Introduction
Lead is a heavy metal and can easily cause a
toxicity (called plumbism). Other heavy metals, notably zinc, can
also cause toxicity.
Cause
Birds are sometimes drawn to shiny objects, hence
they will eat metallic objects that can contain lead. Birds are
natural chewers and will chew cage bars and painted walls. In older
homes there are sometimes layers of paint below the surface layer
that contain lead. Lead particles can build up on the
ventriculus
(gizzard) and become toxic if in large enough quantity.
Lead is a heavy metal that is poorly absorbed by
the intestines. Unfortunately, only a small amount is needed to cause
problems. It eventually gets distributed to all body tissues, with
particular emphasis on the digestive system, the red blood cells, the
bone marrow, the liver and the nervous system.
Sources of lead could include; old paint, old
cages, solder, stained glass, curtain weights, foil, fishing weights,
batteries, linoleum, plaster, and putty.
Symptoms
Symptoms depend on how much lead is ingested over
how long a period of time. The disease is sometimes broken down into
acute lead toxicity and chronic lead toxicity.
In the acute version birds might be weak,
depressed, produce abnormal droppings, and vomit. Neurologic signs
could include walking in circles, twitching, incoordination and even
convulsions.
This bird
has neurologic signs. It is unsteady as it perches, and it
constantly jerks its head to the left. It is a short
Quicktime movie, so double click on it to make it
play.
Chronically infected birds can have similar
symptoms to acute toxicity. In addition, they might lose weight, be
partially or fully paralyzed, and even blind.
Diagnosis
History
In some lead infected birds there is a history
of recent chewing of paint on the walls. In some cases the owners
did not suspect any exposure to lead.
Physical Exam
The physical exam may or may not reveal
significant abnormalities. It all depends on how much lead has
been ingested over how long a period of time.
This
bird has lead toxicity. It chewed the paint on the
floor after the owner did some remodeling in an old
home. He is alert and eating well but cannot walk well
on his back legs.
Diagnostic Tests
A blood panel might be useful in this disease. In some birds
we might see anemia or evidence of liver disease. When we suspect lead toxicity
we can run a lead level on the blood.
This
bird has changes consistent with liver disease. The
arrows point to the liver tests which are very
elevated.
This is from the bird above. His lead
level is 0.5 parts per million, far above the normal
range of less than 0.06
Some brids can have a zinc toxicity
also.
One of the most consistent ways to diagnose
lead toxicity is with an x-ray. Lead is a heavy metal and will
show up vividly on a radiograph, usually in the ventriculus
(gizzard).
This
radiograph is also from the above bird. It has normal
grit in the gizzard, but if you look closely some of the
grit looks brighter than normal. The brighter objects are
lead particles, not grit.
Treatment
Birds that are weak, losing weight, or not eating
need supportive care. This consists of fluids and supplemental
feeding. We will frequently hospitalize them until they regain their
strength. If they are having seizures we can put them on
anticonvulsant medication.
It is important to try to remove the lead from the
ventriculus. Treatment with lubricating agents or even peanut butter
will help pull the lead out of the gizzard to be passed in the
droppings. On rare occasions, especially if the lead particles in the
ventriculus are too large to pass, we will perform surgery to remove
them.
Once your bird is stable and we have attempted to
remove the lead from its ventriculus we use a class of medications
called chelating agents. Their job is to go into the organs,
especially the bone, where the lead has accumulated and counteract
its affects. It can take several courses of treatment to completely
treat your bird. These medications are not without risk, so they are
used intermittently to give your bird a rest period in between
doses.
We will treat until the lead level in the blood
test is back to normal and there is no more radiographic evidence of
lead in the ventriculus.
Prevention
It is the nature of birds to be chewers and put metallic objects
in their mouth. Minimizing their exposure to lead containing objects is an obvious
way to prevent this problem. Also, feeding them a balanced diet (not just seed)
will help keep them from looking for nutrients they need and are not receiving
in their diets.
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