New research has revealed that ticks are more likely to carry the bacteria that causes Lyme disease in areas where pheasants are released.
The research was carried out by the University of Exeter and the UK Health Security Agency, which subsequently published the study titled ‘The release of non-native gamebirds is associated with amplified zoonotic disease risk’ in the journal Ecology Letters recently.
According to Bird Watch Ireland, pheasants are not native to Ireland or the UK, but rather to Asia, where they were imported from and first introduced here as game birds in the 16th century by the Normans.
Pheasants
Researchers from the University of Exeter have claimed that approximately 47 million pheasants are released into the wild in the UK each year for recreational shooting.
To conduct the research, scientists at the university studied ticks in 25 woodland areas in south-west England where pheasants were released and 25 nearby control sites where no pheasants were released.
They discovered that Borrelia spp. – the bacteria that causes Lyme disease – was almost 2.5 times more prevalent in ticks in the pheasant-release areas compared to the control areas.
Head researcher from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall, Emile Michels said: “Borrelia bacteria can live in a wide range of hosts, including pheasants, wild birds and mammals and humans.
“Pheasants are known to be competent hosts of Borrelia spp, meaning they have a relatively high likelihood of contracting and retransmitting the bacteria.
“More research is needed, but our findings suggest there may be an increased risk of potential exposure to Borrelia-infected ticks for people, such as gamekeepers, who work in woodlands where pheasants are released in numbers.”
According to researchers, the control sites in the study were 1-2km from the pheasant-release sites, so more research would be required to see if Borrelia spp in ticks declines further at greater distances.
Researchers tested ticks at different life stages, nymphs and adults, and found that, overall, the proportion containing Borrelia spp was 7.8% in pheasant-release woodlands, and 3.2% where pheasants were not released.
University of Exeter professor, Dr. Barbara Tschirren said: “Our findings are evidence of spillback, where non-native species increase the prevalence of native pathogens. This can be an important route for the emergence of zoonoses (diseases that animals can give to humans).”
Head of the Medical Entomology and Zoonoses Ecology team at UKHSA, Dr. Jolyon Medlock also commented on the study:
“While we have observed an increase in the bacteria that can cause Lyme disease in ticks, we do not have data on the resulting impact on human health, including evidence of Lyme infection.
“Following these findings, we continue to work with academic partners to better understand what drives Borrelia transmission, including the roles of climate and environmental change.”
Lyme disease
Lyme disease is a bacterial infection that can be spread to humans by infected ticks. According to the HSE, it is usually easier to treat if it is diagnosed early.
According to the Annual Infectious Disease Report, published by the Health Protection Surveillance Centre in conjunction with the HSE on April 28, 2025, seven cases of Lyme disease were diagnosed in Ireland last year, up one from the six reported in 2023.
The HSE has also indicated that about 5% of ticks in Ireland are thought to carry Lyme disease bacteria.
It has urged individuals to remove ticks as soon as possible, explaining that Lyme disease can be prevented if infected ticks are removed within 36 hours of embedding themselves in a person.
It published three steps to remove a tick safely, which included:
- Grasp the tick as close to the skin as possible;
- Slowly pull upwards, taking care not to squeeze or crush the tick – dispose of it carefully;
- Clean the bite with antiseptic or soap and water.
