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)

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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
Glasgow Author(s) Enlighten ID:Pepler, Dr Theo and Zadoks, Professor Ruth and Viora, Dr Lorenzo and Boavida Malcata, Francisco
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 (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

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
173650Support for Evaluation of an on-farm culture systemLorenzo VioraVetoquinol SA (FR) (VETOQ-FR)Viora, Dr LorenzoVets Farm- Farm Animal Clinical Sciences