VetInfo Digest

January 2008

 

Table of Contents:

Waxing and Waning Diseases

A few interesting statistics

Shelter Medicine

 

This month’s Note:

I have talked about how a placebo effect  makes it very difficult to assess the success of treatments and medications in several issues of the VetInfo Digest. This month I have had several clients who I believe exhibit something  that seems to be called the “nocebo” effect  lately.  It is an “anti-placebo” effect. These are people who are so convinced medications will be harmful they are unable to see  the benefits from them or believe that obscure symptoms are due to the medications.  It really is just as hard to determine if a medication is harming these folks as it is to tell if a medication is working in a person with a strong tendency towards the placebo effect. 

I have only found a couple of good studies relating to this effect.  In brief, it appears to hold up to study in these limited studies but may not hold up in a bigger study. This wouldn’t be surprising, since the placebo effect is questionable in the few big review studies that have been done. It appears that coincidence is the reason that improvement appears to occur in some patients, whether or not the medication is a placebo, a nocebo or a medication.  I still find this surprising as I really feel that the placebo effect occurs – but once again the power of coincidence is very strong in people’s minds.  Keep this in mind the next time you think a medication is working or not working!

Beware the Waxing and Waning diseases!

There are a number of diseases and disorders that have a natural course involving periods of illness interspersed with periods of relative comfort.  These disorders are extremely frustrating to gauge treatment success for. They include arthritis, immune mediated diseases, allergies, inflammatory bowel disease, etc. To give you one example of the problems associated with this type of disease,  I tore the meniscal cartilage in my left knee two years ago.  Last December the injury was bothering me quite a bit. My orthopedic  surgeon didn’t think it was necessary to do surgery but felt that injections of hyaluronidase might be beneficial.  The injections have to be pre-approved by my insurance company, which took several days. In the meantime, I realized that I didn’t want to have the injections just prior to Christmas as it could interfere with the holidays. So I put the injections off thinking I would get them in January. In the meantime, my knee improved a great deal.  I decided I didn’t need the injections. If I had been able to have the injections at the time the knee hurt I believe that I would have thought that the hyaluronidase injections had been responsible, even though they were not.  This sort of coincidental timing makes evaluation of the response of most medications for chronic conditions quite difficult.

To give you another example, I was at a meeting on seizure control last year. The speaker said that he had been involved with a study of a new but very expensive seizure control medication.  In this study the clients had to pay for treatment of their pets. Due to the cost, compliance with medication instructions was basically assumed.  During the trial period one of the dogs had no seizures, a very good outcome.  However, this dog was seen for other medical problems and in the course of taking the medical history it became apparent that the dog had not been given the medication during the trial, despite the fact the owner was paying about $300 per month for the medication throughout the two years.  The owner’s explanation?  “ I liked Dr. X so much that I didn’t want to tell him I wasn’t following his directions.” Seizures frequently occur very irregularly and it is not unusual for seizures that have been regular to stop occurring for long periods of time. 

Veterinary medicine is severely hampered by the small number of pets included in most studies. It is just too expensive to use large numbers of pets in studies. This almost eliminates the possibility of determining the rate of coincidental recovery from illnesses during a study.  It makes it very difficult to be certain that veterinary medications work as well as advertised.  It also accounts for a very large percentage of dogs and cats who are reported to suddenly improve when they are put on a new diet or other changes in their environment are made.

I do not have much in the way of useful suggestions for decision making in these circumstances.  It is extremely hard to make similar decisions in people where there is at least the potential for very large studies to be done.  To give another example here it is possible to find studies that support the use of glucosamine and/or chondroitin for prevention and treatment of arthritis. It is equally easy to find studies that seem to show that there is no benefit from these nutriceuticals.  The reason is almost certainly the variability of the course of arthritis in humans.  It waxes and wanes enough that some people are going to experience improvement whenever glucosamine or chondroitin are started.  There is no easy way to compensate for this other than increasing the size of the patient groups in all phases of a study.

It is also possible to have adverse effects occur coincidentally to the start of a medication for a chronic condition.  A flare-up of an immune mediated disease could easily be blamed on a new medication when it may have occurred in any case.   It is difficult to advise a client to continue a medication in the face of symptoms that seem dangerous so most commonly medications that appear to be involved in adverse events are withdrawn.  When the need for the medication is great it may be worthwhile to risk another adverse event to see if the medication was truly responsible for observed reactions. It can take a little courage to do this, though.

When you hear anecdotal evidence that a medication worked or did not work, try to keep in mind the fact that testimonials really don’t weed out beneficial or detrimental coincidences.  It is entirely possible for chronic illnesses to suddenly improve or to worsen quickly.  Try to take a long term approach to evaluating medications for long term conditions.

A few possibly interesting statistics and quick facts:

We all hope that someday there will be no need for animal shelters.  If we do reach that point it will be due to a greater understanding of why pets end up in shelters in the first place.

Only 16% of pets that end up in shelters are recovered by their owners.   (from the National Council on Pet Population Study and Policy)

Approximately 56% of pets entering shelters across the U.S. are euthanized rather than being adopted or being reclaimed by their owners.   (same source)

Behavioral problems are the most common reason dogs are surrendered to shelters and the third most common reason cats are surrendered to shelters by their owners.  (Handbook of Behavior Problems of the Dog and Cat, Landsberg, et al. )

While this is not strictly a shelter issue, it should also be noted that of all euthanasias done at veterinary practices it is estimated that at least 10% are due to behavioral issues rather than medical issues  (same source).

Cancer and Pets

45% of dogs ten or more years of age die from cancer.  Overall, approximately 23% of dogs die from cancer (when age in not factored in).   (Small Animal Clinical Oncology, Withrow & MacEwen).  Well documented statistics for cats concerning cancer as a cause of death are harder to come by, unfortunately.

My clients worry when more than one of their pets dies from cancer, usually suspecting that there is an environmental cause in their household or in the pet’s diet.  If you think about that fact that almost half the dogs who die of natural causes in their later years die of cancer it makes sense that it is not uncommon for more than one pet in a household to die of cancer. 

Ticks

Most ticks can survive being washed along with clothes in a washing machine and even being dried in the dryer for a while at low heat settings. Just one of those strange but apparently true facts!  (John Carroll, United States Department of Agriculture).

Chronic Kidney Disease in Cats

Overall, chronic kidney disease affects 1.1% of all cats, however,  it affects 27% of cats over the age of 10 and 49% of cats over the age of 15 years  (D. Polzin DVM, Veterinary Practice News)

Shelter Medicine

I know that many of the subscribers to VetInfo are involved in some way with animal shelters, either as advisors to folks who have adopted pets, pet adopters or shelter staff.  I hope that this topic isn’t too narrow to interest most of you. I think that the special medical and behavioral needs of pets adopted from shelters is an important topic and one for which it can be difficult to find good information.  There are several aspects of this topic, the two main ones being care of the animals while in the shelter and care of them after they have been adopted.  I am going to focus more on care of pets after adopting them from shelters but inevitably this means discussing shelter operations and disease control to a certain degree.

Dogs and cats are surrendered to animal shelters for a variety of reasons but the main reasons seem to be fairly consistent in shelter surveys.  When a reason is given for turning a pet over to a shelter it is most commonly a behavioral problem.  For cats the problems are often urinating outside the litter box or destructive scratching.  The problems with dogs are things such as excessive barking, destructive chewing in the house, urine marking and aggression.

It isn’t unusual for a dog or cat with a behavioral problem to exhibit the same behaviors in a new home so it is worth asking what the stated reason for abandoning the pet to the shelter was.  It is also not too unusual for behavioral problems at a previous home not to be found in the new home. This seems especially true in our practice for litter box usage problems in cats. Sometimes things like destructive chewing will disappear with a new home, as well.  In our experience aggression problems are less likely to resolve with a new home but this does sometimes occur.  In addition we do have a few clients who seem to accept these problems as a challenge and who do make a strong effort to control behavioral issues through behavioral therapy and who do succeed in their efforts.  You should be very cautious about adopting a dog when there are disclaimers such as “not good with other pets,” or “not good with children,” though.  These are often tip offs that a more severe behavioral problem exists. 

When a dog or cat enters a shelter it is exposed to a large number of other dogs or cats. This inevitably leads to problems with disease control.  Even with a very good infectious disease control program it is hard to entirely eliminate spread of infectious diseases within a shelter.  Many shelters operate with limited funds and find effective disease control programs hard to implement due to the cost of hiring compliant staff and providing adequate facilities.  The effect of exposure to shelter life varies pretty markedly between dogs and cats.

Cats appear to have a much higher susceptibility to infectious diseases than dogs. This may not be due to a genetic susceptibility to viral or bacterial illness, though.  The lifestyle of domesticated and even feral cats is often quite different from the natural lifestyles that exist for wild cat species. It is likely that these changes contribute a great deal to the prevalence of infectious disease in domestic cats and especially to domestic cats living temporarily in animal shelters.

Cats are not strictly loners but most wild felines are not likely to be highly social or to live in groups, with some obvious exceptions such as lion prides.  The tendency of humans to house cats in groups or to encourage colony formation by providing food for groups of feral cats in a central location cause domestic cats to be exposed to infectious disease much more commonly than less crowded cat species in the wild.  Cats are susceptible to a number of viral, bacterial, fungal and protozoal infections. The higher the rate of exposure the more likely it is that these diseases will manifest themselves.  It is extremely hard to keep infectious disease under control in an animal shelter due to this

Shelters could do a lot to help themselves avoid outbreaks of infectious diseases running through their cat populations.  It is a fairly common practice to have exercise areas, display areas and play rooms in shelters where the cats are allowed to mingle.  If these types of common areas are not strictly controlled it is almost inevitable infections will occur. If you visit a shelter seeking to adopt a cat it is a good idea to examine the exercise or “meet the family” rooms carefully to see how they are managed. If there are a number of cats wandering freely about a room, it is more likely the cat you adopt from the shelter will have an infectious illness.

I have spoken a number of times with shelter staff members who feel that it is necessary for cats to have exercise and to mingle with each other. I am not sure that I really believe this but if I concede the point there is still a much better way to handle the situation. Cats that come in on the same day or together in some other fashion could be grouped in small groups and kept together.  The group itself would be isolated from other groups. In this situation disease transmission is mostly limited to members of an individual group rather than to all the cats in the shelter at the time a cat with an infectious illness is taken in.

Obviously most folks don’t have much control over how the cat they are thinking of adopting is cared for in the animal shelter prior to adoption.  This makes it necessary to consider the most common transmissible diseases associated with shelter residence by cats. In our practice these are feline herpes virus infection, feline calicivirus infection, feline coronavirus infection and dermatophytosis (ringworm).

Feline herpes virus (rhinotracheitis virus) and feline calicivirus cause very similar symptoms and are usually grouped under the heading “feline upper respiratory disease complex” or a similar sounding name.  In our practice, several years ago, we had a year during which every single cat that we saw from animal shelters had symptoms of feline upper respiratory disease complex. Most years are significantly better than this but it is a very common condition in cats adopted from animal shelters. Often all that is present initially is sneezing or a runny nose.  Many cat owners are tempted to ignore these signs.  In an effort to avoid antibiotic use unnecessarily some veterinarians are reluctant to dispense antibiotics for cats with upper respiratory disease signs since the two major causes are viral infections.  This is one exception to the general rule that you don’t treat viral infections with antibiotics. These viruses can cause significant damage to the lining to the upper respiratory tract, making it more susceptible to bacterial infection.  A very large percentage of cats with viral upper respiratory infection (URIs) have secondary bacterial infections. If these infections are not treated some cats will have so much damage they have lifelong problems with recurrent nasal passage and upper airway infection. It is best to treat cats with antibiotics when they have upper respiratory infections in many cases. If one antibiotic doesn’t work well don’t give up on antibiotic therapy entirely, try a different antibiotic or different method of administering the antibiotic.

In our experience the best choices for antibiotic therapy orally have been amoxicillin/clavulonic acid combinations (Clavamox Rx) and azithromycin  (Zithromax Rx).  Your vet may have a different set of first choice antibiotics and they may be just  as successful.  If oral therapy really doesn’t seem to be working it sometimes seems to help to us a nebulizer to administer medications, although there is some chance that improvements seen are due more to the nebulization alone than to the antibiotic being used in this manner.  It is possible to get some of the same effect by simply fogging up your bathroom and confining your cat there for 15 minutes or so.

To some extent you just have to accept that there is risk you will have to deal with an upper respiratory infection when you adopt a cat from a shelter or other group home for cats situation. These infections are easily transmitted and very common, making it hard for shelters to completely eliminate them from the cat population at the shelter.

We do not see too many kittens from shelters who have developed feline immunodeficiency virus (FIV)infections or feline leukemia virus  (FeLV, FLV) infections at the shelters.  We do have real dilemmas about how to detect these viruses in young cats despite the availability of easy in-house test procedures.  If a kitten receives antibodies against FIV from its mother they will cause a test of the kitten’s blood to be FIV positive even if the kitten itself does not have the virus.  False positive tests are fairly common until kittens are up to 16 weeks of age so it is best to delay testing at least this long – often after a new owner is very attached to the kitten.  FeLV testing is less problematic in some ways and more in others. The test is very accurate if it says a kitten is not infected with the virus. A positive test, though, is an entirely different matter.  At least 50% of kittens who show no sign of illness but test positive on a FeLV test do not have the virus.  Any positive test should be confirmed using a different testing method before treatment or euthanasia is considered.

Dermatophytosis (ringworm) is perhaps the most frustrating problem we see in kittens from the shelter, at least when the entire family is considered.  Ringworm is a zoonotic disease, which means that it is contagious from cats to people.  I have had two or three clients who have gotten ringworm from kittens they have adopted at animal shelters. In one case the resulting infection took months to resolve and the cost ran into the thousands of dollars.  It can be extremely difficult to clear ringworm from a shelter and it is understandable for shelters to wish to adopt out as many kittens as possible but they should at least make it clear that ringworm is present in the facility or that a kitten may be infected.  An explanation of the severity of the risk might be in order, as well. If you wish to avoid ringworm check kittens carefully for signs of hair loss.  If you adopt a kitten that appears as if it might have ringworm have it examined by your veterinarian as soon as possible.

The most common infectious disease in dogs adopted from shelters is tracheobronchitis, more commonly referred to as “kennel cough”. This is usually caused by either Bordetella bronchiseptica bacteria or Parainfluenza virus in dogs. The cough tends to a little softer with Bordetella but lasts longer. A really harsh “whooping” type cough is more likely to be from parainfluenza virus. It isn’t really critical to know which of these causes is present.  There are a number of other organisms that sometimes cause similar symptoms , the most serious one being canine distemper virus. Fortunately, distemper is no longer a common problem.  For the most part kennel cough is just an annoying illness as most dogs will recover with or without treatment.  

With dogs the bigger problems we see with shelter adoptees are chronic illnesses that are usually prevented by observant owners but are present in dogs turned over to shelters, most notably heartworm disease.  While heartworm disease is treatable it can be quite expensive to treat and some of our clients have been surprised by this.  To treat a large dog for heartworm disease using the safest protocol costs over $500 and sometimes approaches $1000.  Severe periodontal disease is not uncommon in middle aged or older dogs and this is true of dogs in the shelter population, as well.  Allergies appear to me to be a common reason for dogs to be surrendered to shelters.  Dogs with allergies that are untreated often develop severe secondary skin infections .  Sometimes we see dogs we know are going to have problems with allergies in post-adoption examinations and it can be quite difficult to tread a line between scaring these owners and properly informing them of the possible consequences of this diagnosis.  More rarely we see inherited or congenital disorders that have been overlooked or ignored.  These too can be a difficult situation for new pet owners. To be fair, I doubt that shelter staff members are capable of diagnosing these conditions but I sometimes think they are more aware of disorders like allergies than they let on.

Behavioral problems vary from annoying habits to life-threatening aggression.  It surprises me how many people think they can handle an aggressive dog.  I do have clients who manage to do this. I also have clients who have been severely injured trying to control aggression.  One of my clients was bitten through the femoral artery and was very lucky to live through his confrontation with his dog.  Aggressive dogs can be very dangerous and it is irresponsible when shelters gloss over aggression problems and adopt out dogs who have bitten humans previously or are judged very likely to do so.  There are a few folks who can handle an aggressive dog humanely and can even control aggressive behavior.  Most of the people who come to shelters looking for pets aren’t that competent, however.   Don’t fall in love with a dog when it’s history includes warnings such as “not good with kids”, “doesn’t like men”, etc.

I really do think that most shelter employees are trying hard to find good homes for their charges. I don’t think it is wrong to adopt or to adopt out a pet that has medical problems when it appears that the potential new owner is competent to deal with the problems and understands the consequences. I do think it is just too tempting sometimes for shelter staff members to ignore problems in the hope of finding a dog or cat a new home.  Take any pet you adopt from a shelter to your veterinarian as quickly as possible and get an evaluation of the pet’s health status and learn about the problems you might have to deal with, or even better, the lack of problems.  If there are known behavioral problems make sure you discuss them with your vet.  Veterinarians are not always the best people to get behavioral advice from but many are good at helping with behavioral problems and some of the ones who aren’t are good about making referrals to people who can help.

 

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VetInfo Digest

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