Maryn McKenna

Journalist and Author

From Bird Flu to Big Farms: The Rise of China's Agriculture

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Image: Willem vdh/Flickr

Image: Willem vdh/Flickr

In my last post, I talked about the unnerving increase in avian flu H7N9 in China. The novel flu strain, now in its second year, appears to be spreading more rapidly than it did in its first appearance, and also more rapidly than H5N1, the avian flu strain that has caused the most worry internationally.

You can’t have avian flu — or at least, not this avian flu — without birds; most of the people who have been diagnosed with H7N9 had contact with live chickens or visited a market that sold live poultry for slaughter. H7N9 is continuing to spread in China; and so it’s a lucky coincidence that a nonprofit with deep knowledge of Chinese agriculture has just published a series of reports exploring the vast expansion of Chinese production of meat animals, including chickens.

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Antibiotic-Resistant Bacteria Surround Big Swine Farms — In China as Well as the U.S.

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I suspect we think of large-scale confinement agriculture as a uniquely American issue. Possibly that’s because growth-promoter antibiotic use, which makes meat-raising efficient, originated in the United States; more likely, it’s because some of the largest firms in that sector — Smithfield and Tyson, for example — are US-based. But public and private research efforts (including the US Department of Agriculture, the United Nations’ Food and Agriculture Organization and the Pew Charitable Trusts) have documented that intensive livestock-raising is increasing in emerging economies such as India and China; as incomes rise, demand for meat does too.

A paper published Monday in the Proceedings of the National Academy of Sciences demonstrates that the unintended consequences of confinement agriculture are occurring in those countries as well. A multi-national team of researchers from Michigan State University and two campuses of the Chinese Academy of Sciences found — well, I can’t put it better than their paper’s title does: “Diverse and abundant antibiotic resistance genes in Chinese swine farms.”

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Resistant Bacteria in Pork — And Problematic Pharmaceuticals Too

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Bad news today from an investigation conducted by Consumers Union that was released on the web and will be published in the January issue of the nonprofit’s magazine, Consumer Reports. Tests on pork chops and ground pork, bought in six cities under a variety of labels, showed high rates of contamination with a range of bacteria, many of which were antibiotic-resistant — and also showed evidence of a drug so controversial that it is banned in some other countries.

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CDC: First Death From "State Fair Flu"

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The Centers for Disease Control and Prevention today reported the first death from influenza A H3N2 variant (H3N2v), the swine flu strain that has been crossing intermittently from pigs to humans since last year. The victim was an “older adult with multiple underlying health conditions,” according to the CDC, and the Associated Press fills in that the victim was a 61-year-old woman from “central Ohio’s Madison County [who] died this week… after having contact with hogs at the Ross County Fair.” In a statement, the Ohio Department of Health says that she was one of 102 cases so far in the state this year. In total, the CDC says, there have been 289 cases so far this year (with Indiana leading, at 138 cases); in 2011, there were 12. Fifteen people have been hospitalized.

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Staph In Pigs And Pig Farmers: The Latest Reports (ICEID 1)

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Photo: AndJohan/Flickr

I’m spending the first part of this week at the International Conference for Emerging Infectious Diseases, a biennial scary-disease nerdgasm that is sponsored by the Centers for Disease Control and Prevention, the American Society for Microbiology and other worthy organizations, and in this iteration has drawn about 1,600 participants from more than 50 countries. (You can see the program here. I had planned to live-blog it, but the hotel was just renovated and apparently they built a Faraday cage into it, since connectivity is a painful trickle.)

On Monday’s agenda, among other intriguing talks: Two updates on MRSA, methicillin-resistant S. aureus, among farmers in two states.

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Government Health Agency Agrees Mega-Farms Are A Health Risk (In The UK)

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It’s very odd sometimes watching how the same issues play out in different parts of the world. The French environment ministry confidently ascribes the growth of seaweed choking its beaches to farm runoff. The European Parliament denounces the establishment of very large-scale “meat factories.” China (China!) enacts a ban on growth-promoting uses of antibiotics in agriculture.

Here in the United States, on the other hand, the government gropes unsuccessfully for a way to put controls on confinement agriculture, despite evidence of its environmental harm, while at the same time those farms grow by an estimated 4,600 hogs and 5,800 broiler chickens per day.

For more of that difference between Europe and the US, look this week to England, where the Health Protection Agency has just rejected the zoning application for a hog farm that was small by US standards, with a plan for only 2,500 sows producing about 20,000 piglets. The HPA said:

… those living up to 150 meters downwind of an intensive swine farming installation could be at risk of adverse human health effects associated with exposure to multi-drug resistant organisms. (this .pdf, p.30 of 44)

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Warning on ST398: Monitor this now

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Drawing your attention: I have a story up tonight at CIDRAP on a new paper by Dr. Jan Kluytmans, a Dutch physician and microbiologist and one of the lead researchers tracking “pig MRSA,” ST398. (All past stories on ST398 here.) It’s a review paper, which is to say that it summarizes key existing findings rather than presenting original research.

Still, it’s important reading because Kluytmans is one of the few scientists who have some history with this bug and understand how quickly and unpredictably it has spread across borders and oceans, from pigs to other livestock, to pig farmers and veterinarians, into health care workers and hospital patients who have no known livestock contact, and now into retail meat in Europe, Canada and the United States.

Take-away: A plea and warning for better surveillance, so that we can track not only the bug’s vast range, but also its evolution as it moves into new ecological niches — including humans who are buying that retail meat and possibly becoming colonized with it as they prep it for cooking in their home kitchens.

To honor fair use (and in hopes you’ll kindly click over to CIDRAP), I won’t quote much, but here’s the walk-off:

Because the novel strain has spread so widely and has already been identified as a cause of hospital outbreaks, it should not be allowed to spread further without surveillance, Kluytmans argues.”It is unlikely that this reservoir will be eradicated easily,” he writes. “Considering the potential implications of the reservoir in food production animals and the widespread presence in meat, the epidemiology of [MRSA] ST398 in humans needs to be monitored carefully.”

The cite is: Kluytmans JAJW. Methicillin-resistant Staphylococcus aureus in food products: cause for concern or case for complacency? Clin Microbiol Infect 2010 Jan;16(1):11-5. The abstract is here.

"Pig MRSA" in the EU – long-awaited survey

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It’s not very likely that people will be eating much pork today — OK, maybe some pancetta in the Brussels sprouts — and that’s good, because there’s lots of news today about MRSA in pigs.

(In fact, there’s a ton of news just this week. Make it stop.)

The European Food Safety Authority has published a long-awaited, European Union-wide survey looking for the presence of MRSA in pigs. Here’s the key points: Investigators found MRSA on 1 out of 4 farms where pigs were being raised and in 17 of the 24 EU states. (Two non-member states were included in the analysis.)

Strictly speaking, this is not a survey of MRSA in pigs; the study samples not the pigs themselves, but the dust in pig-raising sheds. The sites were 1,421 breeding farms and 3,176 farms where pig are raised to slaughter age. By far the most common strain was MRSA ST398, though other strains were detected, including some known human strains. The prevalence in various countries went from a low of 0 to as high as 46% of farms. (Highest, in descending order: Spain, Germany, Belgium, Italy, Portugal. The Netherlands, where St398 was first identified, had a prevalence of 12.8%. Countries reporting no MRSA: Bulgaria, Cyprus, Denmark, Estonia, Finland, Hungary, Ireland, Latvia. Lithuania, Luxembourg, Sweden, the United Kingdom, Norway and Switzerland.)

The report closes by recommending comprehensive monitoring of pigs for MRSA, as well as monitoring of poultry and cattle.

About the potential of ST398 crossing to humans, it has this to say:

In humans, colonisation with MRSA ST398 originating from pigs has been identified as an occupational health risk for farmers and veterinarians and their families. Although MRSA ST398 represents only a small proportion of the total number of reports of human MRSA infections in the EU… in some countries with a low prevalence of human MRSA infection, CC398 is a major contributor to the overall MRSA burden.
In most cases, colonisation with MRSA ST398 in humans is not associated with disease, although clinical cases associated with MRSA ST398 have been reported. MRSA ST398 can be introduced into hospitals via colonised farmers and other persons in a region with intensive pig farming. Therefore, MRSA ST398 may add substantially to the MRSA introduced in health care settings. However, it seems that the capacity for dissemination in humans (patient-to-patient transmission) of livestock-origin MRSA, in particular ST398, is lower as compared to hospital-associated MRSA).
… Food may be contaminated by MRSA (including ST398), however there is currently no evidence for increased risk of human colonisation or infection following contact or consumption of food contaminated by ST398 both in the community and in hospital.

Britain’s Soil Association, which pressed for the study to be done, has released a statement quoting the food safety agency warning that the testing method may have underestimated MRSA’s presence on farms, and warning that if ST398 is not yet in England, it is certainly soon to arrive. Germany’s Federal Institute for Risk Assessment also released a statement, admitting that ST398 in German pig stocks is “widespread.”

The report is here, executive summary here, and press release here. All well worth reading.

Restricting antibiotics in animals: Start by restricting access

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Constant readers, those of you who follow the pressing issue of MRSA in animals will know the work of J. Scott Weese, DVS, associate professor of pathobiology at the University of Guelph in Ontario and supervising author of many crucial papers on MRSA in food and companion animals, including the first finding of MRSA in pigs and pig farmers in North America.

You may not know that Weese and his postdoc Maureen Anderson publish an excellent blog on veterinary and zoonotic diseases called Worms and Germs. This weekend they have an important post that deserves wider attention: Antibiotics: A Dose of Common Sense. In it, they propose that one way to reduce the overuse of drugs in food animals is to make animal antibiotics prescription-only. It’s worth taking the time to read it.

Those of you in the cities may not know this, but out here in the Great Flyover, antibiotics for veterinary use are surprisingly easy to buy (as I discovered when I stumbled into a farm-related store in search of a Carhartt jacket against the Minnesota winter). They’re not even over-the-counter — they’re on the shelf, or stacked on the floor with the implements and feed, or blended into the feed itself. And as Weese points out in this post, they are also available without prescription over the Internet (as human antibiotics are too).

It’s a potentially controversial proposal: I don’t think I have any farming readers, but I would imagine their response would start with an objection to the extra cost of hiring a veterinarian to assess whatever situation might require the drugs. And since most farmers (NB: not the overarching ag-biz companies, but the farmers themselves) exist on razor-thin economic margins, they would have a point. But as we know from the excellent work of Extending the Cure and the Center for a Livable Future, unnecessary antibiotic use comes with a cost as well — one that is borne by all of us when antimicrobial resistance prevents antibiotics from working.

MRSA in pig-farm workers – very high rates

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Let’s go back for a moment to what I think of as the “third epidemic” of MRSA: ST398 and the other strains that reside in animals and cross to humans. (In my personal taxonomy, the first and second epidemics are hospital-acquired and community-associated.)

Via Emerging Infectious Diseases, the open-access journal published by the CDC (Do I have to keep telling you to read it? It’s free. It’s good. Your tax dollars pay for it.), comes a report of surveillance for MRSA colonization of pig-farm workers, conducted in Belgium by researchers from Erasmus Hospital of the Free University of Brussels, and the Veterinary and Agrochemical Research Centre of Brussels. The group persuaded 127 farm workers on 49 farms to be tested for colonization, or asymptomatic carriage, of MRSA; at the same time, they tested 30 randomly selected pigs on each farm.

They found very high rates of colonization, higher than have been found in patients in hospitals or residents of nursing homes: 38% of the farm workers carried MRSA ST398, the pig strain (plus, an additional 17% carried various strains of MSSA, drug-susceptible staph). There was a clear association between colonized farmers and colonized pigs: Out of 1500 pigs sampled, 44% carried ST398 — and half of the workers on farms with colonized pigs were colonized also, compared to only 3% of workers on farms where pigs did not carry the bug.

In a bit of good news, the researchers found only one farm worker who had suffered any MRSA disease from ST398, a man with a lesion on his hand. There was no invasive disease, though ST398 has been associated in the past with pneumonia and endocarditis.

Workers were more likely to acquire the bug if they had regular contact with pigs, dogs or horses, which makes intuitive sense. But in an odd finding, their odds of acquiring ST398 did not go down if they wore protective clothing — which is to say, aprons, gloves and masks did not protect them from picking up the bug, leading the researchers to wonder whether airborne spread or contaminated surfaces are playing a role in transmission.

So what does this mean? The lack of invasive disease in this population must be good news; and it’s consistent with a number of papers that have reported low rates of disease from ST398 even when colonization is present. But to me, the high rate of colonization must be bad news. The more of this bug there is (and every researcher who looks for it seems to find it), the more chance there is of the bug adapting in an unpredictable — potentialy more resistant, potentially more virulent — way. If that did happen, it could well go undetected for a while — because as swine flu has been teaching us, disease surveillance in animals is patchy at best, and new pathogens can and do arise and ciruclate for years before being detected.

For more on the paucity of surveillance in animals, see my CIDRAP colleague Lisa Schnirring’s story here. For a complete archive of posts on “pig MRSA” ST398, go here.

The cite is: Denis O, Suetens C, Hallin M, Catry B, Ramboer I, Dispas M, et al. Methicillin-resistant Staphylococcus aureus ST398 in swine farm personnel, Belgium. Emerg Infect Dis. 2009 Jul; [Epub ahead of print] DOI: 10.3201/eid1507.080652.