What is Lyme disease?
Lyme disease (LD), also known as Lyme borreliosis, is a condition caused by an infection with the bacteria Borrelia burgdorferi, which is spread through the bites of infected blacklegged ticks. The World Health Organisation classifies LD as an infectious or parasitic disease. People who work outside or spend time in woodland areas are most likely to be affected. In the United States, about 30,000 cases of Lyme disease are reported to the Centers for Disease Control and Prevention every year.
Subtypes of Lyme disease
There are three subtypes of Lyme disease.
The third type of LD, late Lyme disease tends to be slightly more common in children and older adults.
The symptoms of Lyme disease may differ, depending on whether a person has early LD or late LD. The trademark feature of Lyme disease is the erythema migrans rash. This is a distinctive skin irritation shaped like a bull’s eye, and its presence is proof of of LD. This rash usually appears at the site of a tick bite, but can appear elsewhere on the body.
Good to know: A tick bite itself is not an indication of Lyme disease.
In localized LD, the erythema migrans rash takes the form of an inflammation, surrounded by a circular border of non-irritated skin, followed by a final, circular border of irritated skin. It can increase to up to 30 centimetres in diameter and can be painful or itchy.
The rash appears on average 11 to 18 days after the tick has detached or was removed. It is possible to have more than one bull’s eye rash on the body, but it is also possible to contract LD without developing the rash, which only appears in 60 to 80 percent of people who have been infected with LD.
Besides the rash, the symptoms at the onset of Lyme disease may be similar to flu. Early symptoms of LD include:
- Aching muscles
- Cold flushes
- Painful joints
As the bacteria begin to spread, a person can develop disseminated LD. This usually occurs if the early symptoms of LD are not spotted or treated and the infection continues to be present in a person’s body for 1-4 months.
Symptoms of disseminated LD may include more rashes appearing on other parts of the skin to accompany the initial, circular rash at the site of the tick bite and painful, swollen joints. More rarely, affected people may experience neurological problems at this stage, such as difficulty concentrating.
Late Lyme disease usually develops 6 to 36 months after the infectious tick bite. Later symptoms can vary from person to person, but include further pain and swelling in the joints. Although some people may develop neurological problems, these are rare. They may include tingling or numbness in the hands and feet.
Weeks or months after infection has occurred, people may also experience complications with their central nervous system.
See this resource on late lyme disease for more information.
Risk factors of LD
In rare cases. it is possible, for a person to develop further medical conditions after the onset of LD, sometimes months or years after the infection itself has cleared up. This is usually a consequence of untreated or late LD and the result of the infection being present within the body for an extended period of time. Conditions which a person affected by LD is at risk of developing may include:
- Arthritis: This condition characterized by painful swelling in the joints can appear weeks or months after the onset of LD. It is much more likely for people who have been affected by LD to develop Lyme arthritis, which can be treated with antibiotics and anti-inflammatories, than systemic arthritis, such as rheumatoid arthritis.
- Acrodermatitis chronica atrophicans (ACA): This inflammatory skin condition is characterized by red, swollen skin, which is particularly likely to affect the extremities of the body, such as the hands and feet. Over time, the continual inflammation of ACA causes skin tissue to be lost. However, in the early stages, this condition is treatable with antibiotics (including penicillin and doxycycline) and the changes to the skin are reversible.
- Bannwarth syndrome (BS): Also known as nervous system Lyme disease, this is a neurological condition in which intense nerve pain radiates out from the spine. Recent research suggests that effective antibiotic treatment of early LD can significantly reduce the likelihood of developing BS.
Lyme disease is primarily transmitted through the infectious bites of immature blacklegged ticks called nymphs, which feed during the spring and summer months. Ticks wait in grass and plants and cling to the fur or clothing of animals or humans as they pass by. They then bite into the skin, where they anchor themselves firmly and begin feeding. Ticks must be attached for at least 36 to 48 hours before the Lyme disease bacterium Borrelia burgdorferi can be transmitted.
Although ticks can feed anywhere on the body, they prefer thin-skinned areas which are more easily punctured such as the groin, armpits and behind the ears. The bacterium that causes a person to develop Lyme disease is also carried by adult ticks, but they tend to be easier to spot than nymphs and are likely to be removed before infection occurs.
Lyme disease is not thought to be spread by human-to-human contact. For example, people cannot get infected by close bodily contact with somebody who is suffering from Lyme disease. Although animals can contract LD, there is no evidence that it can be passed on to a human from an infected animal, without the involvement of a tick. However, domestic pets, especially dogs, can bring humans into contact with LD by carrying infected ticks in their fur.
If an individual experiences symptoms which include the bull’s eye rash and their history includes a tick bite or possible exposure to ticks, these details are usually sufficient on their own to make a clinical diagnosis of Lyme disease. Most people who fit this description begin treatment without waiting for the results of any blood tests taken.
However, the flu-like symptoms of LD are also symptoms of many other conditions including flu itself, Chronic Fatigue Syndrome (CFS) and relapsing fever. For this reason, in cases where the erythema migrans rash is not present, blood tests will be necessary to rule out other conditions and to diagnose Lyme disease.
Blood tests for Lyme disease work by identifying the levels of various antibodies in the blood. Where LD is present, the levels of antibodies in the blood rise in order to combat the infection. The Enzyme Linked Immunosorbent Assay (ELISA) test is usually the initial test performed to screen for Lyme disease. However, it is not always accurate, and it is important to remember that a negative result does not necessarily rule out the presence of LD, as it can take antibodies 6-8 weeks after infection to appear in blood tests.
A positive ELISA test should be followed by a supplementary Western blot test. This test can detect two different classes of antibodies that the body produces as it reacts against the different molecules, or “antigens”, which are part of the Borrelia burgdorferi bacteria that cause LD.
The body produces IgM antibodies as a first response to LD, so a positive test can be used to make an early diagnosis. One problem with testing for IgM antibodies is that a false positive result is a likely possibility. It can take 4-6 weeks for the body to produce IgG antibodies in large enough quantities for the Western blot test to detect them, so it is not possible to make an early diagnosis of LD by testing for IgG antibodies. However, tests for IgG antibodies tend to be more accurate.
Ticks are most active in the warmer months (April to September) but it is advisable to take precautions against Lyme disease throughout the year, particularly in areas where it is prevalent. The most effective precaution to take against LD is to minimise contact with ticks. When spending time outside, avoid wooded and brushy areas with high grass. If people must spend time outside, walking in the center of trails where the grass is flatter can reduce the chances of contact with infected ticks.
It is also advisable to use a repellent containing 20 percent DEET or more in order to protect clothing and exposed skin from ticks. It is advisable to choose a repellent that lasts for several hours. Take care to avoid the eyes and mouth when applying it. On clothing, use products containing the insect-repellent chemical permethrin at a strength of 0.5 percent. Clothing which already contains the protective permethrin can be purchased, and the effect may last longer.
After spending time outside in long grass, a person should check for ticks and ask family or friends to check any areas they can’t see, such as behind the ears. If a tick is found on the body, it is advisable to remove it as soon as possible. Rapid removal of a tick can prevent infection with LD.
To remove a tick:
- Disinfect the site where the tick has attached with rubbing alcohol
- Use tweezers with pointed ends to hold the tick close to where it enters the skin
- Pull the tick out slowly and carefully
- Disinfect the site of the tick bite again
Pets can be vaccinated against Lyme disease and treated to prevent ticks from hiding in their fur. Although pets cannot pass LD on to humans directly, these measures are helpful for minimising exposure to infected ticks.
“Course and Outcome of Early European Lyme Neuroborreliosis (Bannwarth Syndrome): Clinical and Laboratory Findings.” 08 May 2016. Accessed: 25 February 2018. ↩