Pheasants and Lyme disease

Sir, – Rufus Sage of the Game and Wildlife Conservation Trust (GWCT) contradicts a colleague (“Pheasants, ticks and the science”, Letters, April 7).

Andrew Hoodless, of the GWCT has stated that: “We conclude that pheasants are reservoir competent for Lyme borreliosis spirochetes and potentially play an important role in the maintenance of B. burgdorferi s.l.”

It is far from agreed between the various global scientific bodies that pheasants are not central to the increase in the spread or Lymes and other tick-borne pathogens in the UK.

The study by the Natural Environment Research Council Institute of Virology and Environmental Microbiology, Oxford, UK concluded that, compared to rodents, pheasants are over 50% more effective at transmitting Burgdorferi to ticks.

This suggests that despite higher infection rates in wood mice, pheasants are more prolific transmitters of B. burgorferi, the pathogen responsible for Lyme disease.

Wood mice, the most prolific vector for this pathogen, become more numerous the closer one gets to feeding stations or release pens, as they are attracted by the food provided.

What makes pheasants the fundamental link in the large increase of Lyme disease is their subsequent dispersal on release.

Though the wood mice have the largest rate of infection, they are restricted in how far they travel, thus limiting the spread of infected ticks.

The tick-infested pheasants have a much larger range.

Without the hugely abnormal number of pheasants present, the infections would be localised – the biomass of pheasants released annually is around 41,000 tonnes (2010).

It is also the wood mouse which infects the mountain hare with the pathogens and, like the pheasant, spreads the infected ticks over its range.

The increased number of mountain hares is largely the responsibility of the intensive management of driven grouse moors, which make the perfect territory for them as they are largely artificially devoid of predators, except the golden eagle.

This makes both mountain hares and pheasants a fundamental part of the dispersal process required for the rapid spread of Lyme disease.

Though both these creatures are central to the spread of disease due to man’s manipulation, they are seen in very different lights.

One is seen as a dangerous pest and the other as a valuable prey species.

The real problem at the heart of this human health issue is one of irresponsible interventions by landowners, and their effect on our natural biodiversity. George Murdoch. 4 Auchcairnie Cottages, Laurencekirk.