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Home > Cats > Mercury Poisoning in Cats: How it Happens, Symptoms & Care (Vet Answer)

Mercury Poisoning in Cats: How it Happens, Symptoms & Care (Vet Answer)

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Dr. Leigh Wilder

Veterinarian, DVM

The information is current and up-to-date in accordance with the latest veterinarian research.

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Mercury poisoning is a health issue of historical significance for both humans and animals. Many people have heard of the phrase “mad as a hatter”, a comparison used to describe the unfortunate symptoms of chronic mercury poisoning in hat makers of the Victorian era—but what does this have to do with our feline friends?

The following article will discuss mercury poisoning in cats—including its causes, signs, and care of affected felines—to illuminate how this condition remains relevant for pet owners of the 21st century.

divider-cat What is Mercury Poisoning?

Mercury is a naturally-occurring heavy metal found in the environment in one of several forms:
  • Elemental Mercury: Often referred to as quicksilver, elemental mercury is the shiny, silver metal found in products, such as older thermometers and fluorescent lightbulbs. Elemental mercury is a liquid at room temperature, however, may evaporate into a toxic vapor if it is released from a damaged product or device.
  • Inorganic Mercury: Inorganic mercury is found commonly in the environment, and may combine with other elements to form inorganic salts found in the soil.
  • Organic Mercury: Methylmercury is the most common form of organic mercury, and forms as a result of inorganic mercury cycling through the environment. Mercury present in the air or on land will eventually settle into bodies of water, where it accumulates in the tissues of fish and shellfish. Larger fish that eat other smaller fish typically contain the highest levels of methylmercury.

Poisoning or toxicity can occur secondary to exposure to any of the above-noted forms of mercury and may result in damage or dysfunction of the immune, digestive, integumentary, and nervous systems. Additionally, impaired kidney function and abnormal fetal development can also be seen secondary to mercury poisoning.

sick cat coughing at house porch
Image By: udeenmajid, Shutterstock

What Are the Signs of Mercury Poisoning?

The symptoms associated with mercury poisoning in felines vary depending on both the dose and duration of exposure, as well as the specific form of mercury causing toxicity.

Ingestion of organic, or methylmercury may cause the following symptoms:
  • Blindness
  • Incoordination
  • Muscle weakness
  • Tremors or convulsions
  • Nystagmus (abnormal, involuntary eye movement)
  • Abnormal, exaggerated movements of the limbs
  • Anorexia
  • Depression
  • Paralysis

Young, developing kittens are especially sensitive to the effects of organic mercury poisoning and may exhibit jerky, uncoordinated movements, and death secondary to exposure.

Signs of mercury poisoning secondary to inhalation of elemental mercury, while less common, may include difficulty breathing, respiratory compromise, and death in addition to the symptoms noted above. Mercury poisoning resulting from the ingestion of inorganic mercury often includes signs, such as anorexia, vomiting, diarrhea, inflammation of the mouth and esophagus, and pain due to the compound’s corrosive nature. Sudden death may also occur.

What Are the Causes of Mercury Poisoning?

The most common route of mercury exposure for pets is the ingestion of fish containing methylmercury. The types of fish most frequently implicated as containing high levels of mercury include tuna, swordfish, king mackerel, marlin, shark, and tilefish. Methylmercury ingested from dietary sources is rapidly absorbed in the gastrointestinal tract, however, clinical signs may not become apparent for several weeks after initial exposure.

While felines have been noted to be especially sensitive to even low doses of methylmercury, toxicity from other forms of mercury may also occur. Pets may be exposed to elemental mercury from products, such as older thermometers, appliances, thermostats, or automotive parts. Certain types of sporting equipment, imported skin creams, and jewelry or antiques may also be implicated in cases of elemental mercury poisoning.

Most exposures to elemental mercury occur when it is inadvertently released from a broken or damaged product. Liquid elemental mercury is absorbed poorly through the skin, however, inhalation of the toxic vapor created as this substance evaporates leads to rapid absorption and severe clinical signs.

Sick cat
Image By: Kachalkina Veronika, Shutterstock

How Do I Care for a Pet With Mercury Poisoning?

If your cat is feeling unwell or you have concerns regarding potential mercury poisoning, prompt veterinary attention is recommended. While the clinical signs discussed above may indicate potential mercury poisoning, this condition is overall considered to be uncommon in felines, and a variety of other conditions will likely be considered by your veterinary team.

If your veterinarian diagnoses your cat with mercury poisoning and treatment is advised, options may include medications used to bind mercury in the gastrointestinal tract and limit its absorption, such as activated charcoal. Antioxidants, such as vitamin E and selenium, may also be used to limit cellular damage caused by mercury. Lastly, chelation therapy used to bind mercury in the blood may be beneficial in cases of recent exposure.

While treatment options for this condition do exist, it is important to note that the neurologic and renal (kidney) damage caused by mercury is permanent, and treatment of affected cats may be unrewarding. The prognosis for complete recovery in animals affected by mercury poisoning is, unfortunately, very poor.

divider-cat Frequently Asked Questions (FAQs)

How is Mercury Poisoning Diagnosed?

A diagnosis of mercury poisoning may be made by your veterinarian based on your cat’s history, symptoms, and laboratory test results. Evaluation of mercury concentrations in soft tissues such as the kidneys or liver may demonstrate abnormally elevated levels of this heavy metal. Other lab work such as a urinalysis, complete blood count, and blood chemistry may be supportive of a diagnosis of mercury poisoning.

sick cat covered in blanket lies on the window in winter
Image By: Germanova Antonina, Shutterstock

How Can I Prevent Mercury Poisoning in my Cat?

Ingestion of methylmercury-containing fish is the most common route of mercury exposure in both humans and pets. Unfortunately, data on the levels of mercury in commercial cat foods is lacking, and there are currently no regulations regarding mercury concentrations in pet foods in the United States.

While there are no documented cases of mercury poisoning in cats fed a commercial diet, if you have concerns regarding this risk, avoiding daily feeding of tuna-based cat foods may be considered as a preventative measure. Additionally, foregoing the regular feeding of certain products, such as albacore tuna, may be wise.

divider-cat Conclusion

In summary, mercury poisoning is an uncommon, yet serious medical condition affecting felines. If you have any concerns regarding your cat’s health or its risk for this condition, a discussion with your veterinarian is an appropriate next step—they will be the individual best suited to advise you on the well-being of your furry family member.

Featured Image Credit: Iryna Mylinska, Shutterstock

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