Zinc poisoning in dogs occurs when they eat objects containing a high proportion of the metal or its salts. Dogs frequently eat things we consider non-edible. Amongst the zinc containing items found in dogs, the Lincoln penny is one of the most common. Some pennies minted in 1983 and all of those minted since contain 97.5% zinc. Other items found include metal zippers, batteries, children's board game pieces, screws and nails. Dogs also become poisoned by the ingestion of zinc oxide creams, paints containing zinc salts, shampoos and some herbal supplements.

When metal objects containing zinc reach the stomach of a dog, the acidic gastric juices attack the metal producing salts, which are absorbed into the dog's system from the duodenum. Once absorbed the blood system distributes the toxic salts to all the organs of the body including the liver, kidneys, prostate, muscles, bones and pancreas.

Within the tissues, zinc affects the uptake and usage of other metal ions including copper, iron and calcium. It also has a direct irritant action on tissues and interrupts red blood cell production and properties. The LD 50 of zinc (dose at which 50 % of animals die) is about 100 mg/kg body weight.

A dog in the early stages of zinc toxicosis exhibits the signs of vomiting and anorexia. Later signs include diarrhea, lethargy, jaundice, shock, heart arrhythmias and seizures. Damage to red blood cells causes them to break down and the dog develops intravascular hemolysis. The kidneys remove the hemoglobin resulting in hemoglobinuria with the urine exhibiting a red color. Microscopic examination of the dog's urine reveals hemoglobin casts (imprints of the tubules of the kidney).

If the dog swallowed a metallic object then the diagnosis of zinc poisoning requires an X-ray in which the object in the animal's stomach is clearly visible. If the poisoning occurred from a cream or paint then a blood test revealing high levels of zinc confirms a diagnosis of zinc toxicosis. Zinc is an essential element so a dog has some zinc in its blood streams. The normal serum zinc level found in a dog is 0.7-2 g/ml.

A dog presenting with zinc toxicosis requires stabilization using fluids, oxygen and sometimes blood products. The next step is the removal of any zinc containing foreign objects. The induction of vomiting rarely succeeds in removing such objects as they frequently adhere to the mucosal lining of the stomach. Therefore, successful removal requires endoscopy or surgery.

Promotion of excretion of zinc via the kidneys and prevention of nephrosis caused by hemoglobinuria requires an increase urine flow. The use of a balanced crystalloid solution promotes diuresis.

Some veterinarians use a chelating agent such as calcium disodium ethylene-diamine-tetra-acetate (Ca-EDTA) to aid in the removal of zinc by the kidneys and speed recovery. Others prefer to rely on supportive therapy as chelating the zinc may lead to an increased risk of nephrotoxicity.

Zinc is an essential micro nutrient present in many enzymes in the body. As such, it may be listed in the ingredients of dog food. Without a small amount in the diet, a dog develops vomiting, inflamed eyes, loss of hair pigmentation, retarded growth and emaciation. To little is bad but in any quantity it is fatal Keep your dogs away from sources of zinc rely on the dog food to provide what is necessary. A dog ingesting a Lincoln penny costs a lot more than a cent in veterinarian bills.

Reference Sources:

Merck Veterinary Manual

University of Georgia College of Veterinary Medicine

Learn more about this author, Alison Bowler.
Click here to send this author comments or questions.

---

Add your voice

Know something about Zinc poisoning in dogs: Symptoms and treatments?
We want to hear your view. Write now!