Lyme borreliosis in the Netherlands: strong increase in GP
consultations and hospital admissions in past 10 years
Lyme borreliosis (Lyme disease) is not notifiable in the
Netherlands, and so retrospective studies to determine the national occurrence
of tick bites, erythema migrans and Lyme borreliosis have been carried out.
In 1995, 2002 and 2006, all general practitioners in the country (approximately
8000 GPs with population coverage of 88%, 68% and 71%, respectively) were
asked to complete a postal questionnaire on tick bites and erythema migrans
case-patients seen in the previous year. Annual counts of hospital admissions
for Lyme borreliosis were obtained from a database of the Dutch National Medical
Register, which covers nearly all hospitals in the Netherlands, using version
9 of the International Classification of Diseases (ICD-9) code 104.8. This
code represents ‘other spirochetal infections’, and includes Lyme borreliosis,
leptospirosis, intestinal spirochetosis, non-syphilis treponemas and Plaut-Vincent
angina. A majority of ‘code 104.8’ infections are Lyme borreliosis, because
most of the other infections have their own codes.
Based on the survey responses, the incidence of erythema migrans consultations
was estimated at 39 per 100 000 population in 1994, which doubled to 74
per 100 000 in 2001, and tripled to 103 per 100 000 in 2005. The incidence
of tick bite consultations increased from 191/100 000 people in 1994 to
372/100 000 in 2001, and continued to increase to 446/100 000 in 2005.
The greatest increase in tick bites and erythema migrans was seen in the
south and northeast of the country, and several locations along the coast
in the west (Figure). Hospital admissions coincided geographically with
locations where physicians were consulted for tick bites and erythema migrans.
The estimated annual number of hospital admissions for Lyme borreliosis
increased from 170 patients in 1994 to 229 in 2001, 228 in 2002, 331 in
2003, 411 in 2004, and 435 patients in 2005, with the greatest increase
occurring between 2002 and 2004.
Figure. The geographical distribution of erythema migrans
cases per 100 000 inhabitants of the Netherlands in 1994, 2001, 2005. Source:
It is not certain that the increase of hospital admissions in recent years
represents a true doubling in the occurrence of Lyme borreliosis, as a new
guideline concerning diagnosis and treatment of Lyme disease was published
in mid-2003. This guideline encouraged treatment of severe Lyme borreliosis
with intravenous antibiotics, which are usually administered in hospital.
Analyses of the role of and changes in ecological risk factors and outdoor
recreation, between regions and years, are forthcoming.
Lyme borreliosis appears to be an increasingly important healthcare problem
in the Netherlands. Another study, carried out in the Netherlands between
2000 and 2004, demonstrated that between 0.8% and 11% of the collected ticks
were contaminated with Borrelia burgdorferi sensu lato, varying
between years and types of vegetation. Contamination of ticks with other
pathogens like Anaplasma / Ehrlichia (1%-15%), Rickettsia
(5%–60%*), and Babesia (0%-1%) was
also found . A prospective study in sentinel general practices to determine
the regional differences in the level of infection of ticks removed from
patients for different tick-borne pathogens is planned for 2007. Serological
tests will also be performed for erythema migrans cases seen at these general
practices and their clinical outcome will be observed.
To increase awareness about the severity, diagnosis and treatment of Lyme
disease, the results of the GP surveys in 1994, 2001 and 2005 were communicated
to all general practitioners in the Netherlands. This information was also
sent to municipal health centres, with extra information about the availability
of our new brochure about ticks and Lyme disease. In 2002 and 2006, the
RIVM issued a press release to alert the public about the increase in erythema
migrans case-patients, which received much media attention . Both press
releases referred to the fact sheets and questions and answers on the RIVM
*Correction. This was
corrected from '45%-60%' to '5%-60%' on 26 June 2006
Eurosurveillance editorial office, 26 June 2006.