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Zinc Toxicity

Other Names: New Wire Disease, Zinc Toxicosis

Zinc toxicity occurs when chickens ingest zinc-containing metal objects. Chickens use their beaks to explore objects. They are especially attracted to metallic, shiny objects, making them at higher risk of metal poisoning.

Once ingested, the metal object begins to corrode and the zinc is readily absorbed into their bloodstream. Zinc causes damage to the red blood cells, causing them to rupture, resulting in renal failure secondary to hemoglobinuria.

Common sources of zinc:
  • Fasteners: Nuts, bolts, screws, nails, etc.
  • Coins: US pennies minted after 1982 contain 97% zinc and 2.5% copper.
  • Galvanized zinc: Galvanizing is the most prevalent use of zinc, as it is an anti-corrosion agent. Pretty much any metal intended for use outdoors is likely galvanized. This is why it's really important that when erecting poultry enclosures and predator proofing, to pay attention to any bits of metal cut from hardware cloth, so they don't scatter across the ground for the birds to eventually ingest.
  • Cheap jewelry
  • Zippers
  • Many toys, including monopoly game pieces.
  • Pipe fittings
Free ranging chickens may potentially pick up and ingest buried metal, coins, galvanized nails and other zinc produced products hidden in the soil, especially following a rainstorm.

Clinical Signs


Symptoms of zinc toxicity are non specific, and mimic clinical signs seen in several other diseases. The most common clinical signs observed include:
  • Anemia
  • Ataxia (staggering, loss of balance, difficulty walking, loss of coordination, falling, stumbling, unsteady, tumbling)
  • Diarrhea (loose feces, watery droppings)
  • Pallor (pale face, comb and wattles)
  • Paresis or paralysis of the legs (walking stiffly, unable or inability to move, lower limb rigidity)
  • Polyuria (production of abnormally large volumes of dilute urine)
  • Polydipsia (excessive or excess drinking)
  • Weakness (inability to stand, sitting/resting on hocks, limp/lame)
  • Weight loss

Diagnosis


Zinc toxicity is diagnosed based on history of exposure to zinc-containing objects, clinical signs, radiography, pathologic findings, and blood tests.
  • Radiographs: May identify metallic objects in the GI tract. However, the results do not confirm or deny whether the bird has zinc toxicity.
  • Blood Chemistry: Elevated serum or tissue (liver, pancreas or kidney) zinc concentrations may be helpful to confirm the diagnosis, but the results may take too long to come back in time to be helpful.

Treatment


Treatment for zinc toxicity requires supportive care to help stabilize the bird with fluids and reduction of stress. If a metal object is identified via radiographs, it will need to be removed. Once removed, chelation therapy may be needed since this will result in rapid decrease in zinc levels in the blood. Parenteral CaEDTA is the chelator most recommended for birds with zinc toxicity. Blood transfusions may be needed in some cases.

Clinical Signs

Ataxia
Pale comb
Dark or bright green diarrhea
Paresis
Increased thirst
Seizures
Foul-smelling feces
Regurgitation
Lethargy
Loss of appetite

Diagnosis

  • History of exposure
  • Clinical signs
  • Blood test - plasma zinc concentrations greater than 2 ppm
  • Necropsy - levels greater than 1000 u/g in pancreatic tissue

Reported Cases

  • Case 1: Ingestion of a nail in a Pigeon A 2-year-old female pigeon was evaluated because of a 5-day history of lower than typical activity level, weight loss, and polyuria. Whole-body radiography revealed a linear metallic foreign body in the area of the ventriculus. Fluoroscopy followed by contrast-enhanced CT was performed to further characterize the lesion location, revealing that the foreign body had perforated the ventral aspect of the ventriculus wall and that the ventral extremity of the foreign body was surrounded by a mass, consistent with a granuloma. A midline celiotomy was performed, and a large granuloma was identified ventral to the ventriculus, adherent to the dorsal aspect of the keel bone. The metallic foreign body (a nail) was removed, and the content of the granuloma was debrided. Amoxicillin-clavulanic acid (150 mg/kg [68.2 mg/lb], PO, q 12 h for 10 days), meloxicam (1 mg/kg [0.45 mg/lb], PO, q 12 h for 5 days), and sucralfate (100 mg/kg [45 mg/lb], PO, q 8 h for 10 days) were prescribed. The pigeon made a successful recovery and was still doing well at a 1-year recheck evaluation. Ref

Treatment

NameSummary
Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Calcium disodium edetate30-35 mg/kg IM, IV q8-12h x 3-5 days, off 3-4 days, repeat prnB Speer
Penicillamine50-55 mg/kg PO q24 x 1-6 weeksB Speer
Dimercaptosuccinic acid25-35 mg/kg PO q12h x 5 days/week x 3-5 weeksB Speer
Succimer20 to 40 mg/kg BID given orally for 5 to 10 days and followed by 3 to 5 day rest periods between intervals.
Control of seizuresdiazepam (0.5 to 1.0 mg/kg IV or IM) or midazolam (0.1 mg/kg IM)
Removal of foreign bodySurgery may be required.

Support

Prevention

Be careful when building outdoor enclosures and predator-proofing coops to ensure bits of hardware wire are collected and discarded in the trash--not in the soil or where chickens access.

Scientific References

Risk Factors

  • Carelessly cutting bits of hardware wire which fall to the ground (used for predator proofing and construction of outdoor enclosures for birds).