Streptococcus agalactiae or Group B Streptococcus (GBS) is a bacterial pathogen that causes disease in people, cattle, and fish. Occasionally, it affects other animal species, such as dogs, cats, crocodiles, seals or dolphins. We currently have three projects on S. agalactiae, covering mastitis in cattle, streptococcosis in fish, and neurological disease in stranded sea mammals.
A specific strain of human S. agalactiae that causes disease and death in infants is thought to have emerged from a reservoir of bovine strains. To prevent this from happening again, we need to control S. agalactiae mastitis in cattle. In the 1960s, control schemes were developed in England. Dairy farmers have implemented them with great success. Unfortunately, the bacteria are making a come-back. Denmark has seen a 5-fold increase in the number of herds affected. To understand how this could happen, we investigate the molecular epidemiology of S. agalactiae.
Together with Professors Rowland Kao (Faculty of Veterinary Medicine) and Mark Girolami (Department of Computing Science) at the University of Glasgow, we won funding for a 4-year Lord Kelvin- Adam Smith Ph.D. scholarship to investigate the epidemiology of S. agalactiae. We will use mathematical models and molecular epidemiology tools to test the hypothesis that new herd-level cases due to cattle strains can be explained by cattle movements whilst introductions that are not associated with cattle movements are due to human strains of the bacteria.
A second PhD studentship, funded jointly by the Moredun and the Stirling Institute of Aquaculture, focuses on S. agalactiae in fish, where it may cause massive outbreaks of disease and fish kills, particularly in tilapia. We will characterize fish isolates, compare them with human and bovine isolates using genomic and proteomic methods, and explore their ability to cause disease in tilapia.
Moredun pathologists work together with SAC staff in a Defra funded project to examine the cause of death in stranded sea-mammals. In several seals and dolphins, S. agalactiae was identified. Using molecular methods, we explore whether infections in sea mammals are due to strains originating from humans, cattle or fish.
Insight into sources and transmission mechanisms of S. agalactiae is expected to contribute to improved control of disease in animals and a decreased risk of emergence of new strains that may pose a risk to humans.
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