Lyme borreliosis in England and Wales: 2009

The following information is derived from a dynamic database, remains provisional and is subject to revision.

During 2009, 973 cases of Lyme borreliosis were identified in England and Wales residents.  This gives an incidence rate of 1.79/100,000 total population, and includes 173 people (18%) who are known to have acquired their infection abroad. However, excluding the known overseas acquired cases, the total population incidence throughout all regions of England and Wales is 1.48/100,000 total population.
The age, sex and seasonal distributions of serologically confirmed cases show trends similar to those reported in previous years. People of all ages are susceptible to Lyme borreliosis with the highest proportion of cases occurring in people between the ages of 30 to 59 years with the highest age-specific rates occurring in the 50-59 (3.0/100,000) and 60-64 (3.4/100,000) age groups. Similar numbers of infections were reported in both males and females across all age groups.

Seasonality
The seasonal pattern of infections identified in 2009 was similar to that seen in 2008, 2007 and earlier years.  Approximately 68% of patients had their sera tested for the first time during the months of July, August, September and October. This represents a likely peak onset of symptoms in the early summer months, and is consistent with the major tick feeding period during the early summer months. Twelve percent of blood samples were received and tested during the last two months of 2009, again, this is consistent with exposure to ticks and ‘ticky environments’ in the late summer and early autumn.

Location of Exposure
Approximately two thirds of indigenously-acquired infections were identified in residents of the southern counties of England (the south-west and south-east Health Regions), with population-specific rates of 3.95/100,000 and 4.85/100,000 respectively. These include well-known regional foci of Lyme borreliosis around the New Forest, Salisbury Plain, Exmoor, the South Downs, parts of Wiltshire and Berkshire and Thetford Forest. A number of cases also occur following visits to Scotland where there is a potentially greater proportion of the landscape capable of providing suitable habitats for ticks.  A small number of cases have also occurred following visits to the Irish Republic.

Travel
Patients present with Lyme borreliosis following overseas travel; most of these are in holidaymakers who present after visiting the United States (16%) (usually the eastern seabord) and countries in continental Europe (84%), many of which have considerably higher local incidence rates than are found in England and Wales [1].

Occupational infections
Lyme borreliosis is seldom reported as an occupational infection, but as such, it occurs more frequently in forestry workers, deer managers, gamekeepers and farmers.

Commentary
The incidence and focal distribution patterns of Lyme borreliosis observed in England and Wales are also seen in many other European countries and regions, and can vary from year to year; they are in part, determined by the heterogenous spatial distribution of vector ticks. The incidence in humans can be dependent on a number of climatic and other biotic factors which affect local tick populations including tick densities, survival and feeding behaviour. Exposures to ticks are also influenced by changes in human factors which include residential, occupational and recreational activities, not only in the UK but also overseas. These exposures may in turn be influenced by local, short-term weather conditions which can affect tick activity and also have an impact on human outdoor activity (and therefore human exposure to ticks).
The incidence of Lyme borreliosis in England and Wales is low compared with many European countries, many of which show no marked trends in annual incidence rates. For example, in Germany in 2002, it was estimated that there were at least 60,000 cases, giving an approximate incidence rate of 75/100,000 [2].
Further comparisons of European incidence rates can be found in references [1] and [3].

References

1. Hubalek Z. Epidemiology of Lyme borreliosis. In: Lipsker D, Jaulhac B (eds): Lyme borreliosis. Curr Probl Dermatol. Basel, Karger, 2009, 37:31-50.

2. Mehnert WH, Krause G. Surveillance of Lyme borreliosis in Germany, 2002 and 2003. Eurosurveillance 2005:10(4). Available at http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=531

3. Smith R, Takkinen J. Lyme borreliosis: Europe-wide coordinated surveillance and action needed? Eurosurveillance 2006:11(25). Available at http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=2977

Last reviewed: 20 December 2010