Prevalence and aetiology of sheep mastitis in Alentejo region of Portugal.

Abstract

Mastitis in ewes is responsible for massive economic expenses. Other than the loss of ewes due to clinical mastitis, when subclinical mastitis occurs, because it is not readily detected, the milk with the causative pa- thogens is used to make dairy products. This fact is disadvantageous both for the technological process and for the consumer security. The knowledge of prevalence and aetiological agents of mastitis is of outmost importance to carry out an effective control of mastitis in sheep. The aim of this work is to bring out ovine mastitis in- formation in Portugal. We conducted a study focused on 18 milking producing sheep flocks to determine the prevalence of clinical and subclinical mastitis and to assess the aetiology of mastitis in sheep. Four hundred and fourteen milk samples randomly collected from sheep with subclinical mastitis and 27 milk samples from animals with clinical mastitis were bacteriological analysed according to an adaptation of the National Mastitis Council methodology. Anaerobic bacteria were also assessed. The identification was processed based on biochemical characterization, using the API system, API Staph, API 20 Strep, API 20 E, API 20 NE and API Coryne (BioMérieux). The results revealed high subclinical mastitis (SCM) prevalence (32.2%) and low clinical mastitis (CM) prevalence (1.7%). There was a higher prevalence in mechanically milked sheep than in hand milked animals. Coagulase negative Staphylococci (CNS) were in account of 42.9% of the CM events. Staphylococcus epidermidis represented 25% of all CM causative agents. Regarding subclinical mastitis, 70.1% of aetiological agents were identified as CNS species. From these, 43.4% were identified as Staphylococcus epidermidis accounting for 30.4% of total aetiological agents of SCM. Staphylococcus aureus was isolated from 22 specimens (6.2%) from SCM cases, which is of outmost importance in terms of public health, and Streptococcus agalactiae was isolated 15 times (4.2%) and showed to be in account of subclinical outbreaks with high prevalence rates. The fact that the majority of mastitis events were due to coagulate negative staphylococci out stresses the need for a proper management and rigorous hygienic milking procedure.