Bacterial resistance to antibiotics is a mounting threat, and there is a rich ongoing debate about what is driving this resistance. Evidence is beginning to suggest that resistance may not only be driven by doctors’ historically lackadaisical approach to controlling the antibiotic abuse of their patients—it may also be driven by farmers’ liberal distribution of antibiotics to their farm animals. The beef, chicken, turkey, and pork on our dinner plates may be doing something much more sinister than just providing us with tasty protein.
Since the advent of antibiotics, scientists have been concerned that the bacteria they target could eventually become resistant to medicine’s powers. But it was not until the 1970s that the effects of antibiotic overuse, and the potential for resistance, began to gain widespread recognition. The threat of resistance is particularly frightening given the fact that the discovery of new antibiotics has been on the decline over the same period that resistance has been on the rise. Between 1940 and 1962, 20 new classes of antibiotics were brought to the pharmaceutical market; in the following 50 years only 2 were. This is partially due to the fact that the amount of investment and funding dedicated to antibiotic research has plummeted in recent decades, particularly because marketing is easier and cheaper than developing new classes of drugs. Preserving the efficacy of existing drugs is therefore of primary importance.
Drug resistance spreads in a straightforward manner. In any bacteria-filled environment, there will be some bacteria that are resistant to a particular treatment. When antibiotics are introduced to such an environment, a large number of bacteria are killed, including good bacteria which may be important to animal or human health. In the absence of these “good” and non-resistant bacteria, the resistant bacteria will flourish and multiply within the system.
Therefore, just by using antibiotics, we are guaranteeing that resistance to them will eventually develop. The overuse, and misuse, of these drugs will only accelerate the rate at which vital medicines become ineffective.
There are several why antibiotics are administered to livestock: metaphylaxis, therapy, prophylaxis, and growth promotion. The first two use-cases are widely deemed as acceptable, but the latter two are increasingly being touted as examples of misuse that may ultimately endanger human health.
Metaphylactic antibiotic use refers to giving healthy animals living in the same flock or pen as sick animals antibiotics, while therapeutic use refers to the distribution of medication to ill animals. Both of these use cases are generally considered prudent and necessary. Animals facing a serious threat of illness should be protected, and those that are already sick should be treated. More controversial is the use of antibiotics for prophylactic purposes, or when healthy animals are fed drugs in order to prevent them from falling ill. In such scenarios, antibiotics are often applied haphazardly and liberally. While this practice may keep some illnesses at bay, the broad approach has the potential to strengthen resistant strains without ever addressing an actual illness.
More targeted treatments that use antibiotics to tackle specific illnesses, although more expensive and requiring closer monitoring of livestock, have been shown to be very effective. For a human analogy, this is comparable to encouraging people to wash their hands regularly and practice good hygiene, rather than forcing them to constantly consume antibiotics in order to keep diseases at bay. This type of smarter, more nuanced approach to disease reduces the amount of antibiotics needed, while also diminishing the prevalence of antibiotic-resistant bacteria in animals.
The most contentious of all antibiotics for livestock use-cases is the practice in which animals are fed antibiotics regularly, at low doses, in order to force larger, faster growth. This last practice has come under growing global criticism, and countries including major pork producer Denmark have banned the use of antibiotics for these purposes.
Although restricting the use of antibiotics for growth purposes has been shown to increase the need for therapeutic ones, the overall usage of antibiotics is still lower under these more restrictive systems. In Denmark, for example, the use of veterinary-prescribed antimicrobials (agents used to kill microorganisms, such as bacteria, fungi, or viruses) did increase following the ban on growth-promoting antibiotics in 2000, but this growth displaced the now-eliminated category of antibiotics used for growth promotion. Furthermore, pig production increased substantially in the first decade of the 21st century. In 2013, total use of antimicrobials in the country was actually 43 percent lower than it was in 1994.
Regardless of why they are used, the incorporation of antibiotics into livestock rearing may pose a risk to human health. Antibiotic use can lead to resistance, and the more that are used, the more dominant antibiotic-resistant bacteria become. And while this danger may not be particularly worrying when it comes to many types of antibiotics used by the livestock industry, some are essential to human health. In fact, more than 62 percent of antibiotics sold in the United States (US) in 2013 used for animal production were classified as medically important to humans. Tetracycline, for example, is frequently used on hogs, but is also an effective treatment for Lyme disease, stomach ulcers, urinary, skin, and respiratory infections, and cholera. A resistance build-up in hogs to tetracycline, passed on to humans through the food supply, waste runoff from farms, or by farm workers, can thus make it more difficult to treat these otherwise treatable infections.
The global consumption of antimicrobials in animal production was roughly 63,100 tonnes in 2010, and is expected to increase by 67 percent to 105,500 tonnes by 2030. One of the primary drivers of this increase will be rising global incomes, which in turn drive up demand for animal protein. In Asia alone, the per capita consumption of animal protein has more than quadrupled since 1960. Antimicrobial use is also driven up by the fact that the global growth in meat production has been achieved through the intensification and industrialization of farming practices. Such systems have a higher antibiotic requirement due to the confined, densely populated spaces in which the animals live.
As of 2010, 50 percent of all antibiotic usage in animal production was concentrated in just five countries: China (23 percent), the US (13 percent), Brazil (9 percent), India (3 percent), and Germany (3 percent). By 2030, these numbers are expected to become even more concentrated with China responsible for 30 percent, and the US, Brazil, India, and Mexico for 10, eight, four, and two percent respectively.
The concentration of antibiotic usage in China is not just attributable to the size of the country. It is also driven by the country’s voracious appetite for pork - half of the world’s pigs are in China. And on a global average, pig farmers give their animals four times as much antibiotic medication per pound of meat as cattle farmers. Poultry farmers are a close second behind pork - the confined, densely populated areas in which pigs and poultry are raised means that both require more antibiotics in order to be healthy. Beyond the country’s love for pigs, there are several realities that make China susceptible to the risks associated with antibiotic misuse in livestock: its quickly growing demand for meat, the increasing prevalence of industrial farming in the country, a tendency to overuse antibiotics, and poor regulation.
China is becoming famous for pork production and consumption. In 1975, China produced roughly 8 million tonnes of pig meat and now produces 57 million, helping the country achieve a level of total meat consumption that is more than double that of the US. Despite these impressive production numbers, demand is not being met and China regularly imports over 800,000 tonnes of pork per year.
Agricultural self-sufficiency has long been an important policy for the Chinese government, and few other foods are more important than pork. The central role played by pork became all too apparent in 2007 when “blue ear pig disease” killed 45 million pigs, and China’s consumer price index rose at the fastest rate in almost a decade. In attempts to prevent such instability, the Chinese government now gives its pork industry $22 billion in subsidies each year.