Abstract
The development of circulating antibodies for H. parahaemolyticus was studied in experimentally infected SPF pigs and in-contact SPF pigs. Blood serum titers were determined by a modified complement fixation test with normal SPF swine serum as a source of supplementary complement factor, and by an indirect haemagglutination test.
CF and IHA titers became positive within the first 2 weeks following exposure to H. parahaemolyticus, and reached peak values after 2 to 7 weeks (Figs. 1 to 3). The exposed pigs proved immune, in that they showed no clinical symptoms on challenge after resp. 6, 9 and 11 weeks.
While distinct titers were thus obtained with both tests in SPF swine experimentally exposed to H. parahaemolyticus, the CF test proved more specific than the IHA test when the 2 tests were compared in a field outbreak of polyserositis (Glässers disease) caused by H. parasuis. The CF test would therefore seem to be preferable to the IHA test in field diagnostic work (Table 1).
A noticeable finding was that challenge did not elicit an anamnestic antibody response in any of the immune pigs (Figs. 1 to 3). This fact together with negative bacteriological findings in the animals in question would seem to suggest that the challenge dose was unable to establish a permanent infection in the respiratory tract of the immune pigs.
Keywords: pleuropneumonia, complement-fixation test, Haemophilus parahaemolyticus, indirect haemagglutination test
Sammendrag
Den serologiske reaktion blev undersøgt i sera af SPF grise experimentelt inficeret med Haemophilus parahaemolyticus og af grise i kontakt.
Til undersøgelsen blev benyttet en indirekte hæmagglutinationstest og en modificeret komplementbindingsprøve med normalt SPF svineserum som supplerende faktor ved titreringen af marsvinekomplement.
Inden for de første 2 uger efter at grisene havde været udsat for smitte med Haemophilus parahaemolyticus fandtes positive CF og IHA titre. Titrene nåede maximum efter 2–7 ugers forløb (fig. 1–3). Ved re-infektion efter henholdsvis 6, 9 og 11 ugers forløb viste de undersøgte grise sig at være immune, idet kliniske symptomer ikke blev iagttaget.
I experimentelle undersøgelser fandtes begge serologiske metoder anvendelige. I sammenlignende undersøgelser af sera fra et udbrud af Glässers syndrom i en SPF besætning, hvor Haemophilus parasuis blev isoleret, fandtes CF testen at være mere specifik end IHA testen (tabel 1) og den må derfor foretrækkes i besætningsdiagnostiske undersøgelser. Det må fremhæves, at challenge ikke udløste et anamnestisk respons hos de immune grise (fig. 1–3). Dette forhold sammenholdt med det negative bakteriologiske fund ved aflivning antyder, at bakterien ikke etableredes i de immune grises respirationsveje, og at resistens over for reinfektion måske findes lokalt i respirationsvejene eller på næseslimhinden.
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