What is Lead Poisoning?
Lead poisoning is rare for equines, but it does happen, and it can have serious consequences ranging from joint stiffness to collapse and death. Horses can encounter lead in paint from older buildings and structures, in pastures with contaminated ground, or even in the ashes of wood that had previously been treated with lead. Prompt diagnosis and treatment are crucial if the horse is to recover from lead toxicity as the emergence of symptoms generally indicates that irreversible damage has already taken place.
Lead poisoning in horses can cause dysfunction in the gastrointestinal system as well as the peripheral and central nervous systems. Swift diagnosis and treatment of lead poisoning are critical for successful treatment.
Book First Walk Free!
Symptoms of Lead Poisoning in Horses
The symptoms of lead poisoning are wide-ranging due to the large number of systems it can have an adverse effect on. Some of the symptoms you may see with lead toxicity include:
- Colic symptoms
- Difficulty swallowing
- Eye rolling
- Impaired vision
- Joint stiffness
- Lack of coordination
- Laryngeal paralysis (roaring)
- Muscle weakness
- Poor condition
- Weight loss
Several areas of the body can be adversely affected by lead toxicity. These can include:
- Gastrointestinal system - Toxicosis by metals usually presents with gastrointestinal distress
- Kidneys - Acute lead poisoning caused by high levels of lead is more likely to result in severe damage to the kidneys than the lower levels of lead that lead to chronic poisoning
- Nervous system - Lead poisoning has a profound effect on the nervous system, disrupting both the peripheral and central nervous system
- Reproductive system - Excessive levels of lead in the blood can result in lowered sperm counts for males; lead poisoning in pregnant females is particularly problematic as lead can pass through the placenta and may result in low birth weight, early delivery, and developmental delays in the foal (lead also passes to young foals through the mare’s milk)
Causes of Lead Poisoning in Horses
Because lead is a significant environmental pollutant, there are several ways for horses to acquire excessive levels of lead. Some sources of lead that can contribute to either acute or chronic lead poisoning include:
- Accidental ingestion of lead debris, such as buckshot or fishing weights
- Ashes from treated, burned lumber
- Eating paint from the side of old wooden buildings and structures
- Lead contamination in the water
- Lead leaching into grass or hay from ground contamination
Diagnosis of Lead Poisoning in Horses
Lead poisoning in equines is uncommon, and can easily be overlooked as a diagnosis, so a complete history of the horse’s environment and symptoms is needed. Standard tests may lead your veterinarian to suspect lead poisoning. These tests could include a complete blood count, which may show signs of anemia and a biochemistry profile that may have elevated levels of bilirubin, ALP, and ALT which tends to indicate that damage to the liver has occurred.
Once metal toxicity is suspected, a simple blood test can determine the levels of lead in the blood for a definitive diagnosis, and x-ray technology may be used to view any pieces of metal that may have been swallowed. The veterinarian may also choose to perform neurological tests to help assess the horse’s current functionality. Limb placement tests, holding one leg while the horse moves forward, and walking the horse up and down an incline may all be included and will help the examiner assess the horse’s awareness of the placement of their legs as well as the overall stability of the animal.
Treatment of Lead Poisoning in Horses
If treatment for lead poisoning is to be successful, it must be started early. Once clinical symptoms of toxicity from lead exposure are apparent, it is often too late to reverse the damage, although the damage may be able to be slowed or even halted. As equines are unable to vomit, the veterinarian will usually perform a gastric lavage, using a nasogastric tube, to prevent the absorption of the toxins into the bloodstream. A slurry of activated charcoal will also be will be dispensed to the patient in an attempt to soak up as much of the toxic metal as possible, followed immediately by a laxative. Magnesium sulfate (Epsom salts) or sodium sulfate (Glauber’s salt) is often recommended as a laxative, and mineral oil may be utilized as an intestinal protectant.
Calcium disodium edetate is generally administered to the animal either intravenously or subcutaneously over several days. This treatment is often combined with the administration of thiamine, which helps to ease symptoms as well as reducing the amount of lead that is deposited in the body tissues.
Recovery of Lead Poisoning in Horses
Plenty of clean, fresh water will need to be available for the patient during both treatment and recovery, and caution should be observed when the patient wakes from anesthesia to prevent injury to the horse or its caregivers. It is critical that horses not be urged to stand before they are ready as they may be unsteady when they first awaken, and padded recovery stalls will often be utilized to prevent injuries upon regaining their faculties. The prognosis for exposure to this metal is guarded as lead poisoning, when survived, frequently leads to varying levels of permanent disabilities, both physical and mental.