Systematic review of diagnostic techniques for identification of pathogens in fresh milk from dairy herds with high bulk milk somatic cell count

Abstract

A private veterinary practitioner wants to identify diagnostic techniques that are practical, commercially available, reliable, rapid, and cost-effective to diagnose milk-borne pathogens in dairy herds with high Bulk Milk Somatic Cell Counts (BMSCC). To enable this, a systematic review was done to identify diagnostic techniques to diagnose pathogen(s) in dairy herds with high BMSCC. To enable this, a systematic review was done to identify diagnostic techniques for pathogen(s) identification in dairy herds with high BMSCC.The criteria to identify the diagnostic methods included commercial, rapid, and cost-effective methods with high diagnostic sensitivity and specific for aerobic mastitogenic, zoonotic, food-borne, antimicrobial resistant and state-controlled disease pathogens in fresh milk intended for human consumption. A model using practical methods to identify these pathogens included somatic cell count (SSC) screening, phenotypical culturing/isolation/biochemically identification, anti-microbial resistance evaluation together with conventional PCR and multiplex real-time quantitative PCR. Results from the systematic literature identified the diagnostic sensitivity and specificity of SSC screening to be in the range of 49-94,5% and 57,7-86,8% respectively, while phenotypic identification of aerobic mastitogenic pathogens to be in the range of 9,1 -100% and 28,8- 100% respectively, Immuno-assay identification to be in the range of 75,5% - 100% respectively, conventional PCR 76,7-100% and 98,6-100% respectively and multiplex quantitative real-time PCR (Pathoproof -Thermofisher Scientific) with a 100 % analytic sensitivity and 99-100% analytic specificity as well as diagnostic sensitivity and specificity of 76,9-100% and 63,3-100% respectively , as accurate practical diagnostic techniques. Based on the systematic review results, the high range of sensitivity and specificity using the combined diagnostic model makes it a suitable model that can successfully and with confidence be implemented by a veterinarian in private dairy practice. It will make an enormous contribution in diagnostic surveillance procedures for the milk industry - public health interface in a veterinary One Health orientated practice.