Aids to stockowners / by J. Walker.

  • John Walker
Date:
1930
Catalogue details

Licence: In copyright

Credit: Aids to stockowners / by J. Walker. Source: Wellcome Collection.

    68/198 page 50
    months after abortion, but the danger now is that the organism is situated in the udder and its glands and only waiting for a further pregnancy before it returns to its favourite habitat. Infection is generally carried to a healthy animal by the con¬ tamination of food and water; it is exceedingly rare via the sexual tract and the bull may be virtually excluded as a carrier of the disease. Undoubtedly under certain conditions the bull may transmit infection, either mechanically as when lie semes a clean cow after covering one with a vaginal discharge con¬ taining the organism or by ejaculating into the vagina of a healthy cow the organism in his semen as the result of diseased condition of his genitalia. It has been recognised recently that the flicking of vaginal discharge by the tail may also spread the disease as it is only necessary for a small amount of virulent material to alight on the eye-ball of an adjacent clean cow to infect her. \\ hen the organism is located in the udder the milk is infective. , uc i milk if carelessly spilt over the premises will help to -piead infection hut there is no harm in letting calves have milk from an infected cow as long as they have not reached the breeding age. Symptoms are those of parturition, except when the abortion occurs very early in gestation when no symptoms may be seen at all. Under these circumstances the abortion may occur while the animal is at grass and no one he any the wiser until the cow comes back into “ heat ” in twenty-one days, or unless there is a noticeable vaginal discharge, or there are symptoms of retained membranes. Abortions generally occur in the fifth or sixth months hut they may occur before or after these times. An animal may abort more than once but this is the exception and not the rule. In a few cases a cow, infected with the causal organism and positive to the agglutination test, may never abort at all. These animals are known as “ carriers and are obviously very undesirable members in a herd for they maintain infection and may never he suspected until their blood is subjected to the serum test. Diagnosis is very easily made because several abortions occur practically simultaneously. In all cases of doubt a positive diagnosis can be obtained if blood samples are sent to the laboratory for the serum diagnosis test. Sporadic cases of abortion occur as a sequel to several extraneous causes, e.g. some accident, dipping, result of being chased by dogs or other verm in, poisonous plants, various infectious diseases, etc.
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