Mercury poisoning in cats is rare but can have severe effects in cats. Alexey V Smirnov / Shutterstock.com
Quick Overview: Mercury Poisoning in Cats
Mercury poisoning in cats is rare – thankfully far less common than it used to be. Despite its rarity, this type of poisoning can have serious, and sometimes fatal, effects in cats, even with treatment. Mercury poisoning can also mimic other conditions in cats, such as feline panleukopenia virus (also known as feline parvovirus), so only a veterinarian can accurately diagnose this condition.
We will go through what causes mercury poisoning in cats, what symptoms to look for, and how to treat and prevent it.
Causes of Mercury Poisoning in Cats
Eating tuna is a common source of organic mercury poisoning in cats. Nataly Studio / Shutterstock.com
Mercury poisoning in cats usually occurs when a substance high in mercury, like tuna, is consumed. However, it can also be caused by inhaling mercury vapors.
There are three types of mercury, each of which causes poisoning differently.
1. Elemental Mercury
Elemental mercury is found in everyday household items like thermometers and fluorescent light bulbs. It is poorly absorbed by the skin, but its vapors are highly toxic to cats. For example, if a fluorescent light bulb breaks in your home and your cat inhales the mercury vapors, those vapors are rapidly absorbed in your cat’s lungs, causing severe and often fatal symptoms.
2. Inorganic Mercury Salts
Inorganic mercury salts are found in items like batteries and latex paints. It is poorly absorbed if ingested. In small amounts, such as a tiny lick of paint, inorganic mercury is not toxic to cats. However, this type of mercury is corrosive to the digestive system if ingested in large amounts, causing rapid and severe digestive upset.
3. Organic Mercury
Organic mercury is found in the environment. Inorganic mercury is converted into organic mercury, which tends to accumulate in water, soil, and rocks. Marine animals accumulate organic mercury in their bodies in the form of methylmercury, which is very toxic to cats.
Marine predators at the top of the food chain (e.g., sharks) and tuna contain high levels of mercury. When cats eat tuna and other mercury-containing seafood over a long period, the organic mercury accumulates in their bodies, eventually leading to poisoning. The accumulation is in the brain, kidneys, liver, and muscle.
Mercury poisoning in cats is most frequently due to eating large amounts of seafood, primarily tuna, that contains organic mercury. Poisoning from elemental and inorganic mercury is rare in cats.
Symptoms of Mercury Poisoning in Cats
Depression is a symptom of mercury poisoning in cats. Kachalkina Veronika / Shutterstock.com
Several factors determine the symptoms of mercury poisoning in cats:
Type of mercury
Duration of exposure
How much mercury was ingested
We’ll go through the symptoms according to the type of mercury, starting with organic mercury.
Symptoms of Organic Mercury Poisoning
Symptoms of organic mercury poisoning take at least several days to become apparent. Because organic mercury is not corrosive, cats with this mercury poisoning will not experience digestive upset. Here are the symptoms to look for with organic mercury poisoning:
Incoordination
Ataxia (wobbly gait)
Tremors
Seizures
Depression
Anorexia
Paralysis
Blindness
Excitement
Abnormal behavior
Rigid hindlimbs
Muscle weakness
Nystagmus (involuntary eye movements)
Exaggerated limb movement
Young kittens are especially susceptible to organic mercury poisoning because their nervous systems are still developing. A young kitten with organic mercury poisoning will likely develop cerebellar hypoplasia, which is underdevelopment of the cerebellum. Cerebellar hypoplasia causes symptoms like a wobbly gait and loss of coordination.
Symptoms of Elemental Mercury Poisoning
Cats that inhale elemental mercury vapors rapidly develop severe and often fatal breathing problems.
Symptoms of Inorganic Mercury Poisoning
Symptoms of inorganic mercury poisoning also develop rapidly and are listed below:
Pain
Vomiting
Diarrhea
Inflamed mouth and esophagus
Sudden death
Difficulty breathing
High levels of exposure to inorganic mercury can be fatal within hours.
The symptoms of mercury poisoning are also seen with other conditions, such as feline parvovirus, brain tumors, and insecticide poisoning. Therefore, a diagnosis of mercury poisoning in cats requires a veterinary evaluation.
Diagnosis of Mercury Poisoning in Cats
Diagnosis of mercury poisoning requires a veterinary examination. Maria Sbytova / Shutterstock.com
Take your cat to your vet as soon as possible if you suspect they have mercury poisoning. If treatment is warranted, starting early can minimize the amount of mercury the body absorbs.
A diagnosis of mercury poisoning in cats is typically made using history, clinical signs, and routine lab work.
Your vet will ask you about possible sources of mercury exposure, including diet and household products. They will also ask you about your cat’s symptoms, including when the symptoms first appeared and what they are. The more information you provide your vet, the better. Routine lab work includes bloodwork and urinalysis. Bloodwork may reveal evidence of kidney damage, while urinalysis can indicate the presence of inorganic mercury in the urine.
However, a definitive diagnosis requires a tissue sample to measure mercury levels in the tissue.
Treatment for Cats With Mercury Poisoning
Treatment for mercury poisoning in cats is often unrewarding, and the prognosis is very poor. Death can happen within hours or poisoning with inorganic or elemental mercury, so treatment must begin as soon as possible.
With organic mercury poisoning, damage to the brain and kidneys is often irreversible. Even if a cat recovers, the organ damage will be so debilitating that euthanasia may be the best option.
Here are the treatment options for mercury poisoning in cats:
Activated Charcoal: Prevents absorption by binding the mercury. It is most helpful soon after exposure.
Antioxidants: Vitamin E, selenium and other antioxidants can help limit the cellular damage caused by mercury absorption.
Chelation: A process that binds mercury in the blood. Like activated charcoal, it will be most effective soon after exposure.
Preventing Mercury Poisoning in Cats
Given the poor outcomes with treatment, preventing mercury poisoning is the best way to go. Here are some strategies for preventing it:
Do not feed your cat tuna every day
Limit your cat’s tuna consumption to less than 10% of their diet
Avoid cat foods with albacore tuna, which tends to be high in mercury
Do not feed kittens a diet that contains seafood
Block access to household items that contain mercury
Frequently Asked Questions
Should I worry about my cat eating fish?
The types of fish in cat food, especially tuna, contain mercury. However, you don’t have to eliminate fish from your cat’s diet. Limit your cat’s tuna consumption to no more than 10% of their diet, and do not feed tuna to them daily.
You can also rotate your cat’s protein sources to limit their mercury exposure; freeze-dried minnows and sardines are good alternatives to tuna.
My cat loves tuna. Should I be concerned about mercury buildup?
It depends on how much tuna your cat eats. If your cat eats primarily tuna daily, it is reasonable to be concerned about the possibility of mercury poisoning. If your cat eats tuna only occasionally, then the risk of mercury poisoning is relatively low.
Talk to your veterinarian if you are concerned about how much tuna your cat eats.
Is it safe to give my cat an omega-3 fatty acid supplement?
Fish oil is an excellent source of omega-3 fatty acids, but you may wonder if those supplements also contain mercury. Fortunately, omega-3 fatty acid supplements for cats are tested for the presence of dangerous compounds like mercury.
You can feel confident that giving your cat this supplement is safe. Always consult with your vet before giving your cat any supplements.
