What are Heavy Metal Toxicosis?
Though wild birds are generally poisoned by ammunition and lead sinkers, pet birds are subject to household items, many of which contain toxic levels of metal. Metals can also be ingested through contaminated drinking water, or even from the wire in their cage. While many metals can cause a toxic condition, lead and zinc are the most common. Often, when symptoms are seen, the bird may already be very sick.
Heavy metal poisoning is a toxic condition caused by the ingestion of heavy metals. When the curious nature of birds leads them to chew or ingest various objects, often metal ones, they can swallow too much metal and become poisoned. Ingested metals can cause damage to the digestive tract, nervous system, kidneys, and liver, and can lead to death in severe cases.
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Symptoms of Heavy Metal Toxicosis in Birds
While some birds show no signs of a metal poisoning, others can display various symptoms related to the gastrointestinal, urinary, and nervous systems. The severity of symptoms is also dependent on the amount of heavy metals ingested. Signs include:
- Lack of appetite
- Gradual weight loss
- Pale mucous membranes
- Increased thirst
- Increased urination
- Green, pink, or red urine
- Foul smelling droppings
- Loose droppings
- Bloody or dark droppings
- Green colored droppings that can stain feathers
- Excessively wet droppings
- Vocal changes
- Feather loss
- Feather damaging behavior
- Bluish skin
- Shallow breathing
- Altered mentation
- Droopy posture
- Wing droop
- Loss of body movement control
- Head tilt
- Paralysis of the legs
- Tremors in body and head
There are many types of heavy metal toxicosis found in birds, named after the metal ingested.
Lead poisoning is by far the most common type of heavy metal toxicosis. Birds can ingest lead from common household items, such as toys, curtain weights, jewelry, imported metal cages, caulking compounds, batteries, solder, fishing weights, foil, jig heads, tank linings, bearings, ceramics, plastics, candy wrappers, inks, paint, ammunition, zippers, and leaded glass.
Zinc poisoning ranks second to lead, and can also be found in many household objects. A common object implicated in zinc poisoning is galvanized wire, but zinc can also be found in toys, mesh, bells, chains, keys, pennies minted after 1983, clips, steel wire cages, powder-coated cages, cage accessories, nuts and bolts, padlocks, washers, snap fasteners, galvanized dishes, ammunition, wood preservatives, insecticides, and rubber.
Copper poisoning is rare, and can be ingested from wire, pennies minted before 1982, paints, copper ammunition, and copper sulfate.
Iron poisoning can result from exposure to feeding bowls made of cast iron, or other iron rich objects.
Causes of Heavy Metal Toxicosis in Birds
The cause of heavy metal toxicosis is the ingestion of heavy metals into the body, most commonly lead or zinc. This is often through chewing or swallowing small objects, wire, or particles from metal objects or paint.
Lead, once in the gastrointestinal tract, is absorbed into the bloodstream, soft tissues and bone, where is can cause damage to red blood cells and various organ tissues, including the kidneys, liver, and brain. Zinc, while needed for cell replication and developing bones and cartilage, can have adverse effects in more toxic amounts, and can damage the kidneys and pancreas.
The severity of heavy metal toxicosis can be influenced by several factors, including the type and amount of metal ingested, and the diet, such as those low in calcium or protein.
Diagnosis of Heavy Metal Toxicosis in Birds
A diagnosis can be determined by a physical examination that includes noting the weight, a history of exposure to metal objects or particles, symptoms, and the results of various tests. Various blood tests can reveal high levels of heavy metals in the blood, serum or plasma. This can often identify anemia, or a lead or zinc toxicity, and allow for a definitive diagnosis. X-rays can reveal the presence of metal in the gastrointestinal tract. Your veterinarian will also evaluate your bird for crop stasis, a sign of lead poisoning.
Treatment of Heavy Metal Toxicosis in Birds
Treatment aims to remove the toxic metal from your bird’s body, and can be accomplished a number of ways: chelation therapy, manual removal, and various supportive therapies. Symptoms are also treated, often with medications. The removal of the metal objects from your bird’s environment is an important step towards recovery and preventing future toxicity.
Chelation therapy uses injectable agents, such as calcium EDTA, or oral agents, such as dimercaptosuccinic acid (DMSA) and d-penicillamine, to bind and remove heavy metals. Depending on your bird’s condition, he may need multiple treatments. Oral treatments can be administered at home.
In cases where there are larger pieces of metals present, they can be removed through endoscopy, surgery, gastric lavage, or proventriculotomy. Lubricants and cathartics can be given to aid in metal removal, such as mineral or corn oil, or magnesium sulfate. Bulking agents can be used to assist the removal of toxins from the GI tract, such as psyllium, peanut butter, fiber, methylcellulose, or laxatives.
Other supportive treatments can include fluid and electrolyte therapy, heat therapy, B-complex vitamins, and medications to control tremors and seizures.
Treatments continue until the symptoms are resolved. Often, blood tests and X-rays are taken again to assess your bird’s progress, and continued therapy is given as needed.
Recovery of Heavy Metal Toxicosis in Birds
Recovery of your bird will depend on how severe the toxicosis is. In cases of lead toxicosis, symptoms may only appear in a very sick bird who is near death. If, however, the poisoning is diagnosed and treated early, your bird may recover.
It may not be easy to prevent your bird from ingesting metal, due to the wide variety of toxic objects and the natural curiosity of birds. But there are ways you can minimize the chances of a heavy metal poisoning, such as:
- Identify potential sources of heavy metalsSupervise pet birds when outside of their cage
- Remove sources of heavy metals from your bird’s environment, including cage and toys
- Limit your bird’s exposure to areas with high levels of heavy metals
- Use a mildly acidic solution to scrub any new galvanized cage wiring to reduce zinc levels