Lyme Disease In Bavaria: A Real Threat?

Lyme disease is the most common tick-borne disease in Germany. It is caused by the spirochete Borrelia burgdorferi and is transmitted by the Ixodes species of ticks.

In Germany, Lyme disease is not a nationally notifiable disease. However, nine out of the 16 German federal states have implemented mandatory notification for the three most common Lyme disease manifestations: erythema migrans (EM), acute neuroborreliosis (NB), and Lyme arthritis (LA). These states include Bavaria, which has been reporting Lyme disease cases since 2013.

Lyme disease is prevalent in all regions under surveillance in Germany and occurs in all age groups. The disease shows a marked seasonal pattern, with most cases reported between June and August, peaking in July. The incidence of Lyme disease varies across different regions, with some areas, such as West Mecklenburg, North Brandenburg, and the Bavarian Forest, consistently showing higher incidences.

The populations most affected by Lyme disease in Germany include boys aged 5-9 years and women aged 50-69 years. The predominant clinical manifestation is EM, with 94%-96% of cases presenting with this form. More severe forms, such as NB and LA, are less common but can have serious health consequences.

Overall, Lyme disease remains an important public health concern in Germany, with regional variations in incidence and affected populations. Prevention strategies, including tick-bite prevention and prompt tick removal, are essential to reducing the risk of infection.

Incidence of Lyme Borreliosis in Germany

Lyme borreliosis (LB) is the most common tick-borne disease in Germany. It is caused by the spirochete Borrelia burgdorferi sensu lato and is transmitted by Ixodes species ticks. LB is not a nationally notifiable disease in Germany, but nine out of sixteen federal states have implemented mandatory notification for the three most common LB manifestations (erythema migrans, acute neuroborreliosis, and Lyme arthritis). These nine states cover 42% of the German population.

The average annual incidence of LB in Germany was 37.2 per 100,000 person-years between 2016 and 2020. The incidence varied by spatial level, ranging from 22.9 to 64.6 per 100,000 person-years among the nine states, from 16.8 to 85.6 per 100,000 person-years among 19 regions, and from 2.9 to 172.8 per 100,000 person-years among 158 counties. The overall incidence remained stable during this period, with no clear increase or decrease.

The incidence of LB was particularly high in eastern Germany and Bavaria. In 2022, the number of newly diagnosed LB cases among those with statutory health insurance in Germany was over 135,000, with an average annual incidence of 203 per 100,000 insured people. The highest incidences were found in eastern German states such as Thuringia, Brandenburg, Saxony-Anhalt, and Mecklenburg-Western Pomerania, as well as in Bavaria.

Seasonal Variation

LB in Germany displays a marked seasonal pattern, with most cases reported between June and September, peaking in July. This seasonality is stable and consistent with the tick's host-seeking behavior and increased outdoor activities during the summer months.

Demographic Characteristics

The median age of LB cases in Germany was 54 years, with peaks in boys aged 5-9 years and women aged 50-69 years. Overall, 54-55% of LB cases were female, but more males had acute neuroborreliosis (56%) and Lyme arthritis (53%).

Clinical Manifestations

The predominant clinical manifestation of LB in Germany is erythema migrans (EM), which occurred in 94-96% of cases. Acute neuroborreliosis (NB) and Lyme arthritis (LA) were less common, affecting 2.7% and 2.1% of cases, respectively. Hospitalization was recorded for 10% of LA and 71% of NB cases.

Regional Distribution

LB occurs in all areas under surveillance in Germany, but there is marked regional variation. High-incidence regions include West-Mecklenburg, North Brandenburg, the Erz mountains, Hunsrueck/Eifel, Fraenkische Alb/Steigerwald, and the Bavarian Forest. These regions consistently showed higher LB incidences during the study periods.

Underreporting

Underreporting of LB cases in Germany is common, and the extent of underreporting is currently unknown. Notification data may underestimate the true morbidity of LB due to issues such as under-reporting and misclassification. Claims data and other data sources, such as medical claims and seroprevalence studies, suggest a higher incidence of LB than what is reported in the notification system.

The disease is caused by the spirochete Borrelia burgdorferi

Lyme disease is caused by the spirochete Borrelia burgdorferi, a corkscrew-shaped bacterium. B. burgdorferi is a gram-negative bacterial species of the spirochete class in the genus Borrelia. It is one of the causative agents of Lyme disease in humans.

B. burgdorferi is a microaerophilic, motile spirochete with seven to 11 bundled perisplasmic flagella set at each end that allow the bacterium to move in low- and high-viscosity media. It is slow-growing, with a doubling time of 24 to 48 hours. It requires small amounts of oxygen to undergo glycolysis and survive. B. burgdorferi has a flexible cell well and long, cylindrical cells that are roughly 1 micron wide and 5 to 20 microns in length. Its shape is a flat wave.

B. burgdorferi circulates between Ixodes ticks and a vertebrate host in an enzootic cycle. It is transmitted to humans through the bite of the Ixodes tick, also known as deer ticks or black-legged ticks. These ticks are typically found in wooded and grassy areas. The bacterium infects the skin after a tick attaches for at least 24 hours and then spreads through the blood or lymph to other organs.

Lyme disease may present in one of three stages: early localized disease, early disseminated disease, and late disseminated disease. The characteristic symptom of early localized disease is an annular rash that initially appears as a small red papule or macule that enlarges to form a lesion. This rash may or may not exhibit central clearing. Other symptoms include arthritis, carditis, and, in late stages, encephalopathy. Early disseminated disease is characterized by secondary annular lesions accompanied by headaches, neck stiffness, fever, chills, muscle aches, and malaise. Late disseminated disease, which occurs months to years after infection, can include encephalitis, meningitis, migratory arthropathies, and chronic neurological sequelae such as memory, mood, or sleep disturbances.

B. burgdorferi is the only species of spirochete responsible for Lyme disease in North America. In Europe, four other species (Borrelia afzelii, Borrelia garinii, Borrelia spielmanii, and Borrelia bavariensis) also cause Lyme disease.

Mandatory notification of Lyme Borreliosis in Bavaria

Background

Lyme borreliosis (LB) is the most common tick-borne disease in Germany. The disease is caused by bacteria of the Borrelia burgdorferi sensu lato complex and is transmitted to humans by bites of infected Ixodes species ticks. LB is a multi-system disease, with the most common clinical manifestation being erythema migrans (EM). If the bacteria disseminate, more severe forms like neuroborreliosis (NB), Lyme arthritis (LA) or, less frequently, Lyme carditis can occur.

In Germany, an effective vaccine is not available, and prevention strategies focus on raising awareness, avoiding tick bites, checking for ticks, prompt removal of attached ticks, and early medical consultation if symptoms occur.

In 2013, Bavaria implemented mandatory notification for the three most common LB manifestations (EM, acute NB, and LA). This was in addition to eight other German states that already had mandatory notification in place.

Epidemiology

Between 2013 and 2017, 56,446 cases of LB (annual mean: 11,289; range: 8,902–13,708) were reported in the nine states with mandatory notification. This corresponds to a mean annual incidence of 33/100,000 population (range: 26/100,000 in 2015 to 41/100,000 in 2013). There was no obvious increasing or decreasing trend over time.

The highest number of cases was notified in 2013, especially in states with new implementation of surveillance. In 2014 and 2015, numbers were lower, and they increased again in 2016.

Seasonality

LB displayed a marked seasonal pattern, with 57% of cases reporting disease onset between June and August and peaking in July every year. Seasonality was stable from 2013 to 2017.

Regional Distribution

LB occurred in all areas under surveillance but showed marked regional variation. Despite annual fluctuations in LB incidence overall, the same regions displayed higher LB incidences during the different years of the study period.

Based on mean annual incidence from 2013 to 2017, five regions were identified as having particularly high incidences:

• West-Mecklenburg, including the city of Schwerin, and North-Brandenburg
• The Erz mountains
• Hunsrueck/Eifel region
• Fraenkische Alb/Steigerwald
• The Bavarian forest

Demographic Characteristics and Clinical Information

The median age of those with LB was 54 years (interquartile range: 39–65 years), with 54% of cases being female. A bimodal age distribution was observed, with incidence peaks in boys aged 5–9 years (mean incidence: 34/100,000 population/year) and women aged 50–69 years (mean incidence: 57/100,0000 population/year).

Detailed information on clinical manifestations was available for 99% of cases. Of these, 95% had EM only, while 4.8% suffered from more severe forms: 2.7% had NB, and 2.1% had LA.

Discussion and Prevention

LB remains an important public health concern in Germany, with all regions under surveillance reporting cases. To facilitate early diagnosis and treatment, health authorities should raise awareness among physicians and promote prevention strategies among the general population, including tick-bite prevention, prompt tick removal, and medical consultation.

Effective prevention of LB has proven challenging, and consideration should be given to possible alternatives to the current surveillance system, which poses a substantial burden on physicians, laboratories, and public health authorities.

Clinical manifestations of Lyme Borreliosis

Lyme disease, also known as Lyme borreliosis, is an infectious disease caused by the bacteria Borrelia burgdorferi, which is transmitted through the bite of infected ticks. The disease progresses through three stages: early localized, early disseminated, and late disease.

Early Localized Lyme Disease

The initial symptoms of Lyme disease often include a distinctive "bull's-eye" rash called erythema migrans, which affects around two-thirds of those who develop the disease. This rash typically occurs at the site of the tick bite and may be accompanied by fever, fatigue, malaise, headache, myalgia, and arthralgia.

Early Disseminated Lyme Disease

If left untreated, the infection can spread to other areas of the body, leading to early disseminated Lyme disease. This stage is associated with neurological and cardiac manifestations. Neurological symptoms can include facial nerve palsy, lymphocytic meningitis, radiculopathy, and encephalomyelitis. Cardiac involvement may present as arrhythmias, transient heart block, myocarditis, or pericarditis.

Late Lyme Disease

Late-stage Lyme disease may occur months after the initial infection and is characterized by neurological and musculoskeletal involvement. Common symptoms include sensory axonal polyneuropathy, encephalomyelitis, mononeuropathy, cognitive deficits, encephalopathy, joint pain, and swelling.

Post-Treatment Lyme Disease Syndrome (PTLDS)

Even after treatment with antibiotics, some individuals may develop PTLDS, experiencing lingering symptoms such as fatigue, pain, joint and muscle aches, and cognitive impairment.

Clinical Manifestations in Bavaria, Germany

Lyme borreliosis is the most common tick-borne disease in Germany, and Bavaria is known to be an endemic area. Between 2013 and 2020, the average annual incidence of Lyme borreliosis in Bavaria was 34.3 cases per 100,000 inhabitants, with marked regional variations. The Bavarian Forest and parts of Franconia were identified as high-risk regions. The disease predominantly affects children aged 5-9 years and adults aged 60-69 years, with males having a higher risk of developing severe manifestations. The most common clinical manifestation is erythema migrans, followed by acute neuroborreliosis and Lyme arthritis.

Regional variations in Lyme Borreliosis

Lyme Borreliosis (LB) is the most common tick-borne disease in Germany. The disease is caused by the spirochete Borrelia burgdorferi sensu lato and is transmitted by the Ixodes species of ticks. LB is not a notifiable disease at the federal level in Germany, but nine out of sixteen German federal states have implemented mandatory notification for the three most common LB manifestations: erythema migrans (EM), acute neuroborreliosis (NB), and Lyme arthritis (LA). These nine states cover 42% of the total German population.

Regional Variations in Incidence

The incidence of LB varies significantly across Germany, with some regions consistently showing higher LB incidences. The regions in West Mecklenburg, North Brandenburg, the Erz mountains in Saxony, Hunsrueck/Eifel, Fraenkische Alb/Steigerwald, and the Bavarian Forest have been identified as high-incidence areas in multiple studies. These regions tend to have suitable habitats for ticks and higher tick densities, contributing to the higher incidence of LB.

The incidence of LB also varies by age and sex, with a bimodal age distribution observed in multiple studies. The incidence peaks in boys aged 5-9 years and women aged 50-69 years. This distribution may be due to differences in outdoor behavior and leisure activities between males and females and across age groups.

Underreporting in Notification Data

It is important to note that notification data may underestimate the true morbidity of LB due to underreporting and misclassification. The extent of underreporting in Germany is currently unknown, but it is assumed that the actual number of LB cases is higher than what is reported. Claims data and other data sources, such as medical claims and hospitalisation data, can provide additional insights into the epidemiology of LB and help address the limitations of notification data.

Land Cover Composition and Risk Factors

The association between high-incidence areas and land cover composition has been explored, revealing a significant relationship. Districts with a higher proportion of forests and agricultural areas tend to have higher LB incidences. This finding highlights the importance of environmental factors, such as landscape characteristics, in the spread of LB.

Prevention and Awareness

As there is currently no vaccine available against LB in Germany, prevention strategies focus on raising awareness, tick-bite prevention, prompt tick removal, and early medical consultation. Health authorities should continue to promote these strategies and target their efforts towards identified risk groups, such as individuals living in high-incidence regions and those in the age groups with higher incidence peaks.

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