Feedstuffs is part of the Informa Markets Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Livestock-to-human MRSA transmission far from 'confirmed' (commentary)

Livestock-to-human MRSA transmission far from 'confirmed' (commentary)

A RECENT headline in one of America's daily e-magazines read: "Livestock-to-Human MRSA Transmission Confirmed."

"Confirmed" really can have only one meaning when used in this context, and that is to "prove to be true and correct," according to my dictionary.

The story was about a study published in EMBO Molecular Medicine in March.

I am sure there were other similar headlines that also tried to sway readers to oppose antibiotic use in animals raised for food.

I have no clue as to the veracity of the journal or if its articles are even be peer reviewed, but my point today is about word choice when trying to drive home messages, hidden or not.

The story said, "Using whole-genome sequencing, scientists have found conclusive evidence that a type of methicillin-resistant Staphylococcus aureus (MRSA) that caused infections in Denmark came from livestock -- adding to concerns that food animals are a significant MRSA reservoir for human infections."

Two women in Denmark were diagnosed with MRSA infections, and the researchers noted that both lived on farms.

"Patient A had two cows, two horses and a dog," the study noted. In Nebraska, where I spent the summers and Saturdays of my youth working on a farm, we would call that a small back yard with a fence. We would not glorify it by calling it a farm.

Patient B had a "flock of 10 sheep." We would call her a hobby farmer, at best.

Patient A had MRSA in her nasal passages and in her blood. One of her two cows tested positive for a strain of MRSA that was slightly different than hers but, the scientists said, close enough to link them together.

Okay, so, what was the source?

Patient A was probably colonized with MRSA in her nasal passages, just as 1.5% of all Americans are. Could she have sneezed into her hand and then gently petted her pet cow on the nose, infecting the cow? She most certainly could have.

I am guessing that with two cows, two horses and a dog, Patient A considers all of her animals to be pets, not a future part of the food chain.

In fact, the scientists said while the results suggest that a transmission occurred between the two, the direction of the transmission "remains unclear."

"Remains unclear" is a long way from "CONFIRMED" or "CONCLUSIVE EVIDENCE."

Patient B had a wound isolate that also had three to five DNA variations from two of her sheep. The other sheep had MRSA, but with a greater deal of diversity. The scientists suggested that MRSA perhaps had been introduced into the flock multiple times.

Although I doubt that the flock interacts with other animals on other "farms" in the area, the scientists concluded, "It is most likely that the direction of transmission was from sheep to human."

"Most likely" is stronger language than "remains unclear," but it is still a long way from conclusive evidence.

No doubt, there will be "experts" who claim that this is undeniable proof of animal-to-human transmission.

So, what? Zoonotic diseases, those spread from animals to people, account for 61% of the pathogens known to cause human illnesses. Diseases like O157:H7, hantavirus and monkey pox are zoonotic.

Maybe MRSA will join the list, but not as long as the scientists do not categorically claim, in peer-reviewed articles, that they have confirmed -- with conclusive evidence -- the direction of the spread.

Journalists and the anti-antibiotic crowd cannot and should not make that declaration in what appears (to me, at least) to be an effort to further misinform the public and misconstrue the facts.

I acknowledge that the author of the story I referenced did do proper research for both sides and quoted Iowa State University professor Dr. Scott Hurd as saying, "It is irresponsible science to make conclusions that one came from another in the absence of some other information."

Hurd also noted, "We do all live in the same environmental, bacterial ecosystem."

MRSA is out there, and it started from hospital environments. That it would spread should be no surprise.

Just as Escherichia coli is now considered an environmental hazard that spreads from cows' intestines to leafy vegetables, MRSA has evolved from being just a nosocomial, or hospital-acquired, infection to one that's increasingly being recognized as a community-acquired infection.

Animal antibiotic opponent Rep. Louise Slaughter (D., N.Y.) responded to the recent story by saying, "This study ends any debate."

Wow. Simply saying that the direction of transmission "remains unclear" is really all it takes to "end any debate"?!

Only 18% of all antibiotics SOLD FOR USE IN ANIMALS, by weight, are used in human medicine in the U.S. Let's keep the debate alive, Rep. Slaughter, but let's pepper it with facts, not innuendos and sensationalism.

Here are some facts to chew on:

* Animals get MRSA infections, and animals die from MRSA infections. They are especially common in companion animals, like dogs.

* Who gave our animals the MRSA that used to be limited to humans and was acquired only in hospital settings? We humans did.

* We humans created MRSA in hospital settings. The antibiotics used in animal husbandry did not create MRSA.

*Dr. Richard Raymond is a medical doctor by training and a former undersecretary for food safety at the U.S. Department of Agriculture.

Volume:85 Issue:16

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.