Part II: Evidence of the link between animal agriculture and antimicrobial resistance

Yesterday, I wrote about the basics of animal agriculture and antimicrobials. Today, I’ll dive deeper into the issues.

Part II: Evidence of the link between animal agriculture and antimicrobial resistance

What is antimicrobial resistance and why should I care about it? Antimicrobial resistance occurs when microbes have developed the ability to evade antimicrobials, survive antimicrobial treatment, multiply, and infect others. Microbes are able to survive partly because antimicrobial treatment may kill off the sensitive microbes and leave the more adapted ones to adapt to the antimicrobial and multiply.

Microbes can become resistant to multiple drugs. This makes the infection difficult or impossible to treat. By its very nature, an infection will spread to others, endangering more people with resistant infections.

The FDA has a pretty great video explaining the process of antimicrobial resistance.

Is there any evidence of association between antimicrobial use in animal agriculture and antimicrobial resistance in humans? Yes. Most of the evidence is based on studies of foodborne illness such as Salmonella and Campylobacter because the foodborne route is the most common way that resistant microbes are transferred from animals to humans.

Some resistant bacteria will themselves endanger human health. Others which cannot make humans ill will share their resistant genetic code with microbes that can make humans ill. These previously vulnerable, pathogenic microbes become resistant when they receive the resistant genes.

Using antimicrobials at sub-therapeutic levels to enhance growth means that all bacteria in an animal’s body is regularly exposed to low levels of antimicrobials. The most susceptible microbes will be killed or incapacitated, but the surviving ones will become increasingly resistant to the antimicrobial used.

How does using antimicrobials in animal agriculture contribute to human foodborne illness? The CDC report “Antibiotic resistance threats in the United States, 2013” outlines exactly how these two issues are related:

  1. Antimicrobial-resistant microbes may be formed through biological (e.g. selective pressure, mutations) or human (e.g. antimicrobial misuse, inadequate diagnostics) avenues.
  2. Antimicrobials used in animal agriculture kill off susceptible microorganisms while allowing resistant microbes to survive.
  3. Resistant microbes can be passed from animals to humans through fecal or other forms of contamination of food.
  4. When humans eat contaminated food, they develop infections (e.g. coli) that cannot be treated with antimicrobials. For generally healthy people, this may not be problematic, as their immune system will fight the infection itself. However, some people will need a boost from antimicrobials—antimicrobials that are now useless.

Beacause of this strong connection between animal antimicrobial use and human illness, CDC recommends that antimicrobials are used only to treat infections rather than to enhance growth. The CDC calls this antibiotic stewardship. 

What are some other ways animal agriculture-induced antimicrobial resistance affects human health?

  • Infections that would not have otherwise occurred
  • Treatment failures
  • Increased severity of infections (Source.)

Is animal agriculture the only cause of antimicrobial resistance? Definitely not. The other major contributor to antimicrobial resistance is improper human medical use. For example, when doctors prescribe antibiotics for a viral infection, the antibiotic will not treat the viral infection. However, the antibiotic may kill off a few bacteria from a minor bacterial infection, leaving only the remaining bacteria resistant to the drug.

 

Come back tomorrow for Part III: The Stuff That Will Keep You Up At Night

Part I: The basics of animal agriculture + antimicrobial resistance

Before antimicrobials, strep throat could be fatal. Nearly every child who had bacterial meningitis died. A small cut, once infected, could kill a person. In my mind, antimicrobials are neck-and-neck with vaccines and basic sanitation as the most important health and medical discoveries. And yet we are quickly losing our grasp on treating infections. Multi-drug resistant tuberculosis is on the rise, as is drug resistant gonorrhea, and MRSA strikes fear into anyone working or staying in a hospital.

Animal agriculture may have something to do with this. Antimicrobials are used extensively in the livestock and poultry industries. This piece is Part I of my exploration of the links between animal agriculture and the looming public health crisis of antimicrobial resistance.

The basics of animal agriculture and antimicrobial resistance

What is the difference between antibiotics and antimicrobials? Strictly speaking, an antibiotic is a substance produced by a microorganism that is used to kill or inhibit the growth of other microorganisms. Penicillin, grown from fungus, is an antibiotic.

An antimicrobial can be naturally-occurring, semi-synthetic, or entirely synthetic compound that it used to kill or inhibit the growth of other microorganisms. Antimicrobials include sulfonamides and amoxicillin. Antimicrobials can be used against bacteria, viruses, fungi, and protozoa such as malaria and toxoplasma gondii.

When discussing animal agriculture, the term antibiotic resistance is often used. However, because it doesn’t include synthetic or semi-synthetic antimicrobials, I’m going to follow the lead of the United Nations, the World Health Organization, and the World Organization for Animal Health and use antimicrobial resistance.

How are antimicrobials used in animal agriculture? Antimicrobials are primarily used as growth promoters and are given to livestock and poultry at sub-therapeutic levels, meaning that the levels at which the antimicrobials are administered are below the threshold that would fight off infection. Using antimicrobials as growth promoters is a direct result of the ever-increasing demand for meat and animal products.

Antimicrobials increase animal growth rate by 2-10% and feed conversion efficiency 3-9%. It’s unclear how or why this happens, but some researchers suggest that cytokines released when the immune system fights off infection may stimulate growth-inhibition hormones. Others suggest that antimicrobials keep animals’ gut bacteria in check, allowing the energy that would have been used to stave off infection to instead be used for growth.

Because nearly all animals raised for food are kept in cramped, stressful conditions, antimicrobials are also used for disease prevention and control (metaphylaxis). The animals live in such a way that makes infectious disease likely—packed in very closely, standing their own excrement—and rather than make changes to their living conditions, the various industries choose to feed the animals preventative antimicrobials.

Antimicrobials are also used when animals get sick, or after an injury or surgery. However, these uses make up just a small portion of the antimicrobials used.

Does animal agriculture really use 80% of the world’s antimicrobials? This statistic is often cited. However, there doesn’t seem to be much evidence to support it. However, this figure includes ionophores, which are not used in human medications but are used as growth promoters.

Which antimicrobials are used in animal agriculture? This table shows a selection of the antimicrobials identified as both critical to human medicine and regularly used in animal agriculture in the Congressional Research Service brief “Antibiotic use in agriculture: Background and legislation” by Geoffrey S. Becker. I added the columns “Common drugs in this class” and “Human infections treated by this class (selected).”

Antimicrobial class Common drugs in this class Human infections treated by this class (selected) Use in animal agriculture Level of importance for human medicine as defined by the FDA, based on level of difficulty of transmitting resistance across genera and species
Cephalosporin (3rd generation) Cedax, Fortaz, ceftriaxone Gonorrhea; urinary tract; respiratory; pelvic inflammatory disease; pneumonia Disease treatment in cattle and swine Critical
Fluoroquinolone Cipro, Floxin, Avelox Anthrax; hospital-acquired infections, especially pneumonia; urinary tract Disease treatment in cattle Critical
Penicillin penicillin, amoxicillin, flucoxacillin Meningitis; syphilis; Lyme disease; strep throat Disease treatment in cattle; growth and disease treatment in swine High
Macrolide Zithromax, erythromycin Legionnaire’s Disease; chlamydia Disease treatment and prevention in cattle; growth, disease treatment and prevention in swine Critical
Tetracycline doxycycline, tetracycline, Chlamydia; acne and rosacea; typus; plague Disease treatment and prevention in cattle; growth, disease treatment and prevention in swine High
Lincosamide clindamycin, lincomycin Toxic Shock Syndrome Disease treatment in swine High
Streptogramin pristinamycin, quinupristin Vancomycin-resistant Staphylococcus aureus (VRSA) and enterococcus (VRE) Growth, disease prevention in chickens High

How does antibiotic resistance happen? The National Institute of Allergy and Infectious Disease (NIAID) cites seven ways that microbes can become drug resistant:

Biological causes

  • Selective pressure: only the microbes with genes that make them resistant to antimicrobials are able to survive
  • Mutations: random changes in the genetic code protect some microbes from antimicrobials
  • Gene transfer: microbes can get genes from other, drug-resistant microbes

Human causes

  • Inappropriate use: prescribing antimicrobials for a disease that cannot be cured by them—for example, prescribing an antibiotic for a cold
  • Inadequate diagnostics: using a broad-spectrum antimicrobial when a specific one may be more effective, or being unsure of the underlying cause of illness and prescribing a drug “just in case”
  • Hospital use: hospital patients are susceptible to infections, but giving them high doses of antimicrobials puts them at risk for resistant infections
  • Agricultural use: NIAID states that agricultural use of antimicrobials is still debatable as a public health issue.

Now that we’ve covered the basics, check out Part II!

Health benefits of being single / Health benefits of being in a couple

Happy Valentine’s Day! There are health benefits for you if you’re single or if you’re in a happy relationship. I found a few of them (that could be backed up with some kind of evidence) and listed them in no particular order. Remember, the results of one study does not mean something is true, so take everything on this lighthearted list with a grain of salt...or a candy heart.

 Health benefits of being single Health benefits of being in a couple

Benefits of being single

 

Benefits of being coupled up

  • You are more likely to receive adequate and timely cancer treatment.
  • You are less likely to die after cardiac surgery.
  • Holding hands and hugging may help reduce stress. (Though this isn’t limited to romantic relationships!)
  • If you’re a man, you’re likely to drink less alcohol than your single counterparts.
  • Frequent sex may increase your immunoglobulin level, which is an indicator of immune health
  • Your wounds may heal faster.

Also! My dear friend Lorelei and I started a podcast miniseries about love songs. It’s called Love It! a Music Podcast with Lorelei + Teagan. Our first episode focuses on stories that our friends and family told us about their personally meaningful love songs. Stream or download it for your listening pleasure.

Friday Five: Veterans, birth, ACA, Politifact, #HealthPolicyValentines

It's back by popular demand! (Okay, maybe only Carmen asked if I was ever going to write another Friday Five, but she's so awesome that she counts as at least ten people.) Each Friday, I use five sentences to summarize and comment on five important, interesting, or just plain amusing health stories from the week. Obama signs vet suicide prevention act Yesterday, President Obama signed the Clay Hunt Suicide Prevention for American Veterans Act, legislation aimed at improving the VA’s mental health care and removing barriers that prevent veterans from seeking treatment for mental health conditions. Death by suicide is particularly high among veterans over age 50. While their wish to end their lives may not be directly related to their service, the VA has a responsibility to care for veterans who qualify for VA care and are in need of it. The VA is notoriously problematic, and I hope that the newly-required external audits built into this Act will keep it accountable. After asking them to do what nearly every other American refuses to do, we continually fail our veterans--this Act is just a fraction of what they deserve.

Birth: Home versus hospital A short literature review by Dr. Rikki Lewis reveals interesting findings about the complexities and controversies surrounding home birth.

  • In the US, home births increased by 29% between 2004 and 2009.
  • Among studies investigating the risks and outcomes of home birth, there is little consistency in patient selection and the necessity of reporting infant deaths after transport to the hospital means that those deaths are reported as hospital deaths rather than deaths at home.
  • Policies for deciding to take a woman laboring at home are much clearer in the United Kingdom than in the US.
  • Home births are far less expensive than hospital births, which average about $20,000.

As the hospital versus home birth debate continues, it will be important to use correctly interpreted research as the basis for argument.

ACA open enrollment ends on Sunday The last day to sign up for insurance through the Marketplace is Sunday, February 15. According to the awesome website ACAsignups.net 10.5 million people have already signed up. Originally, the Department of Health and Human Services estimated that 13 million people would receive coverage during the open enrollment period, but later readjusted the estimate to between nine and ten million. If you need insurance and haven’t signed up, do it now...don’t procrastinate! (Also, can we take a moment to wonder why the “marketplace.gov” doesn’t redirect to healthcare.gov? Missed opportunity!)

 

Politifact takes on measles and vaccines One of the best, most useful sites ever, Politifact, evaluated the truthfulness of public statements about measles and vaccines. While their website could use a redesign to make articles like this one easier to read, the information they’ve provided is really valuable. They’re successful in debunking the “vaccines have mercury” claim and Rush Limbaugh’s accusation that Obama’s immigration policy allowed measles to enter the United States through Mexico. Politifact also highlights some of the true statements made by Megyn Kelly and other cable news pundits. While you’re reading their website, take a look at their ratings of statements about health care in general.

Health policy nerds love bad jokes Valentine’s Day isn’t only about romantic love. It can also be a time for you to express your deep, abiding passion for one of the nerdiest arms of public health: policy. Back in 2011, Emma Sandoe started the hashtag #HealthPolicyValentines so we could enjoy gems such as:

and

Groan worthy? Maybe, but totally great anyway.

Have an awesome Friday. I'll be back here tomorrow with a Valentine's Day-themed post!

Writer's Block

I'm struggling with writer's block today. When I started this project, I made myself an editorial calendar. It says that today is supposed to be a personal post. I've started two different pieces, gotten about halfway through, and realized "This is going nowhere." I started working on this one because my creative writing teachers used to say that if you can't think of anything to write, then you should write about how you can't think of anything to write about.

I thought that if I just made myself write for a few hours everyday, I would suddenly become a super writer and would be able to have fully formed ideas, expressed perfectly, flow from my brain and onto your screen. Of course, I'm only eleven days in (twelve when you read this) and of course that hasn't happened. Of course it hasn't! What was I thinking? I consider myself a writer--why was I naive enough to think this would magically become easy after just a few days of discipline?

This has been harder than I thought it would be. Because I feel so passionately about doing appropriate research and talking about things that I actually understand, I often find myself researching a topic, realizing that it is way beyond my ability to write 700 words about it on such a short deadline, and then have to start over. There are plenty of bloggers out there who write about their daily lives and churn out the posts effortlessly. This is a different genre, though, so the prep work of research, writing, and editing is more time consuming.

But I'm also really glad that I decided to do this self-imposed challenge. I like that I'm making something every day, even if it's just a short post complaining about writer's block. I like that I'm learning about new topics. I hope that I'm learning how to research and write more efficiently.

I haven't yet found the ability to achieve the quick turnaround, though I think it's in me somewhere. With more practice, I'll find it.

Would you look at that? I just wrote a personal post. Now I can go check today off my editorial calendar.

Awesome Infographic: The Secret Life of Water

Infographic describing clean water and water sanitation problems worldwide This great infographic put together by Mairi McKay, George Webster, and Matt Baringer of CNN uses data from UNWater to illustrate important facts about drinking water around the world. Some of the stats:

  • 80% of illnesses in the developing world are related to water.
  • 1 in 4 urban residents worldwide do not have access to clean water--only 11% of city dwellers in Uganda can safely consume the water.
  • While nowhere near comparable to what’s happening in the developing world, it’s surprising to see that 3% of Americans living in cities do not have access to safe water.

As water shortages continue and inevitably worsen, these problems will only be exacerbated. Learn more about the issues and proposed solutions from UNWater, water.org, and the WHO.

Study shows no link between HPV vaccine and increased sexual activity

Big news on the sexual health front: a new longitudinal study was published yesterday in JAMA showing that young women who have received the HPV vaccine are no more likely to contract other STIs than unvaccinated women. While it is never a good idea to make generalizations about anything based on one study, this particular one seems well-designed and will hopefully lead to further study on this question. 'The Public Vaccinator' by Lance Calkin. Credit: Wellcome Library, London.

HPV causes cervical, vaginal, and anal cancer and has been connected to various head and neck carcinomas. The vaccine protects against four strains of the virus most often responsible for those cancers. To be clear: the HPV vaccine is a vaccine against cancer. Despite the potential benefits, many parents (and non-parents) fear that by giving their child the HPV vaccine, their child will feel free to engage in risky sexual behavior.

Because of this fear, HPV vaccine uptake has been abysmal in the United States. Only about half of young women and one-third of young men have received the first dose of the HPV, and even fewer have completed the three-dose series.

Looking at a sample group of women over 208,000 women aged 12-18, researchers found that young women recieved the HPV vaccine were no more likely to seek treatment for chlamydia, gonorrhea, herpes, HIV/AIDS, or syphilis than were unvaccinated women. That’s right, there was no evidence that getting the HPV vaccine increased the likelihood of being diagnosed with an STI.

Using pharmacy claims, researchers also determined that vaccinated women were more likely to use oral contraceptives. 17.9% of vaccinated women across age ranges received a prescription for hormonal birth control while 9.2% of unvaccinated women did. This could be due to a few factors: young women who intended to engage in any sexual activity were more likely to request the vaccine as well as contraceptives; the HPV vaccine was suggested by doctor during appointments for acquiring contraceptives; or parent perception of daughters’ likehood of being sexually active influenced their decision to vaccinate or seek contraceptives for their child.

There are, of course, some limitations to this study. The researchers were only able to access records, so by design they missed undiagnosed STIs, may have included STI screenings rather than diagnoses, and omits the use of non-prescription contraceptives like condoms. Researchers were also unable to use records from anonymous clinics. Researchers also could not acquire information about SES and motivations for receiving the vaccine. This study also does not look at young men in the same age range, which would give a more complete picture of how HPV vaccine impacts adolescent sexual activity.

The psychology of vaccine risk perception is fascinating. Beyond the concerns of “naturalness,” parents who are less inclined to vaccinate may feel more responsible for potential injury to their child if the injury is connected to a vaccine rather than to a disease that could have been prevented by that vaccine. A parent whose child has a seizure after the HPV vaccine may feel more responsible for that event than if the child contracts HPV. I wonder how the parents would feel if, after a decade, their child is diagnosed with an HPV-related cancer.

To an extent, I get it. I’m not a parent, but I do possess empathy and can imagine how frightening parenting must be. The world seems full of danger, and parents want to do everything in their power to keep their children safe. Sometimes not acting--not vaccinating--seems safer than risking the side effects of the vaccination or of the disease itself.

Fearing risky adolescent sexual activity also makes some sense to me. Most parents don’t want to see their child become a parent during their sophomore year of high school. Most parents don’t want their child to live with HIV or herpes.

But nearly everyone becomes sexually active at some point in their lives, and about 70% of people have their first sexual experience before age 19.  Half of sexually active men and women will have HPV. That means that means that when parents decide not to vaccinate their children, they allow their children to have a one-in-two chance of contracting HPV. And while most cases of HPV clear up on their own with no adverse effects, there are more than 33,000 cases of HPV-related cancer diagnosed each year in the United States.

No study can stand alone. We should not take the results of this study and make bold proclamations about young women’s behavior and sexual activity. I do believe, however, that this robust study provides some much-needed evidence that reducing young women’s risk of infection does not turn them into crazed sex machines making risky choices. I look forward to subsequent studies that can provide more evidence for parents to use to make informed choices.

Note: I know that women over age 18 don’t need parental permission in order to get the vaccine and may be more inclined to seek it out. But this study looked only at women under age 18, so I stuck to that age group as well.

Daniel Hale Williams, heart surgeon and visionary

As part of my 28 day writing challenge, which coincidentally falls during Black History Month, I plan to highlight some of Black Americans’ contributions to public health, medicine, and wellness. Born in rural Pennsylvania and raised in Baltimore, Daniel Hale Williams, MD, made his mark on medicine in Chicago. When a young woman named Emma Reynolds approached him for help after being denied admission to nursing school, they decided to open a nursing school specifically for Black women. The school would have a hospital associated with it, in part because the nurses would need somewhere to learn, but also because the few Black physicians in Chicago had limited or no admitting privileges in other hospitals.

Daniel Hale Williams successful open heart surgery

Securing funding from prominent Chicago leaders and residents of the surrounding community, the 12-bed Provident Hospital and Training School opened in in 1891. (Contemporary hospital administrators will appreciate that the entire budget for that year totaled $5,429.) Williams was named chief of staff, and Reynold enrolled in the first nursing class. Provident served all people, regardless of race, making it the first desegregated hospital in the United States.

While at Provident Hospital, Williams performed the surgery that would change medical history. When a stabbing victim named James Cornish was in danger of developing life-threatening cardiac tamponade due to a severed pericardium, the sac in which the heart sits, Williams knew he had to operate. He opened Cornish’s chest and found a severed artery and an inch-long tear in the pericardium. Williams repaired both. Cornish recovered, was discharged 51 days later, and lived for another 20 years, making Williams the second doctor to perform open heart surgery.

Of course, this made Williams quite famous. He was soon tapped to be the chief of surgery at Freedmen’s Hospital in Washington, DC. While there, Williams made major changes to the flagging hospital: new, multiracial staff; improved surgical practices; instituted ambulance service; opened a nursing school for black women; and provided staff positions for black doctors. Williams was also among the co-founders of the National Medical Association, created when Black doctors were denied membership in the American Medical Association.

Williams returned to Provident Hospital Chicago in 1898. He was bestowed with numerous awards and accolades, including being the first black man inducted into the American College of Surgeons. Williams continued working until his retirement in 1926. He lived the rest of his years in Idlewild, Michigan, a Black resort community that sounds pretty awesome based on the musical guests alone.

Williams was a revolutionary not only because his surgical prowess enabled him to perform groundbreaking surgery, but because he envisioned a world in which Black medical professionals were afforded the same privileges as white professionals, and he used his stature to work toward that goal. Despite the significant barriers to success that, as a Black man in the post-Civil War United States, he had to overcome, Williams not only championed men but ensured that women would also have a way into the medical field. We have much to thank Williams for, and should remember his contributions to medicine and health.

TissuGlu, measles, and herbs: Cool stuff I read this week

Source. I came across a bunch of interesting articles and bits of news this week, and I thought I’d share them with you. Spend your lazy Sunday catching up on current events.

  • A father asks a California school district to require unvaccinated children to stay home in hopes that his son, whose leukemia is in remission and who cannot be vaccinated, will not be exposed to measles.
  • The names, addresses, social security numbers, and other personal information for up to 80 million Anthem health insurance customers has been accessed by hackers.
  • Prader-Willi Syndrome, one of the only known genetic causes of obesity, causes significant health problems. This piece in the New York Times Magazine highlights Rachelle, a young woman seeking treatment for the syndrome.
  • The BBC published a series of maps illustrating the growth of the Ebola outbreak within Africa and the presence of Ebola on other continents.
  • It’s about time the Americans with Disabilities Act is applied to websites.
  • The FDA has approved a new internal tissue adhesive called TissuGlu (what a creepy name) for use in surgeries removing excess fat or skin and for repairing separated abdominal muscles.
  • Lots and lots of Chinese kids wear glasses.
  • In store-brand herbal supplements, 4 out of 5 contained fillers like powdered rice and asparagus rather than the herbs named on the packaging.

Read up!