Factory farming has become a primary driver of foodborne illness outbreaks. High-density confinement, poor sanitation, and stressful living conditions in these operations create the perfect environment for harmful pathogens like salmonella, e. coli, and listeria to thrive. These bacteria can contaminate meat, dairy, and eggs long before they reach consumers’ kitchens.
Foodborne illnesses occur when people eat contaminated food from afflicted supply chains. Salmonella poisoning, one of the most well-known foodborne illnesses commonly caused by contaminated poultry, meat, eggs, and unpasteurized dairy, causes diarrhea, abdominal cramps, fever, nausea, and vomiting, and can even be fatal. The CDC estimates that salmonella infects more than a million Americans per year, with 25 percent of these infections attributed to poultry alone. A recent North Carolina State University study illustrates the extent to which salmonella is endemic in the poultry industry: researchers found that 52.3 percent of samples from commercial poultry farms were contaminated with salmonella.
E. coli strains linked to factory-farmed beef, pork, and chicken can cause severe complications, including kidney failure and sepsis. Listeria, a serious but less common bacterial illness, can be found in deli meats, fish, and other foods. The problem of foodborne illness is further exacerbated by the overuse and misuse of antibiotics in industrial livestock operations, which breed antibiotic-resistant bacteria and pose growing threats to the efficacy of medical treatment for foodborne and other diseases. In the case of salmonella, multidrug-resistant bacteria have been found in up to 33 percent of contaminated samples from commercial poultry farms.
Many people do not realize that the way we produce food (meat, eggs, and dairy specifically) is closely linked to foodborne illness outbreaks. Over 90 percent of animal products found on the shelves of American stores come from massive, high-confinement animal factories. This means that for most consumers every piece of chicken, for instance, that they have ever purchased originated from an animal raised on a factory farm, and a significant amount of this chicken may be contaminated with salmonella (the CDC estimates that 1 in 25 packages of chicken purchased contains salmonella). The sheer scale and ubiquity of factory farms, therefore, present a significant risk to the public’s health.
As Farm Forward has reported in the past, massive industrial farms are perfect breeding grounds for disease transmission: “Farmed animals today are overwhelmingly genetically uniform, immunocompromised, lodged together by the tens of thousands, and routinely administered subclinical antibiotics—an ideal petri dish for cultivating antibiotic resistance, as well as endemic and emerging zoonotic disease threats.”
Modern factory farming relies heavily on genetically uniform animals. The vast majority of chickens raised for meat in the United States, for example, are Cornish Cross broilers, a breed selected for rapid growth. This uniformity creates vulnerability to disease; genetically diverse populations are more resistant to pernicious disease outbreaks, since genetic variation can help protect against different strains of disease. When every animal shares the same genetic susceptibilities, they are all vulnerable to the same diseases at the same time.
Extreme crowding and confinement are additional hallmarks of industrial animal agriculture and major contributors to disease spread. For instance, a report from the European Food Safety Authority states: “There is conclusive evidence that an increased stocking density [and] larger farms … result in increased occurrence, persistence and spread of salmonella in laying hen flocks.” Similarly, e. coli is often linked to intensive cattle-rearing methods, and the pathogen can travel through the supply chain, from the farm to the slaughterhouse and processing plant, sickening consumers when it reaches their plates. Listeria, too, has a higher incidence rate in industrial animal farms, especially among dairy cows, who spread the disease in high-confinement housing systems and during pregnancy, lactation, and transport.
The problem is not reducible to an occasional lapse in sanitation, but a direct consequence of the industrial model itself: crowding more animals into larger facilities guarantees higher disease prevalence and transmission.
Compounding the problem, animals in factory farms often face environmental stressors such as heat stress, cold stress, overcrowding, nutritional deprivation, and lack of natural sunlight. The poor welfare conditions weaken their immune systems, making them more susceptible to infections. As a result, contaminated animal products enter the food supply.
These issues are amplified throughout the entire factory farming supply chain, as pathogens spread from breeding and growing facilities to transport vehicles, slaughterhouses, and processing plants, where industrial operations and shared equipment create multiple points of cross-contamination.
Headlines focused on foodborne illness outbreaks from fresh produce obscure the full extent of animal agriculture’s role in the transmission of foodborne pathogens, as factory farm pollution and cross-contamination often drive produce outbreaks that appear unrelated to farmed animals.
Factory farms are often the original source of foodborne illnesses, even when the contaminated food is a fruit or vegetable, like lettuce or spinach. Crop fields, for instance, are often irrigated with water from sources located near industrial animal operations such as large-scale dairy farms. When manure from these facilities enters the environment, it can seep into the groundwater or run off into nearby waterways, carrying harmful bacteria. As a result, the water used on crops can become contaminated, spreading pathogens from factory farms to produce fields.
E. coli exemplifies this cross-contamination problem. While e. coli typically lives harmlessly in cattle’s intestines, certain strains produce dangerous toxins that cause severe food poisoning, including bloody diarrhea and kidney failure. These harmful strains spread through contaminated food, water, or contact with infected animals or people, and can survive for months in animal waste and water troughs. Cattle operations, therefore, become long-term reservoirs for contamination, with their pathogens eventually reaching consumer plates through irrigated fruits and vegetables, as well as through fresh produce that has been grown with manure-based fertilizer.
Factory farming contamination cuts across livestock types: from campylobacter in poultry and antibiotic-resistant bacteria in pig operations to e. coli in cattle facilities and salmonella outbreaks traced to industrial egg production. The risk of these bacteria traveling into the environment and contaminating the food system remains high as long as the industrial animal sector continues practices that create the ideal conditions for pathogen proliferation and transmission. To reduce this risk and protect American consumers, the industrial animal sector needs to adopt more responsible methods of raising animals and be held accountable for the ways in which it endangers public health.