Mad Cow

Niels Pedersen: Pets and zoo animals' susceptibility

Niels Pedersen

Professor Niels Pedersen is director of both the Center for Companion Animal Health and the Veterinary Genetics Laboratory in the School of Veterinary Medicine. He is a national authority on infectious and immunologic diseases of dogs and cats. He can discuss the history of bovine spongiform encephalopathy-related diseases in companion animals and zoo animals, and the risk to pets in the U.S. of contracting such a disease.

Q. Which companion animals and zoo animals are known to have contracted BSE during the outbreak in the United Kingdom?

A. This type of disease appeared in cats, ruminant species related to cows that were in zoos, large and small wild cats in zoos and non-human primates. Dogs appear to be resistant

Q. How great is the risk that dogs and cats in the United States might contract mad cow disease via pet food?

A. Virtually none, but only because of the grace of God. Changes in the regulations that were instigated in 1997 in the U.S. and Canada banned the use of brain and spinal cord in the manufacture of foods used for animals consumed by people. However, they did not ban the use of these tissues in pet food or food for non-livestock species.

This is a little strange, given the fact that animal foods made from BSE-affected cattle during the U.K. outbreak apparently caused a number of cases of spongiform encephalopathy in pet cats, cat species in zoos, cow-related zoo animals and non-human primates in the U.K. and continental Europe. Therefore, cats and some other non-livestock species are known to be at risk for prion disease of cattle origin, and foods being fed to any susceptible non-livestock species, whether pets or zoo animals, should have been covered under the ban.

We in the United States have been very fortunate, because, prior to this single case in Washington State, we have not had any prion diseases in decades, and, therefore, meat by-products from American cattle have not been infectious. However, if there were a lot of cases of BSE, as there were in the U.K., and material from these animals got into meat by-products, I would expect the same pattern of pet and non-livestock infections as occurred in Europe.

Q. Could dogs contract BSE from chewing on rawhide toys and cows' hooves?

A. Again, that would be highly, highly unlikely. First, these particular tissues (skin and hooves) would contain extremely low levels of prions, even if the came from an infected cow, and would therefore not be very infectious even in the worst-case scenario. Second, dogs appear to be resistant to the bovine prion disease. Third, except for the recent case, cattle in the U.S. have not had problems with BSE, greatly decreasing the likelihood of these chews being contaminated.

Q. Are the symptoms of BSE in cats similar to those in cows?

A. Yes, the incubation period is similar, as are the clinical signs. Early signs include lack of coordination and muscle control, weight loss and dementia. The signs are slowly or rapidly progressive, depending on the individual. Death is inevitable once clinical signs appear.

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