Primary infection protects pigs against re-infection with Lawsonia intracellularis in experimental challenge studies

In two separate trials previous termpigsnext term were experimentally infected with previous termLawsonia intracellularisnext term at 5–6 weeks of age followed by antibiotic treatment and resolution of the previous termprimary infection and then renext term-inoculated at 12–13 weeks of age. A treatment-control group of previous termpigsnext term received the previous termprimary infectionnext term and antibiotic treatment only, and served as control for the antibiotic treatment of the previous termprimary infection.next term A previous termchallengenext term-control group of previous termpigsnext term received the second inoculation dose only at 12–13 weeks of age to control infectivity of the previous termchallengenext term-dose and susceptibility of previous termpigsnext term to L. previous termintracellularisnext term at this age. previous termPigsnext term were monitored for shedding of L. previous termintracellularisnext term in faeces by PCR, and for the development of antibodies and responses of acute phase proteins in serum.

The presence of L. previous termintracellularisnext term antigen in the intestinal mucosa was examined in post mortem samples by immunohistochemistry. In both trials previous termprimarynext term infected previous termpigsnext term were protected from previous terminfectionnext term after previous termchallengenext term inoculation as evidenced by absence of faecal shedding of L. previous termintracellularisnext term, lack of changes in acute phase protein concentrations after previous termchallengenext term and with low levels of bacterial antigen in the intestinal mucosa of previous termrenext term-inoculated previous termpigsnext term comparable to that of the treatment-control previous termpigs.next term In contrast, previous termchallengenext term-control previous termpigsnext term shed L. previous termintracellularisnext term in faeces, had L. previous termintracellularisnext term antigen extensively present within all layers of the intestinal mucosa and developed a significant acute phase protein response in serum after the previous termexperimental infection.next term The acute phase protein response to L. previous termintracellularis infectionnext term was detected as an increased rise in the serum concentrations of C-reactive protein and haptoglobin from day-6 post previous terminfection,next term and increased serum concentrations of haptoglobin were generally seen 2–3 weeks after inoculation both at 5–6 and 12–13 weeks of age.

In conclusion substantial protection previous termagainstnext term L. previous termintracellularis infectionnext term was found in the previous termrenext term-inoculated previous termpigsnext term in contrast to the development of previous terminfectionnext term in age-matched control previous termpigs.next term The acute phase protein responses reflected both the observed protection previous termagainstnext term L. previous termintracellularis infectionnext term upon secondary previous termchallengenext term and that increased resistance to the previous terminfectionnext term develops with age.