Diagnosis
Lyme disease is diagnosed clinically based on symptoms, objective physical findings (such as erythema migrans, facial palsy, or arthritis), a history of possible exposure to infected ticks, as well as serological tests. When making a diagnosis of Lyme disease, health care providers should consider other diseases that may cause similar illness. Most but not all patients with Lyme disease will develop the characteristic bulls-eye rash, and many may not recall a tick bite. Laboratory testing is not recommended for persons who do not have symptoms of Lyme disease.
Because of the difficulty in culturing Borrelia bacteria in the laboratory, diagnosis of Lyme disease is typically based on the clinical exam findings and a history of exposure to endemic Lyme areas. The EM rash, which does not occur in all cases, is considered sufficient to establish a diagnosis of Lyme disease even when serologies are negative. Serological testing can be used to support a clinically suspected case but is not diagnostic.
Diagnosis of late-stage Lyme disease is often difficult because of the multi-faceted appearance which can mimic symptoms of many other diseases. Lyme disease may be misdiagnosed as multiple sclerosis, rheumatoid arthritis, fibromyalgia, chronic fatigue syndrome (CFS), lupus, or other autoimmune and neurodegenerative diseases.
Causes
Lyme disease is caused by Gram-negative spirochetal bacteria from the genus Borrelia. At least 11 Borrelia species have been described, 3 of which are Lyme related. The Borrelia species known to cause Lyme disease are collectively known as Borrelia burgdorferi sensu lato, and have been found to have greater strain diversity than previously estimated.
Three closely-related species of spirochetes are well-established as causing Lyme disease and are probably responsible for the large majority of cases: B. burgdorferi sensu stricto (predominant in North America, but also in Europe), B. afzelii, and B. garinii (both predominant in Eurasia). Some studies have also proposed that B. bissettii and B. valaisiana may sometimes infect humans, but these species do not seem to be important causes of disease.
Treatment
Antibiotics are the primary treatment for Lyme disease; the most appropriate antibiotic treatment depends upon the patient and the stage of the disease. The antibiotics of choice are doxycycline (in adults), amoxicillin (in children), and ceftriaxone. Alternative choices are cefuroxime and cefotaxime. Macrolide antibiotics have limited efficacy when used alone.
Results of a recent double blind, randomized, placebo-controlled multicenter clinical study, done in Finland, indicated that oral adjunct antibiotics were not justified in the treatment of patients with disseminated Lyme borreliosis who initially received intravenous antibiotics for three weeks. The researchers noted the clinical outcome of said patients should not be evaluated at the completion of intravenous antibiotic treatment but rather 6-12 months afterwards. In patients with chronic post-treatment symptoms, persistent positive levels of antibodies did not seem to provide any useful information for further care of the patient.
In later stages, the bacteria disseminate throughout the body and may cross the blood-brain barrier, making the infection more difficult to treat. Late diagnosed Lyme is treated with oral or IV antibiotics, frequently ceftriaxone for a minimum of four weeks. Minocycline is also indicated for neuroborreliosis for its ability to cross the blood-brain barrier.
Prevention
Attached ticks should be removed promptly. Protective clothing includes a hat and long-sleeved shirts and long pants that are tucked into socks or boots. Light-colored clothing makes the tick more easily visible before it attaches itself. People should use special care in handling and allowing outdoor pets inside homes because they can bring ticks into the house.
A more effective, community wide method of preventing Lyme disease is to reduce the numbers of primary hosts on which the deer tick depends such as rodents, other small mammals, and deer. Reduction of the deer population may over time help break the reproductive cycle of the deer ticks and their ability to flourish in suburban and rural areas.
An unusual, organic approach to control of ticks and prevention of Lyme disease involves the use of domesticated guineafowl. Guinea Fowl are voracious consumers of insects and have a particular fondness for ticks. localized use of domesticated guineafowl may reduce dependence on chemical pest-control methods. Many victims of ticks and others with concern often turn to the Guinea Fowl Breeders Association for advice on this topic.
Transmission
Hard-bodied ticks of the genus Ixodes are the primary vectors of Lyme disease. The majority of infections are caused by ticks in the nymph stage, since adult ticks are more easily detected and removed as a consequence of their relatively large size. Transmission is relatively rare, with only about 1% of recognized tick bites resulting in Lyme disease: this may be due to the fact that an infected tick has to be attached for at least a day for transmission to occur.
In Europe, the sheep tick, castor bean tick, or European castor bean tick (Ixodes ricinus) is the transmitter.
In North America, the black-legged tick or deer tick (Ixodes scapularis) has been identified as the key to the disease's spread on the east coast. Only about 20% of people who become infected with Lyme disease by the deer tick can remember having been bitten, making early detection difficult in the absence of a rash. Tick bites often go unnoticed because of the small size of the tick in its nymphal stage, as well as tick secretions that prevent the host from feeling any itch or pain from the bite. The lone star tick (Amblyomma americanum), which is found throughout the Southeastern United States as far west as Texas, is unlikely to transmit the Lyme disease spirochete Borrelia burgdorferi, though it may be implicated in a related syndrome called southern tick-associated rash illness, which resembles a mild form of Lyme disease.
On the West Coast, the primary vector is the western black-legged tick (Ixodes pacificus). The tendency of this tick species to feed predominantly on host species that are resistant to Borrelia infection appears to diminish transmission of Lyme disease in the West.
While Lyme spirochetes have been found in insects other than ticks, reports of actual infectious transmission appear to be rare. Sexual transmission has been anecdotally reported; Lyme spirochetes have been found in semen and breast milk, however transmission of the spirochete by these routes is not known to occur.
Congenital transmission of Lyme disease can occur from an infected mother to fetus through the placenta during pregnancy, however prompt antibiotic treatment appears to prevent fetal harm.
Vaccination
A recombinant vaccine against Lyme disease, based on the outer surface protein A (OspA) of B. burgdorferi, was developed by GlaxoSmithKline. In clinical trials involving more than 10,000 people, the vaccine, called LYMErix, was found to confer protective immunity to Borrelia in 76% of adults and 100% of children with only mild or moderate and transient adverse effects. LYMErix was approved on the basis of these trials by the U.S. Food and Drug Administration (FDA) on December 21, 1998.
Following approval of the vaccine, its entry in clinical practice was slower than expected for a variety of reasons including its cost, which was often not reimbursed by insurance companies. Subsequently, hundreds of vaccine recipients reported that they had developed autoimmune side effects. Supported by some patient advocacy groups, a number of class-action lawsuits were filed against GlaxoSmithKline alleging that the vaccine had caused these health problems. These claims were investigated by the FDA and the U.S. Centers for Disease Control (CDC), who found no connection between the vaccine and the autoimmune complaints.
Despite the lack of evidence that the complaints were caused by the vaccine, sales plummeted and LYMErix was withdrawn from the U.S. market by GlaxoSmithKline in February 2002 in the setting of negative media coverage and fears of vaccine side effects. The fate of LYMErix was described in the medical literature as a "cautionary tale"; an editorial in Nature cited the withdrawal of LYMErix as an instance in which "unfounded public fears place pressures on vaccine developers that go beyond reasonable safety considerations," while the original developer of the OspA vaccine at the Max Planck Institute told Nature: "This just shows how irrational the world can be... There was no scientific justification for the first OspA vaccine [LYMErix] being pulled."
New vaccines are being researched using outer surface protein C (OspC) and glycolipoprotein as methods of immunization.
Management of Host Animals
Lyme and all other deer-tick-borne diseases can be prevented on a regional level by reducing the deer population that the ticks depend on for reproductive success. This has been demonstrated in the communities of Monhegan, Maine and in Mumford Cove, Connecticut. The black-legged or deer tick (Ixodes scapularis) depends on the white-tailed deer for successful reproduction.
For example, in the US, it is suggested that by reducing the deer population to levels of 8 to 10 per square mile (from the current levels of 60 or more deer per square mile in the areas of the country with the highest Lyme disease rates), the tick numbers can be brought down to levels too low to spread Lyme and other tick-borne diseases. However, such a drastic reduction may be impractical in many areas.
Tick Removal
Many old wives' tales exist about the proper and effective method to remove a tick, however it is generally agreed that the most effective method is to pull it straight out with tweezers. Data have demonstrated that prompt removal of an infected tick, within approximately 36 hours, reduces the risk of transmission to nearly zero; however the small size of the tick, especially in the nymph stage, may make detection difficult.
Prognosis
For early cases, prompt treatment is usually curative. However, the severity and treatment of Lyme disease may be complicated due to late diagnosis, failure of antibiotic treatment, and simultaneous infection with other tick-borne diseases (co-infections) including ehrlichiosis, babesiosis, and bartonella, and immune suppression in the patient.
A meta-analysis published in 2005 found that some patients with Lyme disease have fatigue, joint or muscle pain, and neurocognitive symptoms persisting for years despite antibiotic treatment. Patients with late stage Lyme disease have been shown to experience a level of physical disability equivalent to that seen in congestive heart failure. In rare cases, Lyme disease can be fatal.
