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Introduction
Lyme borreliosis (LB) is caused by the spirochete Borrelia burgdorferi
and is transmitted through bite(s) of Ixodes spp ticks. Like syphilis,
LB is a multi-system infection, which occurs in stages and mimics other
infections. The characteristic bull’s eye rash now known as erythema
migrans was first reported in Sweden in 1909 [2]. LB was recognized
as a distinct disease in 1975-1976 in people living around Old Lyme,
Connecticut, United States (US). Over the past two decades, incidence
of LB has increased and now constitutes an important health problem
in US and many parts of Europe. In Europe, very few countries have
made LB a mandatory notifiable disease and therefore, case rates give
only an approximate estimation of European LB incidence [3] [TABLE
1].
Across Europe the incidence of LB generally increases from west to east.
For Germany, precise incidence data of LB do not exist. It is estimated
that there are around 60 000 new cases a year in Germany [4].
Materials and Methods
LB is not a notifiable disease in Germany, but six of Germany’s
16 states have extended notification systems. The six east German states – Berlin,
Brandenburg, Mecklenburg-Vorpommern, Sachsen, Sachsen-Anhalt and Thüringen,
- have a more comprehensive list of notifiable infections, which include
LB [5]. Physicians in these states have to notify LB cases to the local
health authorities. The local health authorities send the data to the
federal (Bundesland) state authorities, who then forward these to the
Robert Koch-Institut (RKI).
In 2002, the RKI published case definitions for LB surveillance [5].
The case definitions used by local health authorities include clinical,
laboratory and case-exclusion criteria. Since 2002, data on cases of
LB submitted to RKI have been confined to cases with erythema migrans
and/or early neuroborreliosis. The LB cases are checked for missing data
on essential criteria for clinical and laboratory evidence at RKI. When
requested by RKI, missing data are subsequently collected by the local
health authorities [TABLE 2].
Results
In 2002, 3029 cases of LB were submitted to the RKI. In 2003, the number
of submitted cases increased by 32% to 3986 cases. Of these, only cases
declared by the local health authorities as satisfying the inclusion
criteria were included in this analysis. A total of 3019 cases (99.7%)
in 2002, and 3968 (99.5%) in 2003 fullfilled the criteria and were included.
The incidence of LB of the six east German states was 17.8 cases per
100 000 population in 2002. This increased by 31% to 23.3 cases in 2003.
During 2002-2003, LB case reports increased in all of the six east German
states with the highest relative increase in Thüringen [FIGURE 1].
Two states (Brandenburg, Sachsen) accounted for 81% of the cases submitted
by all six states.
Patient ages were bimodally distributed, with incidence peaks among
children aged 5- 9 years (18.3 cases per 100,000 population per year
in 2002, 28.9 in 2003 respectively) and elderly patients, aged 60- 64
in 2002 (39.2 cases per 100,000 population per year), and 65-69 in 2003
(48.6 cases per 100,000 population per year) [FIGURE 2].
One explanation for the age distribution in adults may be the obvious
higher likelihood of exposure to tick-bites and the leisure behaviour
of individuals, aged between 25 and 64, which may influence the likelihood
of their exposure (more outdoor activities, sport, camping and others).
Relatively few cases occurred in people aged over 65 in 2002 and over
70 in 2003, possibly because their activities are less likely to expose
them to ticks. The observed shift of the age peak to the right in 2003
and the incidence peak in children aged 5-9 cannot be explained and needs
further monitoring in the future.
During 2002-2003, incidence increased in both sexes, in females (20.9
cases per 100,000 population per year in 2002, 27.6 in 2003); in males
(18.0 cases per 100,000 population per year in 2002, 23.6 in 2003). In
both years, 55% of patients were female.
A total of 97% of reports for 2002 and 2003 had a date of onset of illness
provided. Around 86% of submitted cases occurred from May to October.
The peak (70% of submitted cases between June and September) coincides
with periods of maximum tick activity and summer-related leisure behaviour.
Fewer than 5% were submitted to have the onset of illness from December
to March [FIGURE 3].
Erythema migrans affected 2697 patients (89.3%) in 2002, and 3442 (86.7%)
in 2003. Early neuroborreliosis affected 97 patients (3.2%) in 2002 and
97 (2.4%) in 2003 respectively. Table 3 shows the number of cases of
early neuroborreliosis with paralysis of the facial nerve, radiculoneuritis
and meningitis in 2002 and 2003. [TABLE 3]
During 2002-2003 no deaths due to LB were submitted. In this period,
the diagnosis of LB was supported in a high percentage of cases by
the detection of specific immunoglobulins: IgM > 85%, IgG > 35%.
Other submitted diagnostic criteria (e.g. direct pathogen detection
by culture or molecular diagnostic methods [PCR] and investigation
of cerebrospinal fluid) were almost negligible (~ 1%).
Conclusions
LB is a potentially serious infection and common in Germany, but few
data about its incidence, distribution, and clinical manifestation
are available. The efforts made in some federal states to monitor confirmed
cases through notification are therefore an important contribution
to the understanding of the LB epidemiology in Germany.
The incidence of LB has increased markedly over the past two decades
in various European countries. Changes in the natural dynamics of European
tickborne zoonoses appear to have occurred towards the end of the 20th
century, largely brought about by human impact on the habitat and wildlife
hosts of ticks. Purely climatic factors may have played some part. At
the same time, raised awareness of ticks as vectors, and the intense
interest in LB have undoubtedly stimulated surveillance and protective
measures [6].
For a vector-borne disease like LB, the risk of infection depends on
the degree of contact between humans and infected vectors, as well as
the time span the tick is attached to the skin of the human. As infectious
ticks are likely to occur throughout Germany [7], it is likely that the
incidence in the remaining ten western German states has also increased.
Special advice and information is needed for individuals at risk – in
particular with respect to avoiding exposure, (e.g. areas or environments
with tick populations, garden places near to forests, grass, bushes,
red deer, mice, squirrels etc.), to inspect skin for ticks after possible
exposure, to remove the tick as soon as it is detected or as fast as
possible, and to seek medical advice if symptoms develop after a tick
bite [8], [9]. In addition, removal of grass or other vegetation as well
as eliminating host animals, such as deer have been used as methods to
control the spread of LB.
Acknowledgements
The authors wish to thank the staff of the federal state and local health
authorities, the hospitals and laboratories in the 6 eastern German states
and the national reference centre for Lyme borreliosis at the Max-von-Pettenkofer-Institut,
Munich, Germany, that provided data for this study.
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