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When the chips are down
Salina Christmas, Web Editor
20 December 2007

"Mice and rats are more susceptible than other species to developing foreign body-induced tumors."
The AVMA says extrapolation of increased incidences of foreign body-induced tumors in mice to increased risk in other species is inappropriate
Photo: Bas van de Wiel

Reliable electronic identification is essential for facilitating animal identification and disease surveillance, says the American Veterinary Medical Association (AVMA) in response to press reports about links between chip implants and tumors in animals.
 
On 5th December 2007, the AVMA published an online background piece and FAQ documents relating to microchips to endorse the use of RFID (radiofrequency identification) chips in animals, following the publication of a report by Dr Katherine Albrechtof US consumer group CASPIAN
 
AVMA’s statement echoes the opinion of the World Small Animal Veterinary Association (WSAVA), which endorses the chipping of companion animals. WSAVA has a dedicated Microchip Committee that promotes the association’s interest and views in relation to RFID.
 
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Dr Rosemary J LoGiudice, DVM Director, Membership & Field Services Division, AVMA, told Animal Pharm: “Both identification and reuniting animals with their owners, and disease surveillance are important reasons for electronic identification.”

She maintained that the first paragraph of the AVMA policy on electronic identification sums up the importance of automatic identification (auto ID) in animals. The association “endorses the use of electronic identification in animals and supports the standardization of materials, procedures, equipment, and registries… to accurately identify animals to aid in reuniting animals with their owners [and] accurately identify animals for regulatory purposes”.

Dr LoGiudice said: “Specifically, in regards to the safety of the food supply, the AVMA has a policy which states that it believes that permanent, dependable identification of animals is essential for tracing the origin and destination of food production animals in order to protect the nation's livestock industry and public health.”

In September 2003, Leon, a nine-year-old male French bulldog was implanted with a microchip for
identification purposes. Eight months later, its owner detected a lump measuring 3x3 cm in the implant area. The mass, identified as a high-grade infiltrative fibrosarcoma attached to the microchip, was later surgically removed
M Vascellari, et al. Fibrosarcoma with typical features of post injection sarcoma at site of microchip implant in a dog: Histologic and immunohistochemical study. Veterinary Pathology. 2006; 43:545-548
She quoted: “The AVMA recommends that a high priority be placed on using alternatives to hot-iron branding, such as RFID or electronic technology*.” (*Policy on Livestock Identification; Approved by the AVMA Executive Board June 1994; revised November 2002; revised April 2006) 

A possible link to tumors?
 
Concerns on animal chip implants were voiced following a press report in September 2007 by Todd Lewan of Associated Press on microchip implants in human beings, which highlights the link between RFID transponders and tumors in laboratory mice.
 
The article uses a series of veterinary and toxicology studies, dating to the mid-1990s, to illustrate its case against the chipping of human beings for medical reasons in the US. The article says that to date, over 2,000 RFID devices have been implanted in humans worldwide.

It generated a considerable amount of coverage by the US consumer press, but also invited an unwelcome scrutiny into the veterinary industry’s microchipping practice.

Associated Press obtained some of its leads from Dr Katherine Albrecht, an anti-RFID activist who is the founder and director of CASPIAN Consumer Privacy.
 
CASPIAN, or Consumers Against Supermarket Privacy Invasion and Numbering, is a US-based consumer group fighting retail surveillance schemes since 1999. It “seeks to educate consumers about marketing strategies that invade their privacy and encourage privacy-conscious shopping habits across the retail spectrum”.
 
On 19th November 2007, CASPIAN released an online report by Dr Katherine Albrecht, Microchip Induced Tumors in Laboratory Rodents and Dogs: A Review of the Literature 1990–2006, to “set the record straight after misleading claims by HomeAgain and VeriChip implant manufacturers”.
 
Gross and microscopic appearance of a microchip-associated tumor
The microchip has been removed from the cavity where it resided in situ (size of microchip 2 x 12mm)
Cavity related to the removed microchip (asterisk)
Le Calvez et al. Experimental and Toxicologic Pathology. 2006;57:255-265
The report reviews 11 oncology and toxicology journals – eight investigating mice and rats, and three investigating dogs – published between 1990 and 2006 addressing the effects of implanted RFID microchips on laboratory animals.

In eight of the articles, researchers observed that malignant sarcomas and other cancers formed around or adjacent to the implanted microchips. CASPIAN said: “The tumors developed in both experimental and control animals, and in two household pets. In nearly all cases, researchers concluded that the microchips had induced the cancers."
 
“The tumors generally occurred in the second year of the studies, after more than one year of exposure to the implant. At the typical time of tumor onset, the animals were in middle to advancing age. The exception to this was the Blanchard (1999) study, in which genetically modified mice developed fast-growing cancers well before six months.”
 
The report says the tumors could have been caused by foreign-body tumorigenesis; post-injection sarcoma; possible genotoxic properties of the implant such as the glass capsule or the polypropylene sheath that is used to bond the transponder to the dog’s subcutaneous tissue; or by radiofrequency energy emissions from the transponder or reader.
 
It recommends that veterinarians “routinely palpate the tissue surrounding microchip implants as part of routine medical care”.
 
“Any lumps or inflammation should be investigated for cancerous or pre-cancerous changes. To avoid the complicating risk of injection-related sarcoma, veterinarians should avoid administering vaccines or other injections at or near the site of an implanted microchip,” the report advises.
 
“Veterinarians should advise pet owners to routinely examine the site of the implanted microchip themselves and immediately report any abnormalities.”
 
Don’t jump to conclusions
 
The Blanchard study is published in the September-October 1999 edition of Toxicologic Pathology. Taylor & Francis publishes the most recent editions of the journal on behalf of the Society of Toxicologic Pathologists.
› More on the journal
› More on Informaworld
“Extrapolation of increased incidences of foreign body-induced tumors in mice to increased risk in other species, including humans, is inappropriate,” said AVMA.

The association said a few factors should be considered when looking into the findings published by the 11 journals.

Firstly, lab rodents are specifically bred for cancer research. Microchips are commonly used to identify individual animals in research. “In-bred mice strains are commonly used in research, and tumor susceptibility varies with strain,” said AVMA. “Mice and rats are more susceptible than other species to developing foreign body-induced tumors.”

A few studies mentioned in the AVMA backgrounder (Johnson et al, 1973; Johnson, 1996; Tillmann et al, 1997; Vascellari, 2006) observed a reaction to foreign bodies such as glass or plastic implants “in species prone to developing tumors”.

Secondly, the size of the microchip in relation to the size of the rodents, and companion animals such as dogs and cats, should be taken into account.
 
“Although microchip size may vary within a narrow range, the majority of microchips used in research and companion animals in the United States are 2 mm in diameter and 12 mm in length.
 
“Therefore, the same size microchip in a mouse presents a markedly larger surface area compared to the animal's body size than it does in a larger species such as a dog or cat. This may partially explain the species differences in the reported incidence of tumors associated with microchip implantation.”
 

About HomeAgain
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Company: Schering-Plough
Chip manufacturer: Destron Fearing, a subsidiary of Digital Angel
Brand portfolio: HomeAgain microchip; HomeAgain Pet Recovery database system
Website: www.homeagain.com

Thirdly, “the possible impact of the carcinogenic substances on the reported incidence of tumor formation should be considered when interpreting the studies”.
 
AVMA also stressed that the majority of the studies were not conducted to determine the frequency of tumor formation associated with microchip implantation alone. The tumors were observed in animals used for ongoing carcinogen and oncogenicity research.

According to AVMA’s backgrounder, the first report of a microchip-associated tumor in a pet was published in 2004. (Vascellari et al, 2004) An 11-year old male, mixed-breed dog developed a liposarcoma at the site of a microchip implanted craniodorsally to the top of the left shoulder blade. This is a common site for microchip implantation as well as vaccine administration. The cancer developed some 18 months after the chip implantation. When the nodule was removed, three years after initial implantation, the microchip was found to be embedded in the tumor. No signs of recurrence were observed three months after surgery.

“The findings reported by Vascellari et al in a 2004 report were similar to those reported by McCarthy et al in 1996, when an 11-year old spayed female, mixed-breed dog developed a liposarcoma associated with a glass foreign body. The authors determined the glass had become implanted when the dog had fallen from a pickup truck onto a gravel roadway ten years prior to discovery of the mass. The foreign body and associated tumor were excised, and no tumor recurrence was observed one year after excision. (McCarthy et al, 1996).”
 
Exception, not the norm
 
Despite its damning views on microchip implants, Dr Albrecht’s report acknowledged that “the fact that we have not seen an epidemic of cancers in pets would suggest that only a small number will be impacted.”

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AVMA advises against “a rush to judgment on the technology”, considering how a large number of pets have been implanted with microchips with a relatively small number of confirmed cases of tumors associated with microchips.

Referring to the British Small Animal Veterinary Association (BSAVA), which instituted a microchip adverse reaction reporting system in 1996, AVMA said: “In the eleven years since inception of the BSAVA's microchip adverse reaction program, two tumors have been reported. More than 4 million pets in the United Kingdom have been implanted with microchips.”

The table summarizes the reported types and incidences of microchip-associated adverse reactions in the United Kingdom
Source: BSAVA 2007/AVMA

While microchip implants are not without problems – other adverse reactions and complications have been recorded – they provide a better means of identification than collars, which can be removed, or tattooing, which is uncomfortable, or ear tags, which can be lost.

The major veterinary associations acknowledge that there is a need for more scientific research into the technology, but they maintain that the benefits outweigh the risks, and that the microchip’s advantages over other means of data capture make the technology more in line with their monitoring objectives.

NOTE: The WSAVA Microchip Committee would be interested to receive details of any cases where tumours have developed in companion animals at the site of transponder implantation, and where there is suspicion of an association. In the first instance, details should be sent to the WSAVA secretariat at fasanne@fasanne.dk

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