CASE NOTES
Sudden death in a calf due to lead toxicity following access to old batteries
Kylie Greentree, Hunter LLS
Posted Flock and Herd August 2024
INTRODUCTION
Lead contamination of food producing animals and animal food commodities is potentially harmful to human and animal health. Cattle are at risk of lead poisoning because they are inquisitive and commonly 'taste test' new finds in their paddock. Sources of lead include lead batteries, old flakey lead paint, lead collars on pipes, silage contaminated by lead shot, farm rubbish dumps and machinery sheds, automotive grease and oil filters, caulking, putty, leadlight windows and sump oil, to name a few. Lead fragments break off and will tend to lodge in the reticulum of ruminants, which provides a reservoir from which the lead can continue to be absorbed into their bodies. Animals that are lead affected must be managed to ensure food safety and market access issues do not occur. Animal tissues containing elevated lead levels are not acceptable for human consumption and will not be until they meet the national food standards. Clinical signs of lead toxicity will vary from no clinical signs to signs of nervous system damage including wandering aimlessly, dullness, unresponsiveness, apparent blindness, running into fences and other obstacles, muscle twitching, coma and death.
CASE REPORT
History
Early May 2024, a producer in the Lower Hunter notified the local District Veterinarian about the sudden loss of a vealer calf (5-6 months of age). This calf was the fourth over the last couple of years that had died suddenly. The calf had been given two clostridial vaccinations (January and February) and was drenched with a pour-on in February. The cattle were not on any supplementary feed and had been in the paddock for some time. The paddock had good pasture with a mix of paspalum, rye and kikuyu. The other cattle in this paddock included one cow and one bull. The cow had been bellowing for the last 48 hours, behaving like she was on heat.
The dead calf was seen 24 hours prior and there were no abnormalities detected.
Clinical Findings
The calf was in good body condition (4/5) and had bloody froth coming from the nostrils, and therefore an Anthrax ICT cow-side test was performed. While waiting 15 minutes for ICT results, the District Veterinarian noticed a pile of batteries in the paddock. The producer had got the batteries from a friend one week prior and was burning them down to make fishing sinkers. The cattle did have access to this battery pile, but the producer said he had not noticed the cattle around the batteries. The Anthrax ICT was negative.
Image 1. Discarded car batteries next to a burnt area
Image 2. Burnt area containing some burned batteries
Post-mortem Findings
A necropsy was performed on the calf. There was noticeable congestion in the cranial lung lobes and trachea. On dissection of the gastrointestinal tract, there were noticeable black hard flakes sitting in the reticulum. The flakes were assumed to be lead from the batteries. No other abnormalities were detected. In most acute cases there are no gross lesions at necropsy (Radostits, 2007).
Image 3. Reticulum on post-mortem showing small black flakes
As lead toxicity was highly suspected as the cause of death, the property was placed under an Individual Biosecurity Direction (IBD) straight away to ensure there were no animal movements off the property.
Laboratory Findings
The calf liver came back at a level of 62µmol/kg of lead wet weight. Normal is <2µmol/kg wet weight. The laboratory confirmed the results of the ICT with the calf negative for Bacillus anthracis on the spleen and blood. Theileria was detected using PCR with low levels of gene copies (3,666), with Theileria orientalis, Buffeli and Ikeda detected. The faecal egg count was 40 eggs per gram of faeces.
Blood was collected from the cow as she was an at-risk animal and had demonstrated clinical signs consistent with lead poisoning. Her whole blood lead level was 2.88µmol/L. Lead levels under 0.24µmol/L are considered acceptable to enter the food chain.
The bull could not have a blood sample taken on the day of the initial property visit. Another property visit was organised before 42 days of removal from the lead source as this timing is the preferred option to ensure security of the food chain (stated in the DPI Procedure Animal Biosecurity lead-affected-food-producing-animals-in-New-South-Wales). The bull whole blood lead level was <0.1µmol/l and did not need to be included on the IBD. The cow and bull had an approved NLIS ear tag attached and recorded on LHMS and the State Residue Coordinator was notified of the cow's NLIS number and her blood test results. This property was updated on the NLIS Database to a PB1 status.
DISCUSSION
Lead poisoning is occasionally diagnosed in cattle, often due to exposure to discarded lead batteries in the paddock. Clinical signs range from acute death to neurological signs and some affected animals are asymptomatic (Waldner, 2002). This variation in clinical signs highlights the importance of testing all animals that have had potential exposure to the lead source. In general, the blood lead concentration decreases slowly over time after removal from the lead source with prolonged retention of lead most likely due to lead fragments in the reticulum slowly releasing lead and lead accumulation in the bones and leaching back into the bloodstream under certain conditions. A recent study presented by Kempsey-based District Veterinarian Ian Poe at the 2024 District Veterinary Conference (to be included in the 2024 Conference Proceedings) showed that eight years after removal from a lead source, a steer remained above the lead maximum residue limit. All lead toxicity cases are carefully monitored and managed under the guidance of the DPI Biosecurity-Lead Affected Food Producing Animals in NSW Policy and Procedure.
In this case, the lead-affected cow was likely to be pregnant. The DPI Biosecurity-Lead Affected Food Producing Animals in NSW Procedure states that calves born to cows with PB1 Status are considered lead affected. These calves must be tagged with an approved NLIS device by three months of age and assigned a PB1 Status. NLIS information is to be passed onto the State Residue Coordinator.
Lead is a potent neurotoxin that can accumulate in the body over time, leading to a range of adverse health effects in animals and humans. The presence of lead-contaminated meat in the food supply chain may expose consumers to health hazards and undermine public trust in food safety regulations. The detection of lead-affected beef in the export market would have significant trade implications for Australia. Importing countries could impose temporary bans or restrictions on Australian beef imports until the situation was resolved and confidence in the safety of Australian beef was restored. Such a trade disruption could result in financial losses for Australian beef producers and exporters and strain diplomatic relations with trading partners.
REFERENCES
- Biosecurity-Lead affected food producing animals in New South Wales Procedure, (2023) Biosecurity - Lead affected food producing animals in New South Wales (nsw.gov.au)
- Bolin L (2022) Lead Affected Cattle Microsoft Word - RDOC23 5120 DPI-primefact-lead affected cattle third edition.docx (nsw.gov.au) NSW DPI Primefact 413, 2022
- Radostits OM, Gay CL, Hinchcliff KW and Constable PD (2007) Veterinary Medicine - A Textbook of the diseases of cattle, horses, sheep, pigs and goats 10th Ed. (2007) Saunders Elsevier
- Waldner C, Checkley S, Blakley B, Pollock C and Mitchell B (2002) Managing lead exposure and toxicity in cow-calf herd to minimize the potential for food residues Journal of Veterinary Diagnostic Investigations 14:481-486