Persistence and transmission of intramammary pathogens causing acute mastitis: the role of chronic intramammary abscesses (PhD)

The Challenge

Mastitis is an inflammation of the mammary gland typically caused by bacterial infection. It is an endemic disease in the UK, affecting up to 7% of ewes each year. Ewe health is affected by pain, loss of udder function, premature culling and sudden death, while lamb growth rates are affected by the reduction in milk yield. Mastitis has farm sustainability as well as welfare and health implications, with costs to the UK Texel sheep industry alone estimated in excess of £120 million/annum.

Transmission of bacteria causing intramammary infections can be from ewe to ewe or from the environment, and individual strains can persist within a flock for a number of years. Within flock transmission routes have not yet been fully characterised and understanding these will be key to developing effective managements to control mastitis.

The Project

My objectives are:

• Use existing epidemiological longitudinal data on udder health of ewes to identify a subset of ewes with 4 milk samples collected over two years with acute mastitis, chronic mastitis and no signs of disease.
• Analyse milk samples collected from that sample of sheep to investigate the patterns of bacteria over time to identify those associated with disease occurrence and to investigate their survival and persistence in healthy udders.
• Use this work to design a longitudinal study to test novel hypotheses on transmission of a species / strain of bacteria.

The first stage of work will look at the following hypotheses:

• Bacterial strains detected in milk from cases of clinical mastitis are detected in the milk of the same and other ewes later in life.
• Persistence of strains in the mammary gland is enhanced by intramammary masses, including across lactations.
• External factors, such as poor diet trigger disease (acute mastitis) in infected sheep.

The aim of this project is to improve the management of mastitis to reduce the economic impact of the disease and so improve the sustainability of sheep farming. Better management of mastitis will increase ewe longevity by improved health and welfare.

The Student

Kate Bamford