Heavy metal poisoning is a potentially life-threatening condition that occurs when horses ingest toxic levels of heavy metals such as lead, arsenic, or mercury.
• Common symptoms include weight loss, diarrhea, and abdominal pain
• In severe cases, heavy metal toxicosis can lead to irreversible organ damage
• Diagnosis of heavy metal toxicosis involves a number of laboratory tests (blood tests, urinalysis, diagnostic imaging), physical examination, and identifying a history of exposure
• Once the source of toxicosis is identified, treatment options include stabilization, decontamination of the stomach, and chelation therapy
• Prognosis is dependent on the type and amount of heavy metal ingested
• Prevention and early medical attention are the best ways to ensure the animal's health
Heavy metals are high density metals that do not degrade and can not be destroyed. Some types of heavy metals are needed in the diet, but in large concentrations they are all poisonous.
Horses might be exposed to heavy metals in various ways, including proximity to industrial plants and waste, topical medications, and excess dietary supplementation.
If close contact with heavy metals is suspected, emergency veterinary care is crucial in ensuring higher chances of a successful outcome.
Heavy metal toxicosis is a life-threatening condition and must be treated as an emergency.
Heavy metal toxicosis can affect any horse regardless of age or sex, but certain factors increase the risk of exposure and accidental ingestion:
• Living in close proximity to chemical and industrial plants
• Access to sources of heavy metals such as old pipes, paints, or contaminated soil
• Overdose of supplements containing heavy metals
• Application of topical products containing heavy metals
Heavy metals are naturally occurring chemical elements found in nature. They can be released into the environment as the result of manufacturing and inappropriate waste disposal.
Heavy metal poisoning is caused by the ingestion of toxic heavy metals, including mercury, lead, and arsenic.
Common symptoms of heavy metal toxicosis include:
• Weight loss • Reduced appetite • Diarrhea • Lethargy
• Weakness • Recumbency • Abdominal pain (colic)
Symptoms of heavy metal toxicosis vary depending on the kind of metal ingested:
Symptoms of lead poisoning
• Seizures • Paralysis • Muscle tremors
• Uncoordinated movement (ataxia) • Difficulty eating
Symptoms of mercury poisoning
• Reduced urination • Sudden death
• Skin ulcerations and crusting
Symptoms of arsenic poisoning
• Excessive salivation • Tremors • Recumbency
• Incoordination (ataxia) • Decreased urination
• Sudden death
Diagnosis of heavy metal poisoning is self-evident if ingestion of heavy metal-containing objects or substances is witnessed. A horse showing symptoms associated with heavy metal poisoning generally undergoes the following diagnostics:
• Physical exam • Blood tests • Urine analysis
• Blood chemistry • Diagnostic imaging • Endoscopy
• Urine or blood heavy metal level testing
Early treatment is focused on stabilization. Typical treatment for heavy metal poisoning includes:
• Medications to protect the stomach lining
• Fluid therapy
• Pain medication
• Gastrointestinal decontamination to remove metals from the stomach
• Activated charcoal to prevent heavy metal absorption
• Chelation therapy: administration of specific medications that bind to heavy metals in the bloodstream and facilitate their excretion
Note: always consult a veterinarian before administering medications, including activated charcoal.
Once treated, long-term monitoring and follow-up are recommended to identify any signs of organ damage.
Prognosis of heavy metal toxicosis depends on the type of heavy metal, amount ingested, and the promptness of treatment. Horses treated in the early stages of toxicosis have the best prognosis, and may recover with no long-term effects.
Left untreated, or if organ damage is present, the prognosis is very poor. In some cases, long-term neurologic deficits such as weakness or uncoordinated movement may develop.
In severe cases, death may occur prior to the onset of symptoms.
Heavy metal toxicosis is not contagious.
The only way to ensure that a horse does not suffer from heavy metal toxicosis is to remove all possible access to heavy metal sources. Strategies include:
• Providing clean water and feed
• Inspecting the animal's environment: potential sources of heavy metals include old paint or pipes; removing them is the only way to prevent accidental ingestion
• Reading labels and following proper dosage instructions of supplements and medications, as overdosing on certain products can increase the risk of heavy metal toxicosis
Heavy metal toxicosis is rare in horses.
• Fluid therapy
• Pain medication
• Gastrointestinal decontamination
• Activated charcoal
• Chelation therapy
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