7 facts you should know about Ileitis

1. A recent study re-confirms: Lawsonia intracellularis is present in most European herds

A recent survey of 144 European pig herds that had suffered a diarrhea outbreak in the previous year found that a staggering 90 percent of herds had been exposed to Lawsonia intracellularis¹. It is clear from this study that Lawsonia intracellularis is widespread and a serious concern.

2. Affected pigs can rapidly infect pen mates

In an assessment of Lawsonia intracellularis’ transmission rate in non-vaccinated pigs, scientists showed that one infectious pig is able to infect three susceptible pigs per week². Within an unprotected population, the number of infected pigs can triplicate every week. 

3. Vaccination reduces Lawsonia intracellularis transmission

It is important to implement a systematic vaccination program to reduce the spread of Ileitis as well as associated growth retardation. In a study², oral live vaccine significantly reduced transmission rates compared to their unprotected counterparts.

4. Local immunity is critical for protection against Lawsonia intracellularis

An infection with Lawsonia intracellularis is restricted to the gut, which is why it is expected that local immunity – so immunity that is limited to a particular organ or tissue – is critical. An ideal vaccine against Ileitis should be able to elicit a balanced immune response – both local and cell mediated immunity – to eliminate the pathogen. Oral vaccination has proven to induce an early local immunity at the gut level³.

5. Disruption of the gut microbiome by Lawsonia intracellularis infection has wide ranging implications for pig health and productivity

The gut microbiome (or microbiota) is known to influence health and productivity of pigs, and an infection with Lawsonia intracellularis appears to have a disturbing effect. An infection increases the susceptibility to Salmonella⁴. What does this mean for your farm? It’s simple: Lawsonia intracellularis behaves like a door opener to other bugs.

6. Oral vaccination reduces shedding of Lawsonia intracellularis and impacts the microbiome 

The microbial community in vaccinated pigs appears to be distinct from that of non-vaccinated and diseased pigs⁵. This change is associated with a drastic reduction in fecal shedding of Lawsonia intracellularis, showing that oral vaccination can have positive consequences on the composition of the gut microbiome, pig performance and transmission of the pathogen^6,7.

7. Pork producers need routine control measures against Ileitis

What do all these scientific findings mean for your farm? As we reduce our reliance on antibiotics, it is becoming clear that we need to implement routine control measures for Lawsonia intracellularis. Oral vaccination is an easy, pig friendly, efficacious and cost effective way to reduce the burden of Ileitis on your farm. Consult with your veterinarian on how to implement the best control option for you.

References

¹ Arnold et al 2019: Prevalence of Lawsonia intracellularis in pig herds in different European countries (nih.gov)

² Vasquez et al, 2019: Impact of vaccination on transmission of Lawsonia intracellularis

Erika Vasquez¹ ; Robert Valeris¹ ; Dana Beckler² ; Fabio Vannucci¹ 
50th Annual Meeting of the American Association of Swine Veterinarians (Orlando; March 9-12, 2019)
¹College of Veterinary Medicine, University of Minnesota; ²Gut Bugs, Inc, Minnesota 

Experimental design
A seeder-pig sentinel model was used (Figure 1). Ninety pigs were divided into three groups: orally vaccinated (Enterisol Ileitis); intramuscularly vaccinated (Porcilis Ileitis) and non-vaccinated. Day 21 post-vaccination, nine seeder pigs were challenged with L. intracellularis. Day 7 post-inoculation, seeder pigs were commingled as described in Figure 1.
Transmission rate and expected probabilities of shedding were assessed with the susceptible-infectious model. Animals were considered infectious when fecal quantitative polymerase chain reaction was equal or more than 103L. intracellularis per gram of feces (Collins et al, 2001).
In practical terms, this would roughly represent a threshold cycle of 31 or less based on the PCR assay offered by the University of Minnesota Veterinary Diagnostic Laboratory.

Results and practical implications

• Vaccination against L. intracellularis has been applied over the years with successful reduction of the clinical signs and fecal shedding, and resulting in significant improvement of growth performance in vaccinated animals.
• The assessment of the transmission rate under a non-vaccinated scenario showed that one infectious pig (shedding more than 103 bacteria per gram of feces) is able to transmit L. intracellularis to three susceptible pigs per week.
• From a practical standpoint, if pigs from infected and naïve flows are commingled at 10 weeks of age (end of the nursery phase) the number of infected pigs triplicate within the population every week.
• The results revealed that the chronic nature of the Lawsonia infection at the individual level is also reflected in the transmission of the disease at the population level characterizing a prolonged spreading of the infection in the finishing barn.
• Although the Lawsonia infection can impact the productive performance in the first weeks of the finishing phase when naïve pigs just started getting infected, the clinical diagnosis is only evident when most of the naïve population is infected and some animals are exhibiting diarrhea. This typical clinical scenario is usually observed only at later stages of the finishing phase when the animals are approaching the marketing age and it can misrepresent the actual impact of the disease in terms of performance throughout the growing-finishing phase.
• In the present study, transmission rates were significantly reduced in both vaccinated groups: 1.8 infected pig per week in the orally-vaccinated and 1.7 infected pig per week in the intramuscularly-vaccinated group.
• The model used to predict transmission over time also showed decreasing in the period of fecal shedding of Lawsonia in both vaccinated groups. While the median period of shedding in non-vaccinated animals was 11.2 weeks, orally- and intramuscularly-vaccinated animals showed 6.3 and 8.3 weeks, respectively.

These results highlight the importance of implementing vaccination programs at system level rather than site-specific interventions. This strategy prevents the risk of commingling batches of pigs from vaccinated and non-vaccinated sources, therefore reducing the impact of the disease in downstream flows.

³ Nogueira et al, 2013: Immunological responses to vaccination following experimental Lawsonia intracellularis virulent challenge in pigs - ScienceDirect

⁴ Beloeil et al, 2004: Risk factors for Salmonella enterica subsp. enterica shedding by market-age pigs in French farrow-to-finish herds - ScienceDirect

⁵ Guevarra et al, 2021: Oral Vaccination against Lawsonia intracellularis Changes the Intestinal Microbiome in Weaned Piglets

⁶ Leite et al, 2021: Frontiers | Oral Vaccination Reduces the Effects of Lawsonia intracellularis Challenge on the Swine Small and Large Intestine Microbiome | Veterinary Science (frontiersin.org)

⁷ Helm et al, 2021: Lawsonia intracellularis infected enterocytes lack sucrase-isomaltase which contributes to reduced pig digestive capacity | Veterinary Research | Full Text (biomedcentral.com)