Poster-presentation NMC 04 by ciq80626

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									Agent-specific risk factors for acute
clinical mastitis in Swedish dairy cows
A. Lindberg1, B. Bengtsson2, T. Ekman1, K. Persson Waller2,
H. Unnerstad2, K. Artursson2, J. Jovanovic2 and M. Nilsson Öst2
1   Swedish Dairy Association, Uppsala, Sweden, 2 National Veterinary Institute, Uppsala, Sweden


    Background
    This study was carried out as a part of a larger investigation aimed at describing the spectrum of bacteria infecting dairy
    cows with acute clinical mastitis, and the resistance pattern in such bacteria.
    Similar prevalence studies have previously been performed in 1983 and in 1995. However, the presence of agent-specific
    risk factors has not been investigated before.
    Since 1995, structural changes in the industry has resulted in an increasing proportion of farms with loose housing systems
    (from 5-10% in 1995 to 27% in 2003) and an increase in average herd size (from 33 in 1995 to 45 cows/herd 2003). Thus,
    there is a need to understand if and how the management systems used promote infection with certain agents.

     Objective
    To investigate the association between the isolation of specific bacteria in conjunction with
    acute clinical mastitis and certain individual and environmental risk factors.
     Conclusions                                                                                                     Table 1. Descriptive statistics and point
                                                                                                                     estimates of odds ratios for 7 agent-specific
     Udder pathogens isolated in connection with acute                                                               models. Colored fields denote candidate
     clinicalmastitis show different patterns with respect to                                                        variables, blue fields denote significant variables
     individual and environmental risk factors.                                                                      (p<0.05) in the final models.
                                                                                                                                                                                                                      Odds ratios
     In this study, and given the variables controlled for;




                                                                                                                                                                                                                                                                 S. dysgalactiae
                                                                                                                                                                                                                                 Klebsiella spp.
                                                                                                                                                                                                                                                   2
                                                                                                                                                                                                                                                   A. pyogenes
     - the risk of isolating S. aureus (rather than any other udder pathogen)




                                                                                                                                                                                                  S. aureus




                                                                                                                                                                                                                                                                                   S. uberis
                                                                                                                                                                                                                      2
     was associated with being housed in tie stalls.




                                                                                                                                                                                                                       E. coli
                                                                                                                                                                                                              CNS 1
     - E. coli was typically isolated from high yielding cows in loose housing                                                                                                  Freq.                             # of cases
                                                                                                                       Variable                         Levels                             %      211         59 161 42 57 150 111
     systems.                                                                                                                             Loose (w. cubicles)
                                                                                                                                                                                (n=734)
                                                                                                                                                                                    242   (33)                        0.00
                                                                                                                                          Tie stalls, long                          141   (19)                        0.90

     - Klebsiella spp was strongly associated with the use of sawdust as                                      Housing 1
                                                                                                                                          Tie stalls, short /Other
                                                                                                                                          No data
                                                                                                                                                                                    349
                                                                                                                                                                                      2
                                                                                                                                                                                          (48)                        0.51


     bedding material.                                                                                                                    Loose (w. cubicles), cold                  57    (8)    0.00
                                                                                                                                          Loose (w. cubicles),warm                  185   (25)    1.93
                                                                                                                                          Tie stalls                                490   (67)    2.47
     - A. pyogenes was associated with low yielding cows and teat tramps.                                     Housing 2                   No data                                     2
                                                                                                                                          Rubber mat/cubicle matress/               517   (70)    0.00

     - there was an increased likelihood of isolating Str. uberis (rather than any                            Floor of cubicle
                                                                                                                                          Concrete / concrete+rubber mat
                                                                                                                                          Other
                                                                                                                                                                                    196
                                                                                                                                                                                     21
                                                                                                                                                                                          (27)
                                                                                                                                                                                           (3)

     other pathogen) from Holstein cows during the early housing season.                                                                  Straw/peat
                                                                                                                                          Mixed
                                                                                                                                                                                    268
                                                                                                                                                                                    217
                                                                                                                                                                                          (36)
                                                                                                                                                                                          (30)
                                                                                                                                                                                                                                 0.00
                                                                                                                                                                                                                                 1.99
                                                                                                                                                                                                                                                                                   0.00
                                                                                                                                                                                                                                                                                   0.89
     Using sawdust as bedding reduced the risk relative to if straw/peat was                                  Bedding 1                   Sawdust                                   249   (34)                                   3.98                                              0.47
                                                                                                                                          Straw                                     255   (35)    0.00 0.00
     used.                                                                                                                                Mixed                                      27    (4)
                                                                                                              Bedding 2                   Sawdust/shavings                          452   (62)

     - the likelihood of isolating S. aureus, A. pyogenes or Str. dysgalactiae,                               Year
                                                                                                                                          2002
                                                                                                                                          2003
                                                                                                                                                                                    481
                                                                                                                                                                                    253
                                                                                                                                                                                          (66)
                                                                                                                                                                                          (34)
                                                                                                                                                                                                              0.00                                                                 0.00


     rather than CNS or E.coli, was relatively higher in cows with tramped                                                                Early housing season (Sep-Dec)
                                                                                                                                          Late housing season (Jan-Apr)
                                                                                                                                                                                    256
                                                                                                                                                                                    249
                                                                                                                                                                                          (35)
                                                                                                                                                                                          (34)
                                                                                                                                                                                                                                 0.00                                              0.00
                                                                                                                                                                                                                                                                                   0.52
     teats.                                                                                                   Season                      Pasture (May-Aug)                         229   (31)                                                                                     1.09
                                                                                                                                          May-Oct                                   349   (48)    0.00
                                                                                                              Season S. aureus 3          Nov-Apr                                   385   (52)    1.72

    Material and methods                                                                                                                  Swedish Red and White                     310   (42)    0.00 0.00                                                                        0.00
                                                                                                                                          Swedish Holstein                          401   (55)                                                                                     1.72

    Study period: May 2002 – April 2003.                                                                      Breed                       Other                                      23
                                                                                                                                                                                    257
                                                                                                                                                                                           (3)
                                                                                                                                                                                          (35)
                                                                                                                                                                                                                                                                                   1.88
                                                                                                                                          1                                                                                      0.00 0.00
                                                                                                                                          2                                         165   (22)
    Sampling: Two-stage; 1) simple random sample of 54 veterinary practices 2) systematic random                                          3                                         139   (19)
    sample during six 2-month study periods until sample size quota was filled.                               Parity                      >3                                        173   (24)
                                                                                                                                          No                                        626   (85)    0.00 0.00 0.00                                   0.00 0.00 0.00
    Inclusion criteria: no previous mastitis during present lactation and somatic cell count <200             Teat tramp                  Yes                                       108   (15)    1.26 0.26 0.25                                   2.75 2.66
                                                                                                                                                                                    637   (87)
    000/ml at latest milk recording, not treated with antibiotics for any reason during the last 30 days.                                 1
                                                                                                                                          2-3                                        97   (13)
                                                                                                                                                                                                  0.00 0.00 0.00
                                                                                                                                                                                                  3.34 2.44 2.78
                                                                                                                                                                                                                                                   0.00 0.00 0.00
                                                                                                                                                                                                                                                   4.61 3.06 2.44
                                                                                                              # diagnoses
                                                                                                                                          1                                         666   (91)    0.00 0.00
    Data collection: Data on individual and environmental risk factors were collected by means of a                                       >1                                         68    (9)         2.43
                                                                                                              # teats infected in total
    questionnaire at the sampling occasion.                                                                                               1                                         702   (96)                                                                   0.00
                                                                                                              # teats with agent          2-3                                        32    (4)
    Resulting sample: 882 isolates / 814 quarters / 734 cows / 571 herds.                                                                                             Median       5 pc   95 pc
                                                                                                              Daily milk yield (kg)                                        31        15    46                         1.04                         0.95
    Editing and statistical analysis: Quarter-level data was summarised at the cow-level (variables:          Days in milk                                                 48         1   284

    teat tramp (on any teat), # teats infected in total, # teats with agent in question) creating a 2-level            1 Coagulase-negative staphylococci
                                                                                                                       2 For variables where milk yield and days in milk were significant, a
    dataset.
                                                                                                                       reduced dataset was used (n=454) due to missing data.
    Univariate associations (at p<0.15) were used to identify candidate predictors. Multivariable
    logistic regression with robust variance estimates was used to account for repeated measures at
    the herd level.
    Dependent variables: Presence of the following agents (1=yes, 0=no): E. coli, S. aureus,
    coagulase negative Staphylococci (CNS), A. pyogenes, Klebsiella spp, Str. dysgalactiae and Str.
    uberis.
    NB! All cows were represented in all models, either as cases or as non-cases. Thus, the group of
    comparison consists of cows with acute mastitis due to other reasons, not healthy cows.

								
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