Economic woes and the reemergence of swine dysentery have hampered control.
Since the organism Lawsonia intracellularis was discovered in 1993, we have learned that porcine proliferative enteropathy, or ileitis, can present itself several different ways clinically, and not everything that we have been calling ileitis was actually caused by this organism. Ileitis was sometimes overdiagnosed, and perceived treatment and vaccine failures were common simply because we were treating something different that looked like ileitis but actually wasn’t.
Today, we have a different set of potential confounders as to perceived and real failures in the control of ileitis.
The U.S. pork industry has just emerged from one of the longest and deepest economic insults ever experienced. To survive, cuts had to be made, including vaccination strategies for ileitis that were once considered an essential disease control tool.
Adding insult to injury has been the apparent reemergence in the last two years of an enteric disease that causes colitis and was thought to have been nearly eradicated: swine dysentery. In the 1990s, adoption of multiple-site production, totally slotted floors and all-in all-out production flows, plus improvements in disease elimination strategies and hygiene, nearly eliminated swine dysentery.
The reemergence of this enteric pathogen started in North Carolina, and veterinary reports indicate it has now spread to the Midwest.
Case Study No. 1
A Midwest producer had successfully used the ileitis oral vaccine to control symptoms in grow-finish for several years. Due to continued economic pressures, last summer the producer decided to discontinue vaccinating to lower cost.
Several months elapsed without incident except for perhaps an increase in the number of softer, pudding-like consistency stools observed in the finishing barns, which were attributed to feed or management changes. Six months after discontinuing vaccine, several market-weight hogs had bloody diarrhea and one died the day after the first cut was taken from the barn. Upon postmortem, the small intestine was filled with a blood clot and the intestinal wall was noticeably thickened in the region of the ileum. Samples were submitted to the diagnostic lab and individual sick pigs were treated with antibiotics. As suspected, the diagnostic lab confirmed ileitis caused by Lawsonia intracellularis.
A treatment protocol utilizing feed-grade antibiotics was established for the pigs in the grower and finisher, and oral vaccination with the avirulent live Lawsonia intracellularis vaccine was resumed in late nursery phase pigs.
This outbreak demonstrated the need for vaccination, but likely the vaccine was working and paying for itself, even through tough times.
Case Study No. 2
Last winter, a producer who fed out large groups of weaned Canadian pigs called to report several pigs in the grower phase with bloody diarrhea, which she thought was due to ileitis. She always vaccinated the pigs during the nursery phase for ileitis and was confident that this group had been vaccinated according to the company’s recommendations. She wanted to know why the vaccine had failed.
Upon examination, it was noticed that in addition to blood in the feces, there appeared to be an unusual amount of mucous mixed in with the bloody diarrhea. This was unusual enough to prompt a decision to sacrifice a pig with the typical symptoms and submit tissues to the diagnostic lab for confirmation. During the postmortem, it was noted that the lesions were confined to the large intestine or colon, which eliminated ileitis as a differential diagnosis, because that organism is confined to the small intestine.
The producer began treating individual pigs with an appropriate antimicrobial, and since there were nearly 5% in the group with clinical signs, it was also recommended that oral, water-based antimicrobials be initiated as soon as possible. The treatment recommendations appeared to improve the clinical picture within a day or two.
The lab reported the diagnosis on the pig that was submitted was swine dysentery, and polymerase chain reaction (PCR) testing of the feces were confirmed positive for Brachyspira hyodysenteriae.
Conclusion
Don’t become complacent! Diseases can produce clinical signs that are similar or even identical to the trained eye of a swine veterinarian. It is imperative to evaluate each swine disease outbreak on a case-by-case basis and make use of the diagnostic laboratory to confirm or deny a diagnosis based solely on clinical symptoms and what the textbooks describe.
Just because you haven’t seen a particular disease for a long time, doesn’t mean that it can’t come back to bite!