Dr. Eoin Healy:

I hope I will not overlap too much with Dr. Schwarzbach's presentation. I will try to be as brief as possible and avoid the areas he has already covered.

Lyme borreliosis is an ancient condition. It affects humans in temperate parts of Europe and the United States. Although it is ancient, the disease was only discovered and described as recently as 1982. The first cases here were described in the mid-1980s and it is now accepted that the disease is endemic here. Cases are not due to somebody having contracted the disease abroad. A few might be, but the majority of cases are contracted here.

The disease is transmitted by the tick, Ixodes ricinus, in this country. It is commonly called the common tick, deer tick, sheep tick and in the west of Ireland it is referred to as an sciortán. It is the same beast. To call something a tick bite is probably a misnomer because the tick remains attached to the victim for several days while it sucks blood. There is no evidence that borreliosis can be transmitted by the bite of a flea, horsefly, mosquito, midge or anything other than a tick. Lack of awareness of the risk of tick bite and of the symptoms of the disease on the part of the public and of general practitioners is the main impediment to both the prevention of the disease and its treatment.

As Dr. Schwarzbach mentioned, the textbook first clinical sign of the disease is the bull's-eye rash, called the erythema migrans, which appears at the site of the tick bite. However, it only appears in approximately 70% of cases of people who proceed to develop full-blown Lyme disease. As a critical symptom, it might not appear at all, so treatment may not be instigated. As the disease progresses, the nervous system in particular may be attacked, but there might also be joint and arthritic involvement as well as cardiac complications. As a result, disease symptoms can vary from person to person.

This can be confusing for patients who may share experiences and general practitioners, GPs, who find it causes problems for diagnosis.

There is an increasing risk of contracting Lyme disease in Ireland. The risk is strongly correlated with the density of ticks in a particular area. Persistence of the tick species transmitting Lyme disease in a particular area requires the presence of a sufficient number of large host animals on which the adult ticks can feed and obtain blood meals prior to producing a new generation of parasites. The animals involved are usually cattle, sheep, goat or deer. In Ireland up to 30 years ago, the particular tick species responsible for Lyme disease was, in relative terms, sparsely distributed. They would have been known by livestock farmers in particular parts of the country as transmitters of a few diseases such as Redwater fever and Louping-ill virus to domestic farm animals. The majority of urban dwellers would never have heard of a tick, let alone seen one.

Significant changes in the landscape have since occurred. Re-afforestation and the development of recreational forest parks have provided ideal habitats for expansion of the population size and distributional area of both the native red deer and the introduced sika deer. Escapees from fenced areas and parks, along with their reproduction in the wild, mean that deer are now widespread across much of rural Ireland. For example, between 1978 and 2008, the distributional area occupied by red deer has shown an overall increase of over 560%.

The behaviour patterns of deer together with their short fur result in them being able to feed far greater numbers of ticks than, say, sheep. As a consequence, we are seeing significant growth in tick numbers in areas where deer are common. In some places, tick numbers are as high as any on continental Europe. Greater use by humans of recreational forest parks and growth in outdoor activities such as hill-walking are resulting in increasing contact between humans and ticks. This increased contact inevitably increases the risk of tick bite and, therefore, the risk of contracting Lyme disease.

A lack of public and medical practitioner awareness of the disease means that a patient presenting with it is often initially overlooked or misdiagnosed. The delay is critical. The longer the delay, the worse the outcome. Most patients will have progressed to late-stage Lyme disease by the time they are treated. Many late-stage patients fail to respond to conventional treatment and the disease can persist in a chronic state.

Improved treatment of Lyme disease in Ireland requires early diagnosis. This demands an educational effort to make the public aware of the risk and potential consequences of tick bites and how to reduce this risk, as well as ensuring medical practitioners have the knowledge and competencies to detect, test for and treat the disease.

As things stand, deer numbers will continue to increase and will, therefore, serve to further amplify the growth in tick numbers. Climate change and farming practices are together creating more favourable conditions for tick survival. Increasing contact between ticks and humans will inevitably result in a rise in the incidence of Lyme disease. It is not possible to significantly reduce either the deer population or the tick population by human effort. In the absence of this, an educational approach will be the cheapest and most effective strategy.