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The establishment of endotoxin limits which satisfy animal welfare considerations in the testing of porcine vaccines

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Marion Wegener, Lukas Bruckner*, Klaus Cußler
Paul-Ehrlich-Institut, D-Langen, *Institut für Viruskrankheiten und Immunprophylaxe, CH-Mittelhäusern
Endotoxin (lipopolysaccharide, LPS) is a constituent of the cell walls of gram-negative bacteria and is found in many vaccines produced from these bacteria. High levels of endotoxin can give rise to a range of pathophysiological reactions, and adverse reactions tend to be seen in animals following vaccination.
In this study, pigs of various ages and weights were vaccinated with licensed porcine vaccines and the endotoxin content of the vaccines was determined with the LAL, conducted according to DAB 10. The experiments followed the DAB guidelines relating to the safety testing of veterinary vaccines. The animals were monitored for 48 h after vaccination, their body temperatures were measured, and blood samples were taken for analysis and for the determination of plasma endotoxin levels.
There was a clear relationship between vaccine endotoxin content and changes in blood cell counts and in the clinical picture. Elevated plasma endotoxin levels correlated with the occurrence of initial leucopenia followed by leucocytosis as well as with clinical symptoms ranging from refusal of food and depression to shock-like symptoms. After 24 h, normal physiological values were regained. Young animals weighing between 10 and 40 kg were found to be very sensitive to elevated endotoxin content in vaccines. The differences in individual reactions could be due not only to differences in vaccine endotoxin content, but also to differences in the reactivity of the organism, and in the type of bacteria used or in the composition of the vaccine.

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