Date Published: June 13, 2008
Publisher: BioMed Central
Author(s): Leena Suojala, Toomas Orro, Hanna Järvinen, Johanna Saatsi, Satu Pyörälä.
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.
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.
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.
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.
Environmental mastitis caused by coliform bacteria is an increasing problem for the dairy industry in many countries [1,2]. Mastitis caused by Escherichia coli is typically self-limiting and of short duration, but can be associated with severe clinical signs, reductions in milk yield and heavy tissue damage to mammary gland [3-5]. The strategies for preventing coliform mastitis include hygiene measures and in some countries prophylactic immunization. Incidence and severity of clinical signs of coliform mastitis were reduced using Escherichia coli core antigen vaccine [6-8].
Using a repeated challenge model at a short interval in the same cows could reveal possible carry-over effects of the previous intramammary infection by the same pathogen . In our study using two consecutive intramammary challenges with E. coli, all cows became infected and developed local (swelling, soreness, clots in milk) and systemic inflammatory reaction. Cows had a moderate systemic clinical response to both challenges, but after the second challenge local signs were significantly milder and disappeared faster. The same pattern was seen for the indicators of inflammation, the difference being statistically significant for serum and milk Hp, milk SAA, and WBC. Milk production returned to the pre-challenge level significantly faster after the second challenge. In the present study, one dose of anti-inflammatory medication was used at 12 h PC which may slightly affect the inflammatory response but given at both challenges, allows comparison of the two subsequent challenges.
The concentrations of SAA and Hp in serum and milk in this E. coli infection model were much higher than those seen in experiments using Gram-positive pathogens, which indicates the strong inflammation induced by E. coli [22,19,50]. Acute phase proteins studied here have been suggested as early markers of mastitis. They would also be useful parameters to monitor the severity of mastitis, to be used, for example, in studies on pathogenesis and effects of treatments. Repeated experimental intramammary induction of the same animals with E. coli bacteria has been used as a model in cross-over studies to reduce the individual variation between different cows. The significant differences between the consecutive challenges seen here suggest that in these studies the interval between challenges should be longer than 2 weeks.
LS was involved in the conception of the study, carried out the experiments, interpretated the results, drafted the manuscript and carried out coordination among authors, TO carried out laboratory analyses of acute phase proteins, statistical analysis and interpretation of the results and drafted the manuscript, HJ and JS carried out the experiments and participated in drafting the manuscript, SP made substantial contribution to conception of the study and revised the manuscript for important intellectual content in detail.