Tara C. Smith is an Assistant Professor of Epidemiology. Her research involves a number of pathogens at the animal-human nexus. She also writes for The Panda's Thumb and previously for WIRED SCIENCE's Correlations. Please note the views expressed on this site are Dr. Smith's alone and may not be representative of the groups mentioned above.
Back in November, I blogged about one of our studies, examining methicillin-resistant Staphylococcus aureus (MRSA) in Iowa meat products. In that post, I mentioned that it was one of two studies we'd finished on the subject. Well, today the second study is out in PLoS ONE (freely available to all). In this study, we focused only on pork products, and included 395 samples from Iowa, Minnesota, and New Jersey. We also looked at not only conventional meats, but also "alternative" meat products. Most of the latter were products labeled "raised without antibiotics" or "raised without antibiotic growth promotants"--in the markets we tested, very few USDA-certified organic products were available unfrozen, and we were looking for fresh meat products.
In our previous paper, we found MRSA on 1.2% of 165 meat samples. In the current study, we found a higher prevalence--6.6% of 395 samples were contaminated with MRSA. (More about the differences in methods between our two studies later). Interestingly, we didn't find a statistically significant difference in MRSA prevalence on conventional versus alternative pork products--a finding that surprised me, as it contradicts what we've found to date looking at the sources of this meat--conventional versus "alternative" pig farms. Other groups have also found differences on-farm versus on-meat: a 2011 study looking at feedlot cattle didn't find any MRSA in animal samples, though the same group found MRSA in beef products. So, our disparate findings between farms and meat samples are not unheard-of. However, even though our sample size was larger than other U.S. studies to date, it was still fairly small overall--300 conventional and 95 alternative pork samples over a 4-week sampling period from 3 states, so larger multi-state studies are needed to further examine this angle.
It also suggests that we need processing plants and packing companies to work with us to determine where products are being contaminated--because while there may be arguments about the public health importance of MRSA on meats (or lack thereof), it's very likely that if S. aureus are ending up on meat products, other pathogens are as well.
What does the molecular typing tell us, speaking of contamination source? We carried out analyses on all the MRSA and found that the most common type of MRSA was ST398, the "livestock" strain that we previously found on pig farms in the U.S. We also found two "human" types were common: USA300 (a "community-associated" strain) and USA100 (typically considered a "hospital-associated" strain). In the simplest analysis of these findings, these molecular types (a combination of "human" and "pig" strains) suggests that MRSA on raw pork products may be coming both from farms and from food handlers. However, in real life, it's not quite so straightforward. USA100 types have also been found in live pigs. So has USA300. As such, the source of contamination and relative contributions of live pigs versus human meat handlers currently isn't certain.
Within the MRSA strains, we found high levels of antibiotic resistance, similar to what was reported in the recent Waters et al. study. In ours, 76.9% were resistant to two or more antibiotics and 38.5% were resistant to three or more antibiotics tested. (I'll note that we only had funding to test the MRSA--we weren't able to do these tests on all the methiciin-susceptible strains).
Did MRSA prevalence increase in the period between our first study (spring 2009) and this one (late summer/fall 2010)? I doubt it. For this paper, we used a different sampling method, adding the samples to a sterile stomacher bag so that the entire sample was immersed in the culture medium; for the first paper we used external swabbing and so likely didn't capture as many bacteria. This current study more likely represents the "true" MRSA prevalence. But--all isolates were only called as positive/negative, and we didn't measure the number of bacteria on each piece of meat. So, there theoretically could have been just a few colonies of MRSA on the entire piece of meat, and that would have been called a positive sample, while another meat product covered with hundreds of MRSA would have been put in the same category. Therefore, more subtle differences may exist that we didn't pick up in this study, but we will examine in other ongoing studies.
So--what's the take-home here? Don't assume that any meat product is contamination-free, and always use good food handling/cooking practices when dealing with raw meats. As far as the titular question, well, we're still hashing that one out.
On June 29, 2011, the Wyoming Department of Health was notified of two laboratory-confirmed cases of Campylobacter jejuni enteritis among persons working at a local sheep ranch. During June, two men had reported onset of symptoms compatible with campylobacteriosis. Both patients had diarrhea, and one also had abdominal cramps, fever, nausea, and vomiting. One patient was hospitalized for 1 day. Both patients recovered without sequelae.
During June, both patients had participated in a multiday event to castrate and dock tails of 1,600 lambs. Both men reported having used their teeth to castrate some of the lambs.
Among the 12 persons who participated in the event, the patients are the only two known to have used their teeth to castrate lambs.
Sadly, this wasn't the first time I've heard of such a procedure. This was on Dirty Jobs a few years back (and yes, Mike Rowe participated--not for the squeamish).
On a related note, my grandma always had sheep on her farm. I helped to shear but never castrate. Now I'll have to ask my dad and uncles what method they used...
Oh, Discover. You're such a tease. You have Ed and Carl and Razib and Phil and Sean, an (all-male, ahem) cluster of science bloggy goodness. But then you also fawn over HIV deniers Lynn Margulis and Peter Duesberg. Why can't you just stick with the science and keep the denial out?*
But no, now they've let it spill into their esteemed blogs. I was interested to see a new blog pop up there, The Crux, a group blog "on big ideas in science and how these ideas are playing out in the world. The blog is written by an outstanding group of writer/bloggers and scientist/writers who will bring you the most compelling thoughts throughout the world of science, the stuff most worth knowing." Sounds ok, let's see what stories are up...oh, one on HPV! Right up my alley. And hey, a woman! Bonus.
I rarely write about climate change. As much as it's been hashed out amongst climate scientists, and even many of the former "climate skeptics" have now changed their tune, I readily accept that climate change is happening, and is happening largely due to human activities. More importantly for my field, climate change is also having effects on human health in a number of different ways, from the movement of insect vectors into new areas, to warming of the seas leading to more extreme weather conditions, to the loss of coral reefs and the freshwater that these reefs protect from the surrounding oceans. It's an immense field, and it seems that every time I turn around, another paper is published detailing the public health effects of climate change.
Luckily for me, many of these examples have been carefully documented in a recent book by Paul Epstein and Dan Ferber, Changing Planet, Changing Health. Epstein was a maverick in this field, trained as a physician who had carried out global health research in several African countries. In his previous position helping to run the Center for Health and the Global Environment at Harvard, he led research into a variety of areas in tropical medicine, including the role of climate in disease epidemiology. Unfortunately, as I was finishing up this book last night, the New York Times reported that Dr. Epstein passed away at the age of 67. This is a huge loss to the field, but work in this area will certainly continue, and we're likely to only see more connections between disease and global warming in the coming years and validation of his passions and ideas.
"Changing Planet, Changing Health" is deceptively expansive. It's a mere 300 pages before notes and index, but it takes you on a journey investigating the movement of mosquitoes in Africa, cyanide in Honduras, soybean rust in Illinois, pine beetles in Colorado, and even flooding in Cedar Rapids, Iowa. And yet, the book never felt disconnected to me--Epstein & Ferber manage to draw the myriad climate-associated threads together into a well-woven tapestry, and fluidly move from one topic to another. They also discuss what needs to be done to curb this destruction in the last chapter.
Of course, the last chapter is also one of the toughest. While climate change is harming our health in a thousand different ways every day, there's still denial in many circles that it's even happening, and none of the solutions to curb it are easy. Furthermore, too many people still see it as "just a polar bear problem" rather than something that actually makes a difference in their lives. This needs to change. Epstein and Ferber succeed in making climate change personal: something everyone who eats and breathes should be concerned about.
Aah, the things one learns when awake at 3AM on a Saturday night. Via a few different Tweeps, I ran across this article from Men's Health magazine, titled "Urgent Warning: Sex with Animals Causes Cancer."
I probably should have just stopped there.
But no, I read the magazine article, which states:
Brazilian researchers polled nearly 500 men from a dozen cities, and found that--we're not joking around here--roughly 35 percent of the men had "made it" with an animal. That's a problem, because screwing a horse, donkey, pig, or any other animal was found to up your likelihood of developing cancers of the penis by 42 percent.
Though the MH write-up makes the research sound ridiculous, it's not a bad paper overall. Starting out with the observation that penile cancer is common in impoverished regions in the world but relatively rare in developed areas, the authors wanted to examine one possible difference in this urban/rural divide: bestiality. So they enrolled 492 individuals who had spent their childhood in rural areas: 118 cases who had penile cancers and 374 controls who were seen at the same clinics for other issues, including check-ups and "cancer prevention" (though it's not really defined what's included in that catch-all). All participants were asked a variety of questions about their sexual history, including sex with animals and humans (frequency, number of partners, the usual drill), circumcision status, as well as other factors that might influence cancer outcomes, such as smoking status and history of sexually transmitted diseases and other health conditions.
The authors did find in the univariate analysis (basically, looking at one factor at a time) that there were several statistically significant differences between the cancer group and the control group. These included smoking, a history of sex with prostitutes, the presence of penile premalignant lesions (not surprising) and phimosis (NSFW), a condition where "the foreskin cannot be fully retracted over the glans penis." As the title suggests, they also found that having sex with animals was significantly higher in the case than the control group (44.0 vs 31.6 percent, p<.008).
When they combined risk factors into their multivariate analysis, a few factors still remained in the model. Phimosis was the big one, with an odds ratio of 10.41; SWA was down the list at 2.07 (95% CI: 1.21-3.52, p=0.007). Penile premalignant lesions and smoking also remained, with odds ratios in the middle of the other two.
Finally, just because I know many of you out there are curious, they also break down those who have SWA by types of animals they, um, frequent:
The animal types most often cited were mares (N = 80), followed by donkeys (N = 73), mules (N = 57), goats (N = 54), chickens (N = 27), calves (N = 18), cows (N = 13), dogs (N = 10), sheep (N = 10), pigs (N = 6), and other species (N = 3).
Yes, chickens for 27 of them. I don't even want to know, but I'm sure if I did, I could find out somewhere on the Internets. Please, don't educate me on that one. They also note that almost a third of the men reported "SWA with a group of men." I'm leaving that one alone as well (especially as that one wasn't any different between cases and controls, so it didn't seem to be an important variable for penile cancer development).
So how do they explain these findings? Their discussion is a bit odd, in my opinion, and narrows in on the SWA finding to the exclusion of their other significant risk factors. Of course, coming from my background, my first thought regarding SWA and cancer jumps to infectious agents. They acknowledge in the introduction that the human papillomavirus (HPV) is associated with about half of penile cancers. Other species of animals can also be infected with papillomaviruses, such as the rabbit of jackalope mythology. A previous study identified five potentially novel papillomaviruses in Australia, just by doing skin swabbing. As such, it's certainly safe to say that we know very little about the diversity of these viruses that exist in other animal species, much less their cancer-causing potential. It would be fascinating to look at tumor samples from the men in this group who were known to have sex with animals, and see if any novel viruses (papillomas or otherwise) could be identified.
However, they don't limit their suggestion to only zoonotic infections. That's when it gets a bit weird to me, as they say things like:
Speculation exists regarding cancer status as an infectious disease in humans [24,25], as studies have suggested that tumor cells can be transmitted from one mammal host to another within the same species [26,27]. PC is frequent in equines [28], but transmission of malignancies between animals and humans has not been reported.Virology does not consider possible viral movement from animals to humans except in cases of zoonosis, such as rabies or pandemic forms of bird or swine flu. However, the hypothesis that the HIV epidemic resulted from simian-human virus transmission has not been fully explored.
Um, huh? First, the citation they use for the HIV claim is from 1999--indeed, at that point there was still a lot that was unknown about cross-species HIV transmission, but that was 12 years ago! The field has moved on since then. I'm baffled as to what they mean by their first sentence--as far as I know, "Virology" doesn't consider anything--"Virologists" do, and why would this not be a zoonosis? Though I think direct transmission of cancer cells (like in the case of the Tasmanian devil transmissible cancer) would be unlikely, transmission of microbes which could lead to cancer development is certainly plausible and well within the realm of virology/bacteriology/etc. In my opinion, it's infinitely more likely than the idea they also suggest of more directly carcinogenic animal secretions.
There were also a number of limitations in the paper. Though they grouped frequency of sex with prostitutes into a "more/less than ten times" dichotomous variable, I don't see any similar "dose" analysis for the frequency of SWA in their models, even though they did ask the men about this. They make one statement that "long-term SWA (>3 years) was reported by 64% of the PC patients and 46.6% of the controls (P = 0.044)." This difference was statistically significant at the usual cutoff (p< .05), but it doesn't appear that they studied this further--why not? If you have a typical dose-response relationship (the more times the men had sex with animals, the more likely they were to develop cancer in the future), that would strengthen their case for a connection between the two. They also didn't ask about sexual orientation or the nature of the self-reported past STDs. Are any of these participants HIV positive, for example?
Anyway, with these limitations in mind, it does appear that Men's Health got it mostly right: don't have sex with animals if you value your penis. But it's unfortunate that they just go for the sensationalism and ignore the more important variables from a public health standpoint, like "don't smoke" and "if you have abnormal penile conditions, you may want to get those checked out, k?"
References
Zequi SD, Guimarães GC, da Fonseca FP, Ferreira U, de Matheus WE, Reis LO, Aita GA, Glina S, Fanni VS, Perez MD, Guidoni LR, Ortiz V, Nogueira L, de Almeida Rocha LC, Cuck G, da Costa WH, Moniz RR, Dantas Jr JH, Soares FA, & Lopes A (2011). Sex with Animals (SWA): Behavioral Characteristics and Possible Association with Penile Cancer. A Multicenter Study. The journal of sexual medicine PMID: 22023719
Let me sum up where the field currently stands. There have been a number of studies looking at S. aureus on raw meat products, carried out both here in North American and in Europe. In a study from the Netherlands, a large percentage of samples were found to harbor MRSA (11.9% overall, but it varied by meat type--35.3% of turkey samples were positive, for example). Most of there were a type called ST398, the "livestock" strain. This was also found in one Canadian study (5.5% MRSA prevalence, and 32% of those were ST398), but no ST398 were found in a second study by the same group.
Here in the US, prevalence has found to be lower than in that Dutch study (from no MRSA found, up to 5% of samples positive). Furthermore, in the previously-published studies, no MRSA ST398 was found in samples of US meat, though this paper did find plenty of methicillin-sensitive S. aureus (MSSA) ST398 strains. Instead, most of the MRSA isolates have been seemingly "human" MRSA types, like USA100 (a common hospital-associated strain) and USA300 (a leading community-acquired strain).
Why am I rehashing all of this? We have a new paper out examining S. aureus in Iowa meats--and did find for the first time MRSA ST398, as well as MRSA USA300 and MSSA strains including both presumptive "human" and "animal" types. This was just a pilot study and numbers are still fairly small, but enough to say that yes, this is here in the heart of flyover country as well as in the other areas already examined.
As I mentioned, this is one of two studies we've completed examining MRSA on meat; the other is still under review and much more controversial, but I will share that as soon as I'm able. And with the USDA grant, we'll be working on better understanding the role that contaminated meats play in the epidemiology and transmission of S. aureus for the next several years, so expect to see more posts on this topic...
References
Hanson et al. Prevalence of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) on retail meat in Iowa. J Infect Public Health. 2011 Sep;4(4):169-74. Link.
Waters et al. Multidrug-Resistant Staphylococcus aureus in US Meat and Poultry . Clin Infect Dis. 2011 May;52(10):1227-30. Link.
Weese et al. Methicillin-resistant Staphylococcus aureus (MRSA) contamination of retail pork. Can Vet J. 2010 July; 51(7): 749-752. Link.
De Boer et al. Prevalence of methicillin-resistant Staphylococcus aureus in meat. Int J Food Microbiol. 2009 Aug 31;134(1-2):52-6. Link.
Pu et al. Isolation and characterization of methicillin-resistant Staphylococcus aureus strains from Louisiana retail meats. Appl Environ Microbiol. 2009 Jan;75(1):265-7. Link.
Bhargava et al. Methicillin-resistant Staphylococcus aureus in retail meat, Detroit, Michigan, USA. Emerg Infect Dis. 2011 Jun;17(6):1135-7. Link.
As you may have noticed from the extended radio silence, it's been a busy few months between classes (both taking them and giving them), tenure packaging, and research. To add another responsibility to the mix, I gave a talk a few weeks back at the National Institute for Animal Agriculture's annual symposium. This year, the featured topic was antibiotics and agriculture, so I was invited to give an overview of methicillin-resistant Staphylococcus aureus and livestock.
While I'm always happy to give talks to new audiences, discussing my work and the state of the field in general, I have to admit that I was a bit nervous. Given that my work hasn't really yielded the results that many in the ag industry want to hear (who wants to hear about yet another ag-related pathogen to deal with? I get that), I knew the audience might not be exactly the most welcoming, as it was composed largely of industry representatives. However, as I was prepping both my talk and reading up on potential issues that might come up during the planned question/answer period, I realized that blogging has provided me with yet another advantage--a really thick skin.
Now sure, simply being a scientist helps with this as well. You have to get used to rejection and a lot of criticism or you won't make it--grants rejected, papers rejected, ideas torn apart in various grad school defenses, etc. You need to possess, or learn, humility. However, blogging on the topics that I do also leads to a lot of less restrained, and more personal, attacks. If you can get used to those, and gain the skill of either ignoring them or responding in a fitting manner, what can your other critics possibly do to you that are any worse? At least in a conference setting, I'm probably not going to get criticized (openly, at least) on my appearance, age, etc.--hopefully, critics will stick to my science and keep their remarks in that realm. And I'm definitely much more comfortable responding to limitations in my study design or analyses and where they fit into the big picture of the field than defending what I'm wearing.
So, was the Q&A a bloodbath? I felt like I was prepared to handle about anything that could be thrown at me, but alas, it ended up to being a disappointment. I was one of the last talks of the day, and we were running behind schedule due to earlier talks, so the moderator cut off our planned discussion portion to give the final speaker almost his full allotted time. When the meeting ended, I was hoping a few people might come to discuss and challenge my results and conclusions, but that didn't happen either. A bit of a bummer, but I suppose it's better to be over-prepared for questions that don't happen than not ready for those that do, and blogging also prepares you for curveballs. Many of my readers are laymen and sometimes have very basic questions over knowledge that I take for granted, just the same as many in the audience at this meeting (a good number were farmers rather than scientists). So, it prepares one to be able to step back a bit as well, in addition to being ready for the hard science questions.
Is this training limited to blogging? Nope. But I think regular blogging helps you to hone these skills--rather than only needing to answer tough questions during talks or presentations, it's a more regular occurrence (and under less stressful circumstances, I might add). Score one more for science blogging.
I've written a few times about chickenpoxparties. The first link refers to a magazine article describing the practice; the second, a few years later, about a Craigslist ad looking to hold such a party "at McDonald [sic] or some place with toys to play on."
Clearly, as chickenpox cases have become more rare in recent decades due to the success of the chickenpox vaccine, moving toward social media to find infections is the way to go. It allows people to find such cases and expose their immunologically naive children to a serious virus, just as easily as googling Jenny McCarthy Body Count." But now, it's gone even farther, with parents on this Facebook page hooking up to not only find cases/parties, but also to ship contaminated samples through the mail:
Shipping any kind of microbial specimen is a huge pain in the rear, specifically because they have the potential to cause harm. Myself and any employees who do this shipping have to be specially trained, and we have to use a number of specialized shipping containers to mail samples, and take precautions to prevent any leakage etc. out of the packages. Yale has a nice overview of shipping specimens at the link--54 pages long. We also have to apply for permits to ship many of these organisms. Now, Varicella zoster (chickenpox) isn't on their list as far as "select agents," but secretions from a person thought to have or diagnosed with chickenpox would be considered a category B agent (moderate risk of harm):
Biological substances, such as diagnostic or clinical specimens from humans or animals that are known to harbor a pathogen or have a high probability of containing a pathogen.
How should you package these?
Triple packaging. Must pass a 1.8 meter or 4 foot drop test. Packages shipped by air must meet a 95 kPa or 14 psi pressure test of primary or secondary container.
You can see pages 10-11 of the pdf for more instructions. This isn't as easy-peasy as "stick it in a Ziploc baggie." These people are putting a dangerous substance in the mail with the possibility (remote, but there) of making people sick. What if your mail carrier had never had the chickenpox or the vaccine? What if s/he is immunocompromised in some way? These people are taking all the dangers of their "chickenpox parties" and putting them in the mail system. Thank you, Andrew Wakefield and Barbara Loe Fisher.
Now, to be generous, their information page has been changed since the story came out to note "ABSOLUTELY NO SENDING VIRUSES THROUGH THE MAIL. This will not be tolerated and will be deleted immediately. Local only." However, c'mon--people still have messaging on Facebook and I doubt that's really going to stop the determined ones. These people simply don't care about anyone but themselves and are in denial about the fact that chickenpox can kill--the one woman who received samples didn't even know the name of the person they were from. This is so many levels of irresponsible I don't even know where to begin.
Finally, not surprisingly, they're deleting any comments that run counter to their propaganda. I replied to a few comments noting that the link between chickenpox and subsequent Streptococcal infection, for example, and it was gone within 20 minutes. I also noted that both my grandmother (shingles which led to pneumonia) and an uncle I never knew (primary chickenpox followed by pneumonia when he was only a year old) died from Varicella infection. The virus isn't a joke, and those of us who had it, like me, are at a much higher risk of developing complications via reactivation (such as shingles) than those who obtained immunity via the vaccine. I wish the vaccine had been available when I was a kid, and I am frustrated as hell that these types of "parties" still exist in the vaccine era.
Our new Scienceblogs overlords sure have great timing with their new pseudonymous blogging rules. For those who haven't run across that yet, National Geographic has decided to eliminate pseudonyms and force everyone with a blog remaining here (which is already dwindling) to blog under their real names. Meanwhile, out here in the real world, there's a new unfortunate case study (short version: "EpiGate") showing how blogging under one's real name can lead to serious threats and potential loss of employment, among other things.
I blog under my own name (obviously), but if I were starting out now, I probably wouldn't make that choice again. There are a lot of things I would love to write about on here, but can't--or won't--for a variety of reasons. For one, I'm untenured and would like to stay gainfully employed, and ideally even promoted and tenured this academic year, so it's difficult for me to talk about some of the more "slice of life" stuff on here. Even talking about being a woman in science and balancing work and personal issues (oh, there are so many stories I could tell there...) is kind of walking a fine line. I don't necessarily want people who google me for my science to come across posts on my kids' latest exploits, or various personal drama that might make for great blog posts, but also make it weird for external reviewers trying to fairly evaluate me, for instance. Second, I don't enjoy being harassed. Long-time readers will note that it's rare that I write about HIV denial, even though that was such a main topic of this blog once-upon-a-time that it even culminated in a journal article. It's just tiring to be harassed personally by deniers--and even moreso to have my colleagues and administration bullied.
And this is just what's happened to my colleague, EpiRen. He managed to tick off an online bully; said bully then called EpiRen's superiors, who gave him a choice between his blogging and his employment. Not surprisingly, EpiRen eventually ended up pulling his public blog and Twitter feed, to the detriment of anyone who wanted a good source of public health information on the internets.
There's an active discussion regarding the differences between blogging science as a scientist, and blogging as a journalist under one's real name. A journalist's job is to write for the public; a scientist's, honestly, is not--and so if National Geographic is serious about wanting to keep good scientists in their lineup (and others have noted that, truly, they likely don't give a shit), their decision to disallow pseudonymous blogging is shooting themselves in the foot. There are many valid reasons why a scientist may not want to be publicly identified on their blog--does that really make the information any less valid? Does NG really think that someone who may carry out experimental work with animals, and discuss animal research on their blog using a 'nym, would really choose their blogging hobby over their livelihood and--potentially--their family's safety? There are animal rights and anti-vaccine extremists to worry about; Carl Zimmer even points out recent threats aimed at Chronic Fatigue Syndrome researchers who have reached conclusions that some patients didn't like or agree with. Who can blame many scientists for wanting badly to share their work and insights with the general public, but doing so in a way that disassociates those posts from their "real life" identity?
These things aren't just theoretical. HIV denier Andrew Maniotis showed up, unannounced, at my work office one day a few years ago. The recently-arrested "David Mabus" showed up at an atheist convention. While using a pseudonym doesn't always protect you--certainly many pseuds have been outed by those willing to do the detective work--it at least offers you some measure of protection from threats, both online and off.
NG claims to have listened to reasons for blogging under a pseudonym, but have made this decision as a way to "establish best practices" in the industry. Well, I call shenanigans. They're freaking National Geographic--they can set the curve, and establish best practices by allowing (hey, even encouraging!) quality pseud bloggers. After all, would Carl Zimmer and Ed Yong be any less awesome if they were instead known as ParasiteGuy and RocketMan?
