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

Lead Research Organisation: University of Warwick
Department Name: School of Life Sciences


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 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.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
BB/M01116X/1 01/10/2015 30/09/2023
1790805 Studentship BB/M01116X/1 03/10/2016 30/09/2020 Kate Emily Bamford
Description During a two-year longitudinal study between 2012 and 2014, 626 milk samples were collected routinely from 89 ewes from 6 farms in early and late lactation and stored at -20°C (Grant et al., 2016). This project looked to analyse the bacterial communities in those milk samples to assess potential transmission routes of mastitis causing pathogens.

Multiple strains were seen more than once within flocks, indicating that some mastitis-associated pathogens are potentially contagious or transmitted from the shared environment. There wasn't a distinct difference between the bacteria isolated in diseased animals compared to bacteria isolated in healthy animals. There was a lower bacterial diversity (number of unique strains) in the communities isolated from diseased sheep, which could suggests that mastitis can be caused by overgrowth of a single opportunistic pathogen that was already present in udder before disease.

A second one-year longitudinal study was carried out in 2018-2019 and aimed to investigate the role of chronic intramammary masses on flock transmission and the impact presence of these masses has on lamb weight.

Lambs born to ewes that had an intrammary mass present during the lactation period took 16 days longer to reach slaughter weight, and were 500g smaller than equivalent lambs born to healthy ewes.
Exploitation Route The agriculture sector could take this research forward to educate farmers on the impact of chronic intramammary masses on their flocks.
Sectors Agriculture, Food and Drink