis in Birds
Recovery attempts are rarely, if at all, successful. The aim is to maintain a low-iron diet (diets containing less than 100 ppm are recommended), watch the bird’s body weight and make attempts to biopsy the liver. Phlebotomy is the preferential long-term treatment strategy. Blood testing and bloodletting is recommended as part of a maintenance program. There is no way to currently determine prognosis of a bird diagnosed with hemochromatosis.