19 February 2003 15:00 GMT

by Alexandra Venter

What, if anything, keeps pet food BSE free? Transmissible spongiform encephalopathies (TSEs) have not been observed in dogs, but close to 90 cases of the feline equivalent of mad cow have been reported in UK cats since 1990. The cats probably fell ill as a result of eating pet food containing infected beef. The owners, according to a report published in 2001, have shown no signs of the human equivalent of the disease, new variant Creutzfeld-Jakob disease (vCJD).

Whether or not pet owners in general could contract TSEs from contact with contaminated pet food or their animal companions is an open question.

UK animal feed guidelines are among the most stringent. Specified risk materials - such as brain tissue and spinal cord of cattle, sheep and goats over a certain age - may not be included in food for "any creature." The Department for Environment, Food, and Rural Affairs (DEFRA), Food Standards Agency, and veterinary associations, all participate in the regulation of pet food in the UK.

North American standards for animal feed are based on the assumption that the region is BSE free. Nevertheless, US and Canadian regulations prohibit feeding ruminants many mammalian proteins. Pet food, which commonly contains the prohibited proteins, is not to be fed to ruminants.

The pet-food industry in Canada is tightly self-regulated, says Steffani MacDonald, manager of the Pet Food Certification Program of the Canadian Veterinary Medical Association (CVMA). The CVMA, which considers its program to be the most rigorous in North America, only certifies products that meet specific nutritional and safety standards. These pet foods may include meat, animal by-products, and meal, a rendered product that may contain "whole animal," inclusive of hoof and horn, but minus any blood.

Sergio Tolusso, Feed Program Co-ordinator with the Canadian Food Inspection Agency, doubts that traditional rendering practices would inactivate prions. Some raw materials must simply be kept out of feed altogether. Pet food manufacturers are becoming more discriminating, says Tolusso. Given the unknown risks of sheep scrapie and chronic wasting disease, Canadian rendering plants no longer accept elk, deer, or older sheep. The petfood brand Iams, which is distributed wordwide, uses ingredients graded for human consumption by the US Food and Drug Administration, a company representative told BioMedNet News.

Canada and the US strictly control protein imports. In Canada, lamb meal is imported from New Zealand and Australia, which are considered scrapie-free. Pet food imports are also restricted, says Tolusso, since pet food, itself, could serve as a vector for introduction of TSEs.

Safety standards regarding TSEs will no doubt continue to evolve. "The rendering industry is in a state of flux," said one veterinary expert from Western Canada. "It's an unfinished story."

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