Dear Dr. Fox:

There has been much discussion in the media about "mad cow disease" now that it has arrived in the United States. However, I have heard no expression of concern about the possible contamination of pet foods. I have some concern about this since I have two cats who eat canned food. What is your thinking on this? I would appreciate your addressing my concern in your column, as I believe it is a question that would interest all cat and dog owners.

C.W.S., Fairfax

Mad cow disease, or bovine spongiform encephalopathy (BSE), which devastated the British beef industry, is caused by a little-understood change in the structure of a type of protein called prions that normally exist without causing any harm to the brain. A mutation may have occurred that made these protein molecules capable of destroying cows' nervous systems, and was spread rapidly when parts of cows that had died from the disease were recycled into livestock feed. Many cattle then became fatally infected, as did humans (150 people died in Britain), cats, a dog in Sweden, and several zoo carnivores fed contaminated beef and meat byproducts. Even though the practice of feeding dead cattle parts to live cattle has been prohibited in the United Kingdom, cases of mad cow disease have still been reported, which supports the theory that some agents (such as a pesticide or copper deficiency) might mutate harmless brain prions into brain destroyers.

According to experts who dealt with the European outbreak, more U.S. cattle are likely to have mad cow disease if cows going to slaughter are not individually tested for mutated prions. One panel has advised the U.S. Department of Agriculture to ban the feeding of beef brains and spinal cord tissue to pigs, poultry and companion and other animals (as has been the case with cows, sheep and goats since 1997), but this advice has yet to be implemented. Some experts maintain that commercial pet foods are processed and tested so as to avoid contamination, but the best way to put your mind at ease is to not feed your cats food containing beef or beef byproducts.

Dear Dr. Fox:

I have two female dachshunds, ages 2 and 3. The 2-year-old, Emma, is very overweight. Both receive the same amount of weight-control food each day, and they spend much of the day chasing squirrels in the backyard. Emma is still seven pounds above her suggested weight limit.

Also, she eats money! I know it is not unusual for a dog to shred tissue or newspaper, but she gets money out of my purse (and money from other family members) and eats it. I have found pieces of money all over the house. I have found portions of $1 and $5 bills buried in the backyard. I have even had to chase her through the house trying to retrieve the $10 bill she had in her mouth. There are some forms of paper she never touches, but certain pieces of mail and any kind of paper money seem to be her weakness. After losing almost $50 to her addiction, the family has learned to keep their wallets out of reach.

What could be causing her weight problem? Could it be related to her cravings for paper money?

S.B., Fort Worth

It is my understanding that in the printing of paper money (at least in the United States), the sizing/finish that is put on the money contains an extract of animal fat or tallow called stearate. Stearates are also present in certain plastics, processed films and many cosmetics, which may explain why cats especially like to lick such materials. So your dog is probably reacting like these cats to the animal-fat extract, which should not cause any health problems -- unless she were to eat an entire wallet!

Baldness in Dogs

Often mistaken for a hormonal imbalance or deficiency, dogs may develop a bald patch on their sides (usually just behind the ribs) that disappears come spring and may get larger the following winter. The bald skin is also darker in color. This condition is called "seasonal flank alopecia," but a blood test should be done to rule out Cushing's disease (which is much more serious and also causes hair thinning and baldness on the flanks).

Treatment with melatonin has helped dogs with seasonal alopecia, but exposure to a full-spectrum emission plant "grow light" or Vitalite (for dogs spending long hours indoors in the winter) will also be beneficial -- and probably help their human companions overcome seasonal depression, too!

Michael Fox, author of many books on animal care, welfare and rights, is a veterinarian with doctoral degrees in medicine and animal behavior. Write to him in care of United Feature Syndicate, 200 Madison Ave., New York, N.Y. 10016. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

(c) 2004, United Feature Syndicate Inc.