Detection of antibodies to Salmonella lipopolysaccharide in muscle fluid from cattle

Abstract

Objective - To compare muscle fluid with serum samples for detection of antibodies to Salmonella lipopolysaccharide. Sample Population - Muscle fluid and serum samples from 2 cattle populations: 1 from the island of Bornholm with no history of salmonellosis (n = 39), and the other from the S dublin-enzootic areas of Jutland (n = 144). Procedure - Salmonella dublin (0:1,9,12), S typhimurium (O:1,4,5,12), and Salmonella 0:9-blocking ELISA were used for testing the samples. Results - In the S dublin ELISA, all serum and muscle fluid samples from cattle on the island of Bornholm had OD450 values well below the cutoff value (0.5). For samples obtained from cattle in the enzootic areas of Jutland, high correlation was found between serum and muscle fluid samples (rs = 0.89, P < 0.001). In addition, 19% (28/144) of the cattle had ELISA-positive muscle fluid and serum samples; 2% (3/144) had positive results for muscle fluid only, whereas 1 animal had positive results for serum only (κ = 0.91, P < 0.0001; sensitivity and specificity of 97%). The same samples had similar significant correlation in the S typhimurium ELISA (rs = 0.88, P < 0.001, κ = 0.7, P < 0.001; sensitivity of 73% and specificity of 98%) and the O:9-blocking ELISA (rs = 0.49, P < 0.001). Conclusion and Clinical Relevance - Muscle fluid samples taken at slaughter can be used as a practical alternative to serum samples for surveillance of Salmonella infections in cattle.