The NMR glossary provides brief definitions and explanations of terms and jargon used on our site.



An agent that causes disease, especially a living microorganism such as a bacterium or fungus

PI (Persistently Infected)

Cattle persistently infected with BVDV are the major virus reservoir for the spread of the virus. Cattle become persistently infected when they are infected as a foetus between the 1st and 4th month of gestation. At this stage of gestation, the foetal immune system is developing. Included in this process is the recognition of self antigens. BVDV circulating during this period is distinguished as a self antigen, preventing an immune response from eliminating the virus. Persistently infected animals who survive are constantly producing and shedding virus into the environment through nasal and oral secretions, urine, and faeces. Live calves born to persistently infected dams will also be persistently infected with BVDV. The detection and elimination of persistently infected animals is key to the control of BVDV on a farm.


Respiratory disease characterized by inflammation of the lung parenchyma (excluding the bronchi) with congestion caused by viruses or bacteria or irritants


Indicator of general environmental contamination. Levels increase with poor pre-milking teat preparation, poor environmental conditions & mastitic milk entering the bulk tank


Bacteria able to grow at refrigeration temperatures (can be found in water). Indicative of inadequately cleaned bulk tank and/or poor milk cooling