Disease Information: Mastitis
What is Mastitis?
Mastitis is an inflammatory response to a bacterial invasion in the mammary gland of the cow. The disease is most clearly indicated on farm by a rise in Somatic Cell Count (SCC), quantified as the number of white blood cells or leukocytes per millilitre of milk.
Mastitis is the most prevalent disease amongst dairy cattle and it is considered impossible to completely eradicate due to the very nature of bacteria. Bacterial development is a process that allows bacteria to develop into different cellular states and thereby become resistant to eradication treatments. On average in the UK, between 47-60% of all cows suffer from mastitis every year (Dairy Co1). The percentage of cases in each lactation can fluctuate due to changes in seasonal weather conditions.
Mastitis can be classified as sub-clinical or clinical, depending on the symptoms and signs displayed by the cow. Clinical mastitis is characterised by obvious signs and symptoms of infection in the cow. Symptoms can include unhealthy milk (usually discoloured or clotted), swollen udders, inflamed teats, high body temperature and obvious discomfort. Sub-clinical mastitis has few evident signs or symptoms and is therefore very difficult to detect. A rise in bulk milk SCC could demonstrate that sub-clinical mastitis is present in the herd, but regular sampling of individual cows is a more reliable, albeit costly, method of identifying sub-clinical cases.
On average, each case of mastitis costs the farmer around £250 - £300 in the UK, according to research carried out at Reading University2. This cost can be attributed to milk production losses, increased labour requirements and the cost of drugs needed for treatment. However, the incidence of mastitis in the UK has dropped significantly in the last ten years. In the 1960s, the incidence rate was 150 cases per 100 cows per year but this has been dramatically reduced to circa 30+ cases per 100 cows . This positive change has come about through management system changes and increased awareness of subclinical cases (Dairy Co3).
Dominant Mastitis Causing Pathogens
Streptococcus uberis is a contagious bacterium which is the main cause of clinical mastitis. The organism lives in the mammary gland and can be transmitted to other cows during milking. Aggressive treatment with antibiotics is recommended, to reduce the risk of the bacteria becoming resistant to low level antibiotics. Meticulous milking routines can be implemented to significantly reduce transmission.
Staphylococcus aureus is a contagious pathogen, however, this organism can survive outside of its host environment, namely, in the teat of the cow. Regular sampling is needed to detect the presence of this bacterium, because it often has a sub-clinical presentation and an ability to ‘hide’, thus surviving phagocytosis (the devouring of an invading cell, in this case the Staph. aureus pathogen). Staph. aureus has the ability to become ‘walled off’ and ignored by the normal immune response. Samples of milk taken to identify this pathogen should be frozen prior to testing, so that the milk cells rupture and expose the bacteria. Cases can be treated using ‘strain typing’, which is a process of identifying the specific strain of bacteria causing the infection, so that treatments can be specifically designed to target the pathogen. This practice is costly and not guaranteed to succeed, as not all strains of a bacterium can be identified.
Escherichia coli is considered the most rapidly damaging environmental bacterium, due to the severe clinical signs of infection displayed within just hours of the bacteria entering the cow's system. This pathogen is present predominantly in faeces, and wet, humid conditions provide a perfect breeding ground. Treatment options are limited as several strains of the bacteria are simultaneously present and the cow has no natural immune defence to the disease. The reason for this is unknown, but means the disease should be identified swiftly and treated vigourously to reduce potential damage to the cow.
Streptococcus agalactiae is a contagious bacterium already present in milk but which can multiply due to under-milking, causing sub-clinical mastitis. The disease is then spread via milking machines and human contact during milking. The bacteria cannot survive for long outside of the host environment but can, unfortunately, remain inside the mammary gland indefinitely. Infected animals are a reservoir of Strep. agalactiae, therefore newly purchased cattle are a potential biosecurity threat when brought onto farm; pre-movement testing is costly but may save money in the long term.
Streptococcus dysgalactiae is generally characterized as an environmental pathogen, however, it appears to have the ability to transmit from animal to animal. It causes a clinical mastitis infection but can be relatively efficiently and quickly treated using teat dipping and dry cow therapy. It is therefore considered a minor pathogen4.
Prevention is often more effective than treatment on a whole farm basis. One simple step is to ensure milking machines are well maintained, with rubber ware replenished at least twice a season. Regular checks will highlight potential problem areas: rough surfaces in liners and ripped or perished tubing are perfect breeding grounds for bacteria. Ensure that a mastitis detection system and protocol is in place and observed by all members of staff. Reducing over- and under-milking will improve mastitis levels as well as cow comfort and parlour efficiency. Another easy step is to integrate the use of pre- and post-teat dipping into the usual milking routine. Ensuring that bedding is regularly changed (twice a day) and passages and loafing areas are scraped out (three times a day) will reduce the conditions readily available for bacteria to flourish.
Bio-Genesys is committed to improving the welfare and conditions of agricultural livestock and we have a range of products available to help reduce the incidence of mastitis within your herd. Prevention is better than cure, so use Auxilium Sprint, to repair teat ends and protect them from damage that would otherwise provide a perfect environment for bacteria to flourish. Another very effective product is Auxilium Barrier, a fast acting, broad-spectrum pre-sealant dip that also improves teat skin health. These can be used in conjunction with our housing and bedding sanitiser, Desysec. This product is ideal to sanitise bedding as it kills any bacteria present and absorbs moisture to prevent further bacteria from surviving in that environment. It reduces ammonia and is easy to apply, as the product is in powder form for spreading over the required areas.
Ariadne Kidson BSc
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 A veterinary book for dairy farmers – R. W. Blowey, 2012, 3rd edition
 Facts and figures for New Zealand Dairy Farmers, Dairy NZ, version 1, 2010-2011