Article

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

ABSTRACT

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.

Download full-text

Full-text

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. "
    [Show abstract] [Hide abstract]
    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.
    No preview · Article · Jul 2015 · The Journal of Agricultural Education and Extension
  • Source
    • "Not wearing milking gloves, not following any plausible milking order, no fly control, and no dry cow treatment were identified as important herd-level risk factors for IMI caused by Staph. aureus (Erskine et al., 1987; Hutton et al., 1990; Bartlett and Miller, 1993; Moret-Stalder et al., 2009; Dufour et al., 2012). As risk factors differ among mastitis-causing pathogens, they may also differ between different Staph. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Bovine mastitis is a frequent problem in Swiss dairy herds. One of the main pathogens causing significant economic loss is Staphylococcus aureus. Various Staph. aureus genotypes with different biological properties have been described. Genotype B (GTB) of Staph. aureus was identified as the most contagious and one of the most prevalent strains in Switzerland. The aim of this study was to identify risk factors associated with the herd-level presence of Staph. aureus GTB and Staph. aureus non-GTB in Swiss dairy herds with an elevated yield-corrected herd somatic cell count (YCHSCC). One hundred dairy herds with a mean YCHSCC between 200,000 and 300,000 cells/mL in 2010 were recruited and each farm was visited once during milking. A standardized protocol investigating demography, mastitis management, cow husbandry, milking system, and milking routine was completed during the visit. A bulk tank milk (BTM) sample was analyzed by real-time PCR for the presence of Staph. aureus GTB to classify the herds into 2 groups: Staph. aureus GTB-positive and Staph. aureus GTB-negative. Moreover, quarter milk samples were aseptically collected for bacteriological culture from cows with a somatic cell count ≥150,000 cells/mL on the last test-day before the visit. The culture results allowed us to allocate the Staph. aureus GTB-negative farms to Staph. aureus non-GTB and Staph. aureus-free groups. Multivariable multinomial logistic regression models were built to identify risk factors associated with the herd-level presence of Staph. aureus GTB and Staph. aureus non-GTB. The prevalence of Staph. aureus GTB herds was 16% (n = 16), whereas that of Staph. aureus non-GTB herds was 38% (n = 38). Herds that sent lactating cows to seasonal communal pastures had significantly higher odds of being infected with Staph. aureus GTB (odds ratio: 10.2, 95% CI: 1.9–56.6), compared with herds without communal pasturing. Herds that purchased heifers had significantly higher odds of being infected with Staph. aureus GTB (rather than Staph. aureus non-GTB) compared with herds without purchase of heifers. Furthermore, herds that did not use udder ointment as supportive therapy for acute mastitis had significantly higher odds of being infected with Staph. aureus GTB (odds ratio: 8.5, 95% CI: 1.6–58.4) or Staph. aureus non-GTB (odds ratio: 6.1, 95% CI: 1.3–27.8) than herds that used udder ointment occasionally or regularly. Herds in which the milker performed unrelated activities during milking had significantly higher odds of being infected with Staph. aureus GTB (rather than Staph. aureus non-GTB) compared with herds in which the milker did not perform unrelated activities at milking. Awareness of 4 potential risk factors identified in this study guides implementation of intervention strategies to improve udder health in both Staph. aureus GTB and Staph. aureus non-GTB herds.
    Preview · Article · Aug 2014 · Journal of Dairy Science
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Jul 2013 · Journal of Animal Science
Show more