An attenuated Salmonella vaccine secreting Lawsonia intracellularis immunogenic antigens confers dual protection against porcine proliferative enteropathy and salmonellosis in a murine model.

Porcine proliferative enteropathy (PPE) caused by Lawsonia intracellularis (LI) is a global cause for substantial economic losses in the swine industry. Here, we constructed live attenuated Salmonella typhimurium (ST) mutant strains expressing and secreting 4 selected immunogenic LI antigens, namely, optA, optB, Lawsonia flagellin (LfliC), and Lawsonia hemolysin (Lhly); the resultant recombinant strains were designated Sal-optA, Sal-optB, Sal-LfliC, or Sal-Lhly, respectively. Using the BALB/c mouse model, we demonstrate that mice vaccinated once orally, either with a mixture of all 4 recombinant strains or with an individual recombinant strain, show significant (p < 0.05) production of LI-specific systemic immunoglobulin (Ig) G and mucosal IgA responses compared to the Salmonella alone group. Upon restimulation of vaccinated splenocytes with the LI-specific antigens, significant (p < 0.05) and comparable production of interferon-γ responses are found in all vaccinated groups, except the Sal-Lhly group, which shows non-significant levels. Challenge studies were performed in C57BL/6 vaccinated mice. On challenge with the LI (106.9 50% tissue culture infectious dose) 14 days post-vaccination, 20% (1/5) of mice in all vaccinated groups, except Sal-Lhly group, show the presence of the LI-specific genomic DNA (gDNA) in stool samples. In contrast, 40% (2/5) and 60% (3/5) of mice vaccinated with the Sal-Lhly strain and the attenuated Salmonella alone, respectively, were found positive for the LI-specific gDNA. Furthermore, 0% mortality was observed in mice vaccinated against the ST challenge compared to the 30% mortality observed in the unvaccinated control group. In conclusion, we demonstrate that the Salmonella-based LI-vaccines induce LI-specific humoral and cell-mediated immunities, and encompass the potential to offer dual protection against PPE and salmonellosis.

Elevated fat skatole levels in immunocastrated, surgically castrated and entire male pigs with acute dysentery.

Boar taint is due to androstenone and skatole (3-methyl-indole) accumulation in fat tissues. During a study to investigate the effect of immunocastration on fattening pigs, an outbreak of acute dysentery occurred caused by Lawsonia intracellularis and Brachyspira hyodysenteriae and resulted in cachexia and high mortality. Low androstenone levels in the immunocastrates (0.25 ± 0.04 µg/g liquid fat) suggested that the immunocastration had been effective, but unusually high skatole concentrations in fat tissues were found not only in entire males, but also in surgical castrates and immunocastrates (0.22 ± 0.15, 0.14 ± 0.08 and 0.18 ± 0.14 µg/g liquid fat, respectively). The findings suggest that boar taint can arise in cases of intestinal infections, even in castrated pigs.

Effects of oral vaccination against Lawsonia intracellularis on growing-finishing pig's performance in a pig production unit with endemic porcine proliferative enteropathy (PPE).

The aim of the present study was to evaluate the effect of oral vaccination against Lawsonia intracellularis (LI) on growing-finishing pig's performance. In a large Hungarian growing-finishing pig production unit, pigs with positive LI status were randomly divided into 2 groups and treated as follows: Group one: growing pigs (n = 4112) were LI vaccinated with an avirulent oral live vaccine (Enterisol Ileitis Boehringer Ingelheim Vetmedica, Inc., St. Joseph, USA). Group two: growing pigs (n = 4188 pigs) have not received LI vaccination. Culling and mortality rates, reasons for culling or mortality, and average daily weight gain were evaluated. Porcine proliferative enteropathy (PPE) caused culling and mortality rates were lower (0.2 % vs. 14.9 %, P < 0.001), and vaccinated pigs had lower none-PPE caused culling and mortality rates compared with the non-vaccinated ones (1.4 vs. 2.6 %, P > 0.05). While systemic infections and social stress or cannibalism related culling or mortality were significantly (P < 0.05) lower in vaccinated than in non-vaccinated pigs, reasons for culling or mortality due to non-LI caused diseases were non-significantly different between the vaccinated and non-vaccinated pigs. Average daily weight gain was higher (P < 0.05) in the LI vaccinated group of animals compared with the non-vaccinated ones (780 +/- 45 g vs. 660 +/- 71 g). The present results indicate that that LI vaccination does not only prevent PPE, but might result in more resistance and tolerance against other infectious and management caused losses.