This infection is now quite rare; it is caused by poor hygiene and milking plant maintenance. Take care not to buy it in with replacements!
Since 2000 there has been a small rise in incidence due to corner cutting as a result of poor milk prices.
The infection causes massive bacterial counts 10 million or more in a cow!
The organism inhabits ducts and cisterns in the mammary gland, however it does not survive in environment and can be eliminated by simultaneous herd treatment.
The infection causes inflammation which blocks ducts and leads to decreased milk production and increased somatic cell counts.