29 minute read
SUPERSYMMETRY OR MULTIVERSE? THE HIGGS BOSON DECIDES.
JUZER VASI `24
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Introduction
July 4th, 2012. For most Americans, this Independence Day was filled with its usual festivities: get-togethers, outdoor barbeques, and fireworks lighting up the endless night sky. Across the Atlantic Ocean, particle physicists in Geneva were also celebrating something remarkable: the detection of a particularly elusive fundamental particle integral to the structure of the universe, the Higgs Boson. The presence of the particle was confirmed by physicists operating the Large Hadron Collider (LHC)—the world’s largest and fastest particle accelerator—at CERN, the European Organization for Nuclear Research. The confirmation of the particle’s existence represented an inflection point in the understanding of the universe, and garnered much attention within the circles of theoretical and particle physicists. After analysis, the Higgs would either suggest that the fundamental nature of the universe relies on an ordered model of elementary particles, such as supersymmetry, or undermine basic understandings of the universe by suggesting a “many worlds” universe known colloquially as the multiverse theory. The very structure of reality was to be determined by one specific property of the infinitesimally small particle: its mass. As CERN set out to calculate the mass of the detected particle, physicists around the globe held their breath.
The Standard Model of Particle Physics
Before discussing CERN’s findings, it is integral to first understand the Higgs Boson itself as well as the competing fundamental theories of supersymmetry and the multiverse. As the Higgs Boson exists in a quantum state, it is crucial to discuss the fundamentals at the basis of particle physics. Atoms are not the true building blocks of the universe. To physicists, protons and neutrons represent another layer of matter composed of incredibly small elementary particles influenced by fundamental forces. As the field of quantum mechanics has developed over time, more of these particles and forces have been detected and compiled into the Standard Model of Particle Physics based on their properties. While the Standard Model (SM) bears much credence, it is still a changing mathematical theory; it is not perfect, and requires the support of supplementary theories to fully explain other phenomena in the universe. Tara Shears, particle physicist at the University of Liverpool, cogently describes the two core groups of the SM in her research: elementary particles known as fermions, and fundamental forces known as bosons. In total there are 12 fermions—six quarks and six leptons—that comprise the true fundamental building blocks of all known matter in the universe. Aside from electrons—a type of lepton—quarks are the most well known of the elementary particles as they combine
to form protons and neutrons. Physicists have discovered and identified six different quarks grouped in pairs forming three generations increasing in mass. The first generation pair of quarks are the up and down quarks (these combine together to form protons and neutrons), followed by the charm and strange, and top and bottom quarks. The other group of fermions known as leptons include six particles: the electron, muon, and tau joined alongside their corresponding particle-pairs known as neutrinos (1). While the 12 fermionic particles are the “building blocks” of matter, Shears indicates the universe would be unable to function without forces acting upon this matter. As fermions compose all known matter, force carrying particles known as bosons interact with fermions to create a dynamic universe. The SM is composed of five bosons: four gauge (vector) bosons and one scalar boson. The four gauge bosons mediate three fundamental forces of nature: strong force, weak force, and electromagnetism.1 Gluons govern strong force akin to forces found within atomic nuclei. The W and Z bosons are responsible for weak interaction, whilst photons mediate electromagnetic interactions. The final boson? The Higgs.
The Higgs Boson
By the 1960s, it became clear to physicists that the functions of two of the major fundamental forces—electromagnetism and weak force—were incredibly similar. Thus, physicists sought to combine these forces into a unified theory describing an “electroweak” force which governs electricity, magnetism, light, and some radioactivity—solidifying the SM in the process. However, there was a catch: while correctly describing the predicted features of an electroweak force, it appeared that mathematical calculations revealed that the individual bosons emerged massless. While this made sense for a photon, it had already been determined that W and Z bosons have large masses nearly a 100 times larger than that of a proton (2). In 1964, efforts by Peter Higgs, Francoise Englert, and Robert Brout led to the proposal of the Brout-Englert-Higgs (BEH) mechanism. Simply
Figure 2 Decorated theoretical physicist and 2013 Nobel Laureate Peter Higgs who proposed the mechanism (alongside François Englert and Robert Brout) predicting the existence of the Higgs Boson in 1964. put, the mechanism assigned mass to elementary particles through their interaction with an energy field known as the Higgs field. The mechanism also allowed for elementary particles to retain the structure of their original interactions, work at high levels of energy, and allowed for photons to remain massless. Finally, the mechanism implicated that the field would materialize itself into a particle with a certain mass: the Higgs Boson (3). Ultimately, the Higgs Boson explains the mass of most elementary particles in the SM, essentially serving as its foundation. Without the Higgs mechanism, the SM would collapse onto itself. Thus began a near 50 year hunt for the particle that would solidify the calculability of the SM, and provide consistency to the years of experimental data collected (4). It was not until the advancement in technologies illustrated in the LHC that physicists were able to complete half a decade’s work and report the existence of the Higgs (5).
Supersymmetry (SUSY)
With a necessary understanding of the vitality of the Higgs Boson to the SM, it is possible to understand the first of the two competing theories of the universe being discussed. By the time physicists were on the verge of detecting the Higgs for the first time, decades of experimental data had boosted the SM to a respectable level of credibility. However, as orderly and fitting as the SM is, it simply does not answer all the questions of the cosmos. That is where supersymmetry (SUSY) comes in. Similar to string theory, SUSY resembles a theoretical extension to the base principles of the SM in an attempt to explain certain phenomena that it cannot. Furthermore, SUSY is not a theory, but rather a principle that is extended to the SM. As such, a crucial and universal aspect of SUSY is that it treats matter and force identically. As a distinguished professor of particle physics at UC Santa Cruz, Howard Haber, succinctly summarizes in terms of the SM, for all matter elementary particles (quarks and leptons), there are “cousin” force particles called squarks, sleptons, and sneutrinos. Similarly, for the force carrying bosons of the SM, their matter SUSY cousins are as follows: Gluinos, Photinos, Zinos, Winos, and finally Higgsinos (6). Despite a lack of any “hard” evidence thus far, SUSY has the potential to explain numerous unsolved mysteries at both the quantum and cosmic levels. Haber mentions dark matter, which has been one of the most perplexing issues for theoretical physicists for decades. Dark matter composes approximately one quarter of the energy density of the universe as well as an incredible proportion of known matter of the universe—a staggering 25 percent. Yet even modern physicists are certain of only a few of its properties: it exists in large amounts, interacts with gravity, and does not absorb or
emit light. However, preconceptions about this hidden matter changed with the development of SUSY. The appeal of SUSY to physicists is its introduction of the slew of new hypothetical cousin particles; one of these particles, dubbed the lightest supersymmetric particle (LSP), resembles exactly what physicists have observed in what a dark matter particle would be—a weakly interacting massive particle (WIMP). While an exact supersymmetric particle has not been identified as the likely dark matter particle, future particle accelerator runs may finally provide experimental data. Until then, SUSY offers the strongest explanation for dark matter (7). Aside from providing answers to pressing issues facing physicists by extending the SM, SUSY also rectifies shortcomings of the SM itself—specifically the mass of the Higgs. According to Baer et al., the mass of the Higgs Boson in conjunction with the SM and LHC, is large. If SUSY is real, the theoretical cousin particles would cancel out the inflated mass of the Higgs from SM, offering a mass confluent with what physicists have observed over the decades (8). SUSY provides an organized and structured explanation of the universe and appeals greatly to physicists disillusioned with more obscure theories such as multiverses. Nonetheless, as promising as SUSY sounds, there has been little experimental data to suggest its viability. With future runs of particle accelerators at CERN planned for the future, SUSY may be given more credibility. For now, all theories of the universe—including the multiverse—are fair game.
Multiverse
Unlike SUSY, the multiverse theory is less rooted in structure, technicality, and arithmetic. Rather, it is based upon a fundamental sociological assertion of cosmologists: the laws of physics observed in this reality are not fundamental, but simply a reflection of a single possibility that the physical reality may have constructed. According to particle physicist David Kaplan, proponents of the multiverse believe that all measured physical data in the universe were “generated randomly” out of a vast array of possibilities. The laws of physics observed in this universe create structures capable of constructing what is perceived as reality (e.g., the sun, earth, life, and humans). By virtue of the fact that humans exist within this universe, there is bias towards what we perceive as the fundamental laws of physics that govern the universe (9). While the multiverse theory is more or less entrenched in theoretical philosophy, there are some quantitative details to help explain why this theory has become prevalent in recent times. As Larsen, Nomura, and Roberts indicate, in the 1980s, astronomers discovered cosmic inflation: the expansion of the universe. Before this discovery however, there existed a cosmological constant, Λ, a single number that described the universe. After the discovery of cosmic inflation, the rate of expansion was measured to be trillions of times faster than what would have been previously expected. This caused a major problem for theoretical physicists: the cosmological constant, a value that described the specific parameters of the universe, was com -
pletely off (10). This apparent discrepancy caused physicists to begin to question the very structure of the universe. It is vital to note that multiverse does not suggest the existence of different “bubbled” universes with corresponding doppelgangers; it questions whether physicists know anything about the universe at all. Regardless, as much as the multiverse theory asserts a lack of structure, there is one essential prediction of the theory that makes internal theoretical sense: the existence of the Higgs at a certain mass. Ultimately, SUSY and multiverse are opposite predictions of the mysterious inner workings of the universe. Earlier it was stated that the credibility of each theory would depend on the specific value of the detected boson mass. SUSY predicted a Higgs Boson with a mass exactly 115 GeV; the multiverse theory projected a heavier mass of 140 GeV. The result? 125 GeV.
Conclusion
Weeks of data analysis following the run of the LHC revealed a mass almost exactly in the middle between the two predictions. Ultimately, the 2012 Independence Day Higgs did not decide between SUSY and multiverse. Regardless, the discovery of the Higgs itself was a massive accomplishment, as each theory as well as the SM itself depended on its existence. However, the implications of the mass of the Higgs remain a mystery. The LHC has been shut down since 2018, and engineers have focused on upgrading the collider with the hopes of new particle discoveries. The LHC is expected to run again this spring. There is ultimately only one predictable characteristic of the universe: unpredictability. While physicists at CERN in 2012 did not achieve all the answers necessary to fully understand the universe, they completed a fifty-year hunt for the most elusive, mysterious, and consequential particle in the universe. While the Higgs Boson did not end up deciding the fate of the universe in 2012, it still remains the quantum mechanical keystone that will likely play a significant role in future discoveries
Figure 4 A segment of the LHC tunnel in which particles would travel at high speeds prior to collision.
References
1. T. Shears, The standard model. Philosophical Transactions of the Royal Society A 370, 1-13 (2012). 2. The Brout-Englert-Higgs mechanism. CERN, (2021). 3. H. Gray and B. Mansoulié, The higgs boson: the hunt, the discovery, the study and some future perspectives. Atlas Experiment, (2018). 4. J. Ellis, M. Gaillard, and D. Nanopoulos, A historical profile of the higgs boson. World Scientific, 255-274 (2016). doi: 10.1142/9789814733519_0014. 5. S. Wu, Brief history for the search and discovery of the higgs particle — a personal perspective. International Journal of Modern Physics A 29, 1-34 (2014). doi: 10.1142/S0217751X14300622. 6. H. Haber, Supersymmetry, part i (theory). Particle Data Group, (2013). 7. G. Jungman, M. Kamionkowski, and K. Griest, Supersymmetric dark matter. Semantic Scholar, (1992). 8. H. Baer, et al., Higgs and superparticle mass predictions from the string theory landscape. Cornell University, (2018). 9. David Kaplan video Supersymmetry. CERN, (2021). 10. G. Larsen, Y. Nomura, and H. Roberts, The cosmological constant in the quantum multiverse. Cornell University, (2011).
Images retrieved from:
1. Graphic Illustration by Komal Grewal `23 2. www.flickr.com/photos/bnsd/11253401126 3. Graphic Illustration by Komal Grewal `23 4. commons.wikimedia.org/wiki/File:Views_of_the_LHC_tunnel_sector_3-4,_tirage_2.jpg
Traditional Chinese Medicine—a Hidden Science?
EAN TAM `23
Figure 2 A variety of dried plant and animal parts on sale, including mushrooms, coiled snakes, and turtle shells.
Introduction
On May 25th, 2019, the World Health Organization (WHO) adopted the eleventh version of the International Classification of Disease, also known as the ICD-11, which provides medical practitioners with diagnostic codes. For example, if a patient has cholera, the doctor will enter the corresponding ICD-11 code, 1A00, into a database. Given the scale of the ICD, the database and codes allow institutions and nations to track mortality and morbidity statistics, as well as resource allocation. In 2020, Stony Brook’s Distinguished Professor of Pharmacological Sciences Arthur P. Grollman criticized the ICD-11. Grollman’s point of contention is the ICD-11’s inclusion of health conditions treated by traditional Chinese medicine, also known as TCM. Grollman finds the inclusion of TCM to be counterproductive to the advancement of modern medicine (1). Those who share Grollman’s point of view argue that TCM is a pseudoscience, and by providing diagnostic codes for TCM conditions, the WHO is directly supporting the use of TCM in the modern world. It is important to distinguish that the ICD-11 is not expressing which specific TCM products should be used; rather, it recognizes the the health conditions that may only be treatable by TCM. For example, the ICD-11 references insomnia and tinnitus as treatable conditions of TCM, but it also references traditional East Asian conditions. Conditions include qi deficiency (lacking in essential life energy) and yin and yang disruptions (imbalance in opposing forces within the body) (1). Whereas insomnia and tinnitus have possible treatments in modern medicine, conditions involving qi and yin-yang do not. Thus, by giving official recognition to conditions exclusive to TCM, the ICD-11 acknowledges whichever TCM product is hailed to be a solution. The concern of TCM opponents is that the research and development behind TCM is lacking or unsafe. In order to address this concern, the following two issues should be considered: the adequacy of studies of TCM’s molecular basis and the transparency of sourcing and environmental implications.
Figure 3 A batch of pangolin scales discovered in Cameroon. These scales were among the three metric tons seized and later burned by the Cameroonian government in 2017 to deter illegal traders.
Studying the Molecular Basis of TCM
Passed down from generations, TCM as it is used today is built upon centuries of homeopathic-oriented treatments from East Asia. Although referred to as traditional Chinese medicine, TCM includes many practices and ingredients used in other countries like Japan and Korea. TCM revolves around the idea of qi, a term to denote the vital energy within the human body (2). Although the phenomenon of qi has no scientific bearing, the idea of qi and TCM use is very much embedded in East Asian cultures, where TCM is used as home remedies or even recommended medical alternatives. In 2016, 15.8% of the medical services delivered in China were TCM, and TCM “hospitals” and clinics provided care for approximately 962 million Chinese citizens (3). Granted, when TCM products were first established centuries ago, the users most certainly did not comprehend the importance of the molecular basis behind medicine. But with time and given the advent of new technology, analysis of proposed medicine is commonplace. TCM is no exception, although the researchers are candid in acknowledging the limited research supporting the benefits of TCM. A 2020 meta-analysis published in the Journal of Pain and Symptom Management gathered studies concerning TCM used for relieving pain in breast cancer patients being treated with aromatase inhibitors (AI). AI treatment can lead to aromatase inhibitor-associated musculoskeletal symptoms (AIMSS), characterized by pain in muscles and joints. All of the studies analyzed were randomized controlled trials, and the breast cancer patients self-reported pain levels from AMISS. Across the studies, TCM products administered to the research participants ranged from herbal remedies to acupuncture. The meta-analysis pinpointed four of these TCM products that alleviated AIMSS-related pain: tiger bone powder, ear acupuncture, Bushen Qiangjin capsules, and Yi Shen Jian Gu (YSJG) granules (with the latter two composed of a mixture of herbs). There were significant differences in self-reported pain levels between the treatment groups and their respective placebo counterparts. For example, the group of patients who took YSGJ reported a 50.2% decrease in pain compared to the 26.9% decrease in pain in the placebo group (4). While such data does lend some support for these TCM products as an effective treatment, it is important to note that self-reporting is subjective and the sample sizes in the studies never exceeded 77. Moreover, this meta-analysis of various TCM products accomplished nothing more than observing the effects of TCM without explaining their scientific basis. The study admitted in its final sentence, “However, further investigation on the molecular pathway involved and an in-depth safety profile is needed” (4). But for advocates of TCM, not all is lost.
COVID-19 Studies
The COVID-19 pandemic caused by the SARS-CoV-2 has led to a global search for vaccines and therapeutics. In China, the pursuit for therapies to treat COVID-related symptoms has included TCM. From this research, the benefits of at least two TCM products, Lianhua Qingwen and Jinhua Qinggan, have not only been observed but also explained on a molecular basis. Lianhua Qingwen capsules are made of thirteen Chinese medicines including the fruit of the forsythia plant and granules of gypsum fibrosum stone. In a randomized, controlled experiment with 284 symptomatic COVID-positive patients, a 14-day regiment of 12 Lianhua Qingwen capsules a day improved the rate of recovery of fever, fatigue, and cough (2). A separate study revealed the in vitro effects of Lianhua Qingwen on slowing down the replication of SARS-CoV-2 and preventing cytokine storms— life-threatening inflammatory responses by the body due to viral infection (2).
COVID-19. In a controlled experiment with 123 patients, Jinhua Qinggan improved common symptoms like cough, fever, and fatigue, but it was also said to lessen the patients’ anxiety. The reported molecular basis: Jinhua Qinggan binds to ACE2—a transmembrane protein that is effectively SARSCoV-2’s gateway into the cell—and blocks the virus’ ability to replicate in other cells (2). Although the researchers provided molecular explanations, they came far from isolating the specific compound(s) in each treatment that led to the observed therapeutic benefits. Recall, Lianhua Qingwen and Jinhua Qinggan are composed of thirteen and twelve different Chinese medicines, respectively. Thus, despite the positive results, the researchers were left unable to pinpoint which component was the definitive cause. Even more troubling, researchers at the Nanjing University of Chinese Medicine issued a response to the study of Lianhua Qingwen, questioning the recommendation that Lianhua Qingwen be used against COVID-19. They wrote, “However, the use of [Lianhua Qingwen] is not preferred because of their unclear representation of absorbed bioactive compounds (ABCs). Furthermore, their unabsorbed compounds, concentrations of absorbed compounds, excipients, metal ions, and impurities in crude extract may lead to false responses ex vivo after administration” (5). Additionally, further research is needed given the small sample sizes of the patient experiments (no greater than 300) and the lack of consideration into drug interactions, diversified demographics, and length of course of treatment. Conversely, the Moderna and Pfizer COVID-19 vaccine trials involved 30,420 and 43,548 participants, respectively (6). Although pregnant women and younger children were not examined in these two vaccine trials, the volunteer pool was diversified in age, health conditions, and race.
Risks of Taking TCM
In a paper published in EMBO Reports, Grollman and Marcus documented the WHO’s odd affinity for TCM. They explained that regardless of TCM’s socio-economic benefits (which the WHO leadership under Margaret Chan highlighted), the adequate research in TCM’s favor is simply not present. Given that 88% of the UN member states do not have the capabilities to carry out research on their own, the WHO is responsible for disseminating reliable information for a global audience (7). Yet, the WHO may fail to do so. For instance, it often overlooks that many TCM products contain ingredients that are dangerous to humans, such as aristolochic acid, a herb found in many TCM products. Research has found that aristolochic acid can lead to liver cancer in mice “in a similar fashion to the genetic pathogenesis of human liver cancers” (8). The researchers also concluded that Chinese patients were most at risk simply because Chinese patients are more likely to consume the TCM products containing aristolochic acid (9).
Outside of the Lab: Environmental Implications
The second issue concerning TCM is sourcing and environmental implications. In studies performed with TCM products sold in Australia, half of the TCM samples the researchers analyzed contained DNA from animals and plants that the product labels had not even listed. Some of those animals were endangered, and some of the included plants were poisonous (1). One of the potentially dangerous plants include Ephedra, which was banned in the United States after it was found responsible for the death of Major League Baseball player Steve Bechler. Ephedra was one of the herbs included in the Lianhua Qingwen and Jinhua Qinggan capsules used for COVID-19 therapeutic studies, and it was described to be one of the most beneficial ingredients in Jinhua Qinggan (2). Additionally, the sourcing of TCM products comes under scrutiny for damaging the conservation efforts of at-risk species. Examples include the Malaysian sun bear, which is illegally targeted and sourced for a variety of TCM products, their bile being the most prized. In Malaysia, sun bears are found with their meat, paws, and gallbladders removed—all desired TCM products. Other body parts like bones and skin are seen as trophies and are collected as well. The poaching of sun bear parts is broadcasted on Facebook; these parts are subsequently sold at local markets. Sun bears that survive immediate butchering may be left injured from traps or kept as pets. Without much regard to its illegality, domestic and foreign poachers remain attracted to the TCM business existing in Malaysia (9). Another prime example is the pangolin species, which is near extinct because poachers seek pangolin scales and other body parts for TCM (3). From 2010 to 2015, an estimated 100,000 pangolins were illegally trafficked. Pangolins have also been found to be a possible source of the SARS-CoV-2 virus (10). Even with regulations and animal-protection laws, the blackmarket business for TCM will result in the further endangerment of at-risks species and increased possibility of zoonotic diseases.
Conclusion
The WHO’s decision to include health conditions treated by TCM in the ICD-11 has warranted concern from some scientists. They argue that recognizing such conditions may pave the way for TCM to achieve broader acceptance into modern healthcare. This is worrisome given that TCM products are so extensive in its applications and ingredient sources, yet many TCM products lack a definitive molecular basis. The United States National Institutes of Health warns consumers that TCM studies in general are of poor quality. This was seen with the Linhua Qingwen and Jinhua Qinggan experiments; the products were reported to be effective therapeutics for COVID-19 patients, but the research may not contain the necessary elements of a drug trial, such as large and diverse sample sizes and, most importantly, a clear mechanism of action. In addition, the studies that support TCM ignore its possible dangers. This includes the contamination of products by extraneous ingredients, incorporation of toxic components like aristolochic acid, and black market business fueling TCM. All three of those concerns have been highlighted in more extensive research, particularly by researchers outside of China. The ICD-11 will come into effect in 2022. It is unlikely that sufficient research with the appropriate components of drug trials could be published before then: the field of TCM is too large, and time is lacking. Although the WHO has made its decision, for now, TCM remains a hidden science.
References
1. D. Cyranoski, Why Chinese medicine is heading for clinics around the world. Nature 561, 448450 (2018). doi: 10.1038/d41586-018-06782-7. 2. Q. Li, et al., The role played by traditional Chinese medicine in preventing and treating COVID-19 in China. Frontiers of Medicine 14, 681–688 (2020). doi: 10.1007/s11684-020-0801-x. 3. Y. Wang, et al., Knowledge and attitudes about the use of pangolin scale products in traditional Chinese medicine (TCM) within China. People and Nature 2, 903-912 (2020). doi: 10.1002/ pan3.10150. 4. C. Long Poo, et al., Effect of traditional Chinese medicine on musculoskeletal symptoms in breast cancer: a systematic review and meta-analysis. Journal of Pain and Symptom Management 20, (2020). doi: 10.1016/j.jpainsymman.2020.11.024. 5. X. Huang, et al., Letter to the editor in response to the articles ‘Lianhuaqingwen exerts anti-viral and anti-inflammatory activities against novel coronavirus (SARS-CoV-2)’ and ‘Liu Shen capsule shows antiviral and anti-inflammatory abilities against novel coronavirus SARS-CoV-2 via suppression of NF-κB signaling pathway.’ Pharmacology Research 163, 1-4 (2021). doi: 10.1016/j. phrs.2020.105289. 6. C. Corti, et al., Current perspectives: SARS-CoV-2 vaccines for cancer patients: a call to action. European Journal of Cancer, 1-25 (2021). doi: 10.1016/j.ejca.2021.01.046. 7. A. Grollman and D. Marcus, Is there a role for botanical medicines in the twenty-first century? EMBO Reports 21, 1-3 (2020). doi: 10.15252/embr.202051376. 8. Z. Lu, et al., The mutational features of aristolochic acid-induced mouse and human liver cancers. Hepatology 71, 929-942 (2019). doi: 10.1002/hep.30863. 9. L. Gomez, et al., Illegal trade of sun bear parts in the Malaysian states of Sabah and Sarawak. Endangered Species Research 41, 279-287 (2020). doi: 10.3354/esr01028. 10. T. Zhang, et al., Probable pangolin origin of SARS-CoV-2 associated with the COVID-19 outbreak. Current Biology 30, 1346-1351 (2020). doi: 10.1016/j.cub.2020.03.022.
Images retrieved from: 1. https://commons.wikimedia.org/wiki/File:2016_366_287_Traditional_Chinese_Medicine_ (30227026751).jpg 2. https://commons.wikimedia.org/wiki/File:Traditional_Chinese_medicine_in_Xi%27an_market.jpg 3. https://commons.wikimedia.org/wiki/File:Pangolin_scale_burn_in_Cameroon._Credit-_Kenneth_Cameron_-_USFWS_(2)_(32575640450).jpg
Leeching into the Past: A Modern-Day Revival of Medicinal Leech Therapy
HARSHINI SURESH `23
Upon mention of the bloodsucking, predatory worms known as leeches, a sense of fear and revulsion is instantly elicited from the general public. Distant cousins of the earthworm, leeches are freshwater parasitic worms that feed on the blood of both animals and humans. Leeches were widely used in a practice called bloodletting, wherein physicians applied these worms on patients to restore balance of bodily fluids, or humors, and eradicate illness. The entire body was thought to benefit from leech therapy, exemplified by its usage in treating headaches, ear infections, and hemorrhoids (1-2). The effectiveness of this practice was later disproved via clinical research studies; thus, leeching began to decline in popularity. Recently, the use of leeches has re-emerged in modern medicine, particularly in select cases of reconstructive surgery (3). Despite their frightening connotation, these creepy crawlers possess healing properties that, if harnessed, can save patients’ limbs, if not lives. Blood - letting, an ancient medical treatment in which blood was withdrawn from the veins of a patient using leeches, began around 3000 years ago in societies around the world, as depicted in the writings of esteemed Chinese and Ti- betan physicians, African shamans, and Mayan priests. The implementation of this therapeutic practice into Western medicine originated from the Greeks, who passed it onto the Egyptians, and in turn, bloodletting was slowly integrated into Roman society. Hippocrates (460–370 BC), an ancient Greek physician and prominent figure in medicine, founded the humoral theory, which proposed that an imbalance in humors (body fluids) such as blood, phlegm, black bile, and yellow bile, caused many physical and mental illnesses. To combat this imbalance, Hippocrates proposed bloodletting, purging, catharsis, and diuresis as means to remove excess humor. Galen of Pergamum (129–200 AD), a famous Roman physician, declared blood the most influential humor; through his ideas and writings, bloodletting by leeches became the standard treatment for a wide range of conditions including mental illnesses, eye disorders, cysts, boils, pneumonia, and tonsillitis (2). Hirudo medicinalis, a European medicinal leech, was typically used for bloodletting; at each feeding, this leech was engorged by approximate- ly five to ten milliliters of the patient’s blood (1-2). Many physicians ardently believed in bloodletting, notably Dr. Benjamin Rush (1745-1813). He had a simplistic view of disease: all febrile (fever-related) illnesses were due to the convulsive action of blood vessels. As a result, Dr. Rush often removed large amounts of blood several times to dampen
the excitement of the patient’s vasculature. Towards the beginning of the nineteenth century, leeching became the most common medical procedure in both Europe and America as a means of preventing or treating infection and disease. In some cases, patients lost as much as 80 percent of their blood in a single leeching session (2). The popularity of bloodletting waned as this mode of treatment was implicated in the deaths of both Charles II of England and United States President George Washington (2). Due to the implication of the practice in various deaths, researchers began to study the proposed benefits of bloodletting. An increasing number of research studies debunked the efficacy of this practice, notably one study conducted by Dr. Pierre Louis, widely regarded as the father of epidemiology. Dr. Louis examined the clinical outcomes of 77 patients with acute pneumonia and compared the results of patients treated with bloodletting in the early phase versus late phase of illness. Statistical evidence from his experiment showed that bloodletting was ineffective for pneumonia, a febrile illness, diminishing the value of this treatment in society. Through a series of studies with bacteria, German clinician Dr. Koch established the germ theory, which stated that pathogenic microorganisms can cause disease. With the advent of this scientific theory, the current basis for many diseases, the humoral theory of disease was invalidated, and thus, the use of bloodletting slowly decreased (2-3). Today, medicinal leeches are primarily utilized in Western medicine for reattachment operations, skin grafts, and reconstructive plastic surgeries (6). These procedures utilize microsurgical techniques involving a microscope and other specialized instruments, and have a 98% success rate (3). In rare cases, however, a flap or reattached body part develops venous congestion. This dangerous condition occurs when tiny, thin-walled veins involved in these microsurgical procedures cannot carry an appropriate amount of blood away from the surgical site. Consequently, deoxygenated blood pools in the veins and cannot flow back to the heart and lungs for reoxygenation. If this condition is left untreated, carbon dioxide accumulates in the stagnant blood and causes tissue death. To remedy this condition, physicians recommend medicinal leech therapy (3-4). Leech saliva contains hirudin, an anticoag-
ulant and antiplatelet agent that acts to prevent blood clots and re- duce the amount of congested blood in tissues. Other chemicals in the saliva promote blood flow to the dam- aged area and eradicate stagnation, thus prevent- ing tissue necrosis or death in the reattached body part (3, 6). In these cases, one to two leeches can be applied to the area to feed for approximately 30 minutes, ingesting about 15 grams (0.5 ounce) of blood (1). Once fully engorged, the leech detaches itself and the appendage bleeds for an average of 10 hours, resulting in 120 grams of blood lost. When the bleeding has almost stopped, another leech is applied to the appendage to stimulate angiogenesis, or the development of new blood vessels, while existing veins widen and accommodate more blood flow (3-6). In a study conducted by Hebrew University-Hadassah Medical School researcher Dr. Mumcuoglu, 15 patients afflicted with venous congestion of skin flaps received treatment consisting of application of an average of 9.2 leeches to each flap. The tissue of these patients gradually regained a working circulation network of new blood vessels and a good blood supply within three to five days (7). This treatment is also painless and promotes healing: when a leech bites, it releases a naturally occuring anesthetic that numbs the specific area and a local vasodilator to improve blood supply in that area. Additionally, to reduce the risk of infection from leech therapy, medicinal leeches are bred specifically for medical use in leech farms, sanitized before attachment Figure 1 The ancient application of leech therapy in the late 1800s. to the patient, and only used once. After they have been fed, the leeches are cropped off, anesthetized, and disposed of as medical waste (4, 6). The U.S. Food and Drug Administration approved use of leeches in 2004 for localized venous congestion after surgery, acknowledging these organisms as living medical devices (3, 6). A growing number of research articles has been published on the various ther- apeutic applications of leeches, particularly in cardiovascular disease. Clinical trials have shown that leech therapy also serves as a good treatment option for osteoarthritis, a common degenerative joint disease. Dr. Michalsen and his team at the
