Here's the bottom line: Veterinarians have been micro-chipping dogs, cats, ferrets, rabbits and horses for more than 25 years now, and there has not been a single published study by a veterinarian confirming that microchips cause cancer in companion animals.
Dr. Larry McGill, of Salt Lake City, UT, of the American College of Veterinary Pathology and also chairman of the American Veterinary Medical Association Member Services Committee, concedes that rumors about microchips causing cancer have persisted for years.
"We looked at three or four thousand cats in 2003, and there wasn't a single instance of sarcoma induced by a microchip," McGill said. "If it (cancer at the site of a microchip) occurs, it's so rare that it just isn't reported, ever."
McGill says the only confirmed instance involved one cat who had a sarcoma at the site of a vaccine, and a microchip was there." McGill doesn't know for certain if that cancer was caused by the vaccine or the microchip. But, he adds, "We know vaccines can - in very rare cases - be associated with sarcoma (however) we are not convinced that is the case for microchips. It's not a lack of evidence that microchips cause cancer; it's no evidence whatsoever."
McGill doesn't doubt that microchips may cause cancer in lab mice, but points out that companion animals are much larger. Microchips, used to identify a pet's owner, are the size of a grain of rice. McGill says that this size is likely insignificant for even a small dog or a ferret, compared to a mouse. McGill does note that foreign bodies, such as pacemakers, very occasionally do cause tumors in people.
Could it be that just as there's an apparent genetic predisposition for cancer at the site of vaccines in some cats, the same may be true for lab rodents? Could there be a predisposition for cancer where a chip is implanted in some lab animals? "You bet. Now you're on to something we should look at," says McGill.
McGill doesn't know if the type of microchip used matters. Those recent press reports on studies relating to microchips causing cancer referred to a kind of chip which emits a signal.
Microchips used in pets are read by scanners but do not emit a signal.
