A robust vaccination protocol at the sow and finisher levels greatly contributed to a low prevalence of Lawsonia intracellularis (Li), according to the results of a recent study led by Hannah Walker, a student in the Carlson College of Veterinary Medicine at Oregon State University.
She participated in the Swine Veterinary Internship Program last summer and conducted a Li surveillance study with her host farm Country View Family Farms and sponsor Pharmgate Animal Health. She also developed a sampling method.
“Li is the organism that causes the disease known as ileitis or proliferative enteropathy,” she said during the 2025 American Association of Swine Veterinarians annual meeting. “This is an endemic disease across many systems and can be a contributor to poor growth and poor feed efficiency, thus affecting a producer’s bottom line.”
She presented the results of her study in a poster competition at AASV titled, “Developing a Lawsonia intracellularis surveillance program to define prevalence in a commercial swine operation.”
Maximize Herd Health and Efficiency
Her goal was to create a surveillance program that can be utilized by other systems to determine herd prevalence. She says this information can then be used to help make decisions on herd management and vaccination protocols.
“Understanding the prevalence of this disease in your system can help you maximize your herd health and efficiency,” Walker says.
She looked at five different flows as part of her project. They consisted of one sow farm and at least one downstream finisher site. Of these flows, she studied vaccinated and unvaccinated finisher sites and NAE flows.
At the sow farms, blood and fecal swabs were collected on gilts and P1-P3 sows, Walker explains. From those samples, she ran blood ELISAs and fecal PCRs for Li. At the finisher sites, group oral fluids were collected via ropes for Li PCRs. Samples were collected three times over the growth period at 16, 20 and 24 weeks of age.
“In the system I was surveying, there was very low disease prevalence,” she says. “From the results, I was able to conclude that the antibody levels for Li were nearly consistent across all flows, despite the flow differences. I also saw that overall, there was little detection of Li via PCR in addition to the lack of clinical signs, even at the age of expected Li prevalence in finishing pigs.”
She says this research shows there are various factors that contribute to disease prevalence, which should be taken into account when looking at disease prevalence in a system. This includes, but is not limited to, maternal antibodies, rodent control and feed/water medications.
“Whether you vaccinate for Li at the finisher level or not, it is important to have sound maternal antibodies in your sow herd,” Walker says. “If you are not vaccinating your finisher pigs, there may be potential impact of environmental build-up over time that should be accounted for in your plan. Lastly, by determining herd disease prevalence, you can better manage your system, improve treatment programs and increase feed efficiency.”
Walker was one of 15 students who competed in the Veterinary Student Poster Competition at the AASV annual meeting. Read more here.
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