Seal pups contract food poisoning infection due to human pollution

Grey seal pups have contracted a form of the Campylobacter bacterium, the leading cause of gastroenteritis, which is likely to have come from human pollution, a new study has revealed.

The study, led by researchers from the Moredun Research Institute, Edinburgh in collaboration with the College of Medicine at Swansea University and the Sea Mammal Research Unit, University of St Andrews was recently published in Molecular Ecology.

The bacterium was detected in grey seals breeding on the Isle of May, an island in the Firth of Forth near Edinburgh, Scotland, which is one of the largest seal colonies on the east coast.  Analysis showed that the likely source of infection was human activity, including sewage and waste from farming and livestock, which contaminated the water.  Evidence also suggested that the bacterium was associated with gastroenteritis in grey seals.

Seal pup looking at cameraGrey seals are a common sight around the coastline of Britain and are top predators in the food chain in UK waters. 

Marine mammals are sometimes regarded as “sentinel species”, which means that their health and welfare is a pointer to the condition of our seas and marine life in general.

The study is the first to isolate these species of bacteria in the grey seal.  In humans, Campylobacter is the most commonly reported cause of bacterial gastroenteritis.

In the UK, each year there are over 500,000 community cases, 20,000 hospitalisations and 110 deaths.  However, very little is known about its transmission to wild animals.

The team studied newborn and juvenile grey seals on the Isle of May.  Their samples included living seals and pups who had died in the wild.   They studied three different breeding habitats: rocky stagnant pools, muddy grassy slopes, and tidal boulder beaches

The research found:

•    The Campylobacter jejuni bacterium was present in half of all seal pups sampled: 70 out of 140.  (24 of the 50 dead seals and 46 of the 90 live seals).

•    The majority (79%) of the seal samples taken were attributed to human and agricultural sources

•    Prolonged residence on the Isle of May was associated with a higher rate of infection. Pups that left the island to go to sea for the first time earlier than others had a lower rate.  Infection rates were also lower in seal pups born on the tidal boulder beach of the island, and in pups that stranded live and were taken into a rehabilitation centre on the mainland.  This distribution of infection is evidence of contamination by exposure to pollutants.

Campylobacter jejuni bacterium

Picture: the campylobacter jejuni bacterium

Professor Samuel Sheppard and Dr Guillaume Meric of the College of Medicine at Swansea University collaborated with Dr Johanna Baily and Dr Mark Dagleish from Moredun Research Institute, Edinburgh and Dr Ailsa Hall of the Sea Mammal Research Institute, University of St Andrews.  

Professor Samuel Sheppard of Swansea University College of Medicine said:

“Large numbers of grey seals were infected with Campylobacter types that are commonly associated with human infection, not the species that are usually isolated from marine mammals. The infected seals also showed symptoms consistent with gastro-enteritis – comparable to that in humans.  This is striking as it shows that this important human pathogen may be spreading to vulnerable wildlife species where its disease potential is unknown.

Although this study looked at seals in Scottish waters, it is likely that seals off the coast of Wales, and across the UK, would be similarly affected.  More research is needed to find out the scale of the problem”  

Dr Johanna Baily of Moredun Research Institute said:

“The findings are consistent with either a common source or direct transmission of human and grey seal Campylobacter infection.  They raise concerns about the environmental pollution of British coastlines with faecal bacteria, and the subsequent spread of human pathogens to wildlife marine sentinel species”

Dr Ailsa Hall, Director of the Sea Mammal Research Unit, said

“Determining the causes of infection and disease in grey seal pups during the breeding season is critical to our understanding of the factors that affect the early health and ultimately the survival rates in these animals.  The results of this study have shown that the link between the health of marine mammals around our coast is closely linked to man’s activities, both on land as well as in the ocean.”

Read the research paper

Swansea University College of Medicine