For all three bacteria, the severity of disease in mares varies. There are two states of infection:
The active state in which the main outward sign is a vulval discharge which may range from very mild to extremely profuse.
The carrier state in which there are no outward signs of infection. However, the mare remains capable of transmitting infection because the bacteria are established on the surface of the clitoris, in the clitoral fossa and sinuses and, in the case of K. pneumoniae and P. aeruginosa, sometimes in the urethra and bladder.
Remember: 'stallion' means mating stallions, teasers and stallions used for AI.
Infected stallions do not usually show clinical signs of infection but the bacteria are present on their penis, sheath and, in the case of K. pneumoniae and P. aeruginosa, sometimes in the urethra and bladder. These stallions can infect mares during mating, teasing or AI.
Occasionally, the bacteria may invade the stallion’s sex glands, causing pus and bacteria to contaminate the semen.