DEAR READERS: After I informed you about a class-action lawsuit concerning prescription-only pet foods, I received comments from two practicing veterinarians on these special diets, which are marketed in several countries.

From California veterinarian Dr. Greg Martinez:

"Many years ago, prescription diets were the only diets available that attempted to address common medical problems in pets. The 'sensitive stomach' and 'intestinal diets' had fewer allergenic ingredients than the common pet food on the shelves. These days, limited ingredient diets are healthy alternatives to help dogs with food allergies and intolerances to wheat gluten, beef and chicken. These commercially produced diets -- containing meats like fish, venison and rabbit, or carbohydrates like rice, peas or potato -- are commonly available at pet stores. Hydrolyzed prescription diets from soy have been helpful for those dogs and cats who don't tolerate animal proteins.

"The birth of prescription diets came after Mark Morris, DVM, adapted the human kidney-failure diets to his canine patients. The lower protein and phosphorus of kidney diets has extended the life of both dogs and cats with failing kidneys. Research shows that failing kidneys may benefit from these restrictions, but the very hint of kidney problems drive many vets to add kidney diets to the treatment plan before the lower protein diet is needed. An alternate sensible choice may be a moister food, like a senior diet canned food or home-cooked lower protein recipe with 30 percent meat and organs instead of 50 to 60 percent. Blue Buffalo's kidney support and senior diets are made with a better mix of ingredients than most other commercial brands.

"Omega-3 fatty acids are healthy antioxidants and may help with many organs. You don't always have to depend on the commercial or prescription diets when you can add fish oil or sardines in water to the diet!

"Urinary crystals and stones may result from a lack of moisture in the diet, food intolerances or allergens causing an irritated and infected bladder, and a genetic tendency to form stones. Struvite crystals and stones may benefit from canned or homemade food, cranberry extract, glucosamine-chondroitin supplements, antibiotics for infection and even probiotics. Oxalate and urate crystals and stones usually need a prescription diet like Royal Canin S/O or others to help prevent recurrence.

"For more details, visit my website, dogdishdiet.com and dogaware.com/health/kidneydiet, a great kidney disease diet resource."

Veterinarian Dr. Martin L. Whitehead from Oxford, England, where these same prescription diets are marketed as they are across much of the rest of Europe, sent me his opinion:

"My view on prescription diets is like that for nutraceuticals and supplements -- they each need to be assessed on their merits. I believe many prescription diets (cancer, congestive heart failure, cognitive decline) and many nutraceuticals and supplements are, at best, based on 'theoretical considerations' rather than actual evidence of efficacy. We sell very little in the way of prescription diets. I think the only use for them my practice has are:

"1. Restricted ingredient and/or hydrolyzed diets used short-term as exclusion diets to test for food allergies or intolerances in chronic GI and skin cases.

"2. Renal diets in advanced kidney failure cases. (I am not convinced they are optimal, but there is very good evidence that they are better than standard commercial foods in this circumstance.)

"3. Dissolving struvite stones.

"4. Something like Hill's a/D can be good for getting plenty of nutrients and energy into severely ill animals.

"Even so, the functions of each of these can be achieved using other foods and/or meds, but the manufactured diets are convenient ways of doing so for busy or uncommitted owners. The way I see it, all foods have their pros and cons. For feeding dogs and cats in general, in the absence of good evidence for what is best, my approach is to advocate variety. As an (economically unfortunate) result of that, as a practice we sell very little food because we don't promote any particular type.

"'Raw feeding' is growing in popularity in the U.K., and recently a Raw Feeding Veterinary Society (rfvs.info/) has been formed. I'm a member, although not a very popular one as I am fairly skeptical of much of what the other members claim. I don't have much objection to raw feeding (although I actively advise against it in families with pregnant women or young children), and I don't have much objection to pets eating manufactured foods, but I don't think either raw food or processed pet foods should be the only food animals get, and feeding an animal only one brand of manufactured food for months or years has always seemed outright peculiar to me."

MERCURY RISING

Thanks to Robert F. Kennedy Jr., the global concerns over mercury pollution and poisoning are gaining greater public awareness. Sources include coal-burning power plants that lead to mercury contamination, especially of tuna and other seafood; amalgam dental fillings; and especially vaccines containing the mercury-based preservative thimerosal, which is 50 times as toxic to human tissue as the methylmercury in amalgams and fish. The link between mercury exposure and brain damage leading to infantile autism is documented in Kennedy's article posted on Ecowatch: ecowatch.com/mercury-linked-autism-kennedy-2116850430.html.

As I have pointed out for several years, companion animals can also be at risk to develop neurological and cognitive problems from mercury-contaminated pet foods and vaccines, which are given more often than to most children during these animals' lives.

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox's website at DrFoxVet.net.)

DEAR DR. FOX: A friend once told me that pet owners should never buy rawhide treats made in China for canine friends due to health concerns. Is this valid? I have similar concerns over rawhide treats in general, regardless of where they are made, but my dogs love them. My current rule is to give only one or two a month, and only a small bone or chew stick at that. Your opinion would be appreciated. -- D.S., Louisiana, Missouri

DEAR D.S.: After the massive poisoning of thousands of dogs and cats in 2007 from a pet food ingredient imported from China, documented in the book "Not Fit for a Dog," which I co-authored with two other veterinarians, and because the U.S. government has little if any effective oversight of Chinese manufacturers, I advise against purchasing any pet product -- including pet beds and chew toys -- that indicate they are made in China. If the label says the product is "distributed" by a company in the U.S. but gives no indication as to country of origin or manufacture, I advise against purchasing it.

More recently, thousands of companion animals have been sickened and have even died from various chews and treats manufactured in China, even bearing well-known multinational food company labels (as distributors). Some of these products have been subjected to irradiation to kill bacteria and essentially mummify them, an issue that I have previously addressed in my column. So let's not throw caution to the wind with attractive packaging and thinking that a little bit won't cause any harm.

Check petzlife.com for some safe dental chews and other natural products -- all manufactured in the U.S. -- and visit smaller pet stores in your area, where clerks can show you other products, including rawhide chews that are organic and come from the U.S.

Check my website, DrFoxVet.net, for my buckwheat-based dog cookie recipe. Avoid U.S.-produced smoked and dried pig ears and other body parts for dogs because of potential bacterial contamination.

I advise a weekly 10-minute chew time for dogs using safe products such as rawhide strips and raw, scalded beef marrow bones to help clean teeth, limiting the time to avoid possible injuries like cracking teeth.

DEAR DR. FOX: I have a 15-year-old female tuxedo cat who has been drinking excessive amounts of water for the past three or four months. She is urinating a lot, so I believe her kidneys are working. I haven't changed her diet. She's basically an inside cat -- she goes outside only in my backyard when I'm out there.

Any idea why she would be consuming so much water daily? -- P.P., Toms River, New Jersey

DEAR P.P.: I urge you to seek a veterinary appointment and have your cat given a full wellness examination.

You are making an assumption that your cat's kidneys are working fine because she is drinking and urinating more than usual. This could be a sign of chronic kidney failure or some other health issue, such as diabetes or hyperthyroidism.

Kidney problems in cats are often associated with chronic, neglected dental problems. Your cat's fluid balance and electrolytes may be way off, and the kidneys are being overworked; in the process, she may be passing too much protein and certain vital minerals that ultimately mean your cat wastes away, a condition called sarcopenia. Complications can arise, such as high blood pressure, stroke and blindness.

So please waste no time and have the cat seen by a veterinarian without delay. Some do in-home visits, which are less stressful for many cats.

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Universal Uclick, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox's website at DrFoxVet.net.)

DEAR DR. FOX: I have two cats: Maggie, a mellow and sweet English shorthair (age 10), and Simon, a rambunctious part-Burmese (age 7).

I adopted Simon out of concern that Maggie was lonely. What was I thinking? Sadly, my ability to time travel is lacking.

Simon continually instigates conflict with Maggie to get my attention, whether it's because his food, water or litter box are not to his satisfaction, or just to be a pain. This has been going on since Simon joined us as a kitten. However, it's now causing such stress for Maggie that she has licked her belly almost bare of fur. She is always looking warily around for him.

I'm not willing to rehome either one, as they're both so dear to me. I visited the vet this weekend, who prescribed a light dose of Prozac for Maggie to "help take the edge off."

I have been separating them at night so Maggie (and I, for that matter) can get some sleep, and I play with Simon in the hope of wearing him out at bedtime. While I find that Simon is getting marginally better at my verbal commands to leave Maggie alone, I wonder if you have any other suggestions as to how to help calm things down -- to be honest, I'm not wild about medicating the "victim" here.

To the best of my knowledge, they seem to be fine during the day, but then again, I'm at work.

Perhaps I'm the problem? -- L.H., Auburn, California

DEAR L.H.: You wonder if you may be part of the problem, and that is a good question to ask.

Have you read anything about cat behavior and psychology? Check out my DVD and books, posted on my website, DrFoxVet.net, which may give you more insight. My books "Cat Body, Cat Mind" and "Supercat" have helped many cats and people get along better and enjoy life.

Do you spend time engaging in interactive games with the cats? Do you groom them in turn, during which time you can teach them that taking turns and enjoying and receiving equal and fair attention is the rule of the house?

Some cats can be pushy, even bullies, demanding all the attention and pushing the other cat or cats away to get the best spot -- examples of so called "situational dominance." This is when you may effectively intervene and discipline the domineering one with a loud "No" and a tap on the nose or rear end. Most cats are quite trainable; they know what's going on!

Consider the possibility that your older cat is arthritic; it may be painful for her to engage in this kind of rough play. Simon should chase a lure on a string that you can engage him with early in the evening, when cats are often most active. Try massaging Maggie as per my other cat book, "The Healing Touch for Cats." You can also add a few drops of fish oil in her food every day. She may enjoy a pinch of calming catnip or a small amount of melatonin before bedtime.

Her excessive grooming could be stress-related, or it could be a sign of hyperactive thyroid disease or food allergy, so keep the latter possibilities in mind when you see the veterinarian for her next wellness examination.

I know of several situations like yours where introducing a third, younger cat made all the difference, giving the older, stressed and harried cat a break while the more active cat of the pair has a third one to romp and play-fight with!

Keep me posted with your progress!

DEAR DR. FOX: We rescued a male cocker spaniel from our local animal shelter two and a half years ago. He will be 4 years old on March 31.

During his time with the family, he has begun having a series of spasms and seizures on a daily basis. He will sit looking upward and begin a low growl than go to a full bark. After approximately two or three minutes, he will begin to chase his tail area without touching any body parts. This will continue for about three to five minutes and may occur again during the day.

About a month ago, we started him on melatonin with our vet's approval, hoping it would calm him. However, the seizures continue. My wife and I are at our wits' end.

When we rescued him, we knew that he had been caged up to 11 hours per day at a very young age. In the beginning, we thought this was the problem, and it would go away over time.

Based upon what background we have provided, can you help with some relief? -- J.E.M., St. Louis

DEAR J.E.M.: Staring, snapping at nothing, tail-chasing and other obsessive behaviors in dogs can be indicative of epilepsy; many dogs do not actually go into a full grand mal seizure. Sometimes a change in diet can help. A gluten-free diet can stop the so-called epileptoid cramping syndrome in border terriers and probably other breeds and individuals with gluten intolerance.

Let me know if a dietary solution works out before the usual treatment with phenobarbital and other anti-seizure drugs. In my experience, it is regrettable that too many dogs are put on such drugs.

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Universal Uclick, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox's website at DrFoxVet.net.)