Not only does the US partake is large-scale confinement agriculture — or livestock-raising — but, as wealth and populations grow, developing countries like China and India do as well. The use of growth-promotor antibiotics began in the US and has spread to China, the world’s biggest producer and consumer of antibiotics. Half of the antibiotics China makes in-house are used in the country’s agriculture: a staggering 96 million kilograms, which is almost seven times more than the US uses every year. China’s food safety regulation is falling by the wayside, as the industry is pressurized to manufacture heaping quantities of meat and make heaping quantities of money.
In both China and the US, no regulations exist for reporting which agricultural antibiotics go into what species, and no systematized method exists to track side effects. Chinese researchers, seeing a problem, published a paper this week that addressed these issues, “Diverse and abundant antibiotic resistance genes in Chinese swine farms”.
The team visited three farms — big by Chinese standards, and from three different regions in China — to gather research for this paper. Each farm raises around 10,000 pigs every year, which, by EPA‘s definition, is on the small side of large “confined animal feeding operations.” The researchers sampled fresh pig manure from each farm: as the manure was being made into fertilizer, and from farm soil where the fertilizer had already been used. Their controls were samples of soil from a virgin forest in China, and manure from American pigs that had never taken antibiotics.
American researchers analyzed the samples to look for any antibiotic-resistant genes. The researchers detected 149 unique resistance genes, existing 192 to 28,000 times more frequently in the Chinese farm samples than in the control samples. A similar presence of transposase was found as well, an enzyme that allows resistant genes to move from one bacterium to the next.
The researchers found that the process of resistance genes grouping and moving to other bateria has greatly developed by the use of metals like zinc, copper and arsenic on farms. Additionally, resistance can be present on farms where antibiotics have never been used, even where evolutionary practices on bacteria and genes haven’t been employed.
According to the researchers’ paper, “The diversity and abundance of antibiotic resistance genes reported in this study is alarming, and clearly indicates that unmonitored use of antibiotics and metals on swine farms has expanded the diversity and abundance of the antibiotic resistance reservoir in the farm environment. The coenrichment of ARGs and transposases [enzymes] further exacerbates the risks of transfer of ARGs from livestock animals to human-associated bacteria, and then spread among human populations.”
The agriculture industry has been refuting this argument for years: if, when antibiotic resistance develops on farms, it will transfer from farms to people with no link to the farms. While the agriculture industry says no, the Chinese researchers think it’s just a question of when. As the concentration of antibiotic resistance grows, so too does the probability that it will move into the environment outside the farms.
As in any credible scientific investigations affecting animal and human health, data-based-driven debates must go on until all key stakeholders agree on a cost-effective, practical and sustainable course of action.
Conceived, Developed and Written by Dr. Subodh Das and Tara Mahadevan
February 15, 2013
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