Brucella abortus shedder conditions in twenty cows
AuthorsB. S. Henry
C. M. Haring
Authors AffiliationsB. S. Henry was Associate in Veterinary Science, resigned September 30, 1931; C. M. Haring was Professor of Veterinary Science and Veterinarian in the Experiment Station; J. Teaum was Professor of Veterinary Science and Veterinarian in the Experiment Station.
Hilgardia 9(11):543-566. DOI:10.3733/hilg.v09n11p543. November 1935.
Abstract does not appear. First page follows.
Since Schroeder and Cotton,(1) and Smith and Fabyan(2) first demonstrated the presence of Brucella abortus in the milk of cows, there have been numerous reports of investigations carried on to determine the number of Br. abortus organisms excreted, the proportion of infected animals which eliminate the organism in their milk, the duration of this shedder condition, and its relation to blood-serum and whey tests. In most cases these reports have been based upon single tests of a large or small number of infected animals, and as would be expected the results have been exceedingly variable.
Fitch and Lubbehusen(3) found that 29.1 per cent of the cattle which were positive to the agglutination test were shedders of Brucella abortus in their milk, but that none of these organisms were found in the milk of animals whose blood-serum titers were less than 1-100 at the time of the test.
Results comparable with those of Fitch and Lubbehusen were obtained by Sheather,(4) who found that 34 per cent of the positive animals were shedders of Brucella abortus in their milk, but that 14 per cent of the samples of milk containing the organism gave negative results to the whey agglutination test.
In a group of cows with blood titers of 1-200 or over, Schroeder and Cotton(5) found that 83.3 per cent shed Brucella abortus in their milk. In a more recent study, Mitchell and Humphreys(6) reported 75 per cent of the animals in an infected herd to be shedders. However, if those animals in the herd whose blood titers were less than 1-100 were omitted, the percentage of reacting animals which were shedders would have been about 83. These last figures agree rather well with those obtained at this station, as shown later (page 551).
Pröscholdt(7) has stated that only 3 per cent of cows with blood-serum titers less than 1-100 eliminate Brucella abortus in the milk, but that cows with whey titers of 1-80 or higher almost certainly are shedders. He states that a whey titer of 1-10 to 1-40 is less certain evidence of infection.
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