The Incidence of Lyme Disease has been Steadily Rising Around the World
The incidence of Lyme disease has steadily risen in the United States since its discovery. The incidence in some regions of Europe is believed to be increasing as well.
Lyme Disease in Europe
A possible reason for the increase in Lyme disease in Europe is that climate change has caused an increased density and broader geographic distribution of Ixodes ticks. Additionally, an increase in the deer population in the northeastern United States and changes in land management practices have contributed to the rise in incidence of Lyme disease. A particularly virulent strain of B. burgdorferi called OspC type A is prevalent in the northeastern United States and has a high transmission frequency among ticks. Unfortunately, this strain may be increasing in frequency in nature, and may have been important in the emergence of Lyme disease in the northeastern United States during the late 20th century.
Lyme Disease in the United States
United States — From 2003 to 2012, a total of 279,509 cases of Lyme disease were reported in the United States; cases increased 45 percent, from 21,273 in 2003 to 30,831 in 2012. It is currently the seventh most common reportable disease in the United States. Although all age groups are affected by Lyme disease, the distribution of cases is bimodal, with peaks in the 5 to 10 and 35 to 55 year-old age groups. Over half of cases (53 percent) occur in males. This age and gender pattern may reflect the amount of time certain groups spend outdoors in contact with forested habitats.
Lyme Disease in Asia
Europe and Asia — Although the etiology of Lyme disease was unknown until the early 1980s, cases of acrodermatitis chronica atrophicans (a skin manifestation of Lyme disease in Europe) have been described in Europe as far back as 1883. In Europe, as in the United States, there are regions of high prevalence of Lyme disease in forested areas. The regions of Europe with the highest prevalence are Germany, Austria, Slovenia, and Sweden. In 1995, the incidence in Slovenia and Austria was estimated to be 120 to 130 cases per 100,000 population.
Lyme disease also occurs in Russia, Japan, and China.
Chronic Lyme Disease
The treatment of Lyme Disease can be divided into two stages: acute treatment and chronic Lyme treatment. Here, we discuss chronic Lyme disease only. Most patients with early disease have complete resolution of the signs and symptoms of infection within 20 days. However, the response to therapy is often slower in patients with late disease, particularly late neurologic manifestations. Furthermore, microbiologic treatment failure does occur. Although no strain of B. burgdorferi has been described as resistant to primary antibiotics, treatment failure is attributed to poor absorption or noncompliance with treatment.
When the term “treatment failure” is used, it usually refers to symptoms that have persisted or recurred. Some Lyme disease patients have mild subjective symptoms, such as headache, musculoskeletal pain, arthralgia, lethargy, cognitive complaints, and/or fatigue, that persist for weeks to months after treatment
The following observations have attempted to address the issue of persistent symptoms:
- In a trial of patients with early Lyme disease, mild subjective symptoms were noted after treatment in almost one-half of patients and correlated significantly with the severity of the initial illness. Extending antibiotic therapy from 10 to 20 days had no effect on the frequency of these symptoms, which typically resolve within six months
- In a retrospective cohort study, patients with a history of treated Lyme disease were significantly more likely than controls to report joint pains and memory impairment at a mean of six years after treatment. However, physical examination and neurocognitive studies performed in a blinded fashion showed no differences between cases and controls.
- Randomized controlled trials of repeat antimicrobial therapy in patients with persistent symptoms after recommended therapy for Lyme disease have not shown benefit. By contrast, prolonged treatment with antibiotics has been associated with a variety of adverse effects (including death) as well as enhancing selection of resistant bacteria.
Inflammation Caused by Chronic Lyme Disease and the Need for a Treatment
Based upon such observations, the Infectious Diseases Society of America (IDSA) in 2006, the American Academy of Neurology in 2007, and the Ad Hoc International Lyme Disease Group in 2007 concluded that the chronic subjective symptoms that may occur after recommended courses of antibiotic therapy for Lyme disease are not due to persistent infection with B. burgdorferi. However, this may not reflect patients that lived with undiagnosed Lyme disease that has allowed for extensive pathogen colonization and persistent localized immune damage resulting from the release of proteases such matrix metalloproteinases. Altogether, persistent infection and chronic low-grade inflammation may cultivate the subjective symptoms suffered by chronic Lyme patients.