What is Lyme disease?
Lyme disease, also known as Lyme borreliosis, is found widespread in the USA, Europe, Russia, and the Far East.
It is caused by a spirochete i.e. a spiral bacteria, from the genus Borrelia. It is commonly caused by Borrelia burgdorferi, which has at least 11 different genomic species out of which four are known to cause Lyme disease. It is a zoonosis, as it is transmitted from an animal reservoir to humans by a vector. The vector transmitting the infection from animal to man, in this case, is a tick of the genus Ixodes. Deer are the main animal reservoir along with small mammals and birds.
Once B. burgdorferi has been introduced into the skin by the bite of an infected Ixodes tick, the spirochetes then multiply and spread within the skin. The response to the bacteria in the skin causes the characteristic rash. Tick saliva will prevent the destruction of the bacteria and this will result in the bacteria surviving and eventually spreading throughout the body.
Days to weeks following the bite, the bacteria spread via the bloodstream to involve multiple systems such as skin, joints, heart, and nervous system, where it gives rise to a variety of symptoms. If left untreated, the bacteria can persist for months or even years, even though the immune system produces antibodies against B. burgdorferi.
What are the symptoms and clinical features of Lyme disease?
There are three stages of Lyme infection:
Stage 1 of the disease is a localized infection, which usually presents about a week after the tick bite. Symptoms can include:
- A red color rash is known as erythema migrans at the site of the bite. This rash is usually neither itchy nor painful.
- The rash is often associated with fever, chills, fatigue, and headache. Rarely, these associated symptoms may be the only presentation without the rash.
Stage 2 of the disease occurs several days to weeks after the appearance of the rash due to the systemic spread of the bacteria.
- Patients may develop a more widespread rash unrelated to the tick bite site.
- Around 15% of untreated cases develop neurological complications such as meningitis, encephalitis, cranial or peripheral neuritis, and radiculopathies. The patients most commonly show a loss of the ability to move one or both sides of the face and severe headaches with neck stiffness.
- About 5% of untreated patients will have cardiac complications such as carditis, heart block, congestive heart failure. The most frequent cardiac complication is heart palpitations.
- Arthritis presenting with joint pain may also occur at this stage.
Stage 3 of the disease occurs after several months in an untreated patient. Common complications include:
- Chronic arthritis (usually of the knees and other large joints)
- Chronic neurological disorders such as chronic encephalomyelitis and polyneuropathy.
- Chronic skin disorders such as acrodermatitis chronica atrophicans.
Diagnosis is mainly made based on a combination of a history of tick exposure and symptoms as the diagnosis is rarely confirmed by laboratory tests.
Laboratory confirmation is by isolation of the organisms from blood, skin lesions, or cerebrospinal fluid. The body produces antibodies against the bacteria and the detection of such antibodies may also be used to diagnose the disease.
Preventative measures are recommended in tick-infested areas. Most common measures include:
- Protective clothing should be worn and insect repellents such as DEET should be used.
- Using pesticides to reduce tick numbers may also be effective.
Prompt removal of any tick is essential as the infection is unlikely to occur unless the tick has been attached for more than 48 hours. Ticks should be grasped with forceps near the point of attachment to the skin and then pulled by gentle traction and the wound should then be washed with soap and water.
Antibiotics such as doxycycline, amoxicillin, or azithromycin are the main treatment for Lyme disease and are given orally in the early stages of the disease. Later stages of Lyme disease with systemic involvement should be treated with 2–4 weeks of intravenous ceftriaxone. Long-term antibiotic therapy for persistent symptoms has not proven to be useful. Although a vaccine for Lyme disease, LYMErix, was approved by the Food and Drug Administration in 1998 there were concerns regarding its effects and 3 years later was withdrawn from the market.
Lyme disease’s typical first sign, the erythema migrans rash, usually resolves within a few weeks even without treatment. In untreated individuals, the infection can disseminate and cause permanent damage to the nervous system, heart, or joints.
People who receive antibiotics within several days of the appearance of the initial rash have the best prognosis, however, recovery may not be total or immediate. The percentage of people achieving full recovery in the United States at the end of treatment for the rash is about 64–71% and it increases to about 84–90% after 30 months.
Treatment failure, which can be the persistence of original symptoms or appearance of new signs of the disease, occurs only in a few people. The remaining people can be considered cured but can continue to experience symptoms such as joint or muscle pains or fatigue. These symptoms usually are mild and not disabling.
Lyme disease is an infectious disease caused by the bacteria Borrelia and is spread by ticks. However, it should be kept in mind that the disease is not transmissible between people, by other animals, or through food. The most common sign of infection is a red rash that appears at the site of the tick bite after a week. If left untreated, symptoms may progress and affect multiple organ systems leading to chronic problems. Lyme disease can be treated with antibiotics but, despite treatment, about 10 to 20% of people may have persistent symptoms for at least six months. Therefore preventive measures such as wearing clothing to cover the arms and legs and using insect repellents should be taken if living in a tick-infested area. The loss of the LYMErix vaccine as a tool for treatment has directed researchers to invest efforts in finding alternate vaccines or therapeutic options against Lyme disease.