What is Lyme disease?
What is Lyme disease?
Lyme is the most commonly reported vector borne disease in the United States. New estimates released by the CDC in 2021 are that 476,000 people are diagnosed and treated for Lyme disease each year.
- Schwartz AM, Kugeler KJ, Nelson CA, et al. Evaluation of commercial insurance claims as an annual data source for Lyme disease diagnoses. Emerg Infect Dis. 2021;27(2).
- Kugeler KJ, Schwartz AM, Delorey M, et al. Estimating the frequency of Lyme disease diagnoses —United States, 2010-2018. Emerg Infect Dis. 2021;27(2).
Lyme is a multi-systemic disease caused by a spirochete bacterial infection in humans, pets and other animals in the US and worldwide. When Lyme disease is accurately diagnosed and properly treated patients often recover completely. However, some individuals experience long-term, debilitating effects, if left untreated or even after completing standard treatment.
Though it has been in existence for millions of years, it was only first described in Germany more than 130 years ago. Lyme disease is most often transmitted by the bite of an infected black-legged tick, commonly known as a “deer tick.”
Lyme disease is caused by four main species of bacteria: Borrelia burgdorferi, Borrelia mayonii, Borrelia afzelii and Borrelia garinii bacteria. Borrelia burgdorferi and Borrelia mayonii cause Lyme disease in the United States, while Borrelia afzelii and Borrelia garinii are the leading causes of Lyme disease in Europe and Asia and are the most common tick-borne illnesses in these regions. Lyme in the United States wasn’t recognized until 1975 when a cluster of children and adults residing in the Lyme, Connecticut area experienced uncommon arthritic symptoms. However, the spirochetal bacteria responsible for this illness, Borrelia burgdorferi (Bb) wasn’t officially classified until 1981 by Dr. Wilhelm “Willy” Burgdorfer, for which the bacteria is named. There are approximately 300 strains of B. burgdorferi sensu lato, known worldwide, with about 100 strains prevalent in the US.
In 2013, an additional bacteria was identified in the United States by the Mayo Clinic as another causative agent for Lyme and has recently been classified as Borrelia mayonii. It has only been detected in patients from the upper Midwest states at this time. B. mayonii appears to be associated with more nausea and vomiting, diffuse rashes, and a higher concentration of bacteria in the blood than B. burgdorferi. Lyme disease has become increasingly common especially throughout the Northeast, north central Midwest, and in the Western coastal states. Lyme disease has been reported through CDC surveillance in all 50 states of the US and can be found worldwide.
Many small mammals, birds and other wildlife act as reservoir hosts for these bacteria on which the ticks feed and acquire infection. Borrelia bacteria are then transmitted by the bite of a tick to other animals and humans. Lyme can be a debilitating or even deadly illness if not diagnosed and treated properly early in the disease process. Preventing tick bites is the best way to avoid this infection but, when prevention measures fail, early recognition of the signs and symptoms of disease is critical to the best outcome for patients!
The CDC has found that “Since 1991, when standardized surveillance and reporting began, Lyme disease case counts have increased steadily in number and in geographical distribution in the eastern United States”. Similar trends have been observed for Anaplasmosis and Babesiosis.
The CDC has also stated that “Each year, more than 30,000 cases of Lyme disease are reported to the CDC, making it the most commonly reported tick-borne illness in the United States. The new estimate suggests that the total number of people diagnosed with Lyme disease is roughly 10 times higher than the yearly reported number. This new estimate supports studies published in the 1990s indicating that the true number of cases is between 3- and 12-fold higher than the number of reported cases”. Estimated cases based on CDC reports for 2017 reached over 400,000.
According to the CDC, the highest infection rates of Lyme disease occur in children, ages 5 to 9. Approximately one in four people infected in the U.S. each year is a child.
Tick infection rates are highly variable even within endemic states, for reasons that are not yet fully understood. In addition to the Lyme bacteria, ticks often carry other pathogens that cause co-infections such as Babesiosis, Anaplasmosis, Ehrlichiosis and others in their human hosts, which can further complicate diagnosis and treatment.
Lyme can be a debilitating and sometimes deadly illness if not diagnosed and treated early in the disease process. Even with early treatment it is estimated that 20%, or greater, of patients experience relapse and/or development of persistent symptoms after short courses of antibiotics.
When Lyme symptoms do not resolve after initial or repeated treatment it is called “Chronic Lyme”. The CDC refers to this condition as “Post-Treatment Lyme Disease Syndrome” (PTLDS). There is controversy about whether these ongoing symptoms represent a chronic infection, or an ongoing immune response.
Hundreds of peer reviewed articles, compiled by Drs. Robert Bransfield, Bernt-Dieter Huismans, Steven Phillips, John Scott and Raphael Stricker, offer evidence of disease persistence. Unfortunately, with no test yet available to determine if the bacteria has been eradicated from the body following treatment, the controversy between the two beliefs continues. Scientists are still working to define the reasons for treatment failure and persistence of disease and/or symptoms. Unfortunately, the divided beliefs surrounding persistence of disease in the medical community leaves patients and physicians to navigate conflicting recommendations. A definitive cure for this disease has not yet been discovered.
The bacteria responsible for most cases of Lyme disease in the US, B. burdorferi and B. mayonii. The primary vectors of this disease in the US are the “deer tick” or blacklegged tick (Ixodes scapularis) common to the Northeast and upper Midwest, and the “Pacific”or western black legged tick (Ixodes pacificus) found in the West. Combined, these vectors of B. burgdorferi and other disease agents now have been identified in a total of 1,531 (49.2%) counties spread across 43 states within the US as presented in the 2016 CDC surveillance report. I. pacificus is known to occur in Colorado’s adjacent western states of Utah and Arizona however, the presence of the Lyme bacteria has not been confirmed in these tick populations. I. scapularis is also known to occur in Kansas as well as Nebraska. Lone star ticks, Amblyomma americanum have recently been implicated in causing Lyme disease in the Southern US.
Other lesser known Ixodes tick species, that occur nationwide have been found to be competent vectors for many of the same diseases transmitted by the blacklegged ticks. Many of these species occur in regions currently considered “low risk” for Lyme disease, however standardized surveillance has been minimal non-existent in many of these regions.
Awareness and education of Lyme disease for Coloradans can help both physicians and patients get accurate and timely diagnosis as well as appropriate testing and treatment for this often complex disease regardless of where exposure to this disease may occur.
Resources:
