Antibiotics abuse makes China's pork industry a hotbed for drug-resistant bugs

Growth addiction

Antibiotics abuse makes China's pork industry a hotbed for drug-resistant bugs


"When I was a kid, people bred pigs on a household basis,” said Zhu Yongguan, director of the Chinese Academy of Sciences' Institute of Urban Environment in Xiamen. In the countryside near Shanghai each family had just two or three pigs, he said, raised on slops and ready for slaughter when Spring Festival feasting rolled around.

So when Zhu first visited a modern Chinese farm for his research into the genes that cause drug-resistant bacteria in farm animals, he was surprised by how many pigs had been crammed into one place.

"I just felt it was too crowded for the pigs. But for intensive farming systems, for efficiency and economic income, I guess nowadays you have to do that or it’s not profitable,” Zhu said. That change from family farming to large-scale agribusiness in China can be taken both as a sign of progress and potential cause for concern.

As Chinese agriculture scales up, key features of industrial farming – including antibiotics overuse, large-scale farms and breeding practices – could prime the pump for drug-resistant disease to take a serious toll on the country's porcine population. A veneer of modernization is also helping popularize the companies that have adopted these practices among consumers who are already on high alert for more immediate food safety problems. The size of that pork-hungry populace means a major loss in domestic swine stocks would have serious ramifications for the global meat market and undermine Beijing's efforts to secure an adequate domestic supply.

Also potentially troubling is the possibility of such resistance spreading in a way that could pose a direct threat to human populations, and scientists are have begun to research the extent to which these practices may actually endanger people. Accurately gauging the likelihood and potential severity of these outcomes would require extensive industry data that scientists and policymakers don't yet have but urgently need.

"With such large scale use, drug resistant microbes generated in animals can be later transferred to humans through the food chain,” said Martin Taylor, team leader for health systems at the World Health Organization’s China office. “Major change is needed to find new ways to treat infection, and to change how we produce, prescribe and use antibiotics in both people and animals in China and worldwide.”

By popular demand

The difficulty of regulating China's farms is regularly emblazoned across newspaper front pages and smart phone screens nationwide, but the coin behind this on-and-off cycle of regulatory whack-a-mole comes from the growing purchasing power of the country's increasingly carnivorous population. With much of the country having pulled itself out of poverty during the last 40 years, the role of meat has changed from a festival treat seldom savored to a staple of the modern mainland diet.

That, together with a billion-plus-sized population, led to China's annual meat consumption growing to more than double that of the United States in 2012, up from less than a third in 1978, according to figures from the Earth Policy Institute. A recent report from the Institute for Agriculture and Trade Policy estimated pork accounted for 65% of all meat consumed in China, and in 2014 domestic pork consumption totaled just over 57 million tons, outstripping pork production by around half a million tons based on estimates from the US Department of Agriculture. Dutch agricultural financing giant Rabobank predicts that China will produce an annual total of 60 million tons of pork by 2020, an increase just shy of 53 million tons over production in 1976.

Outside of Mao Zedong’s disastrous attempt at agricultural collectivization in the late 1950s, 20th Century China was largely characterized by small-scale, family based farming. That model still accounted for 27% of mainland pork production in 2012, according to Rabobank, but that year a majority of about 57% of pigs came from specialized farms able produce up to 1,000 hogs a year, while large-scale intensive farms turning out up to 50,000 porkers supplied 15% of the total. Such growth has put serious pressure on the country's largely self-sufficient grains sector, and looks unlikely to let up any time soon.

"There is a big push to move to large scale operations and this will continue. The small scale farmers persist, however, especially in poorer western provinces and mountainous areas,” said Fred Gale, a senior economist at the US Department of Agriculture’s Economic Research Service. Gale said that recent signs, such as meat shipment-handling facilities that have been built at several of China’s ports, suggest that officials are gearing up for more pork imports. But while imports are gaining a bigger share of domestic consumption in China, he said, “they will never dominate such a large market.”

Breeds apart

The drive toward larger farms makes sense in light of Beijing’s desire to keep the country’s pork coffers well-stocked with domestically supplied meat. Such large-scale farms and mass-production practices follow US industry templates which, when copy-pasted onto a mainland Chinese canvas, carry with them a clutch of endemic issues that create further complications in a more lax regulatory environment.

Industrial farming has allowed China to grow most of its own hogs, but the breeds raised aren’t local. The IATP report cites an official from the agriculture ministry as estimating that 90% of the country’s pork was produced from exotics, predominantly made up of Duroc, Landrace and Yorkshire swine—breeds introduced in the 1980s that were bred to grow quickly on feed in tightly controlled, sealed barns.

Said import models’ prevalence makes for less genetic diversity among the country’s massive swine populace, so if disease strikes one there is a greater chance that pigs nearby will catch the same bug. That gene pool is further restricted by large industrial farms’ reliance on sows to birth large herds of related hogs—most are typically half-brothers or half-sisters.

In addition to lacking the fat and other features that appeal to traditional Chinese tastes, these swine varieties were imported for their ability to survive in biosecure barns, Gale said. In Chinese farms they are often subjected to temperature extremes, flies, mosquitoes, rats and moldy feed, resulting in serious health problems. Yet according to a USDA report co-authored by Gale, most officials believe that small-scale backyard farms are the true source of animal disease epidemics in China and that a modernized industry chain will bring both price stability and address food safety and disease issues.

Drugs of choice

Consumers seem to agree, even in the face of plentiful evidence to the contrary. A 2012 study of urban consumer beliefs found that industrial production systems were the most trusted producers of pork, perceived as a move away from low-cost, low-quality and low-safety family farms to a more modern model representing greater quality and safety.

Those perceptions had persisted despite a scandal the year before in which hundreds fell ill after eating pork products containing clenbuterol, a steroid used to burn fat to spur muscle growth that causes nausea and dizziness when consumed by humans. Clenbuterol is prohibited for use on hogs destined for human consumption in China, yet contrary to popular expectation the poisonous pork’s producer was an affiliate of Shuanghui, the country’s largest meat processor.

A few years later a plague of more than 16,000 pig carcasses were discovered floating down tributaries of Shanghai’s Huangpu River. Coverage of the bobbing bodies abounded, but the dumping of what turned out to be diseased pigs might have been preferable, if barely, to the popular alternative: Gale said the slaughter and sale of diseased hogs was a longstanding problem still of big concern to Chinese authorities.

"There are inspectors in Chinese plants, and many of them have nice equipment... but there are thousands of slaughterhouses and it’s impossible to monitor all of them,” he said. While authorities have a plan in place to consolidate slaughterhouses and gain better control, Gale added it was unclear how fast that was progressing, and noted that despite crackdowns, news media continued to report on illegal butchers popping up.

Antibiotics offer industrial farms a straightforward way to prevent and combat disease, and are a far more common means than clenbuterol for boosting weight in China's mass-produced hogs. Antibiotic drugs like tetracycline are generally used in place of healthy living conditions at industrial farms to promote growth without spending more on feed. Yongguan Zhu at the Chinese Academy of Sciences said that with so many pigs living in small areas, "they’re likely to get infected by pathogens, and the pathogens can move around. So you have to use the antibiotics to maintain the productivity in this intensive animal farming system.”

Zhu is by no means the only one in China sounding the alarm. "Antimicrobial resistance (AMR) is a very serious problem in China in both human beings and animals," said Professor Xiao Yonghong, an infectious disease specialist at Zhejiang University and expert in AMR surveillance. Xiao conducted a survey in 2007 that estimated over half of the 230,000 tons of antibiotics produced in China went to animals, and the rest to humans; in 2010 he told Phoenix news that antibiotics made up about 25% of all medicine sales in China.

That figure seems set to rise as backyard farming’s share of pig production continues to shrink. A 2015 study published in the journal Proceedings of the National Academy of Sciences (PNAS) suggested antibiotic use in China will double by 2030 thanks to a growing market for meat and poor regulation.

Growing resistance

Unlike the steroid clenbuterol, antibiotics aren’t directly harmful to people who eat meat from hogs that receive regular doses. Repeated, low-dosage ingestion does, however, fail to kill off all the pathogens in a pig, leaving unharmed those bacteria whose genes provide immunity and thus encouraging the evolution and proliferation of drug-resistant bugs.

It can be difficult to demonstrate direct links between a specific antibiotic’s overuse and broader increased resistance, but the implications of such overuse are troubling. A 2013 study published in PNAS and co-authored by Zhu looked at the soil adjacent to three large-scale pig farms near major cities including Beijing and found the surrounding manure-soaked environs contained high levels of the antibiotic tetracycline, as well as tetracycline-resistant bacteria. Indeed, the prevalence of antibiotic resistance genes was 28,000-fold greater than that of control sample soil.

Antibiotic resistance genes and the pathogens that carry them are usually different for humans and pigs. But there is some overlap between the drugs used against harmful bacteria in both species, and the potential for fostering resistance to those common antibacterial agents – tetracycline among them – is a real concern. Xiao, at Zhejiang University, pointed to a 2014 study he co-authored comparing the abundance of antibiotic resistance genes in the gut microbes of people from China, Denmark and Spain. Chinese guts, it turned out, were home to a greater number of microbes with resistance genes—mainly for tetracycline. That correlated with greater Chinese consumption of antibiotic medicine and antibiotics-fed hogs.

This overuse stems in part from regulatory myopia: Existing laws in China, already spottily enforced, pertain to food safety only so far as consumer health is directly affected. A lack of any monitoring system for livestock antibiotics use means it is impossible to attain a fuller picture of their use and how they may relate to resistance. And while the Ministry of Agriculture does report on outbreaks, these are likely underrepresented because diseased livestock may not show symptoms for months after infection. (Those that do are often quickly slaughtered and sold, according to regular media reports.)

Niche vs national

There is, for the Chinese middle and upper classes, a burgeoning organic pork industry that eschews antibiotics abuse. That sector has gotten plenty of press, with one prominent profile of the country's nascent organic farming industry shining a spotlight on Mahota Farm, a Shanghai-based business that turns a profit selling organic pork from its 20,000-hog-strong farming outfit.

Profit margins aside, this market currently comprises only 1.01% of all food purchased, and that is mostly made up of vegetables rather than meat, according to an industry overview (pdf) from Chinese organic food exhibition group CINHOE. And while China’s economy is the second largest globally and still growing, the country is constrained by a lack of agriculturally viable land. Thanks to tightly-packed, large-scale farms, industrial production takes significantly less area per hog to produce the same amount of meat compared to traditional farming.

More likely than a shift to organic pork is an increase in imported meat. Although Chinese policymakers have long held self-sufficiency in food to be the holy grail of agricultural achievement, the recent move to industrial pork production has led to soaring imports of feed. Combined with the environmental and social challenges of animal waste, health scares and public perceptions, the official outlook on pork imports is likely to become more permissive. The UN Food and Agriculture Organization predicts a rise in pork imports for China and slowing domestic production growth in its Agricultural Outlook 2014-2023.

The size of the China market still means that it would be difficult for imports to become anything more than a supplement to domestic pork, but that could still exert profound influence on the world market. The USDA's 2012 report on China's swine sector found that although less than 1% of pork consumed in China and Hong Kong from 2000 to 2006 was imported, the weight of annual imports during the period nonetheless ranged between 500,000 and 600,000 metric tons. In 2014 USDA statistics showed pork imports had reached 810,000 metric tons, but that still only accounted for about 1.4% of annual consumption.

This all points to a future where pork imports flow increasingly to China even as domestic production continues to grow as pig farms consolidate and more closely resemble those of the US. That helps explain why global consumption of antibiotics is expected to increase by 67% between 2010 and 2030 and to nearly double in BRICS countries, according to a study published this year in PNAS.

Unknown dangers

Gale, at the USDA, said that despite extensive use of antibiotics on swine in China, there wasn’t enough information to comment on the extent of resulting antibiotic resistance. This dearth of data is a serious barrier to assessing the potential threat posed by drug-resistant bacteria to China’s pigs. Taylor, with the WHO, said even the success of measures to combat resistance could only be determined in the light of more and better information.

"Improving surveillance of drug resistance is crucial, because it is the basis for informing global strategies, monitoring the effectiveness of public health interventions, and detecting new trends and threats,” Taylor said.  “Currently, key tools to measure antibiotic resistance in people and animals – such as basic systems to track and monitor the problem – include major gaps or do not exist in many countries, including in China.”

Zhu, at the Academy of Sciences, said that while there might be monitoring systems for so-called superbugs in Chinese hospitals, no such programs existed for animal populations and other key environments. “We basically lack systemic data on the issue," he said, "and I think we should improve our monitoring systems so that we know what’s going on."

In addition to recommending better regulations, improved enforcement and incentives to encourage the private sector to end its dependence on antibiotics, Zhu noted he was in the early stages of research on which pathogens pose the greatest threat to human populations should resistance proliferate in China. Xiao, meanwhile, stressed the need for public education that went beyond health professionals to their patients and the country's farmers, whose demand for antibiotics helps drive overuse in livestock and over-prescription for people on the mainland.

The issue, however, is ultimately global, Taylor said, and concerted international action is needed to reduce antibiotic overuse and avoid a post-antibiotic era in which many common infections could prove far more deadly once they no longer have a cure. China is only one country among many – including the United States – that does not have systems in place to monitor and regulate antibiotics.

There is some hope from efforts like that seen in Denmark where, after a slight dip in 1998 when a ban on using antibiotics to boost hog growth came into effect, the pig farming industry's production levels grew steadily for eight consecutive years, according to an in-depth analysis by the Veterinary Information Network. That policy spread as the entire European Union banned such use of antibiotics in 2006.

Yet with global population projected to reach 9 billion in the next 35 years, countries will become increasingly interdependent and competitive for food, and a microbe’s adaptation in one locale now likely has more potential than ever to spread across the globe. That means China, along with the rest of the world, needs to better regulate its pork production. Fast. 

Author: Hudson Lockett (@KangHexin)

Research: Georgie Barber