Use of milk amyloid A in the diagnosis of subclinical mastitis in dairy ewes

Subclinical mastitis (SM) is one of the most important diseases affecting dairy ewes worldwide, withnegativeimpactontheanimalhealth,farmincomeandpublichealth.AnimalswithSMoftenremainuntreatedbecausethediseasemaynotberevealed.Increaseinsomaticcellcount (SCC)andpositivebacteriologyformastitispathogensinmilksamplesareindicativeofSMbuttheevidenceofonlyoneof thesealterations mustsuggestan uncertain SM(UM).UMisdefinedwhen positivebacteriologicalexamination (Latent-SM) or SCC>500000cells/ml (non-specific-SM) are detected in milk.Nevertheless, SCC and bacteriological examination are expensive, time consuming and are not yetinuseatthefarmlevelindairyewes.Recently,asensitiveacutephaseprotein,amyloidA,displayingmultiple isoforms in plasma and different body fluids including mammary secretion (milk amyloidA-MAA),hasbeeninvestigatedasamarkerofmastitisincowsand,inafewstudies,insheep.Theaimof this trial was to compare the concentration of MAA of single udder-halves in ewes with healthyudder-halves (HU-control group) and naturally occurring subclinical mastitis, both confirmed (SMgroup)anduncertain(UMgroups:Latent-SMandnon-specific-SM),formonitoringudderhealth.Thereliability of a specific ELISA kit for the measurement of MAAwas also tested. During a 3-month trialperiod, 153 udder halves were assigned to the experimental groups based on their health status: 25with SM, 40 with UM (11 with latent-SM and 29 with non-specific-SM) and 88 HU. SCC andbacteriologicalanalysiswereperformedtoestablishthecontrolandsubclinicalmastitisgroups.MAAconcentrationsinmilksamplesweremeasuredusingaspecificcommerciallymilkELISAkit.Thedatawere submitted to statistical analysis. Significant (P<0·05) differences among the groups SM, non-specific-SM and HU were detected with the SM having the highest level and HU the lowest. MAAconcentration is affected by the udder health status and is a useful indicator of subclinical mastitisand increased SCC in sheep.