Dangers

• When mercury builds up in the body at high doses, it can act as a neurotoxin and cause havoc in the brain and nervous system. Odorless and invisible, mercury enters the body through consumption of contaminated seafood, particularly tuna, swordfish and king mackerel.
  
  

Symptoms

• According the the Merck Veterinary Manual, signs of mercury poisoning in cats may include over-excitement, irritability, incoordination, convulsions, stiff hind legs, tremors and blindness.
  
  

Study of Cats

• A 1974 study in the journal Acta Neuropathologica looked at kittens who were fed a daily diet that included tuna containing 0.5 ppm mercury. After 11 months, the researchers "observed neurological disturbances similar to...mercury intoxication."
  
  

Canned Tuna

• Canned tuna can legally have twice as much mercury as was given to the cats in the 1974 study: a staggering 1.0 ppm, as of 2009. So if you are feeding your cat canned tuna every day, you are risking mercury poisoning. But giving a little tuna every now and then is probably OK.
  
  

Commercial Foods

• A massive recall in 2007 brought widespread attention to commercial pet food safety. Pet food makers claim their products are safe, but some people are skeptical. Veterinarian/author Richard Pitcairn, for example, says, "Pet foods containing fish and fish byproducts may contain high levels of mercury."
  
  

If You Suspect Mercury Poisoning

• If you suspect your cat has mercury poisoning, contact your vet right away.