Acute-phase protein response in pigs experimentally infected with Haemophilus parasuis

The acute-phase protein (APP) response to an infection caused by Haemophilus parasuis, the etiological agent of Glässer's disease in pigs, was characterized measuring serum concentrations of pig major acute-phase protein (pig MAP), haptoglobin (HPT), C-reactive protein (CRP) and apolipoprotein A-I (ApoA-I) in colostrum-deprived pigs. They were divided into six experimental groups: non-immunized control group (I); immunized with a non-commercial bacterin (II); with an OMP-vaccine (III); with a sublethal dose (IV); and with two commercial bacterins (V and VI). All groups were challenged intratracheally with 5 × 10(9)CFU of H. parasuis 37 days after immunisation. The highest levels of the positive APPs (pig MAP, HPT and CRP) and the lowest levels of the negative APPs (ApoA-I) were observed in the animals that died as a consequence of the infection, both those in the non-immunized and in the immunized groups. However, the surviving animals (all of them in groups II, V and VI, two pigs in group III, and three in group IV) showed a minor variation in APP response, mainly on day 1 post-challenge (p.c.), and then tended to recover the initial values. APP response was still less pronounced in the groups of pigs previously immunized with bacterins. In conclusion, APP response can reflect Glässer-disease ongoing, showing a correlation between the severity and duration of the clinical signs and lesions and the magnitude of changes in the APP levels.