The pork industry has spent millions on air filtration, feed safety and strict farm entry biosecurity protocols, but it has largely left the “water tap” wide open. Given that pigs drink more than double the volume of what they eat, untreated or unmonitored water represents a massive, overlooked vector for disease transmission, explains Dr. Gabi Doughan, veterinarian and technical project specialist in the College of Veterinary Medicine at Iowa State University.
The Vulnerability of Water Sources
Understanding the source of your pigs’ water is a good place to start the conversation. Most pig farms either have a surface water source, well water source or rural or municipal-treated water source.
“With some of those sources, specifically surface water and well water, we can have some potential risk for biosecurity there,” Doughan says. “Because these sources are exposed to the environment, pathogens could potentially be in those locations.”
The Iowa Department of Natural Resources demonstrated that approximately 40% of wells sampled over a 15-year period in Iowa were contaminated with fecal coliform bacteria while other studies have demonstrated viral pathogen contamination in up to 30% of private wells and groundwater sources, Doughan notes.
“Water is one of the largest inputs entering into swine farms that remains generally untreated and unmonitored for contaminants before it is consumed,” she says.
What’s the Risk?
Doughan’s master’s research evaluated swine water sources – specifically deep and shallow wells – to determine if they present a pathway for swine pathogens to enter farms. Results successfully identified porcine circovirus type 2 (PCV2) and swine manure markers in farm well water.
“This confirms that water sources can contain swine pathogens and may serve as active pathways for environmental and swine-specific pathogens to enter farms,” she says.
Although testing for other pathogens like porcine reproductive and respiratory syndrome (PRRS), porcine epidemic diarrhea (PED) virus and influenza are still being refined for swine water systems, water remains a known vector for viral and bacterial spread.
Research identified swine-specific manure markers in swine farm wells demonstrating a surface to groundwater contamination pathway, which demonstrates a biosecurity risk for farms.
“This is a very new area of study,” Doughan says. “We are essentially adapting human water-testing methodologies and converting them for use in agricultural swine spaces, which requires working out some technical kinks and further evaluation.”
The Biofilm Threat
Another way pathogens can enter the swine farm is through swine water distribution systems that provide areas for potential contamination within the farm leading to the formation of biofilms. Water quality changes drastically from the wellhead to the actual room where the pigs drink, especially on a biological level.
Biofilms (the bacterial slime that forms on the inside of pipes) act as a shield for pathogens. Biofilms contribute significantly to decreased water quality because they constantly shed bacteria, such as coliforms, directly into the drinking water.
Doughan’s recent PhD research revealed that even after a thorough terminal line cleaning, biofilms can grow back within just three days without continuous disinfection. Because of this, farms cannot rely on a single, one-time treatment; they must have a long-term, continuous cleaning plan, she says.
“We use water to wash and power-wash barns to disinfect them,” she points out. “If the water source itself is contaminated, we are inadvertently spraying pathogens directly into the environment we are trying to clean.”
Antimicrobial Resistance in Water Lines
Because water lines are frequently used to administer medications, Doughan took a closer look at antimicrobial resistance within biofilm organisms. She evaluated this through two distinct lenses – genotypic capability and phenotypic reality.
“We looked for antimicrobial resistance genes (ARGs) to see if the bacteria had the mechanism to be resistant,” she says. “Having the gene doesn’t guarantee the bacteria is actively using it; it simply means they are carriers with the capability to turn that resistance on.”
She found a significant number of these genes, coinciding with up to 14 different drug classes—including several classes that are not even used in swine production.
“This was eye-opening,” Doughan says. “It demonstrates that multidrug-resistant organisms are highly prevalent in the agricultural environment, and we do not necessarily have to use a specific drug on a farm for its corresponding resistance gene to show up.”
She took the research a step further to see if these biofilm organisms would actually grow when exposed to real-world drug concentrations.
“Using chlortetracycline (CTC) and lincomycin at the exact concentrations routinely administered through farm medicators into water lines, we found that quite a few organisms easily grew in their presence,” she says. “This confirmed active, phenotypic resistance to drugs we rely on.”
What Does This Mean for U.S. Pig Farms?
These findings have massive implications for antimicrobial stewardship and treatment planning on the farm. If biofilm bacteria are actively resisting these medications, it underscores why calibrating your medicator and ensuring accurate dosing is so critical. Under-dosing only accelerates this resistance.
“If we want to keep our pigs healthy, we must protect the efficacy of our veterinary drugs and do everything we can to be excellent stewards of these resources,” Doughan says.
