This is a presentation I gave in London in 2012 at a conference sponsored by the Royal College of Veterinary Surgeons.
The Sceptical Vet: Evidence or Eminence?
This is the slide deck:
And this is a recording of the session.
A brief look at why individual uncontrolled observations are often unreliable. This was my opening statement in a debate at the 2012 Annual Convention of the AVMA on the subject of “Which is Better: Clinical Trials or Clinical Intuition?”
This is a lecture I gave at the 2012 Annual Convention of the American Veterinary Medical Association.
This is the third section of a four-hour series of lectures I gave at the Kansas State University School of Veterinary Medicine.
The Frank W. Jordan Seminar, 2012
The Science Behind Alternative Medicine in Animal Health
This is the second section of a four-hour series of lectures I gave at the Kansas State University School of Veterinary Medicine.
The Frank W. Jordan Seminar, 2012
The Science Behind Alternative Medicine in Animal Health
This is the first section of a four-hour series of lectures I gave at the Kansas State University School of Veterinary Medicine.
The Frank W. Jordan Seminar, 2012
The Science Behind Alternative Medicine in Animal Health
I recently received an email promoting one of the strangest therapies I’ve looked into while writing this blog—leeches.
10 FACTS HOW LEECHES HELP DOGS!
1. Leeches a new wave in alternative animal medicine?
No way! Over 3000 years ago leeches have been successfully used in medicine. One knew relatively little about the origin of their healing effectiveness, but that they had a positive effect was why they were used. They were mostly used for arthritis, gout, varicose veins, for sepsis prophylaxis and above all for handling wounds. Today, their use is not used less by any means, but the knowledge about their use has largely been established.2. What makes these little helpers stand out?
The medical leech — Hirudo Medicinalis — belongs to the family of ring worms (annelid) and has a head and a tail with suction cup, with which he can hold on perfectly tight. With the head end he sucks the blood. His jaws are fitted with approx. 80 small chalky teeth, which saw through the skin and create a small wound. The blood that is taken in is separated into firm components and blood plasma still while in the sucking process. A grown leech can absorb 20 and 50 ml of blood whereby he is then plumply full and shines in wonderful colors. He now is full and is pretty much full for the next 2 years.3. How does the leech function?
The saliva of the leech is a mystery. When attaching, when sucking and when releasing the leech injects saliva into the wound. In this saliva there are a lot of substances that enter the wound and also in the entire organism. Of the suspected 30 to 100 saliva secretions only very few can be named. The known substances act as anticoagulants and anti-inflammatory. They have a bacterial, antibiotic and pain reducing effect.4. What can be treated?
There is a number of indications for leech therapy. Abscesses, ear hematomas, poorly healing wounds, lymphatic blockages are only a small part of the area of application. This holds true: Who heals is right. Important is always, that the one handling the indication has adequate knowledge for the therapeutic treatment.5. How does the leech affect arthritis?
The leech can be effectively employed for arthritis therapy. Even for chronic arthritis they can be excellently used. Placed goal-oriented they minimize the arthritis pain and the dog is then capable of moving the affected joint. Due to the additional blood flow to the joint a better transport of sludge is guaranteed. Moreover this physical movement leads to definitive measures in reducing pain. If an ossification during the arthritis is present, the treatment with leeches speeds up the process. Due to this the stiff joint is then pain free.6. What must be mandatory to address?
Prior to any treatment a comprehensive case history has to be taken by the therapist. By only knowing the medical history, the current status of the health and the knowledge concerning the eventual necessary medicines can a decision be made, if the treatment is indicated or if it is contra-indicated.7. What are the contra-indicators?
Anemia, poor blood coagulation, diabetes mellitus, fever, histamine allergy, leukemia, malignant tumors, stomach ulcers are some of the contra-indicators. Medicines that are blood thinners, also lead to leeches not being used. Certain pain medications cause blood thinning and should not be used three days before treatment.8. How often is the treatment required?
First and foremost this is based on the presented indication. There are cases where only one treatment is necessary to achieve an effective healing. With arthritis often several treatments are necessary in using the leeches. The span of using them becomes greater after each use, as the dog becomes free of pain and more mobile.9. How does the dog handle the treatment?
Yes, actually very well. Dogs often no longer react to the bite of the leech and many dose off during the treatment. Also the secondary hemorrhaging is not a problem, which is different with other wounds, where here the dog does not even try to lick the wound. Secondary hemorrhage can last up to 36 hours and should not be stopped by applying a pressure bandage. That would cause bleeding into the wound itself and that should be avoided at all costs.10. Who is permitted to apply this treatment?
The therapy with leeches is subject to very clearly defined legal guidelines. Acquiring medicinal leeches can only be done through pharmacies. They are considered drugs and acquiring them and utilizing them by a therapist has to be documented. The usage of leeches is not to be underestimated — the healing effectiveness is enormous — but the risks are not to be underestimated. Treatment should only be done by one who is certified and trained.From:the German magazine “Hunde Welt” May 2013 edition
Apart from the little quirks introduced by translation, this article sounds pretty strange. However, even the most superficially odd therapies deserve to be evaluated with an open mind, so I took a deeper look into the veterinary use of leeches. As is so often the case with therapies promoted by alternative medicine practitioners (which is where this article came from), there is a foundation of real science upon which a rather shaky structure has been built.
What is Leech Therapy?
Historically, leeches were used as part of the pre-scientific folk medicine of various cultures. The most common use was to remove blood, which was thought to be helpful in balancing the “vital humors” in the model of humoral medicine which dominated European medical thinking from classical times into the 19th century and which is connected with other pre-scientific medical systems such as Ayurvedic Medicine and so-called Traditional Chinese Medicine. The humoral system, unfortunately, represents one of the most popular and enduring mistakes in the history of medicine, and the notion that bloodletting, by leech or any other method, is a beneficial therapy is nonsense for all but a couple of rare and exotic conditions (such as polycythemia).
The notion, then, that the ancients, in their wisdom, knew of the benefits of leech therapy and that modern science is merely rediscovering this knowledge, is a fairy tale. Because it fits with the general narrative and ideology off much alternative medicine, which values intuitive and historical knowledge more than rational and scientific knowledge and which often seeks to validate therapies by reference to historical use when science fails to support their value, alternative medicine proponents frequently tell this myth of ancient wisdom rediscovered in the modern age. If a chemical in a plant is found to have medicinal value, for example, a narrative will be created in which ancient folk use of that plant is characterized as having identified this value long ago. This is not, however, generally consistent with historical reality. Most herbal remedies have been used ineffectively for dozens of different problems in various cultures around the world. The coincidental correspondence of one such use with a modern scientific discovery doesn’t mean the ancients knew what they were doing, and it doesn’t explain the far more numerous historical uses which were ineffective or even actively harmful.
Science may discover therapies in places where the ancients looked, as well as in places they never considered. It will also, far more often, discover that pre-scientific theories were mistaken and that therapies based on these theories were ineffective or dangerous. Ultimately, historical use can, at most, suggest a subject for scientific investigation. It cannot serve as a validation of any particular therapy since most medical practices invented throughout history have failed to improve health and have been justly forgotten or, in a few unfortunate cases, remodeled and marketed as “alternative medicine.”
As science began to demonstrate that bloodletting did more harm than good, and that health and disease were not determined by the balance of mystical humors or body fluids, leech therapy went out of style. However, scientific evaluation of leech therapy continued and did manage to discover that more than simply removing a small amount of blood, leeches impact circulation through both their feeding and through a complex and poorly understood collection of chemicals they secrete into the patient. These include substances which prevent blood clotting and which may help break down clots, allowing blood collected in a space or in small vessels to drain freely. There may also be anti-inflammatory and analgesic substances in the leech saliva, but the clinical importance of these is not well understood.
In conventional human medicine, leeches are an established therapy in reconstructive surgery, used to treat congestion of blood in veins which can hamper the healing of wounds, skin grafts, and re-attached body parts. There is also some use for arthritis pain and hematomas, pockets of blood that accumulates in tissue, usually associated with trauma. The veterinary use of leeches generally follows the use in humans, though as always with unconventional therapies some people recommend them for a wide range of unrelated and bizarre uses, such as treatment of epilepsy, abscesses and neurologic disorders, “detoxification,” and other more implausible indications.
Does It Work?
The use of leeches in reconstructive surgery is widely accepted in human medicine, and there is some research evidence to support it. A systematic review of 277 cases concluded:
The overall reported “success” rate following leech therapy was 77.98% (216/277). In terms of secondary outcome measures, 49.75% of cases (N = 101) required blood transfusions, 79.05% received antibiotics (N = 166) and 54.29% received concomitant anticoagulant therapy. The overall complication rate was 21.8%.
The cases reviewed were not generally from randomized controlled trials, and a wide variety of surgical problems, different methods of using the leeches, and combinations with other treatments were present in these cases. Without any controls for differences in aspects of the clinical problem and of the other treatments given, it is impossible to be certain that successful outcomes were more or less likely with leech therapy. If, for example, leeches are primarily tried in healthier patients with fewer risk factors for failure of the surgical procedure than in patients not treated with leeches, the leeches might be associated with better outcomes even if they had no effect or even reduced the real success rate. In the absence of better evidence, however, these reports provide at least some tentative support for the practice.
Similarly, there is some evidence to support the use of leeches in osteoarthritis treatment in humans. A 2012 systematic review found three randomized clinical trials including 237 patients and concluded:
This systematic review found moderate to strong evidence for the reduction of pain, functional impairment, and joint stiffness after medical leech therapy in patients with osteoarthritis of the knee. Given the low number of reported adverse events, leech therapy may be a useful approach in treating this condition. Further high-quality RCTs are required for the conclusive judgment of its effectiveness and safety.
The review includes only a few studies, very few patients, and the same kind of subjective measures of outcome that always bedevil studies of therapies for treatment of pain, but it provides at least preliminary evidence to suggest leeches might have some value in treating arthritis pain in humans. Of course, even if leeches can reduce pain, comparative studies of this practice versus other established therapies would need to be done to show that the benefit is significant and the risk small enough to make this a reasonable alternative or adjunct to existing therapies.
As usual, there are no published clinical trials for veterinary patients investigating the safety or efficacy of leech therapy. Use in dogs, cats, and horses is based entirely on extrapolation from use in humans and a small number of case reports and uncontrolled anecdotes. It is therefore plausible but entirely unproven that this therapy could have benefits in veterinary patients.
Is It Safe?
It cannot be repeated often enough that you can’t get something for nothing in medicine. If leech therapy has benefits, it is going to have costs as well. Because the body fluids of leeches come into contact with the blood of the patient, leeches are a great vehicle for the transmission of disease. Because of this, the leeches used must be specially raised medical leeches. This biggest risk of leech therapy appears to be infection.(3-4) Infections have been reported in anywhere from 2.% to 20% of patients treated with leeches, and serious complications, including death, have been seen. Any patient with a comrpmised immune system is at increased risk and probably should not have leech therapy. Leeches can also transmit disease between patients if inappropriately used on more than one patient.
Another potential risk is excessive blood loss. While leeches themselves only consume small quantities of blood, the wounds they make can continue to bleed for anywhere from a few hours to a couple of days. In patients with anemia or with a reason to have imperfect clotting ability, significant loss of blood can occur and blood transfusions may be required.
The direct cost of medical leeches are not high, but they require very specific conditions and care, so the cost of leech therapy can easily be more than $100 per leech. And the procedure can take up to 45 minutes, during which time the patient must be relatively still in order not to disturb the leech, which might detach or regurgitate its stomach contents into the patient’s bloodstream.
Because of some of the risks and inconveniences of this practice, research is being done to identify potential alternatives to leech therapy that might be as or more effective and have fewer disadvantages.(5)
Bottom Line
The historical medical uses of leeches were irrational and almost certainly ineffective and unsafe. However, science has discovered a few potential uses for specially raised medical leeches.
There is moderate evidence to support the use of leech therapy to reduce venous congestion and promote healing in surgical graft, reattachment, transplant, and wound care procedures in humans. There is weak evidence to support some pain relief in human patients with arthritis, though this research has not effectively controlled for placebo effects or compared leech therapy with other established treatments.
There is no controlled research evidence evaluating leech therapy in companion animals for any indication. Anecdotal evidence exists suggesting benefit for the same conditions in which leeches are used in humans.
There are a number of risks to leech therapy, including infection and excessive blood loss. And the therapy is relatively costly and can be inconvenient.
Overall, there is some reason to believe leech therapy may be useful in certain kinds of reconstructive surgery for veterinary patients and might provide some pain relief for patients with arthritis, though this remains unproven and supported mostly but extrapolation from limited evidence in humans and anecdote. There is no good evidence to support any other suggested use for leeches in veterinary patients.
References
1. Iain S. Whitaker, Omar Oboumarzouk, Warren M. Rozen, Naghmeh Naderi, S.P. Balasubramanian, Ernest A. Azzopardi, Moshe Kon. The efficacy of medicinal leeches in plastic and reconstructive surgery: A systematic review of 277 reported clinical cases. Microsurgery. 2012;32(3):240-50.
2. Lauche R, Cramer H, Langhorst J, Dobos G. A Systematic Review and Meta-Analysis of Medical Leech Therapy for Osteoarthritis of the Knee. Clin J Pain. 2013 Feb 26. [Epub ahead of print]
3. BS Porshinsky, S Saha, MD Grossman, PR Beery II, SPA Stawicki. Clinical uses of the medicinal leech: A practical review. Journal of Postgraduate Medicine. 2011;57(1):65-71.
4. Tiene G. M. Bauters, Franky M. A. Buyle, Gerda Verschraegen, Karen Vermis, Dirk Vogelaers, Geert Claeys, Hugo Robays. Infection risk related to the use of medicinal leeches. Pharmacy World & Science. June 2007, Volume 29, Issue 3, pp 122-125
5. Azzopardi EA, Whitaker IS, Rozen WM, Naderi N, Kon M. Chemical and mechanical alternatives to leech therapy: a systematic review and critical appraisal. J Reconstr Microsurg. 2011 Oct;27(8):481-6. doi: 10.1055/s-0031-1284233. Epub 2011 Jul 21.
While some of the disagreements between skeptics and proponents of complementary and alternative medicine (CAM) are disagreements about details, interpretation of data or the finer points of methodology, it is often overlooked that fundamental, irreconcilable philosophical differences also exist. Some CAM practitioners actively reject the whole model of science and scientific research as the best method for understanding health and disease. Whether this is a genuine a priori disagreement, or simply the result of casting about for some approach that will validate their beliefs once science has shown them to be false, we cannot know for certain. However, there is ample evidence that such radically alternative philosophical approaches underlie much of alternative medicine, despite claims that CAM practitioners value science and scientific evidence or that specific therapies are “scientifically proven.”
I discussed a number of the philosophical conflicts between evidence-based medicine (EBM) and CAM in a presentation given at the American Veterinary Medical Association (AVMA) annual conference in 2012, and in an article for the journal of the AVMA. However, I recently came across a new perspective on the subject in the Journal of Case Studies in Homeopathy, which claims to refute the entire basis of EBM and propose an alternative that supports the “radical-phenomenological approach of homeopathy.
Wittenburg, C. Cognition-Based Medicine: A new paradigm fro medicine- applied to Homeopathy. Journal of Case Studies in Homeopathy. 2013;1(2):7-16.
The article begins, humbly enough, by stating that its purpose is “to introduce the concept of Cognition Based Medicine (CBM) as a convincing alternative to Evidence Based Medicine (EBM). CBM was developed on the basis of a refutation of the positivist paradigm…Contrary to Hume´s ideas, we are well capable to discern causality by observation in single cases.”
The foundation for CBM appears to be on “single-case-cognition as the basis of progress in medicine.” Clinical trials involving groups are apparently not necessary because it is possible to identify the causes of disease and evaluate the results of our interventions solely on the basis of individual, uncontrolled evaluation of individual patients. Since that is largely how homeopathy is practiced, it would be nice for homeopaths if that were true. In fact, it is clear from the outset that the author’s goal is to replace science with something else more likely to validate her existing belief in homeopathy: “Where do we find an epistemological approach which suits homoeopathy? It has to be a theory which is substantially different to – and hopefully more convincing than – positivism.”
Such a paradigm shift would, however, require us to ignore the history of medical, and indeed all scientific progress in the last several centuries, and all the unprecedented changes in human well-being and longevity that have accompanied the rise of the scientific method. So how does this article make such an earth-shattering case?
As it happens, it never does. It merely identifies the principles supposedly underlying EBM and then asserts that they have been overturned. It cites simple thought experiments, and articles in the mainstream medical literature that show people drawing conclusions from single cases and then simply asserts that since we do this, it must be a reliable and effective method for establishing causality.
For example:
Duncker, a German philosopher, refuted Hume´s idea of causality. Based on simple examples from every-day-cognition he demonstrated that the ´singular causal-gestalt´ of the cause stretches into the ´gestalt´ of its effect. Gestalt means: form, structure, process. We recognize the gestalt of a car having crossed a field in the traces its wheels leave…
The idea that, perhaps the tracks we see might not have been made by a car, and thus our conclusion may be in error, appears not to have occurred to this clever philosopher.
Similarly:
Kiene and his colleagues undertook research on four years of published volumes of “The Lancet” (1996-1999), revising articles to find proof for the concept of singular causal-cognition. Interestingly, many of the articles gave evidence of application of convincing non-experimental evidence: skilled practitioners applied their ability, their personal judgement, based on ´tacit knowledge´ to solve therapeutic problems or to introduce new techniques.
Since clinicians clearly do make causal judgments based on non-experimental evidence, there must be no need for experimental evidence—QED (or not….)
Similar kindergarten logic (“I said it, so it must be true!”) is applied to the concept of the placebo effect, which the author blithely dismisses as not proven to exist and as merely a political tool to privilege the randomized clinical trial as the only legitimate kind of evidence for medical therapies (which is itself, a straw man fallacy often directed against EBM). The author even goes so far as to claim that homeopathy, and its inexplicable yet obvious success, was the primary motive for development of the RCT and of EBM:
RCTs become a dogma… All other forms of clinical trials and ways of judging the effectiveness of a given therapy are phased out. EBM is becoming the reigning paradigm, with RCTs as the gold-standard of clinical research.
…any drug-effect which is superior to “the powerful placebo” must be a really important one. This was a strategy to introduce RCTs as the gold-standard for scientific research in EBM, and is built on the good results of homoeopathy… Homoeopathy, which gave the ultimate push for the development of EBM, can´t make much use of RCTs itself. They merely serve for refutation of EBM´s assertion ´potentised homeopathic medicines are placebo´ through randomized, placebo-controlled experiments on plants.
Even making allowances for the problem of translation (the author is German and the article is in English), this is an example of the level of incoherence throughout the article, which verges at times on complete gibberish.
And after a few pages of such nonsense, the author declares the case proven: “By now, we have identified single-case causal cognition as the basis of progress in medicine… A new paradigm for CAM and homoeopathy was created through refutation of Hume´s definition of causality, replacing it by the concept of gestalt-cognition.” Wow, is that all?!
The author then goes on to explain why case studies in homeopathy can now be relied on as the best evidence on which to make diagnostic and treatment decisions.
Such a blithe dismissal, with nothing even approaching a coherent or cogent argument, of several centuries of progress in philosophy and science, is an illustration of just how out of touch with reality proponents of homeopathy often are. It also illustrates how disingenuous and self-serving their claims to respect scientific evidence are. As I demonstrated in my extensive evaluation of the homeopathy literature, including the studies cherry-picked by the Academy of Veterinary Homeopathy to defend their practices, homeopaths are willing to cite scientific studies, even of poor quality with significant uncontrolled bias, if they support what homeopaths believe. However, they are fundamentally unwilling to accept any negative verdict on their practices, so they either dismiss or ignore negative studies, or they seek out ludicrous alternatives to the epistemology of science and imagine they have successfully overthrown the methods of seeking knowledge that the rest f the world recognizes have been more successful than any other in history; the methods of science. It is hard to imagine a more compelling illustration of why the claims of judgment of such homeopaths should not be taken seriously.
Much of complementary and alternative medicine (CAM) is offered either as an addition to conventional, science-based treatment or in situations in which conventional therapies are unavailable or ineffective. This doesn’t excuse offering treatments that haven’t been properly tested, and it doesn’t mean such therapies can’t do harm. However, such an approach at least avoids the harm that can come from delaying or rejecting effective treatment.
However, sometimes CAM providers actually believe their practices are an appropriate and effective substitute for conventional medicine, even in the case of serious disease. This attitude is truly inexcusable when, as is usually the case, there is no sound evidence to support the belief and when irrational and inaccurate denigration of conventional treatments is used to scare people away from medicine that could really help their pets. One of the most egregious examples of this kind of irresponsible medicine is the promotion of “natural” or “holistic” methods for preventing and treating heartworm disease in dogs.
Heartworm disease is a parasitic infestation transmitted from infected dogs (or other animals) to uninfected individuals by specific kinds of mosquitos. It is, of course, most common in areas that have both a reservoir of infected hosts and a population of the right kind of mosquitos. In the U.S., heartworm disease is quite common in warm, humid regions, and transmission often varies seasonally with the mosquito population. Heartworms can cause devastating, often fatal disease.
Fortunately, there are safe and effective medicines to prevent heartworm infestation. While all medications have risks as well as benefits, the risks of these preventatives are well understood and very, very small. Certainly, in areas where heartworm disease is endemic, the risk of preventatives pales in comparison to the risk of the disease. So despite the often hysterical nonsense about these “chemicals” and “insecticides,” the real facts are clear: heartworm prevention is safe and effective and far better for your pet than getting heartworm disease.
If your dog is unfortunate enough to become infected with heartworms, there are effective treatments. The risk of treatment is, however, significantly higher than the risk of prevention, though in most cases still far less than the risk of leaving the disease untreated. The American Heartworm Society (AHS) has a thorough discussion of the pros and cons of different treatment options, and working with your veterinarian you can almost certainly cure this disease and minimize the risks of treatment.
The AHS is also very clear about alternative therapies for this disease: “No “natural” or herbal therapies have been shown to be safe and effective prevention or treatment for heartworm disease.” And fortunately, many proponents of alternative therapies also recognize that no CAM therapies have been shown safe and effective for preventing or treating this disease. The most popular veterinary herbal medicine textbook states, “The authors do not recommend substituting an unproven herbal formula for effective conventional therapy.” Even as radical a proponent of alternative therapies as Dr. Karen Becker at mercola.com grudgingly agrees that,“treatment for heartworm infection is one area where conventional veterinary medicine offers valuable options [and] is preferable to leaving the dog untreated, or using unproven, alternative methods that may have no effect or even be harmful.”
Unfortunately, there are still plenty of unscrupulous companies, and sadly even veterinarians, willing to exaggerate the risks of conventional prevention and treatment and claim that unproven alternatives are safe and effective. Below is a long list of sites promoting unproven methods of preventing or treating heartworm disease. None of these have been demonstrated to be legitimate or reliable, and trusting your dog’s life to any of them is a dangerous mistake.
http://www.theherbsplace.com/Heartworm_Prevention_sp_104.html
http://www.alternativeheartwormcure.com/index.html
http://www.earthclinic.com/Pets/heartworm.html
http://www.oursimplefarm.com/2012/04/my-dogs-experience-with-heartworms.html#.UcuCIm3n_IU
http://www.unchainyourdog.org/news/NaturalHeartworm.htm
http://www.holisticvetexpert.com/NATURAL-HEARTWORM-TREATMENT.html
http://www.holisticvetclinic.net/pages/heartworm_treatment
http://www.homeovet.net/content/lifestyle/section4.html
http://drmark1961.hubpages.com/hub/safe-herbal-heartworm-treatment-for-your-dog
http://www.dogsnaturallymagazine.com/heartworm/
I’ve been a bit remiss lately in posting, due to some exams and deadlines that have kept me unusually busy, but I wanted to briefly promote a new tool in the effort to develop novel, evidence-based therapies for cancer. The National Veterinary Cancer Registry (NVCR) is an effort to build a database of information about veterinary cancer patients. This will allow both epidemiologic studies using the data to better understand the patterns in naturally occurring cancer and also to connect patients with clinical studies of new therapies for their specific disease. This serves the veterinary patient population as a whole as well as the individual patient.
The NVCR is a joint effort between the CARE Foundation, Baylor University Medical Center (BUMC) at Dallas and the Texas Veterinary Oncology Group. This type of database has been of great value in improving the understanding and treatment of cancer in humans, and it is exciting to see such an effort beginning in the veterinary field. I encourage owners of pets with cancer to register your pets as a way to contribute to the growth of our ability to help others going through what you are going through.
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