Friday, July 31, 2015

Use and misuse

National conventions are terrific ways to spread diseases.  People jetting in from all over, immune systems weakened by the stress of travel, confined in small rooms, mixing and mingling in shared facilities, then jetting back to wherever.  It would be hard to design a better system to distribute pathogens.

Goats have their own conventions, and the same rules obtain.  Mostly, goat shows are small affairs, a couple of hundred goats from a dozen counties, and the risks are slight.  However, the Real Doctor recently took five of our animals to the national show of the American Dairy Goat Association.  The goats spent four hours in a truck, then five days in six-by-four pens in a barn with hundreds of other goats, then another four hours to get back home.  While at the show, they were in the competition, which meant walking around in an arena used by zillions of other goats from all over the U.S.A. 

Our beasties did better than we had expected--nobody won their classes, but they all made the first cut and finished between 15th and 10th in their classes, and got some nice notices.  So nobody got ribbons, but they did (despite a lot of effort and sanitizing) get some ickies. 

By the last day, Opera had developed a fever and was looking pretty listless.  Some banamine (works in goats like acetomeniphen in us) perked her up, and a course of ceftiofur (a cephalosporin antibiotic) has left her right as rain.  Helen had a slightly elevated temperature too, which was also treated.  But, in the two weeks since the show, a cough has spread through our kids, one at a time, and it may be correlated with a couple of the young kids getting the poops.  Right now, Helen is back on ceftiofur after developing another fever, and Cavatina is finally coming off of a fever that spiked at 107.4 and has had her miserable for four days.  So, hurrah! for ceftiofur and banamine and their judicious use.

So far, ceftiofur works.  It works against Gram-positives and -negatives, and penecillin-resistant bugs.  But for how much longer?  Every dose of antibiotic, especially if I am not careful with it, is an additional bit of selection pressure that will favor the spread of antibiotic resistance genes in the environment.   (Genes, not bacteria.  First, genes are much easier to detect, since they don't need to be cultured.  Second, the bacterial predisposition to promiscuous lateral gene transfer means that once a gene is out there, it will get around.)

So I read in Science a charming article about the hog farming and spread of antibiotic resistance genes in waterways in China.  Antibiotics are a wonderful tool for rescuing sick animals, but it wasn't long after they were introduced that somebody noticed that you can just give your young animals lots of antibiotics all the time and they will grow faster.  Never mind that they will excrete most of the antibiotic in their urine, and it will go out into the environment and give that selective nudge to the genes that will make antibiotics useless, profit is to be had!

Needless to say, hog farming in China is epic in its scale.  So is the abuse of antibiotics.  About half of the antibiotics produced in China are used to fatten up the little piggies.  How much is that?  About 100,000 tons. 

Since I am human, I have a hard time visualizing numbers over 100 or 1000.  So, a ton of water is a cubic meter.  We'll assume that the density of dry antibiotic is the same as water, which is true to an order of magnitude.  So, I am picturing a mound of antibiotic, as long and as wide as a football field, and as tall as the tips of the field goal posts.  Or maybe a cube, half a football field on each side.  Now that is some selection pressure.

(Question for those interested--how big a mound of antibiotics is used in American meat production?  Answer here, if you highlight it:  Ten thousand tons.   Picture a cube about twenty meters on a side.  Still some selection pressure.) 

Sometimes, I feel like scientists giving humanity antibiotics was like giving a hormone-raddled teenager the keys to a Ferrari.  Are we really mature enough to not wreck ourselves?

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