Infection can be transmitted between horses in any of the following ways:
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direct transmission during natural mating;
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direct transmission during teasing. An infected teaser can transmit disease to mares through contact with his genitalia;
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indirect transmission during teasing. A teaser can transmit infected vulval discharge between mares through genital or naso-genital contact;
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transmission to mares if semen used for AI comes from infected stallions or has been contaminated with the bacteria during semen collection or processing;
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indirect transmission via the hands and equipment of staff or veterinary surgeons who have handled the tail or genitalia of an infected horse.
