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Assessing the impact of changing migratory patterns and population size of greylag geese on livestock and public health

Assessing the impact of changing migratory patterns and population size of greylag geese on livestock and public health

  • Biodiversity
  • 2022-2027
Sustainable Development icon: good health and wellbeing
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The migratory behaviour of wild birds is influenced by changes in climate, sometimes resulting in considerable population expansions that impact ecosystems. Wildlife species can carry pathogens that can be transmitted to other wildlife species, farm animals and humans. They can also harbour antimicrobial-resistant bacteria and antimicrobial resistance genes (ARGs) and play a role in the dissemination of these bacteria and genes within the environment. Antimicrobial resistance (AMR) has become a major threat to human health worldwide and this phenomenon has been largely overlooked in studies within environmental settings.

Scotland is home to a native population of the Greylag goose. However, over the last 20 years, populations of Icelandic Greylag geese on the Orkney Isles have increased dramatically in density. This includes the establishment of a large resident population and an even larger population of wintering birds, which are present during the autumn and winter months, with the potential to introduce microbial risks from overseas. Furthermore, the breeding population on Orkney may also winter in other sites within the UK providing further routes of microbial transmission. These major changes are believed to have been driven at least partly by behavioural adaptations to changes in climate, as warmer weather influences grass growth on the Isles, providing a replenishable food source during the winter months.

The geese have greatly impacted the farming community in Orkney, causing considerable harm to farmlands and widespread faecal contamination. The geese carry Cryptosporidium spp., and given the density of the geese populations, it is believed that this may contribute to the incidence of neonatal calf diarrhoea and potentially impact public health. Cryptosporidium parvum is an important zoonotic parasite responsible for causing diarrhoeal disease in neonatal animals, as well as humans where it can cause severe disease in the young, elderly, or immune-compromised.

The infective stage of the parasite (oocyst), shed in the faeces of infected animals, is extremely robust and can survive for prolonged periods in the environment, including on pasture, in cattle sheds and watercourses. Oocysts are extremely resistant and can survive many of the commonly used on-farm disinfectants, as well as inactivation procedures implemented by water treatment plants, including chlorination. Thus, Cryptosporidium is a significant issue not only for farmers and public health officials but also for the water industry.

There is an immediate need for an improved understanding of pathogen threats from this newly established population of Greylag geese. Currently, there is limited knowledge regarding the role of wildlife populations in the spread of antimicrobial resistance genes, particularly in migratory species. There is also a lack of tools to discriminate between individuals, and therefore resident and migratory goose populations, which would allow risks associated with specific cohorts to be defined. There is also a paucity of understanding of climate change-driven microbial threats within our natural and farmed ecosystems. Finally, there are few case studies and roadmaps for engaging with stakeholder groups in terms of economic, social, and ecological impacts, in the context of microbial risks.


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We have previously conducted a pilot study focussed on a small number of samples collected from geese and calves in Orkney. This study revealed a high prevalence of C. parvum in in geese suggesting they may be a risk factor in the transmission of the parasite to livestock and public water supplies.


Dynamics of Cryptosporidium parvum between geese, calves, and the environment 

This project builds on the pilot study and samples a larger number of geese and calves on different beef farms in Orkney and includes water samples collected from public water reservoirs by Scottish Water. The sampling of calves and geese pre- and post-turn out to pasture allows for sub-types of C. parvum to be compared to help understand transmission routes of the parasite between geese, livestock and the environment.


Comparative genomic analysis to investigate the transmission of Campylobacter between Greylag geese, cattle and the wider environment

In addition to pathogen and antimicrobial-resistant genes analysis for geese sampled during the wintering season, we are developing molecular tools to genotype geese using faecal samples, to distinguish migratory and resident Greylag goose populations. This enables specific microbial risks, in terms of pathogen carriage and antimicrobial-resistant genes dissemination, to be correlated with migratory or resident geese.


Antimicrobial resistome and the presumed flow of ARGs between Greylag geese, cattle and the wider environment

Previous studies have also highlighted geese as potentially important vectors of zoonotic diseases but little is known regarding the carriage of other microbes by the greylag geese and the potential for the introduction of bacterial pathogens and ARGs to livestock and human populations. We investigate the carriage and transmission of zoonotic bacteria and ARGs between geese and cattle. Remote and sensitive environments, such as this exemplar catchment on the Orkney Isles, provide ideal settings to study the acquisition and dissemination of AMR by a dense population of wild birds, with migratory behaviour. We also sample the wider ecosystem, including wildlife, soil and watercourses to assess the role of the environment in pathogen and ARG transmission and associated risks to public health.


Assessment of microbial risks associated with migratory and resident cohorts of geese 

We assess the carriage of Campylobacter by geese and cattle populations at an individual level and will perform whole genome sequencing to assess strain diversity and transmission between groups. The aim is to distinguish migratory and resident greylag goose populations. This enables specific microbial risks, in terms of pathogen carriage and ARG dissemination, to be correlated with migratory or resident geese.


We are producing case studies that consider impacts on all major stakeholders in terms of social, economic and conservation aspects. Recommendations are being co-developed with stakeholders as well as exploring potential solutions and approaches, such as sustainable farming practices, and conservation measures.

Project Partners



2022 / 2023
2022 / 2023

Sampling campaigns have been planned following discussions with BioSS and representatives of the Orkney Goose Management Group. Methods for sample collection and processing have been assessed and optimised to ensure the stability of samples during transport following field collection. Optimised culturing methods for Campylobacter from goose faecal samples have been determined in order to ensure maximum recovery of this fastidious bacterium. To enable assessment of microbial carriage during the wintering season on Orkney, 200 goose faecal samples have been collected from nine farms. These samples were processed for Campylobacter culturing using enrichment broths and selective culture media as well as for the isolation of Cryptosporidium oocysts with subsequent extraction of protozoan DNA. Sub-samples have also been archived for host genotyping and detection of ARGs in years 2 to 5 of the project. Methods to extract goose DNA from faeces have been assessed and optimised using local faecal material. Quality of DNA was assessed alongside molecular methods to amplify host DNA for sequencing enabling selection of an optimal method. Discussions have also been held with Scottish Water to arrange collection of suitable water samples for analysis.

All knowledge exchange objectives have been completed by the principal investigators including an initial kick off meeting with Orkney Goose Management Group representatives, attendance at two Ecosystems and Land Use Policy Engagement Group (ELPEG) meetings and preparation of material for the ELPEG bulletin, as well as attendance at one Ecosystems and Land Use Stakeholders Engagement Group meeting. An article describing the project has been published in the Orcadian newspaper, raising awareness as well as assisting with farmer recruitment. The project was presented within a seminar entitle "Zoonoses and antimicrobial resistance in Scottish wildlife populations" at the University of Saskatchewan, hosted by the Vaccine and Infectious Disease Organisation (Canada). The Biggar Science festival and the Royal Highland Show provided opportunities to discuss the aims and scope of this project with the general public. 

Expertise within this group, related to the detection of microbial risks in wild birds was called upon through participation in the NatureScot Scientific Advisory Committee sub-group on HPAI (Avian influenza): wild bird surveillance, monitoring and research. The project has also been presented to the Cabinet Minister for Rural Affairs and Islands, Mairi Gougeon and Dr Sheila Voas, Chief Veterinary Officer, Scotland, as well as to visiting groups of Rural and Environmental Science and Analytical Services, to raise awareness of the need for research focussing on microbial risks associated with rapidly expanding wildlife populations. The project was outlined within the Ecosystems and Land Use Policy Engagement Group bulletin for distribution amongst stakeholders from Scottish Government and key government agencies including NatureScot and the Scottish Environment Protection Agency (SEPA).

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