Extensive countrywide field investigation of subclinical mastitis in sheep in Greece

Abstract

The objectives of this work were (1) to investigate prevalence of subclinical mastitis, (2) to identify etiological agents involved, and (3) to study factors potentially predisposing ewes to subclinical mastitis. Milk samples were collected from 2,198 ewes in 111 farms with a total population of 35,925 ewes, in all 13 administrative regions of Greece, for bacteriological and cytological examination. Prevalence of subclinical mastitis was 0.260. Main etiological agents were staphylococci (Staphylococcus aureus and coagulase-negative species), which accounted for 0.699 of all isolates recovered; prevalence of staphylococcal mastitis was 0.191. In a multivariable mixed-effects analysis, the primary factor found to be associated with increased prevalence of subclinical mastitis was the management system practiced in flocks (flocks under a semi-intensive system had the highest prevalence). Other factors that were included in the multivariable model were the stage of lactation period (ewes in the 2nd month postpartum showed the highest prevalence) and application of postmilking teat dipping. In contrast, measures taken at the end of a lactation period (e.g., intramammary administration of antimicrobial agents) were not found to have an effect on prevalence of subclinical mastitis. The results confirmed the significance of subclinical mastitis as a frequent problem of ewes, with staphylococci as the primary etiological agent. The findings confirm the multifactorial nature of subclinical mastitis and indicate that its control should rely on many approaches.

Predisposing factors for bacterial mastitis in ewes

“…In a recent study performed in Greece, that had evaluated the importance of various factors and their interactions by using multivariable analysis, it emerged that only the management system applied in farms (European Food Safety Authority, ) was of importance for mastitis (Vasileiou, Cripps, et al, ). The results indicated that mastitis occurred more frequently in farms managed under an intensive or semi‐intensive system (Vasileiou, Cripps, et al, ). “Management system” includes various aspects of flock husbandry and organization (e.g.…”

“…The potential effects of post‐milking teat dipping in ewes have not been studied as extensively as in cows (Bergonier et al, ; Vasileiou, Cripps, et al, ). Nevertheless, omission of the practice can lead to a 3‐fold increase in the prevalence of subclinical mastitis (Vasileiou, Cripps, et al, ).…”

“…The potential effects of post‐milking teat dipping in ewes have not been studied as extensively as in cows (Bergonier et al, ; Vasileiou, Cripps, et al, ). Nevertheless, omission of the practice can lead to a 3‐fold increase in the prevalence of subclinical mastitis (Vasileiou, Cripps, et al, ). Incorrect application of teat dipping can also predispose to mastitis: use of dense solutions may cause teat chapping, which increases risk of mammary infection (Fragkou, Papaioannou, et al, ; Mavrogianni et al, ), whilst contaminated products may result in mastitis by sporadic pathogens (e.g.…”

“…In ewes, frequency of clinical mastitis immediately post‐partum is not as high as in cows (Bergonier & Berthelot, ). At that stage of the lactation period, Escherichia coli predominates as a causal agent (Jones & Lanyon, ; Vasileiou, Cripps, et al, ). Clinical mastitis can occur more often when lambs are taken away from their dams and milking starts (Bergonier & Berthelot, ; Fthenakis & Jones, ).…”

“…Clinical mastitis can occur more often when lambs are taken away from their dams and milking starts (Bergonier & Berthelot, ; Fthenakis & Jones, ). At that stage and thereafter, staphylococci are the primary causal agents of the infection (Vasileiou, Cripps, et al, ).…”