Pigs at a farm in Beijing peer out at visitors. Half of all the pigs in the world live in China.
There's a global campaign to force meat producers to rein in their
use of antibiotics on pigs, chickens and cattle. European countries,
especially Denmark and the Netherlands, have
taken the lead. The U.S. is
moving,
haltingly, toward similar restrictions. Now the concerns about rampant
antibiotic use appear to have reached China, where meat production and
antibiotic use have been growing fast.
Half of all the pigs in the world live in China — a consequence of the country's swelling
appetite
for pork. And like pork producers in many other countries, Chinese
farmers have turned to antibiotics and other feed additives to control
disease in their herds and also to make the animals grow faster.
The
exact extent of antibiotic use in Chinese agriculture is unknown,
because authorities don't monitor it. But researchers have sometimes
found disturbingly high levels of antibiotic residues in manure from
Chinese pig farms.
A
study published Monday by the
Proceedings of the National Academy of Sciences adds to evidence that antibiotic use by Chinese pork producers poses health risks. According to the study, manure from pig farms doesn't just
contain antibiotic residues. It also carries high concentrations of
bacteria that are resistant to antibiotics. This increases the risk that
antibiotic resistance will move into bacteria that infect humans, and
the resulting diseases will be more difficult to treat.
But
there's also good news. Scientists from the Chinese Academy of Sciences,
who took the lead in the new study, are increasingly aware of the
problem and looking for ways to fight it. They invited
James Tiedje, a microbiologist from Michigan State University, to join their effort.
"They were quite forthcoming," Tiedje tells The Salt.
The
Chinese scientists monitored antibiotic residues in manure from three
different pig farms. They found plenty, but not at exceptionally high
levels.
Tiedje then tested those manure samples, looking for
genes that make bacteria resistant to particular antibiotics. That's
when he hit the jackpot: He found more than 100 different resistance
genes. The concentration of resistance genes was almost 200 times higher
in these samples, compared to manure from a pig farm that had never
used antibiotics.
"We're not trying to single out the Chinese
here. This is a global problem," says Tiedje. Similar levels of
antibiotic residues, for instance, have been found in manure on European
farms.
The study indicates that treating the manure after it
leaves the farm can significantly reduce the potential for this manure
to spread antibiotic resistance to other bacteria in the surrounding
environment. Composting it, for instance, cuts the total population of
microbes in manure – which means fewer microbes carrying antibiotic
resistance genes.
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