Heavy metal toxicoses in pet birds: Watch for combination of gastrointestinal and nervous systems signs
Jan 01, 2006
The toxic effects of lead are numerous due to its ability to disrupt many biochemical processes within the body.
Lead intoxication may cause an anemia (microcytic hypochromic) as a result of decreased life span of the red blood cells and disruption of heme synthesis. The exact biochemical process is not known; however, the effects are usually accompanied by inhibition of sodium-potassium dependent ATPases.
A nephropathy associated with lead toxicosis is a common occurrence. The biochemical processes involved in lead toxicity include a decrease in energy-dependent transport functions including aminoaciduria, glucosuria and ion transport. These changes are possibly related to leads effect on mitochondrial respiration and phosphorylation.
Lead toxicity can directly or indirectly alter many aspects of bone cell formation. The accumulation of lead in bone occurs under many of the same mechanisms involved in regulating calcium influx and efflux, including parathyroid hormone, calcitonin and vitamin D. Lead is also reported to compete with calcium for absorption from the gastrointestinal tract.
In general, acute lead toxicosis is more common in companion avian species while chronic lead toxicosis is seen more often in free-ranging avian species, especially waterfowl. Interestingly, chickens are reported to be more resistant to lead toxicosis than waterfowl.
Clinical signs of lead toxicosis can vary depending upon the amount of lead ingested. However, any bird with a combination of gastrointestinal and nervous systems signs should have heavy metal toxicosis high on the list of differential diagnoses. Once the lead enters the circulatory system clinical signs may be pansystemic. Anorexia, weight loss, emaciation, regurgitation, vomiting, diarrhea, increased gastrointestinal transit time, depression, ataxia and weakness, seizures, blindness, hematuria, hemoglobinuria, polyuria and polydipsia, and death are all signs associated with lead toxicosis.