The accurate and permanent identification of pet cats is both important and desirable, and has been regarded as an essential component of cats’ welfare.
Having this information is vital in reuniting cats with their owners should a cat ever stray, escape or get lost. While collars with tags can be used to identify cats and carry contact information, these are not ideal as they can sometimes cause serious and life-threatening injury and/or can be broken or separated from the cat.

Microchips for cats
ISFM is in agreement with both the World Small Animal Veterinary Association
(WSAVA) and the American Veterinary Medical Association (AVMA) in affirming
that microchipping of dogs and cats is safe and very rarely associated with any
significant problems.

A permanent microchip conforming to the internationally recognised ISO Full Duplex standard (numbers ISO 11784 and 11785) is the best option for the
identification of cats. These are available from a wide range of manufacturers/suppliers and the standards ensure the microchip can be widely identified throughout the world by using a suitable ISO-compatible scanner.

The microchip itself is a tiny implant, typically about the size of a grain of rice, inserted under the skin and is usually implanted in a very similar way to administering a vaccine. The microchip is then linked to a central database (eg, the National PetLog Database) that holds all the details of the pet and the owner. Should the cat become lost or separated from its owner, a microchip scanner can be used to identify the cat and the owner. Both veterinary clinics and rescue shelters routinely use microchip scanners to identify pets and cats that have become separated from their owners.

Importantly, in addition to being able to identify lost cats, the use of microchips allows the results of tests (eg, genetic tests for certain diseases) to be stored alongside a cat’s unique microchip number. For such purposes, samples (eg,
cheek swabs or blood samples) should be collected and submitted to a testing
laboratory by a veterinary surgeon, who checks and certifies the microchip number at the same time.

Safety concerns with microchips
While the procedure should cause little or no discomfort, it is important that only a veterinary surgeon or other properly trained individual administers the microchip, as the incorrect placement of a microchip can have severe consequences. Significant complications from the appropriate implantation of microchips in cats appear to be exceptionally rare. Data reviewed by the WSAVA suggest microchips are a safe and effective means of identifying pets. They also state that, of the many millions of animals that have been microchipped, only a tiny proportion have had any type of problem reported (and usually simply related to movement or loss of the chip).

The Microchip Advisory Group (MAG) monitors adverse events associated with microchipping in the UK. Between 1996 and 2011 a total of 431 adverse events had been reported in all species (dogs, cats, exotics, etc), representing an average of approximately 27 each year.

The most common adverse events reported were:

• Movement of the microchip away from the implantation site (56%)
• Loss or failure of the microchip (28%)
• Infection at the site of implantation (6%)
• Swelling at the site of implantation (6%)

The British Small Animal Veterinary Association (BSAVA) released a report from the MAG in 2004 which documented that adverse events had been reported in a total of 235 dogs from an estimated 2.3 million that had been microchipped (ie, in
approximately 0.01% of microchipped dogs). In the same data there had been 36
adverse events reported in cats.

Concern has been raised by some about the potential for implanted microchips to
cause some types of cancer at the microchip site (eg, fibrosarcomas), and this has been suggested as a reason to avoid microchipping. However, if microchips ever cause the formation of tumours in dogs and cats, the risk appears to be incredibly low. Data from the MAG show that from 1996 to 2011 there were just three reports of a tumour developing possibly as a result of the microchip
across all species. Currently in the published literature we are also aware of two case reports of cats and two case reports of dogs developing tumours at, or adjacent to, the site of a microchip. However, in none of these cases could the formation of the tumour be directly linked to the microchip itself.

If microchips are a cause of certain cancers in either dogs or cats, this appears to be exceptionally rare, and the benefits of microchips in providing permanent identification of cats (and dogs) vastly outweigh any potential risks. Nevertheless, where adverse events are suspected, it is important that these are always documented and notified to the appropriate authorities.

Additional reading
1. AVMA Microchipping of Animals, Backgrounder. https://www.avma.org/KB/Resources/Backgrounders/Pages/Microchipping-of-Animals-Backgrounder.aspx (2009. accessed August 24, 2012).
2. AVMA Microchipping of Animals FAQ.
https://www.avma.org/KB/Resources/FAQs/Pages/Microchipping-of-animals-FAQ.aspx. (2012, accessed August 24, 2012).
3. Carminato A, Vascellari M, Marchioro W, et al.
Microchip-associated fibrosarcoma in a cat. Vet Dermatol 2011; 22: 565–569.
4. Daly MK, Saba CF, Crochik SS, et al.
Fibrosarcoma adjacent to the site of microchip implantation in a cat. J Feline Med Surg 2008; 10: 202–205.
5. Laurence C. Microchipping update. J Small Anim Pract 2010; 51: suppl 4–7.
6. Lord LK, Griffin B, Slater MR, et al. Evaluation of collars and microchips for visual and permanent identification of pet cats. J Am Vet Med Assoc 2012; 237: 387–394.
7. Nind F. BSAVA MAG microchip report 2004
8. Swift S. Microchip adverse reactions. J Small Anim Pract 2000; 41: 232.
9. Vascellari M, Melchiotti E and Mutinelli F. Fibrosarcoma with typical features of
postinjection sarcoma at site of microchip implant in a dog: histologic and immunohistochemical study. Vet Pathol 2006; 43: 545–548.
10. Vascellari M, Mutinelli F, Cossettini R, et al. Liposarcoma at the site of an implanted microchip in a dog. Vet J 2004; 168: 188–190.
11. WSAVA Microchip identification. http://www.wsava.org/MicrochipID.htm.
(accessed August 28, 2012).