December 16, 2016 — From the air, the Pearl River Delta in southern China’s Guangdong province resembles a mass of human cells under a microscope. Hundreds of thousands of tiny rectangular blocks, all of them shades of green, are clustered between cities and waterways. Livestock pens are scattered among the thousands of seafood farms that form the heart of the country’s aquaculture industry, the largest in the world.
Beside one of those fish farms near Zhaoqing, on a muggy day in June, a farmhand wearing a broad-brimmed straw hat hoses down the cement floor of a piggery where white and roan hogs sniff and snort. The dirty water from the pens flows into a metal pipe, which empties directly into a pond shared by dozens of geese. As the yellowish-brown water splashes from the pipe, tilapia flap and jump, hungry for an afternoon feeding.
Chinese agriculture has thrived for thousands of years on this kind of recycling—the nutrients that fatten the pigs and geese also feed the fish. But the introduction of antibiotics into animal feed has transformed ecological efficiency into a threat to global public health.
At another farm, in Jiangmen, a farmer scatters a scoop of grain to rouse her slumbering swine, penned on the edge of a pond with 20,000 Mandarin fish. The feed contains three kinds of antibiotics, including colistin, which in humans is considered an antibiotic of last resort. Colistin is banned for swine use in the U.S., but until November, when the Chinese government finally clamped down, it was used extensively in animal feed in China. Vials and containers for nine other antibiotics lie around the 20-sow piggery—on shelves, in shopping bags, and atop trash piles. Seven of those drugs have been deemed critically important for human medicine by the World Health Organization.
The overuse of antibiotics has transformed what had been a hypothetical menace into a clear and present one: superbugs, bacteria that are highly resistant to antibiotics. By British government estimates, about 700,000 people die each year from antibiotic-resistant infections worldwide. If trends continue, that number is expected to soar to 10 million a year globally by 2050—more people than currently die from cancer.
In November 2015 scientists reported the discovery of a colistin-resistant gene in China that can turn a dozen or more types of bacteria into superbugs. Since then the gene has been found in patients, food, and environmental samples in more than 20 countries, including at least four patients in the U.S. Food, it now appears, can be a crucial vector. “People eating their shrimp cocktails and paella may be getting more than they bargained for,” says Dr. Martin Blaser, a professor of microbiology and an infectious diseases physician at New York University Langone Medical Center who chairs President Barack Obama’s advisory panel for combating antibiotic-resistant bacteria. “The penetration of antibiotics through the food chain is a big problem.”
Research has found that as much as 90 percent of the antibiotics administered to pigs pass undegraded through their urine and feces. This has a direct impact on farmed seafood. The waste from the pigpens at the Jiangmen farm flowing into the ponds, for example, exposes the fish to almost the same doses of medicine the livestock get—and that’s in addition to the antibiotics added to the water to prevent and treat aquatic disease outbreaks. The fish pond drains into a canal connected to the West River, which eventually empties into the Pearl River estuary, on which sit Guangzhou, Shenzhen, Hong Kong, and Macau. The estuary receives 193 metric tons (213 tons) of antibiotics a year, Chinese scientists estimated in 2013.