What is Lyme Disease?
Lyme disease was first identified in the 1970s in a small town called Lyme, Connecticut. It is a multisystem inflammatory zoonotic disease caused by a spirochete bacterium from the Borrelia genus. A majority of the cases in the U.S. are caused by the Borrelia burgdorferi strain, which is spread by the black-legged tick (Ixodes scapularis) and the western black-legged tick (Ixodes pacificus); these are both commonly known as the deer tick.
Epidemiology
There is evidence that Lyme disease has been around for hundreds of years. The archetypal bulls-eye rash, erythema migrans (EM), was first described over 130 years ago.
Erythema Migrans: Image source CDC.gov
The Lyme Disease Association indicates that the disease has now been diagnosed in over 80 countries, including the sub Antarctic region. Lyme disease is a significant issue in areas of Asia, central, eastern and northwest Europe, as well as the U.S. The main geographic regions with increases in Lyme disease are the forested areas of Asia, northwestern, and central and eastern Europe (WHO). According to the World Health Organization, Europe has a reported 360,000 cases over the past two decades. A current theory on this uptick in cases is an increase in the number of deer, mice and other host animals, ticks (vector), and global warming, discussed below.
According to the Bay Area Lyme Foundation, Lyme disease has reached epidemic levels and is the fastest growing vector borne Illness in the U.S. While the reported incidence varies among sources, the Centers for Disease Control (CDC) estimates the number of people diagnosed with Lyme disease each year to be greater than 30,000 in the U.S. Although 49 states have reported cases of Lyme disease (Hawaii has no reported cases) the Northeastern States have the highest incidence. The CDC reports that 15 states and the District of Columbia represent over 90 percent of all diagnosed cases of Lyme disease. Listed in descending incidence, these states are: Vermont, Maine, Pennsylvania, Rhode Island, Connecticut, New Jersey, Massachusetts, Delaware, New Hampshire, Minnesota, Maryland, New York, West Virginia, Virginia, and Wisconsin.
Transmission: Vectors and Lifecycles
Understanding the transmission cycle is necessary to see how global warming may be responsible for the increasing prevalence of Lyme disease.
The blacklegged ticks feed on hosts (usually deer but also mice, birds, reptiles amphibians, and humans) at each of the four stages of life. The highest risk of human infection is not the adult stage (easy to see and pull off the tick) but at the nymph and larval stage. During the eight-legged nymph stage, the tick is a tiny black dot, nearly impossible to see. The tick has more time to transmit the Borrelia bacteria to the unsuspecting host.
According to some researchers, the rise in Lyme disease cases is related to an increase in mice populations due to changing ecologies and warmer temperatures allowing for longer feeding times for the ticks. This is bad news for humans on both fronts. Children are the most rapidly growing demographic to be infected.
Disease Course
Lyme disease is generally characterized by two stages (for B. burgdorferi):
• First stage or Acute infection (3-30 days): The archetypal bull’s-eye red rash (erythema migrains) may develop usually within the first month. According to the CDC, the EM occurs in approximately 70- 80 percent of all reported cases. The rash may start out small and increase in diameter over time. The rash is typically not itchy or warm. Additionally, many people will exhibit flu-like symptoms, ranging from a headache to fatigue, fever, and chills. Again, these symptoms are not consistent for all those infected. For a majority of patients these are the only symptoms they experience.
(Image from Shapiro, 2014)
• Late stage and post-treatment Lyme disease syndrome: If Lyme disease is left untreated, patients may develop severe debilitating symptoms such as arthritis, neurological symptoms (memory loss, mood swings, lack of concentration), facial paralysis, heart palpitations (Lyme carditis), meningitis, and short-term memory loss. These symptoms may present days to months post-infection. Wormser, et. al. (2007) indicate that some patients may develop what is called Post-Treatment Lyme disease Syndrome (commonly referred to as “chronic Lyme disease”) , in which symptoms continue or may reappear after completion of treatment for initial disease.
Treatment
Recognition and early treatment of Lyme disease usually results in complete recovery. The CDC recommends using the treatment practice guidelines published by the Infectious Diseases Society of America in 2006. A new version of these guidelines will be published in 2018.
The authors recommend that clinicians refer to the practice guidelines for specifics regarding treatment recommendations and contraindications at all stages and outcomes of Lyme disease.
Is there a vaccine for Lyme disease?
According to the CDC, human vaccines for Lyme disease are not currently available. A vaccine was developed but discontinued in 2002. The protection afforded by the vaccine diminishes over time. Thus, if you received a vaccination prior to 2002, you are probably not protected from Lyme disease.