Microchips for Pet Identification

Laurie Anne Walden, DVM

Microchips are a type of permanent identification that helps families reunite with lost pets. Pets should also have visible forms of identification like collar tags, but microchips can’t be pulled off by accident and are an important backup. Microchips are also required in some situations, like transporting animals.
 
Microchips connect owners to lost pets only if the owner’s contact information is registered in a microchip database. The United States does not have a central microchip registry. Microchip manufacturers and pet recovery services maintain their own databases. It’s essential to keep your contact information up to date in your pet’s microchip database.
 
If you’re not sure where your pet’s microchip is registered, enter the microchip number in the American Animal Hospital Association microchip lookup tool:
http://www.petmicrochiplookup.org/
If you don’t know the microchip number, your veterinarian’s office can scan your pet if the number is not already entered in your pet’s medical record.
 
What Are Microchips?
Microchips are radiofrequency identification transponders about the size and shape of a grain of rice. Microchips are implanted under the skin. In dogs and cats, they are implanted between the shoulder blades. You can’t usually feel a microchip under your pet’s skin, but you can see it on an x-ray image.
 
A microchip is not a GPS device and can’t be used to track your pet.
 
How Are Microchips Implanted?
A microchip is injected under the skin through a needle, similar to the way a vaccine is injected (although the needle is a bit larger). Animals do not need anesthesia during microchip insertion. Your veterinarian can implant a microchip during an office visit.
 
How Does Scanning Work?
Shelters and veterinary clinics routinely scan stray dogs and cats for microchips. If the animal has a microchip and the owner’s information in the database is accurate, the staff can contact the owner.
 
A microchip scanner emits a low-power radiofrequency signal that activates the microchip. When a microchip scanner passes over a microchip, the chip transmits a number that the scanner displays on a screen. The number is unique to that microchip, so once you’ve registered it, it’s also unique to your pet.
 
Microchip manufacturers around the world make microchips that use different radiofrequencies. Not all scanners detect all microchip frequencies. Universal scanners read multiple frequencies. Microchips that meet the International Standards Organization (ISO) global standard transmit a specific radiofrequency that can be read by an ISO-standard scanner. Some countries require ISO-compliant microchips for imported animals.
 
Are Microchips Safe?
The benefits of microchipping are generally far greater than the potential risks. Adverse reactions to microchips are rare. Animals could bleed a little or have mild, short-lived discomfort at the injection site. Infection and swelling at the injection site are possible but not common. Microchips can theoretically cause inflammation that leads to cancer, but almost all reports of cancer near a microchip implantation site have been in laboratory rodents. Only a few cases in cats and dogs have been reported, and in most it was not clear if the cancer was linked to the microchip.
 
Are Microchips Reliable?
It’s possible for an animal to have a microchip that isn’t found on a scan. A microchip might use a different radiofrequency than the scanner can detect (if the scanner isn’t universal). Microchips occasionally migrate under the skin, usually to the side of the shoulder or front leg. People scanning for microchips typically scan a wide area of the body for this reason. And a microchip might not work at all (or stop working). Ask your veterinarian to check your pet’s microchip at the next clinic visit.
 
For more information, see Microchipping of Animals FAQ on the American Veterinary Medical Association (AVMA) website.
 
The AVMA Microchipping of Animals backgrounder page was also a source for this article.

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