Vetinfo Digest        June 2000
 

This Month:

Therapeutic Diets for Pets

Glucose monitoring

Heartworm Prevention and Flea Control Medication Choices

Despite reservations, Michal and I have decided to see if advertising will work to help support the www.vetinfo.com web site. Starting in June, we will have banner ads that are arranged by an advertising agency.. By keeping the advertising in the hands of a third party, we are hoping to avoid conflicts with advertisers. We do not necessarily endorse the products that will be advertised. We do not anticipate any advertising in the VetInfo Digest nor in the subscriber area online. If advertising does work and we continue to feel that we can provide the information we think is best without compromise, we will use the revenue to provide an even better web site and to provide some additional services. If advertising doesn't work out well on the site, we will discontinue it when the contract expires.

I apologize for slow responses to some questions this month. This is the last year of high school for our youngest daughter. It has been important to my wife and I to attend the last of her high school crew races and other events associated with the last year of high school. Thanks for allowing us this time.

Therapeutic Diets for Pets

There are a number of companies that make diets formulated for specific health problems and sell these diets exclusively through veterinarians. Therapeutic diets can be very helpful for certain conditions. However, formulating a diet to help a pet with a specific condition means that the diet may not be capable of supporting all stages of life or that it may have effects that can be harmful to pets. Like all treatments, these diets have to be evaluated carefully before use and pets on these diets may have to be monitored to ensure that no unwanted side effects are occurring. It is as important to know when these diets are not appropriate as it is to know when they might help.

Due to the number of available diets it is not possible to cover all of them in detail. It is even likely that I am going to miss some of the companies making these diets, entirely. If your pet is on a diet that is not mentioned, I will happy to look into the recommendations for use and to put together another list of diets for a future issue of the VetInfo Digest.

While I am not certain of this, I believe that the original therapeutic diets were developed by Hill's. These diets are sold under the brand name "Prescription Diet" (tm). I think that most states do not recognize these diets as actual prescription medications, though. In Virginia it is illegal for a veterinarian to fill a prescription written by another veterinarian but it is not illegal to sell Prescription Diet c/d (tm) to a non-client. As far as I know, this is true for all of the current diets that are available through veterinarians only.

Hill's (Prescription Diets), Purina (CNM Diets), Iams (Eukanuba Veterinary Diets), Waltham (Waltham Veterinary Diets) and Innovative Diets are some of the companies that make specialized diets at the present time. This makes it possible to find a diet that works for many conditions and that most pets with special needs will eat. Most veterinarians only deal with one or two of the companies that make diets, so it may be necessary to ask your vet about the availability of similar diets, if your pet simply refuses to eat the brand that your vet stocks.

Cats with feline lower urinary tract disorder (FLUTD), also called feline urologic syndrome (FUS), were the first patients to benefit from specialized diets. Approximately 1% of cats have FLUTD. It is a frightening condition when a male cat is affected, as crystals or mucous plugs obstruct the urethra near the tip of the penis and make it impossible for a cat to urinate. This leads to severe pain and eventually death. Due to the severity of this condition, dietary control provided a huge measure of comfort to many cat owners. At first, it seemed necessary to restrict ash content and magnesium in order to control this syndrome but the current thinking is that these diets work because they acidify the urine. Magnesium levels are usually kept very low in these diets as there is some benefit to this, as well. These diets are effective for cats whose FLUTD symptoms are due to struvite crystal formation.

On the other hand, these diets actually promote the formation of calcium oxalate stones. Since calcium oxalate stone formation may approach 1 to 2% in cats on these diets, it is important not to feed all cats diets made for control of feline lower urinary tract disorder. These diets should be reserved for cats who have exhibited repeated bouts of FLUTD. It is also important to remember that diets that acidify the urine should not be used in growing or pregnant pets. They should not be used in cats with renal failure. It is important not to use other means of urinary acidification, such as Vitamin C administration, cranberry juice or urinary acidifying medications at the same time as diets made to acidify urine.

Examples of diets that acidify urine are Hill's Prescription Diet c/d (tm), Purina CNM UR (tm), Waltham Feline Control pHormula (tm) and Eukanuba Low pH/S Feline diet (tm).

For patients with severe struvite crystal formation, or struvite bladder stones, there is a diet made to dissolve struvite, Prescription Diet s/d. This diet is meant for short term use to attempt to dissolve bladder stones or to help with acute crises involving struvite crystals. It is best not to feed s/d diet for more than 90 days and it is questionable whether it is ever appropriate to use this diet in a pet that is growing or pregnant. One other problem with s/d diet is that it only works well for struvite bladder stones. When it is possible to collect a bladder stone and have it analyzed without doing surgery, or if a prior surgery in which bladders stones were removed and found to be struvite has occurred, it is easy to recommend this diet. When it is a guess whether or not the bladder stone in question is actually composed of struvite, it is much harder to decide if attempting to dissolve the stone with s/d is appropriate.

Dogs with chronic cystitis (bladder infections) may also benefit from diets that acidify the urine. These diets help to control bacterial infections, since many of the bacteria that cause cystitis can not survive in acidic urine and they also limit struvite formation in this species, as well. In dogs, struvite bladder stones are closely associated with chronic cystitis. Hill's c/d (tm) diet is often used in dogs. Again, it is really important to consider the necessity of dietary control, since urinary acidification may promote formation of calcium oxalate stones, is harmful if kidney damage is present, and may cause problems with calcium and phosphorous regulation which is detrimental in growing puppies and pregnant bitches. Hill's also makes s/d diet for dogs, for situations in which struvite stones are known to be present and it seems reasonable to manipulate the diet to produce dissolution of the bladder stones. The criteria for making this decision are the same in dogs and cats.

Of course, the increase in calcium oxalate stone formation that has occurred in cats and dogs has led to diets that aid in control of these stones. To the best of my knowledge, there is no diet that will help dissolve a calcium oxalate stone that is already present. Diets that cause the urine to be basic (high pH) help to prevent calcium oxalate stones. Hill's makes Prescription Diet c/d-oxl, for cats, which is specifically directed to this problem. Iams makes Moderate pH/O/Feline (tm) diet specifically for this problem, as well. Diets made for kidney failure are also made to keep the urine basic, although the protein and phosphorous restriction in these diets is not specifically necessary to reduce the chance of calcium oxalate stone formation.

It is obviously important to try to be sure of the type of crystal formation occurring in a patient prior to choosing a diet to control the pet's problem, since diets that aid in control of struvite promote calcium oxalate, and diets that control calcium oxalate promote struvite formation.

In cats, diets for kidney failure are also recommended frequently by veterinarians. These diets are also used in dogs. The original premise for these diets was that protein restriction would help to decrease the progression of kidney failure. This does not appear to be true, in dogs, at this time, but the diets also helped reduce dietary phosphorous and salt, which does seem to help control the progression of kidney failure. In cats, low protein diets appear to work better than in dogs. In acute and end stage kidney failure, in dogs, there is a clear benefit to protein restriction. For this reason, there are diets for dogs with acute renal failure and for dogs with chronic renal failure but the cat renal failure diets usually come in one low protein formula. In addition to protein restriction, these diets also help to keep the blood slightly basic (high pH), as this is beneficial to the kidneys. They are usually supplemented with extra B vitamins, which may be lost more easily in patients with kidney failure.

It is important to remember that when total protein is restricted a very high quality protein must be used in order to ensure that adequate amounts of the necessary amino acids that compose proteins are present in the diet. Ideally, the diet would contain exactly the right combination of amino acids each individual patient needs for one day, but it is not possible to achieve that sort of precision. Use of proteins that contain approximately the correct amino acid profiles, such as protein from egg or meat sources, does make it possible to limit the amount of excess protein in the diet while providing adequate total quantities, though.

Diets for dogs with chronic renal failure that has not reached the end stages include Eukanuba Nutritional Kidney Formula Early Stage Canine (tm), Hill's Prescription Diet k/d (tm), Purina CNM NF (tm) and Waltham Medium Protein Diets (tm).

Diets for dogs with advanced renal failure include Waltham Low Protein Diet (tm), Hill's Prescription Diet u/d (tm) and Eukanuba Nutritional Kidney Formula Advanced Stage (canine) Diet (tm).

Cats with kidney failure may be fed Hills Prescription Diet k/d (tm), Purina CNM NF (tm) and Waltham Veterinary Diet Low Protein.

The amount of protein restriction in the diets for acute or end stage renal failure makes these diets inappropriate for growing or pregnant pets.

In cats, there is an interesting dietary problem that occurs when cats who have a history of FLUTD develop kidney failure later in life. The diets that help to control FLUTD are detrimental to the kidneys. On the other hand, diets that are beneficial to the kidneys tend to create the high pH conditions in the urine that promote struvite formation. In these cats, in our clinic, we choose to use the diets that are beneficial to the kidneys, often with fluid supplementation. Our experience has been that this rarely leads to a recurrence of FLUTD symptoms. We do alert cat owners to the possibility that dietary changes may lead to problems and ask that they be vigilant for signs of FLUTD, such as repeated visits to the litter pan with little urine production, loss of appetite or straining to urinate and seek immediate treatment if signs appear. Our thinking is that FLUTD is a condition we can treat as each episode occurs, while kidney failure is an ongoing process. Therefore, it makes more sense to treat the FLUTD if it occurs, rather than continue to feed a diet that we know may be harmful to the kidneys of a patient we know has renal failure. There may be patients in which it is reasonable to take the other approach and continue to feed a diet that promotes acidic urine, due to the severity of the lower urinary tract disease but so far, we have not had to make this choice.

Obesity control is another area for which many diets are available. In truth, my personal opinion is that these diets are not all that beneficial. There are many combinations of moderate to high fiber, low calorie and low fat diets. However, none of these diets is highly beneficial for a patient who is fed free choice. They all work best if the amount of food for the day is carefully measured, if the pet is encouraged to exercise moderately and if a pet is confined to an area in which food is not available. It is just as easy to measure proper portions of an ordinary dog food as it is to measure portions of a specialized diet, so I usually just advise my clients to do that. Moderate exercise helps a great deal in weight control and most obese patients have to be supervised to ensure they are active enough. Having a large yard to exercise in does not ensure that exercise will occur. Cutting back on treats would be helpful for many dogs but it changes the relationship with the owner. So we advise feeding treats that are low calorie, such as rice cakes or carrots. If that doesn't work, it is OK to feed dog biscuits if good quality ones are chosen and the amount of calories accounted for in figuring out the daily feeding amounts.

It is necessary to be very cautious when attempting to put a cat on a diet. Cats are very susceptible to a liver disorder, hepatic lipidosis, that can be induced by severe calorie restriction. Seek specific dietary advice for your individual cat from your veterinarian or be very cautious about the amount of calorie restriction used when dieting cats. Dogs, on the other hand, are very resistant to problems from calorie restriction. In fact, I have heard a couple of veterinary nutritionists state that it is possible to simply withhold all food from a dog until it reaches the desired weight and then resume feeding. This is not an advocated diet method but it is possible to restrict calories in a dog with much less trepidation than a cat.

Specialized versions of the obesity control diets are beneficial to some groups of patients, though. Hills w/d diet seems to help some of the kittens with chronic diarrhea. Purina CNM OM, Hill's w/d diet and Waltham's high fiber diet all may be helpful in diabetic patients and Iams makes Eukanuba Glucose-control diet (tm), which is similar in nature, specifically for patients with diabetes. Purina also makes a more specialized diet for diabetes, CNM DCO (tm). These diets also seem to help some patients with colitis. Chronic pancreatitis may also respond to low fat or moderate fiber diets, such as those listed above.

Diets for dogs and cats with gastrointestinal disorders are frequently "prescribed". The usual prescription is for a bland diet that will help a dog recover from a gastrointestinal illness. Examples of these diets include Hill's i/d (tm), Waltham Veterinary Low Fat Canine (tm) and Purina CNM EN (tm). Most veterinary nutritionists seem to advocate this particular dietary strategy, however I have some reservations about this approach. One of the major causes of gastrointestinal problems is a sudden change in diet. So why does it make sense to take a pet that already has a gastrointestinal problem and suddenly change its diet? Since I am still unsure of the answer to that question, I tend to use these diets only after a gastrointestinal problem persists for a few days. In the meantime, I tend to advise restricting food for twenty-four to forty-eight hours and then starting to feed small amounts of the pets ordinary diet. If it then seems necessary to go to a bland diet we advise doing this gradually by mixing the new diet with the old over the course of several days. I do have patients with chronic gastro-intestinal disease that seem to do better when placed on these diets, or on Eukanuba Low Residue (tm) diets as their permanent diet, so I am glad these diets are available. I am just slower to use them than most vets. These diets are not likely to cause other problems and can be used in all life stages, in most cases.

Food allergies are another condition for which specialized diets may make a huge difference in patient comfort or health. Food allergies most commonly cause itching, especially around the feet and ears, in dogs. In cats, there may be multiple small scabs on the skin, itchiness and increased vomiting. Pets with food allergies are usually allergic to one or two specific food ingredients, such as beef, corn, soybean, wheat or chicken. They are not allergic to whole foods, such as Alpo (tm) or Pedigree (tm).

To discover what food items a dog or cat might be allergic to, it is necessary to feed a diet that contains NO ingredients that a pet may have eaten previously. You might think it would be hard to find such a diet, but there are a large number of diets available at this time that contain protein and carbohydrate sources that are not usually found in dog or cat food. It is important that pet owners understand why these diets are being used.

For a number of years it was possible to attempt to diagnose food allergies by feeding a diet that contained lamb and rice. These were ingredients not commonly found in pet foods. However, after a number of veterinarians advised feeding these diets in an effort to diagnose the cause of itchy skin, pet owners came to believe that lamb and rice were beneficial to skin and began to ask for these ingredients in pet foods. Pet food companies are happy to comply with consumer demand and so there are now a lot of foods with lamb and rice in them.

Diets made to help diagnose and treat food allergies for dogs and cats now contain ingredients like salmon, ostrich, venison, alligator, trout and other exotic proteins that are not likely to show up in pet food. Salmon won't work as a food trial diet for cats since it is a common food ingredient in that species and it is becoming so widely available now that I suspect it may show up in dog food soon. Potatoes and rice are common carbohydrate ingredients. Purina makes a specialized diet that contains modified protein which is so small in size that it is not considered to be allergenic. This diet, CNM HA (tm) is a good choice it is acceptable to the patient. . I think it is only made in a dog version at this time. Purina makes a diet, CNM LA (tm), that is meant for long term use once a patient's food allergies have been confirmed. Limited antigen diets are made by all of the companies mentioned so far, as well as Innovative Diets (tm), a division of Nature's Recipe Pet Foods.

The biggest problem we have with using specialized diets to aid in the diagnosis of food allergies is convincing pet owners that these diets are the ONLY thing that their pet can eat during the three to eight week long trial period. It is very important that dogs and cats be fed nothing but these diets. No treats, no scavenged food, no raiding of the cat litter pan (dogs) and no chance of getting to food offered to other pets in the family. No matter how carefully I explain this concept, most of my clients still give their pets treats and then tell me, "it was only a small little dog biscuit" or ask me, "how could one Pounce (tm) make a difference". Even a flavored heartworm pill can make it difficult to determine if an allergy to beef is present in a highly sensitive dog or cat. If you are going to make an effort to see if a food allergy is present, make sure that you don't mess up the results. Feed your dog or cat nothing but the recommended diet. Confine them so that they do not have access to other food sources and walk dogs on a leash to prevent food foraging. It is very hard to do this but it only lasts a month or two and the benefits can be lifelong.

Cats with chronic constipation problems or with megacolon often do best when fed a food that is very highly digestible, allowing minimal stool production. The most commonly recommended diet for this situation is Eukanuba Low Residue (tm) diet for cats. Some of the premium maintenance diets are also low residue as is Hill's a/d diet. Oddly, some cats with constipation seem to do better when fed a moderate fiber diet such as Hill's w/d (tm) diet. It may take a little experimentation to determine which approach is best. At the present time we start with low residue diets first, in our practice.

Pets with heart disease may benefit from sodium restriction, potassium supplementation and moderate protein restriction. Diets such as Prescription Diet h/d (tm) and CNM CV (tm) are made to meet these requirements. Severe sodium restriction makes diets less palatable but it is not acceptable to add salt to the diet to get a dog to eat it. I didn't used to give this warning but one of my clients came in to the office just to let me know that dogs wouldn't eat h/d diet they might be more inclined to do so if I added salt to it. I am not sure why he thought of adding salt to the dog food but it does defeat the purpose. These diets are sometimes more palatable if they are warmed slightly prior to feeding, especially in cats. If a pet on a sodium restricted diet develops diarrhea or vomiting it is important to report this to the vet immediately, as either of these conditions can lead to further sodium loss. It may be necessary to feed a diet that is not sodium restricted until the gastrointestinal disease can be controlled.

Dogs and cats with liver disease can experience a great deal of improvement in the quality of their life with dietary changes. Low protein/high quality protein diets are very beneficial to patients with liver disease, especially if there are central nervous system signs present as a result of the liver problems. Addition of omega-3 fatty acids, vitamin supplementation and attempting to favor branched chain amino acids over aromatic amino acid formations is also helpful. Hills makes both canine and feline l/d (tm) diet which attempts to meet these requirements. Purina CNM NF (tm) and Waltham Low Protein Low Phosphorous (tm) diet also meets most of the requirements (no added omega fatty acids, though).

Hills has also produced a diet that is meant to aid in the treatment of cancer in dogs. This diet, Prescription Diet Canine n/d (tm), is based upon a diet recommended at Colorado State University for dogs with lymphoma. The diet does seem to help dogs with this particular cancer but I am not aware of studies that strongly support its use in other forms of cancer. It is reasonable to assume that it does have benefits for other cancers, though. The diet is high in fat and protein, based on the observation that lymphoma seems to require carbohydrates as an energy source and to decrease lactate formation by cancers (part of the cause of decreased appetite and sense of well being in cancer patients). In addition there are high levels of omega-3 fatty acids, which is the particular type of omega fatty acid that is thought to be beneficial in cancer patients. The diet is very different from ordinary dog foods because it is impossible to achieve high n3 omega fatty acid levels using ingredients that are normally found in dog food, so it causes gastrointestinal upsets in a number of patients. This is less likely to happen if the dog is slowly transitioned to the new food, over the course of a week or more, by slowly adding the n/d diet to its normal food. Dogs with a history of repeated bouts of pancreatitis should not be put on n/d diet.

There are actually a number of other specialized diets for dogs and cats, some of which are restricted to sale by veterinarians. It is almost always worth asking your vet if there is dietary advice or an available diet to aid in control of a chronic problem your pet may be experiencing. It is also important to ask your vet to tell you the specific problems with each of the specialized diets and to give you advice on the circumstances that should prompt you to stop using them.

Blood Glucose Monitoring for Diabetic Pets

We have recently discovered a new way to help clients monitor cats who have diabetes by using glucometers at home. A glucometer is a machine that measures blood glucose. In people, a small blood sample is obtained by pricking a finger with a sharp stylus (lancet) and putting the drop of blood that collects at the puncture site on a test strip and then into the glucometer. The big problem with a glucometer in cats and dogs is obtaining a blood sample and getting it onto the test strip. People just let the blood drip off their finger onto the test strip but it is hard to explain that concept to a pet and it is necessary to prick the inside of the lip (works in dogs), the inside of the ear (usually only works in dogs) or the blood vessels in the ear margin (cats and dogs with prominent ear vessels, such as dachshunds). This makes it pretty hard to get the blood on the glucometer strip, especially for machines in which the strip must be inserted first.

Our new solution to this problem is to prick the lip or ear margin and then suck the small drop of blood that wells up into a disposable pipette. This makes it easier to transfer it to the test strip. The plastic pipettes are inexpensive and most veterinary hospitals are already ordering them (or getting them free) for use in other tests. It helps in long haired cats to put a small amount of vaseline or alcohol on the hair along the ear margin so that the blood wells up rather than spreading through the hair. Shining a flashlight through the ear helps to identify where the blood vessels are but most clients only find this to be necessary until they learn where to stick the needle ( we use a 25 or 27 gauge needle rather than the triggered stylets that come with the glucometers).

Monitoring blood glucose is the best way to really obtain good control of blood sugar in a diabetic patient. At least 50% of our clients can obtain blood samples from their pets easily enough that they keep going with this testing method. I think that percentage will improve, especially in cats, with the addition of an easier way to get the blood onto the test strip.

Medications for Heartworm Prevention and Flea and Tick Control

Direct advertising to consumers has many of our clients very confused about which heartworm medication and which flea and tick medications to use --- or even about which medications are for which problem. This is a quick review of the presently available products and the situations in which it is best to use them.

Selamectin (Revolution Rx) is the product causing the most confusion, because it has the broadest spectrum claim. This product is applied topically and it prevents heartworms, kills roundworms, hookworms, whipworms, fleas, ear mites, sarcoptic mange and at least one type of tick. There is no cost savings in using this product when compared with using separate heartworm and flea or tick products. This product is approved for both dogs and cats. If ticks are not a major problem in your area and the convenience of once a month dosing for both fleas and heartworm control appeals to you, this medication is a good choice.

Lufenuron and milbemycin in combination, Sentinel Rx, prevents heartworms, kills roundworms, hookworms, whipworms and prevents flea reproduction. This product works best for pets that are confined to a small area, as prevention of flea reproduction only works well to keep fleas off of pets who do not collect more adult fleas from the environment after their original ones die. Sentinel is also priced about the same as buying its ingredients separately. There is not a cat version of this medication.

The rest of the products that are advertised are not quite as broad in spectrum.

Ivermectin and pyrantel, available as Heartgard Plus (Rx), kills hookworms, roundworms and prevents heartworms. At the present time ivermectin is considered to be the best heartworm preventative for covering gaps in heartworm prevention therapy (if you miss a month it is the least likely to matter when using Heartgard Plus). Both dog and cat versions of this medication are available.

Milbemycin is available as Interceptor (Rx), which kills hookworms, whipworms and roundworms as well as preventing heartworms. The heartworm prevention dosage for milbemycin is about half the dosage necessary to kill whipworms, so this is a good medication to consider if your pet tends to hover right around the boundary lines for the medications, such as a dog that weighs in at 100 lbs.

Moxidectin (ProHeart Rx) is the least expensive of the monthly heartworm prevention medications. It has no label claims other than heartworm prevention. For situations in which cost is a major factor, this medication is a reliable heartworm preventative and is worth considering.

Fipronil ( Frontline, Frontline Topspot tm) kills fleas and ticks on dogs and cats. It will kill fleas for up to three months on dogs, according to the label, but our experience has been that it rarely works well past six to eight weeks for most of our clients. It will kill ticks for one month. It only works for one month for both fleas and ticks on cats. It is labeled for a number of tick species. It does not wash off easily. Some pets do experience irritation at the sites the product is applied to. We like the combination of Heartgard Plus (tm) and Frontline Topspot (tm) in our practice, but that is because we live in an area in which ticks, fleas and heartworms are all prevalent. The option to choose when to treat for fleas and ticks and when to use heartworm prevention separately is a good choice for our area, since the seasons for these parasites overlap but do not exactly correlate with each other.

Imidocarb (Advantage Rx) is a good flea product but it does not kill ticks. It also sometimes causes irritation at the site that it is applied. In areas in which ticks are not a major problem this is a very good product to consider for flea control. Advantage washes off more easily than Frontline, so if there is major exposure to water or frequent bathing, it may be better to use Frontline.

I like the ability to use separate flea and tick products from heartworm preventatives since it is possible to use only one of these products when necessary. However, I can see where the convenience of a once a month product that prevents heartworms and kills ticks and fleas is appealing, especially in cats. Thinking about how long you must use a flea and tick product and how long you must treat for heartworms where you live can help you decide whether to use a combination product or two separate products to achieve good control of fleas, ticks and heartworms at the lowest cost.

Thanks for Your Support!

If you send us e-mail, remember that Michal Justis answers the e-mail at vetinfo@vetinfo.com. E-mail sent to mervet@inna.net is answered by Dr. Michael Richards.

The VetInfo Digest is published by TierCom, Inc., P.O. Box 476, Cobbs Creek, VA 23035. The opinions expressed in this newsletter are those of Michael Richards, DVM., author.

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