Lead is a common cause of poisoning of domestic animals throughout the world. The Queensland situation is no exception. Since 2000, Biosecurity Queensland laboratories have diagnosed about 10 cases of lead poisoning each year.

The proportion of the actual number of poisonings from lead ingestion is unknown. Therefore, stock owners should remain aware that lead poisoning could occur and understand its effects on farm animals.

Cattle are the most susceptible livestock, with calves the most likely victims. However, lead poisoning can occur in all domestic animals, including horses, birds/poultry and dogs. Pigs are the least susceptible.

On this page:

• Major sources of lead on the farm
• Clinical signs of lead poisoning
• Differential diagnoses
• Submitting specimens for lab examination
• Reporting obligations
• Treating lead poisoning
• Disposing of lead sources
• Food safety of animals with elevated lead levels

Major sources of lead on the farm

Livestock may find lead in rubbish dumps, and around farm buildings and machinery. Lead can occur in:

• discarded sump oil
• dumped lead batteries
• flaking lead-based paint or old paint tins
• linoleum, grease, putty, oil filters, metallic lead and other sources.

Stock may find sump oil and other sources of lead attractive because lead compounds can have a sweet taste.

Silage contaminated by lead shot, automotive grease, oil filters, putty and even leadlight windows have also previously caused fatal lead poisoning in stock. Water fowl, such as ducks and geese, can swallow lead shot and fisherpeople's sinkers from the bottom of lakes and ponds.

Contributing factors may include boredom from confinement, and depraved appetites from malnutrition and phosphorus deficiency. However, predisposing factors are not essential for poisoning to occur.

Clinical signs of lead poisoning

A combination of gastro-intestinal and nervous signs may occur. The gastro-intestinal effects may produce either constipation or diarrhoea.

Acute poisoning

In cases of acute poisoning, stock may be found dead or display combinations of several signs for a few hours before death, including:

• colic
• staggering gait
• rolling eyes
• slobbering
• muscle spasms
• blindness
• uncoordinated attempts to climb obstacles
• excessive response to external stimuli
• head pressing
• convulsions.

Subacute poisoning

Animals with subacute poisoning may display:

• dullness
• loss of appetite
• abdominal pain
• diarrhoea.

Chronic poisoning

In chronic poisoning, animals show:

• wasting
• loss of appetite
• anaemia
• constipation
• recumbency
• breathing difficulty.

Sometimes acute attacks may occur during the course of chronic poisoning. Paralysis and death may also occur.

Differential diagnoses

Similar nervous system effects can be induced by various diseases affecting the brain, including:

• cerebral babesiosis - tick fever
• nutritional and metabolic deficiencies, e.g. hypomagnesaemia, ketosis, thiamine deficiency, vitamin A deficiency
• other poisons, e.g. mercury, organophosphates, organochlorines
• plant poisoning, e.g. Noogoora burr, pyrrolizidine alkaloid poisoning
• enterotoxaemia, e.g. Clostridium perfringens type D
• viral infections, e.g. infectious bovine rhinotracheitis (IBR), sporadic bovine encephalomyelitis (SBE), and bovine malignant catarrh (BMC)
• bacterial infections e.g. listeriosis.

Clinical lead poisoning in adult ruminant stock is associated with liver or kidney levels exceeding 10 mg/kg but fatal poisoning can occur with lower tissue levels.

A normal blood level of less than 0.24 umol/l (<0.05 mg/kg) is adopted for lead residue management purposes.

Submitting specimens for laboratory examination

You should submit clotted blood and faeces from live animals.

From dead animals, submit liver and kidney unpreserved. Preserved liver/kidney, EDTA blood and a blood smear may also assist differential diagnosis.

In addition, supply samples of any suspected sources of lead.

Reporting obligations

You should regard any stock suspected to have lead poisoning as suspected to be affected by a contaminant and have residue disease.

This is a notifiable disease under the Stock Act 1915.

Livestock owners, veterinary surgeons and other scientists who suspect that livestock is affected by exposure to lead are obliged to notify a biosecurity inspector or Government veterinary officer.

Treating lead poisoning 

We recommend treating animals with calcium versenate as a chelating agent by intravenous injection. Treatment over several days may be necessary. Treated animals will need to be under the care of a veterinary surgeon.

Provide supportive therapy, including fluids, and sedatives to combat convulsions.

Disposing of lead sources

You may be able to sell lead batteries to scrap metal merchants. In some areas, local garages may accept sump oil and batteries for disposal. Do not dispose of such wastes in general rubbish dumps. Council dumps often provide for toxic waste disposal.

Food safety of animals with elevated lead levels

Any livestock that accesses a source of lead may survive but may have lead residues in the meat or offal, making the product unsuitable for human consumption. Exposed animals may have lead residues that exceed the maximum level set in the Food Standards Code, regardless of whether the animals show clinical signs of lead poisoning.

Contaminated stock may be restricted from sale or movement to adequately manage any public health and safety risk. The detection of significant levels of lead in meat may also affect access to overseas markets.

Further information

• Your local veterinary officer or biosecurity inspector
• DEEDI Customer Service Centre