Manageable risk factors associated with the lactational incidence, elimination, and prevalence of Staphylococcus aureus intramammary infections in dairy cows

Canadian Bovine Mastitis Research Network, CP 5000, St-Hyacinthe, Quebec J2S 7C6, Canada.
Journal of Dairy Science (Impact Factor: 2.57). 03/2012; 95(3):1283-300. DOI: 10.3168/jds.2011-4711
Source: PubMed


Staphylococcus aureus intramammary infections (IMI) are a major cause of mastitis on farms worldwide. Incidence and elimination rates are the key determinants of prevalence of Staph. aureus, and risk factors associated with these rates must be identified, prioritized, and controlled to obtain long-term reduction in prevalence. The objectives of this study were to identify manageable risk factors associated with the lactational incidence, elimination, and prevalence of Staph. aureus IMI. A cohort of 90 Canadian dairy farms was recruited and followed in 2007 and 2008. Quarter milk samples were collected repeatedly from a selection of cows, and bacteriological culture was realized to assess incidence, elimination, and prevalence of Staph. aureus IMI. Practices used on farms were measured using direct observations and a validated questionnaire. A linear regression model was used to explore the relationship between herd IMI prevalence and incidence and elimination rates. Multilevel logistic regression models were used to compute measures of associations between practices used on farms and IMI incidence, elimination, and prevalence. The herd incidence rate was the most important predictor of herd IMI prevalence: a reduction of the incidence rate equivalent to its interquartile range (0.011 new IMI/quarter-month) was associated with a prevalence reduction of 2.2 percentage points; in comparison, an equivalent increase of the elimination rate by its interquartile range (0.36 eliminated IMI/quarter-month) resulted in a prevalence reduction of 0.4 percentage points. Postmilking teat disinfection and blanket dry-cow therapy were already implemented by most herds. Most of the practices associated with Staph. aureus IMI incidence were related to milking procedures. Among these, wearing gloves during milking showed desirable associations with IMI incidence, elimination, and prevalence. Similarly, adequate teat-end condition and use of premilking teat disinfection were associated with lower IMI incidence and prevalence. The initial herd prevalence of Staph. aureus IMI was positively associated with subsequent IMI incidence. This indicates that, in some situations, an initial reduction of the pool of infected quarters could be justified. Some housing practices were associated with IMI incidence, elimination, or prevalence. The effects of these latter practices, however, were often influenced by specific cow characteristics such as parity or days in milk. These results highlight the importance of good milking practices to prevent Staph. aureus IMI acquisition and, therefore, reduce their prevalence.

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Available from: Herman Wildrik Barkema, Sep 09, 2015
    • "The economic gains of best practice with regard to animal health have been well documented (Young, Eidman, and Reneau 1985; Marsh 1999; Bennett 2003) with much consideration given to dairy herd health (Esslemont and Peeler 1993; Stott 2011; Bruijnis et al. 2013) and in particular to the economics of mastitis (Barkema et al. 1998, 1999; Dufour et al. 2011, 2012). Mastitis is the inflammation of the mammary gland caused by bacterial infection (Huijps 2009) and remains a particular and costly challenge for the dairy industry given its subsequent impact on milk quality due to both yield and compositional effects. "
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    ABSTRACT: Purpose: To examine the role of agricultural education and extension in influencing the adoption of best practice with regard to herd-level mastitis management. Design/Methodology/Approach: Somatic cell count (SCC) is an indicator of herd health with regard to mastitis and is negatively related to productivity and profitability. Panel data regression methods are utilised here to quantify the role of agricultural education and extension in reducing cell count and in influencing farmer best practice with regard to herd health. The impact of education and extension on farmer uptake of milk recording is of particular interest. Data utilised is farm-level Farm Accountancy Data Network (FADN) data for Ireland over a five-year period (2008–2012). Findings: Farmer uptake of formal agricultural training and liaison with agricultural extension services are shown to significantly improve mastitis herd health. Collectively, education, extension and milk recording results in an overall SCC reduction of 25% for the average herd. Farmers who undertook agricultural training were ten times more likely to monitor milk quality through milk recording compared to those who had not. Additionally, those farmers in contact with an extension service and also participated in a dairy discussion group were seven times more likely to practice milk recording. Practical Implications: The importance of farmer behaviour in the optimum management of herd health has been validated, as has the role of agricultural education and extension in influencing the uptake of best practice by farmers. Originality/Value: To date little research has been conducted using nationally representative herd-level data on the role of agricultural education and extension in improving animal health best practice.
    The Journal of Agricultural Education and Extension 07/2015; DOI:10.1080/1389224X.2015.1063518
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    • "Mastitis, the most common disease of dairy herds worldwide (Fessler et al., 2010), can be caused by over 150 different microorganisms, such as Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus epidermidis, Corynebacterium bovis, Corynebacterium pyogenes, and Candida albicans. Among all of these microorganisms, the most important is S. aureus, which is a common cause of mastitis on dairy farms (Olde Riekerink et al., 2008) and the most frequently isolated pathogen in heifer mastitis (Delgado et al., 2011; Dufour et al., 2012). In Brazil, studies report the predominance of S. aureus over other disease-causing agents in all regions of the country (Brito, 1996). "
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    ABSTRACT: Bovine mastitis is the primary disease of dairy cattle worldwide and it causes huge economic losses. Among several microorganisms that are the causative agents of this disease, S. aureus is the most prevalent. Although antibiotic therapy is still the most widely used procedure for the treatment of bovine mastitis, alternative means of treatment are necessary due to the presence of antibiotic residues in milk, which is a growing concern because of its interference with the production of milk derivatives and the selection of resistant bacterial strains. The use of bacteriophages as a tool for the control of pathogens is an alternative treatment to antibiotic therapy. In this work, to obtain phages with the potential for use in phage therapy as a treatment for mastitis, we isolated and identified the bacteria from the milk of mastitis-positive cows. A total of 19% of the animals from small and medium farms of the Zona da Mata Mineira, Brazil was positive for bovine mastitis, and bacteria of the genus Staphylococcus were the most prevalent pathogens. The majority of the S. aureus isolates tested was resistant to penicillin and ampicillin. In parallel, we isolated 10 bacteriophages able to infect some of these S. aureus isolates. We determined that these phages contained DNA genomes of approximately 175 kb in length, and the protein profiles indicated the presence of four major proteins. Electron microscopy revealed that the phages are caudate and belong to the Myoviridae family. The isolates exhibited interesting features for their use in phage therapy such as a high lytic potential, a wide range of hosts and thermostability, all of which favor their use in the field.
    Journal of Animal Science 07/2013; 91(8). DOI:10.2527/jas.2012-5884 · 2.11 Impact Factor
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    • "The presence of the pathogen in raw milk represents a potential source for introduction of S. aureus into the dairy products supply chain (D'amico and Donnelly, 2010). Contamination of milk with S. aureus originates mainly from animals with intramammary infections (Dufour et al., 2012); however, other sources of contamination can be milker's hands, the farm environment, and production utensils either in ovine (Vautor et al., 2005) or caprine ( Jakobsen et al., 2011) milk. "
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    ABSTRACT: Abstract The presence of Staphylococcus aureus in raw milk can represent a potential threat to human health, due to the introduction of pathogenic strains into dairy food supply chain. The present study was performed to investigate the genetic variation among S. aureus strains isolated from bulk tank goat's milk. The virulence profiles were also assessed to link the isolates with the potential source of milk contamination. A population study was performed on 60 strains using distance-based methods such as pulsed-field gel electrophoresis (PFGE), and the output was analyzed using Structure statistical software (University of Chicago; ). This Bayesian clustering model tool allows one to assign individuals into a population with no predefined structure. In order to assess partition of genetic variability among isolates, groups obtained by Structure were also investigated using analysis of molecular variance. S. aureus was recovered in 60 out of 78 samples (76.9%) collected from 26 farms. According to PFGE analysis, the strains were divided into 25 different pulsotypes and grouped into two main clusters. Restriction profiles, analyzed by Structure, allowed us to identify two distinct S. aureus genetic groups. Within each group, the strains showed a high coefficient of membership. A great part of genetic variability was attributable to within-groups variation. On the basis of the virulence profile, 45% of the isolates were linked to "animal" biovar, while 6.7% could be assigned to "human" biovar. Out of 60 strains, 27 were characterized by in vitro production of either enterotoxins A (5.0%), C (38.3%), or D (1.7%). The present study showed a high prevalence of bulk tank goat's milk contamination with S. aureus of animal origin. The presence in goat's milk of S. aureus strains able to produce enterotoxins and their potential introduction into dairy chain may represent a serious threat to human health.
    Foodborne Pathogens and Disease 03/2013; 10(4). DOI:10.1089/fpd.2012.1356 · 1.91 Impact Factor
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