Control efforts have slowed the advance of this pesky bacterial organism.
Haven't heard much about ileitis lately? There may be a reason. Lawsonia intracellularis, the organism that causes ileitis, is certainly still around, but great strides have been made in methods to control it.
The organism that causes ileitis (and the various clinical and subclinical manifestations) was discovered in 1993. It can present several different clinical faces and even affect pigs without signs of clinical disease.
Subclinical ileitis (the low level infection without clinical signs) is our main focus today. If left unchecked, it reduces feed intake and average daily gain, lowering performance. This form of the disease often goes unnoticed until individual pigs become chronically infected. These chronic pigs never achieve market weight, and if they survive, are often considered of no value at closeout. Typically, they gain slower than their peers and take more feed per pound of gain to reach market weight.
Clinical outbreaks of ileitis still occur and for reasons not understood. These outbreaks seem to occur more often in the heat of summer. There is speculation that the added stress of summer heat, coupled with an increase in moisture in the pens, allows the pathogen to escape the control measures we commonly use. Always be on the lookout for clinical signs after the first market hogs are sorted off.
Perhaps the most novel approach to controlling ileitis has been the development of an avirulent (nonpathogenic) live vaccine. It has had a large impact on both the incidence and severity of ileitis outbreaks, and has reduced the reliance on antimicrobials in both replacement gilts and in grow-finish populations.
The vaccine was licensed and introduced to the market in 2001, and it has been estimated that nearly a third of all U.S. swine are now vaccinated annually. To be effective, pigs must be vaccinated 3-4 weeks prior to exposure to the organism. In some cases, feed-grade antimicrobials have proven very effective in controlling or treating ileitis in its various forms.
Despite these treatments, outbreaks among growing pigs and replacement gilts still occasionally occur. Besides the cost of these tools, questions also remain about the subclinical form of the disease and its impact on growth performance.
Case Study No. 1
In the past two summers, a wean-to-finish producer has found heavy-weight hogs, just prior to marketing, that developed bloody, loose stools. He often found a dead hog with bloodstained rear quarters in a pen of seemingly normal hogs. A postmortem exam and lab submissions revealed the clinical symptoms were due to acute proliferative hemorrhagic enteropathy (PHE) caused by Lawsonia intracellularis.
After using antimicrobials to bring the outbreak under control, the producer vaccinated with the water-soluble ileitis vaccine from Boehringer Ingelheim (Enterisol Ileitis). Since clinical signs usually occurred late in the finisher, it offered a wider window of opportunity to vaccinate and immunize the pigs ahead of exposure.
All feed medications were removed from the barns to be vaccinated 9-10 weeks postweaning or the first week of finishing. This allowed the vaccine to be applied in the middle of the non-medicated window so as to not destroy the avirulent live vaccine. The producer worked closely with his veterinarian to assure vaccination protocol was performed correctly.
Since initiating vaccination, clinical signs have been eliminated, growth rate has improved about 5% and there are fewer deaths of market weight hogs due to PHE during the summer months.
Case Study No. 2
Danish colleagues have had to deal with severe restrictions on the use of antimicrobials in swine since 1999. After the ban on growth promotion use of antibiotics, Danish vets and producers have looked to control an explosion in ileitis cases.
Swine dysentery and Mycoplasmal pneumonia had been successfully eliminated from populations of pigs, so Lawsonia intracellularis seemed a natural target of elimination efforts. Swine practitioners worked with swine technical services veterinarians to create protocols for elimination.
To maximize chances for successful elimination, the Danes limited their attempts to startup farms or complete depopulation/repopulation situations.
The protocol called for feeding antimicrobials effective against Lawsonia, such as tylosin or tiamulin, for 28 days prior to populating the site and thoroughly washing and disinfecting every gilt prior to entry into the clean facilities.
To date, the Danes have been successful in elimination in many cases. The average time between elimination and rebreaking with Lawsonia is about 18 months, but one herd has stayed free for over six years. Growth rates of pigs in the absence of Lawsonia have been phenomenal, commonly surpassing 2.2 lb./day in the grow-finish phase without direct-fed antimicrobials.