Toucan

Old World Aviaries

Hemochromatosis: A metabolic disease of softbills

by Darrel K. Styles, DVM

One of the biggest challenges of keeping and maintaining a large softbill collection or just a single pet is the problem of the iron storage disease known as hemochromatosis. This disease affects a wide range of species including mynahs, toucans, tanagers, birds-of-paradise, and many others. It is not a disease we see in parrots, finches, or canaries. Hemochromatosis is probably the leading cause of death of mynas and toucans in captivity, and collections of birds-of-paradise have been decimated by this malady.

The cause is unknown, but the effect is a massive uptake and storage of iron in the liver. This excessive storage leads to hepatomegaly or liver enlargement. Consequently, some degree of liver dysfunction is observed. However, the most remarkable aspect of the pathology of the disease is liver enlargement. This enlargement leads to ascites or fluid exuded into the air sacs. This fluid in combination with an oversized liver results in dyspnea, or difficulty in breathing. The clinical presentation of these birds is often a myna or toucan with a swollen abdominal area accompanied by open-mouthed breathing. I have seen this problem displayed so severely in mynahs that if you changed their position from upright to lateral, the birds began to drown in their own fluids, which were leaking from the air sacs into the lung. Large quantities of fluid may be taken from a small bird.

If the bird is an adequate surgical risk, a liver biopsy can be taken for histopathological examination. Using specialized staining techniques, the pathologist can confirm the diagnosis by typical golden-brown deposits of iron in the majority of liver cells. The clinician also can make a tentative diagnosis by examining certain liver enzymes and based on clinical presentation. Often, an X-ray is helpful in determining liver enlargement but does not confirm a positive diagnosis without proper histopathological results. Ancillary pathologies occur, such as cardiomegaly or enlargement of the heart. It is unknown whether this development is a primary problem or a secondary problem due to excess fluid.

Once the diagnosis is reached, treatment options are limited. The same therapy used in humans, where hemochromatosis also occurs, does not seem to work in birds, probably because the causes are different. Drugs such as penicillamine, which control human cases, are ineffective in birds. However, a viable treatment, although ancient in origin, is phlebotomy or bleeding. The logic behind this procedure is: (a) blood contains iron, (b) the liver contains excess iron, (c) bleeding causes anemia and more iron is needed to make more blood, and (d) the liver provides the source of iron so the excess iron is depleted via natural mechanisms. This therapy has been used with some success in toucans. But bleeding must be repeated on a timely basis, usually once or twice a month, and must be continual. Obviously, this is simply a palliative measure because the inciting cause, which is unknown, has not been removed. Also, if the heart is involved, therapies useful in treating cardiac deficiencies have been used.

The obvious answer is prevention. Current knowledge strongly suggests that the cause is dietary, although other theories such as a viral cause have been advanced. Several commercial manufacturers market low-iron foods for mynas and other softbills. These foods, although of high quality, have been used with varying degrees of success. But they are the best alternative we have now. Others go to the extreme of limiting the types of iron-rich fruits the birds receive. Most of this information is anecdotal, and clinical studies are needed.

The Bronx Zoo conducted a study on different foods when it was having problems in the bird-of-paradise collection. However, no clear results were established. Some physiologists and nutritionists speculate that it is not how much iron is in the food but what form the iron is in. Certain forms of iron are more bioavailable, such as those that come from animal sources like bone or blood meal. Plant forms and inorganic forms may have a lower bioavailability and thus not accumulate rapidly. However, there is no conclusive evidence to support these claims.

Some noted softbill aviculturists use a cheap quality dog food and have little problem. I suspect, and this is merely speculation, that this dog food is a soya based product and is supplemented with inorganic iron, a cheap way to make dog food. However, this provides a vegetable-based protein for the birds and perhaps a lower iron bioavailability.

Meat is not the problem to which anyone who has owned toucan can attest. I have seen toucans eat mice, lizards, and the occasional hapless finch that wonders into their cages without any problems.

My own theory about this disease is that these birds come from an iron deficient environment. Rain forest soils are leached daily by rains, which deplete the soils of minerals. Hence, the only source for minerals, such as iron, are clays and vegetable matter. We have all seen the picture of the macaws hanging on the cliff scraping clay soil. The caption insists that they are consuming clays that neutralize plant toxins they have ingested. I think this is wrong. I think that these macaws are eating soil for mineral content. However, the softbills, not being afforded a nice hard beak, do not have this option.

I think that some metabolic mechanism in softbills is highly conservative toward the scarcity of iron. I would further speculate that we are over supplying a highly bioavailable form of iron in their food. However, much research needs to be conducted in this area before any conclusive statements can be made.

The bottom line is that if you deal with softbills, you will encounter hemochromatosis sooner or later. A diet low in iron, especially low in highly bioavailable iron sources, should be given to the birds until a cause can be established. Much work needs to be done in this area.

Conservation of softbills is essential because many of these species are highly endangered. Softbills are wonderful aviary specimens and more aviculturists should become involved in their propagation. Softbills are a colorful and quieter alternative to psittacines, and are ideal for the backyard aviculturist.

Photo courtesy of phototakeout.com.


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