Acute phase response in two consecutive experimentally induced E. coli intramammary infections in dairy cows.
BACKGROUND
Acute phase proteins haptoglobin (Hp), serum amyloid A (SAA) and lipopolysaccharide binding protein (LBP) have suggested to be suitable inflammatory markers for bovine mastitis. The aim of the study was to investigate acute phase markers along with clinical parameters in two consecutive intramammary challenges with Escherichia coli and to evaluate the possible carry-over effect when same animals are used in an experimental model.


METHODS
Mastitis was induced with a dose of 1500 cfu of E. coli in one quarter of six cows and inoculation repeated in another quarter after an interval of 14 days. Concentrations of acute phase proteins haptoglobin (Hp), serum amyloid A (SAA) and lipopolysaccharide binding protein (LBP) were determined in serum and milk.


RESULTS
In both challenges all cows became infected and developed clinical mastitis within 12 hours of inoculation. Clinical disease and acute phase response was generally milder in the second challenge. Concentrations of SAA in milk started to increase 12 hours after inoculation and peaked at 60 hours after the first challenge and at 44 hours after the second challenge. Concentrations of SAA in serum increased more slowly and peaked at the same times as in milk; concentrations in serum were about one third of those in milk. Hp started to increase in milk similarly and peaked at 36-44 hours. In serum, the concentration of Hp peaked at 60-68 hours and was twice as high as in milk. LBP concentrations in milk and serum started to increase after 12 hours and peaked at 36 hours, being higher in milk. The concentrations of acute phase proteins in serum and milk in the E. coli infection model were much higher than those recorded in experiments using Gram-positive pathogens, indicating the severe inflammation induced by E. coli.


CONCLUSIONS
Acute phase proteins would be useful parameters as mastitis indicators and to assess the severity of mastitis. If repeated experimental intramammary induction of the same animals with E. coli is used in cross-over studies, the interval between challenges should be longer than 2 weeks, due to the carry-over effect from the first infection.
Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, FI-04920 Saarentaus, Finland. leena.suojala@fimnet.fi
Leena
L
Suojala
Toomas
T
Orro
Hanna
H
Järvinen
Johanna
J
Saatsi
Satu
S
Pyörälä
D000209:Acute-Phase Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D000210:Acute-Phase Reaction / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D004927:Escherichia coli Infections / Q000097:blood / Q000378:metabolism / Q000662:veterinary*; D005260:Female; D005786:Gene Expression Regulation; D008414:Mastitis, Bovine / Q000097:blood / Q000378:metabolism / Q000382:microbiology*; D008892:Milk / Q000737:chemistry; D013997:Time Factors
D000209:Acute-Phase Proteins