Bovine Mastitis in Egypt: Bacterial Etiology and Evaluation of Diagnostic Biomarkers

Abstract

This study is providing new techniques for diagnosis of bovine mastitis using multiplex real-time PCR and detection of some inflammatory markers at an early stage of infection. The consequences of bacterial culture and PCR for the identification of the 8 etiological agents of mastitis clinical or subclinical were demonstrated. Some pathogens recognized by conventional culture techniques were confirmed by PCR. Corynebacterium and mycoplasma were only distinguished by PCR. These data indicated moderate accord among the positive results of bacterial culture and PCR. Mixed infection of 2 or more mastitic bacterial agents were also identified more frequently by PCR while the measured blood and milk indices could separate healthy from mastitis and subclinical mastitic animals, it could not do so either between mastitis and subclinical mastitis or between single and mixed infection. Regarding inflammatory markers, most blood indices differed significantly between healthy vs mastitis animals, except for monocyte. Haptoglobin expression in milk varied significantly altering on mastitis circumstances and type of infection with mean fold change values of 1.87 in negative cases, 7.26 in single infected, and 10.64 in mixed infection. Also, a highly significant between the type of infection and immune-histocompatibility was detected. As immune histocompatibility was strongly expressed with mixed infection and wasn’t detected in negative cases. From a diagnostic point of view, TLC, lymphocyte, and neutrophil were considered good biomarkers for mastitis (Area under curve >0.9), and haptoglobin was the best biomarker for subclinical mastitis (AUC>0.9). Haptoglobin and basophils were the only markers having high AUC (being 0.6 and 0.7, respectively) discriminating single from mixed infection. Therefore, our diagnostic strategy has been deservedly proved its effectiveness as a rapid, complementary, and sensitive substitute to traditional techniques.