HPSC has designated the week beginning May 2^nd, 2016, as Lyme Awareness Week.  

Lyme disease (also known as Lyme borreliosis - LB) is an infection caused by a spiral-shaped bacterium called Borrelia burgdorferi that is transmitted to humans by bites from ticks infected with the bacteria. The infection is generally mild and affects only the skin. Occasionally, however, it can be more severe, leading to extensive, systemic involvement of the nervous system and heart. 

Campers, walkers and certain occupational groups such as forestry workers, conservation workers, deer cullers and farmers appear to be at particular risk of exposure. The ticks responsible are generally hard-bodied ticks (Ixodidae) – these are a type of mite. Ixodes ticks are hosted by a wide range of mammals including deer, sheep and cows; their tiny size (less than 2mm unfed) means they can remain undetected for long periods. 

Ticks walk on the ground and climb plants. They latch on to a passing animal host or people by using hooks on their legs. Their preferred habitats are:

• Shady and humid woodland, clearings with grass,
• Open fields and bushes (can vary depending on the tick).

They are present in both urban and rural areas and are active from spring to autumn. From April on is the time when we expect to see cases of Lyme disease most frequently in Ireland.

2012 was the first year in which Lyme borelliosis was notifiable. The notifiable entity is the more severe neurological form of LB; neuroborreliosis.

Table 1.  Neuroborreliosis Notifications Ireland: 2012-2015

Estimates as to the ratio of LB cases to neuroborreliosis cases vary widely. One study in Ireland in looking at a series of 30 Lyme patients identified neuroborreliosis in 50% of the cases.[1]  In Connecticut, in 1989, eight percent of reported Lyme cases had a neurological component.[2] A more commonly cited figure is that, In Europe as a whole, about 20% of Lyme cases will go on to develop neuroborreliosis.[3]  Were this final figure applicable here in Ireland, we would expect that about 50 cases of LB annually in Ireland. It is likely, however, that the figure of 50 LB cases countrywide per annum would be a considerable underestimate. 

The risk of infection is greatest in late spring and early summer, so April is the time to ensure that parents, children and doctors are aware of the risks posed by ticks.

The website of the Health Protection Surveillance Centre has extensive general information on Lyme disease, guidance for clinicians and illustrations showing the characteristic rash of erythema migrans and relative tick sizes.

The ticks that carry LB are prevalent in Ireland, and Irish people love to get into the countryside. This places them (and their pet dogs) at risk of being bitten by infected ticks.  Dogs can carry ticks home and they can then go on to bite family members even those who were not outside. The Centers for Disease Control and Prevention in the US has an excellent section on Lyme and pets. The best way to prevent LB is to prevent being bitten by a tick.

Awareness of LB among clinicians is continually increasing, a recent article in Epi-Insight describes the clinical and public health features of LB. LB is a diagnosis that can easily be missed; asking the patient has s/he been in at-risk areas or if they recall a tick bite (or even the rash of erythema migrans) will often provide important clinical clues. And if diagnosed, HPSC has resources for the clinician to assist diagnosis and management.

Contrary to what is often believed, LB is relatively easy to contract but treatment (especially if identified early) is relatively straightforward. Protect yourself against tick bites and you protect yourself against Lyme disease. 

Dr Paul McKeown, HPSC