The Importance of Staphylococci and Threshold Value of Somatic Cell Count for Diagnosis of Sub-clinical Mastitis in Pirlak Sheep at Mid-lactation

Occurrence of Listeria monocytogenes and Escherichia coli in Raw Sheep's Milk from Farm Bulk Tanks in Central Italy

ABSTRACT

For milk hygiene and safety, the milking phase is a critical moment because it is a probable pathway for the introduction of unwanted microorganisms in the dairy chain. In particular, Listeria monocytogenes and Escherichia coli are known as possible microbial contaminants of raw sheep's milk, although extensive knowledge regarding their contamination dynamics on sheep farms is still lacking. This study aimed to examine the occurrence and concentration of these microorganisms in milk samples collected from farm bulk tanks in the region of Lazio (Central Italy) and to investigate the related risk factors. Over a period of 1 year, we collected 372 milk samples from 87 sheep farms and administered a questionnaire to acquire information regarding relevant farm management variables. L. monocytogenes was not found in any of the samples, which indicates a low occurrence of this pathogen in sheep's bulk tank milk. In contrast, E. coli was found in almost two-thirds of milk samples (61%) but at levels below 102 CFU/mL in most of them (approximately 75%). Statistical analysis indicated that, during the warmest seasons, E. coli presence is more probable and counts are significantly higher. Unexpectedly, milk collected by hand milking had a lower level of contamination. Although further studies are necessary to clarify some aspects, the reported data add to the knowledge about the occurrence of L. monocytogenes and E. coli in raw sheep's milk and will be useful for future risk assessments.

HIGHLIGHTS

Mastitis pathogens and somatic cell count in ewes milk

The aim of this study was to determine the occurrence of pathogens in selected group of ewes and the relationship between somatic cell count (SCC) and the presence of pathogens. The experiment was carried out on a dairy farm, where predominantly breed was a Tsigai. Sampling was carried out in monthly intervals as part of the milk recording test day from February to July 2019. A total of 303 ewes were included in the survey, during the milk recording test day. The ewes with SCC ≥1000 × 103 cells.mL-1 were selected for further sampling at half udder level. Based on SCC the ewes were divided into five groups: <200 ×103; ≥200 <400 × 103; ≥400 <600 × 103; ≥600 <1000 × 103; ≥1000 × 103 cells.mL-1. The first group of SCC contained 33.9% of milk samples, the second 14.1% of samples, the third 5.7% of samples, the fourth 6.2% and the fifth 40.1% of samples. The most common pathogens were coagulase negative staphylococci (CNS). The most frequent CNS was Staphylococcus (S.) simulans (24.4%). S. aureus was identified in 5.3% of bacteriological positive samples. Almost 70% of ewes with bacteriological positive samples were repeated identified the presence of pathogens during tested period. SCC ≥500 × 103 cells.mL-1  were detected in 92.5% bacteriological positive milk samples. The presence of pathogens increased SCC in milk (p <0.001) as compared to samples free of pathogens. In conclusion, the SCC ≥500 × 103 cells.mL-1 could be important for detection of subclinical mastitis at half udder level in dairy ewes.

The Impact of Mastitis on Reproductive Parameters of Dairy Cows

The aim of this study was to evaluate the occurrence of mastitis and its impact on the reproductive parameters in a herd of 180 dairy cows. Based on the herd records 127 cows of Slovak spotted cattle and their crosses with red Holstein were selected for study between 1—2 months after calving. The examination of the health status of the mammary glands consisted of: the clinical examination of the udder, the California mastitis test (CMT) supplemented by the collection of mixed milk samples, and the laboratory examination of bacterial pathogens causing the mastitis. In addition to the mam­mary investigation, reproduction indicators such as the length of the insemination interval, the service period, the intercalving period and the insemination index were also analyzed. The results of this study indicated: a high incidence of mastitis (41.6 %), especially latent (21.2 %), subclinical (15.7 %) and clinical (4.7 %) forms were most common in the herd. The most frequently isolated bacteria from the infected milk samples were: coagulase negative staphylococci (54.1 %), S. aureus (16.9 %), Streptococcus spp. (15.0 %), A. viridans (7.5 %) and Ent. faecalis (6.4 %). According to the available literature, the optimum values of the intercalving period were 365—400 days, the insemination interval 55—80 days, the insemination index 1.2—2 and the service period 60—110 days. In comparison, our results showed increased, unsatisfactory reproductive values in the group of dairy cows with clinical mastitis. While in healthy cows as well as in groups of cows with latent and subclinical mastitis, all of the reproductive indicators were within the optimal levels.

Role of staphylococci in mastitis in sheep

Staphylococci have been isolated from various sites of the body of healthy sheep, as well as from many infections of those animals, the main one being mastitis. The objective of this review is to appraise the importance and significance of staphylococci in causing mastitis in ewes. The review includes a brief classification and taxonomy of staphylococci and describes the procedures for their isolation and identification, as well as their virulence determinants and the mechanisms of resistance to antibacterial agents. Various staphylococcal species have been implicated in staphylococcal mastitis and the characteristics of isolates are discussed with regards to potential virulence factors. Staphylococcal mastitis is explicitly described, with reference to sources of infection, the course of the disease and the relevant control measures. Finally, the potential significance of staphylococci present in ewes' milk for public health is discussed briefly.

Somatic cell count during first and second lactation in ewes

The aim of this study was to describe the frequency of distribution of ewes in SCC groups on the basis SCS (somatic cells score) per lactation and estimate changes of SCC from 1st lactation on 2nd lactation. The experiment was carried at seven farms in 1st observed period (2016 and 2017) and at eight farms in 2nd observed one (2017 and 2018). Within each of periods the same animals were sampled on their 1st and following 2nd lactation in next year of study, only. Totally 1199 milk samples from 159 ewes and 1653 milk samples from 219 ewes were collected during 1st period and 2nd period, respectively. Milk sampling were taken monthly from April to August in both periods. For evaluation only ewes with minimum three sampling per year (minimum six samples per animal) were included in the study within both periods. The ewes were divided into the five SCC groups on basis of their SCS per lactation: G1 = SCC <200 × 103 cells.mL-1, G2 = SCC ≥200 <400 × 103 cells.mL-1, G3 = SCC ≥400 <600 × 103 cells.mL-1, G4 = SCC ≥600 <1000 × 103 cells.mL-1 and G5 = SCC ≥1000 × 103 cells.mL-1. In total statistically significant impact of parity on SCC in 2nd period was detected (p <0.0001) only. From the farm point of view in 1st period only in two farms and in 2nd one in five farms significant effect of parity was found out. Thus in some farms no increase of SCC from first to second lactation was observed. When comparing the changes in SCC from the first to the second lactation in both first and second periods, 6.92% and 10.96%, respectively ewes moved from SCC group G1 to G5. The significant effect of farm management and parity on SCC was demonstrated.

Mastitis Pathogens Isolated from Raw Milk Samples on Sheep Farms Situated in Marginal Parts of Slovakia

Relatively large parts of the Slovak territory are marginal regions, which in terms of the economy of ruminant rearing can effectively produce animal commodities only occasionally. The aim of this study was to evaluate the occurrence and aetiology of mastitis during one milking season in two sheep dairy herds of 224 (A) and 270 (B) ewes situated in the marginal parts of Slovakia. A complex examination of health status of ewes based on: the clinical examination of the udder, macroscopic evaluation of milk with the California mastitis test (CMT) and the bacteriological analysis of raw milk samples from individual halves were carried out at the beginning (April) and at the end (September) of the milking season. The prevalence of intramammary infection (IMI) in the herds of ewes (A and B) were 19.1 % and 14.3 %, respectively. In both herds we confirmed predominantly the subclinical forms of IMI. The highest percentages of aetiological agents were determined for coagulase negative staphylococci (CoNS), such as Staphylococcus chromogenes, Staphylococcus schleiferi, Staphylococcus epidermidis, Staphylococcus xylosus, Staphylococcus piscifermentans and Staphylococcus intermedius, the occurrences of which were determined in 41 (48.2 %) and 37 (47.9 %) positive milk samples, respectively.

Mastitis in sheep--The last 10 years and the future of research

Bacterial mastitis is a significant welfare and financial problem in sheep flocks. This paper reviews the recently published literature, including publications that highlight the significance and virulence factors of the causal agents, especially Staphylococcus aureus and Mannheimia haemolytica, the primary causes of the disease. Research has also contributed to the understanding of risk factors, including genetic susceptibility of animals to infections, supporting future strategies for sustainable disease control. Pathogenetic mechanisms, including the role of the local defenses in the teat, have also been described and can assist formulation of strategies that induce local immune responses in the teat of ewes. Further to well-established diagnostic techniques, i.e., bacteriological tests and somatic cell counting, advanced methodologies, e.g., proteomics technologies, will likely contribute to more rapid and accurate diagnostics, in turn enhancing mastitis control efforts.

Production of enterotoxins of Staphylococcus spp. isolated from samples of sheep milk

In our study was followed occurrence of mastitis in herd of 430 sheep of breed zoslachtena valaska with hand milking technology examined two times during one lactation season. Individual examination consisted from clinical examination of udder and microbiological examination of milk samples. By PCR was determined presence of genes coding production of enterotoxins, and by ELISA methods production individual types of enterotoxins. From individual forms of mastitis were frequently detected subacute (6.7%), subclinical (5.7%) and acute (2.9%). The coagulase-negative staphylococci (CNS) were identified in 102 (65.4%) from all 156 positive isolates. The CNS and S. aureus caused subacute (5.1%), subclinical (3.9%) and acute (2.4%) forms of mastitis. The most frequently isolated were S. epidermidis, followed by S. chromogenes and S. xylosus from ewes with subacute and subclinical mastitis. From acute and chronical forms of mastitis were  predominantly isolated S. aureus, S. uberis and S. epidermidis. The production of staphylococcal enterotoxins (SE) - SEA, SEB, SEC, SED and the presence of genes sec (3), sea (2), seb (2) and sed (2) were determined in S. aureus, S. epidermidis, S. schleiferi and S. chromogenes, respectively. The results suggested on the high occurrence (12.4%) of subacute and subclinical forms. Confirmed production of enterotoxins and presence of genes coding their production present a risk for human health and decreased a quality of milk and products from sheep´s milk.