Establishment of Ascaris suum in the Pig: Development of Immunity Following a Single Primary Infection

Abstract

Development of immunity after a single primary infection of Ascaris suum in pigs was investigated with regard to the worm population dynamics of a superimposed A. suum infection, host immune response and gross liver pathological changes. Group A was given a primary infection of 60 000 infective A. suum eggs and group B was left uninfected. Four weeks later both groups A and B were inoculated with 1000 A. suum eggs, and subgroups were slaughtered 7, 14 and 21 days post challenge infection (p.c.i.). An uninfected control group C was slaughtered on day 21 p.c.i. The challenge worm recovery in group A was reduced compared to group B by 12%, 50% and 75% on day 7, 14 and 21 days p.c.i., respectively. In both groups was the expulsion of worms initiated between day 14 and 21 p.c.i. However, in group A the worms were recovered more posteriorly in the small intestine and 21 days p.c.i. the mean worm length was significantly shorter than in group B (p = 0.01). The results above were associated with significantly higher (p<0.05) antibody response and higher eosinophil counts in group A compared to group B. The present results suggest that the larval growth and survival of a challenge infection are decreased, probably due to higher antibody and eosinophil attack during the migratory phase.

Sammendrag

Effekten af en primær A. suum infektion, på en challenge infektion med A. suum, blev studeret med hensyn til etablering og udvikling af challenge infektionen samt svinets immun reaktion og patologiske forandringer i leveren. En gruppe svin blev podet med 60,000 A. suum og en gruppe var uinficeret. Fire uger senere blev begge grupper podet med 1,000 A. suum og delgrupper blev slagtet efter 7, 14 og 21 dage. Antallet af larver var reduceret med 12%, 50% og 75% på dag 7, 14 og 21 i de immuniserede svin. I begge grupper startede udskydelsen af larver mellem dag 14 og 21, men i de immuniserede dyr var larverne lokaliseret lidt længere tilbage i tyndtarmen og på dag 21 efter infektionen var larverne signifikant kortere på dag 21 end i kontrol dyrene. Disse resultater var associeret med en signifikant højere A. suum antistof reaktion og et højere niveau af eosinoflle leucocyter i de immuniserede svin i forhold til kontrol svinene. Resultaterne viser, at væksten og overlevelsen af larverne fra challenge infektionen var lavere i de immuniserede grise end i kontrol grisene, sikkert som et resultat af højere antistof og eosinofil angreb under den migratoriske fase.