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New findings indicate that ticks in areas where pheasants are released have a heightened likelihood of carrying the bacteria responsible for Lyme disease.
While pheasants are not originally from the UK, an estimated 47 million of them are released annually for the purpose of recreational shooting.
A team of researchers conducted an investigation into tick populations across 25 woodland sites in South West England designated for pheasant releases, alongside 25 nearby sites where no such releases occur.
The study revealed that the presence of Borrelia spp., the bacterium linked to Lyme disease, was nearly 2.5 times more prevalent in ticks found in pheasant-release areas compared to control locations.
This research was undertaken by scholars from the University of Exeter in collaboration with the UK Health Security Agency.
According to Emile Michels of the Centre for Ecology and Conservation at Exeter’s Penryn Campus, “Borrelia bacteria can thrive in various hosts such as pheasants, wild birds, mammals, and even humans.” He also noted that pheasants are considered “competent” hosts for Borrelia, as they have a significant chance of both contracting and transmitting the bacteria.
“While further investigation is warranted, our results indicate a potentially increased risk of exposure to infected ticks for individuals, particularly gamekeepers, who operate in woodlands where pheasant populations are substantial,” Michels added.
The researchers analyzed ticks at various life stages (both nymphs and adults), discovering that in pheasant-release woodlands, 7.8% of ticks contained Borrelia, compared to just 3.2% in areas without pheasant releases.
Dr. Barbara Tschirren, also affiliated with the University of Exeter, highlighted that these results illustrate a phenomenon known as “spillback,” where the introduction of non-native species elevates the prevalence of pathogens that typically affect native species. “This process can play a crucial role in the emergence of zoonoses, or diseases that can be transmitted from animals to humans,” she explained.
Dr. Jolyon Medlock, who leads the Medical Entomology and Zoonoses Ecology team at UKHSA, emphasized that although the study has identified an increase in the bacteria associated with Lyme disease in ticks, there is currently no data on the resultant implications for human health, including confirmed cases of Lyme infection. “In light of these findings, we will continue collaborating with academic partners to deepen our understanding of the factors that influence Borrelia transmission, including climate and environmental changes,” he stated.
The control sites for this research were situated one to two kilometers away from pheasant-release areas, suggesting that additional studies are needed to determine whether the presence of Borrelia in ticks diminishes with increased distance from these sites.
Emile Michels’ doctoral research is supported by the NERC GW4+ DTP scheme.
This study has been published in the journal Ecology Letters under the title: “The release of non-native gamebirds is associated with amplified zoonotic disease risk.”
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