Laboratory-based evaluation of a simplified point-of-care test intended to support treatment decisions in non-severe bovine clinical mastitis

Malcata, F. B., Pepler, P. T. , Zadoks, R. N. and Viora, L. (2021) Laboratory-based evaluation of a simplified point-of-care test intended to support treatment decisions in non-severe bovine clinical mastitis. Journal of Dairy Research, 88(2), pp. 170-175. (doi: 10.1017/S0022029921000303) (PMID:33958019)

Abstract

To limit the use of antimicrobials in dairy cattle, farmers are increasingly encouraged to adopt targeted treatment decisions based on knowledge of the pathogens causing clinical mastitis (CM), whereby treatment of non-severe CM is generally recommended for gram-positive mastitis but not for gram-negative or culture-negative mastitis. The objectives of this study were to conduct a laboratory-based evaluation of the performance of a simplified slide test as a tool to differentiate gram-positive CM from other cases of CM, and to compare its performance against a commercially available on-farm test that is commonly used in our area (VétoRapid). Test outcomes after 24–48 h incubation were compared to results from bacteriological culture and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS). Milk samples (n = 156) were obtained from cases of severe and non-severe CM on seven farms and collected by farm personnel. After removal of small numbers of contaminated samples and organisms with unknown species identity, the simplified slide test showed high sensitivity and accuracy (>80%), similar to the comparator test. For most outcomes of interest (culture positive, Escherichia coli, or gram-positive growth), the specificity of the slide test was higher than the specificity of the comparator test. When considering non-severe cases of CM only, and interpreting detection of gram-positive organisms as indicative of the need for antimicrobial treatment, the simplified test had higher specificity (77.4% v. 60.4%) and higher positive predictive value (79.7% v. 70.0%) than the comparator test and similar sensitivity (83.9% v. 87.5%). The proportion of sampled CM cases, contaminated samples and gram-positive mastitis cases – which affects the positive and negative predictive value, the economic value of diagnostic testing and its potential to reduce antimicrobial use – differed between farms. The simplicity and accuracy of the slide test could make it an attractive tool for farmers to target antimicrobial treatment of non-severe clinical mastitis.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Zadoks, Professor Ruth and Pepler, Dr Theo and Boavida Malcata, Francisco and Viora, Dr Lorenzo
• Authors: Malcata, F. B., Pepler, P. T., Zadoks, R. N., and Viora, L.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Journal of Dairy Research
• Publisher: Cambridge University Press
• ISSN: 0022-0299
• ISSN (Online): 1469-7629
• Published Online: 07 May 2021
• Copyright Holders: Copyright © The Author(s), 2021
• First Published: First published in Journal of Dairy Research 2021
• Publisher Policy: Reproduced under a Creative Commons Licence

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
173650		Support for Evaluation of an on-farm culture system	Lorenzo Viora	Vetoquinol SA (FR) (VETOQ-FR)	Viora, Dr Lorenzo	Vets Farm- Farm Animal Clinical Sciences