Contagious mastitis patterns in dairy cows

Find out about the characteristics of contagious mastits patterns in cows. 

Contagious mastitis patterns are characterised by the spread of infection between cows; the main source of infection for uninfected cows is other infected cows in the herd. This is clearly different from environmental mastitis patterns, in which environment-to-cow transmission predominates.

Herds with contagious mastitis infections in lactation typically see a large proportion of ‘persistently infected’ or “chronic” cows (i.e. individual cows with an SCC above a threshold of 200,000 cells/ml on several occasions).

Many of these persistently infected cows may have been infected in previous lactations. These herds also tend to have high bulk milk SCCs. However, this on its own is not enough to categorise herds –more information is required before making decisions about control. With contagious mastitis we typically see:

• a large proportion of ‘persistently infected’ or “chonic” cows (i.e. those that have several SCC results over 200,000 cells/ml)
• an increased new infection rate in lactation (i.e. over 10% of cows moving above 200,000 cells/ml between milk recordings)
• new, non-seasonal infections that are increased all year round
• poor cure rates across the dry period (cows dried off with a high SCC calve back with high SCC)
• poor cure rates in lactation, especially first clinical cases in a lactation

KPI:

• Cure rate in dry period 85% or higher (cell count high in and low out of the dry period)
• Percentage of animals with an SCC equal to or over 200,000 cells/ml should be less than 20%
• No more than 5% of low cell count milking cows should move above the 200,000 cells/ml threshold between milk recordings in lactation
• No more than 2 in 12 cows (or less than 16%) should be affected with a new case of clinical mastitis after 30 days of lactation