A scientific review shows that the bacterium known to cause ileitis in pigs is not becoming resistant to antibiotic treatment. The real culprit may be misdiagnosis or mismanagement of the disease.
An international expert on porcine proliferative enteropathy (PPE), commonly called ileitis, says the disease-causing bacterium Lawsonia intracellularis has not become resistant to antibiotic treatment.
Steven McOrist, DVM, is a veterinary pathologist from Australia. "Bacteria such as L. intracellularis don't possess some of the critical cell components needed to allow resistance to occur," says McOrist, who spoke at the American Association of Swine Practitioners annual meeting. "In addition, numerous studies continue to show this particular bacterium is still as susceptible as ever to antibiotics such as tylosin."
Some producers and veterinarians have speculated about antibiotic resistance to products such as Tylan, says McOrist. "This may be due to misdiagnosis because of a similarity between the characteristics of ileitis and other diseases, inadequate dosing or pigs simply not eating enough medicated feed for efficacy."
Propping Up Feeding Levels Poor feed intake can make it especially difficult to control ileitis, points out David Bane, DVM, and senior technical consultant for Elanco Animal Health. This is a particular problem for breeding females that are affected with the acute, hemorrhagic form of ileitis.
"We have recommended that producers increase the amount of feed fed. A lot of breeding animals are limit-fed. They are fed but once a day, and so they are getting less than the proper amount of medication that is in the ration. (The Tylan ileitis claim is for 100 g./ton for prevention and control.) We are suggesting they feed those females multiple times a day, especially during stressful times," says Bane.
Finishing hogs are fed the same rate, 100 g./ton, but since they are fed ad lib, those animals are more likely to receive the proper amount of the medication to prevent and control ileitis.
Current practices of 50-60% annual female turnover rates and the growing number of repopulated herds result in large numbers of young breeding females entering a herd. This adds to stress, which can trigger the disease, says Bane. The problem is pronounced in large herds that are introducing large numbers of new females almost on a continuous basis.
"It seems inevitable that your operation will get the organism that causes ileitis - and with stress you may get the disease," adds McOrist. "We can control the organism, but it is hard to control the stress."
Besides breeding animals, ileitis affects grow-finish hogs, typically 12-20 weeks of age. Studies now show exposure varies from late nursery to early grower phase.
Strikes High-Health Herds Why does it seem that PPE or ileitis strikes high-health herds most?
McOrist speculates that the best-managed operations may have more problems with ileitis because they already have cleared up enteric pathogens that cause swine dysentery and the various forms of E. coli that might mask ileitis. Plus, the modern, commercial genetics used in these systems also seem predisposed to ileitis.
Improved diagnostics have heightened the industry's ability to detect the ileitis organism, increasing awareness and identification of the problem, says Bane. Ileitis is often a subclinical problem that may go unnoticed without solid production records.
"The longer the pigs are in the system, the more the problem of variability in growth increases," stresses Bane. "That's why we suggest first identify that you are dealing with ileitis. Get a good diagnosis. Find out where the problem is occurring. Weigh a few pigs to confirm variability problems. Then try to prevent those problems from occurring with good sanitation and disinfection, management and a strategic medication program."