Lyme disease is an infection with a bacterium (germ). Humans can get
Lyme disease if they are bitten by an infected tick. The first and
typical symptom is usually a rash that spreads out from the site of the
tick bite. Left untreated, the bacteria can spread to other areas of
the body. In some cases this can cause serious symptoms - often months
after the initial tick bite. A course of antibiotics will usually clear
the infection.
What is Lyme disease?
Lyme disease is an infection with a bacterium (germ) called Borrelia. There are various subtypes of Borrelia bacteria but Borrelia burgdorferi causes
most cases of Lyme disease. The bacterium is passed to humans from
infected ticks. It is called Lyme disease because in 1975 in a town
called Old Lyme in the USA there was an outbreak of arthritis in young
children which was found to be due to this infection. This was the
first time that this bacterium was proved to be the cause of a medical
condition.
Where is Lyme disease a problem?
Since 1975,
thousands of cases have been reported in the USA. However, Lyme disease
is quite rare in the UK. About 600 cases are reported in the UK each
year. Most cases in the UK occur where infected ticks are found -
mainly in Exmoor, the New Forest, the South Downs, parts of Wiltshire
and Berkshire, Thetford Forest, the Lake District, the Yorkshire moors
and the Scottish Highlands. Most people affected are forestry workers
and other outdoor workers, but visitors and holiday makers to these
areas are at risk.
How do humans get Lyme disease?
The
bacterium that causes Lyme disease lives in certain animals. This is
mainly rodents such as mice and deer. The bacterium is usually harmless
to the animals.
Ticks are small insects, about the size of a
pin head. Ticks feed by biting the skin and sucking blood from animals
such as mice and deer, and sometimes humans. In this way, some ticks
get infected with the bacterium that causes Lyme disease. If an
infected tick bites a human, then the bacteria may be passed into the
human. The bacterium that causes Lyme disease is not passed from person
to person.
Note: most ticks in the UK are not infected by the
bacterium that causes Lyme disease. Therefore, most tick bites will not
cause Lyme disease.
It normally takes 24-48 hours for bacteria
in the tick to pass into the human after being bitten. (Ticks are tiny
and 'cling on' to you once they bite you. They then suck blood and
'engorge' with blood which they feed off. The bacteria are normally
carried in their gut, and only travel up to their mouth and into your
skin once they have been feeding for more than 24 hours and are
engorged.) Therefore, if you remove a tick soon after being bitten -
within 24 hours - you are very unlikely to develop Lyme disease, even
if it was an infected tick.
So, it is only certain infected
ticks that bite, and are not noticed clinging onto your skin, that can
cause Lyme disease. However, ticks are very small, and often do not
hurt when they bite. It is quite easy to have a tick bite without you
noticing. For example, on your leg or back. Many people who develop
Lyme disease cannot remember being bitten by a tick.
Once
bacteria are passed from the infected tick into your skin, they then
multiply and travel in the bloodstream to other parts of the body to
cause symptoms. The parts of the body that are mainly affected by this
bacteria are: skin, joints, nerves and heart.
What are the symptoms of Lyme disease?
The symptoms and effects of Lyme disease can be divided into three stages.
Stage one - early reaction to the local skin infection
This can develop anytime between 2 and 30 days after being bitten by an infected tick.
Rash.
The classical symptom of Lyme disease is a typical rash called erythema
migrans. This occurs in about 8 in 10 cases. The rash is usually a
single circular red mark that spreads outwards slowly over several
days. The circle gets bigger and bigger with the centre of the circle
being where the tick bite occurred. As it spreads outward a paler area
of skin emerges on the inner part of the circle. So, the rash is often
called a 'bulls eye' rash. The rash may just be a few centimeters in
diameter, but in some cases grows to up to 30 cm. It is not usually
painful or particularly itchy. You may not even notice it if it is on
your back. Without treatment, erythema migrans typically fades within
3-4 weeks.
Note: many insect bites cause a small red blotchy
'allergic' rash to appear soon after the skin is bitten. These soon go
away. The rash of erythema migrans is different in that it usually
develops several days after the bite, and has a typical spreading
circular appearance.
Flu-like symptoms occur in about
half of cases. Symptoms include tiredness, general aches and pains,
headache, fever, chills and neck stiffness. These symptoms are often
mild and go within a few days even without treatment (but the infection
may not have gone).
In some cases, the infection does not
progress any further, even without treatment, as the immune system may
clear the infection. However, in about half of cases that are not
treated, the disease progresses to stage two.
Stage two - early disseminated disease
This
may develop in untreated people weeks or months after the bite.
Symptoms are variable but can include one or more of the following.
Joint problems
in one or more joints. They most commonly affect the knee joint or jaw
joint (temporomandibular joint). The severity of joint problems can
range from episodes of mild joint pains, to severe joint inflammation
(arthritis) causing a lot of pain. Episodes of joint inflammation last,
on average, three months.
Nerve and brain problems.
Some affected people develop inflammation to nerves, particularly the
nerves around the face. This may cause the nerve to stop working and
cause facial weakness. Meningitis and encephalitis (brain inflammation)
may occur.
Heart problems. Some affected people develop
inflammation of the heart (myocarditis) and other heart problems. This
may cause symptoms such as dizziness, breathlessness, chest pain and
palpitations.
Rash. Several areas of the skin (not where
the tick bite occurred) may develop a rash similar to erythema migrans
(described above). These 'secondary' rashes tend to be smaller than the
original stage one rash. These tend to fade within 3-4 weeks.
Rarely, other organs such as the eyes, kidneys and liver are affected.
Stage three - chronic (persistent) Lyme disease
This
may develop months to years after infection. It may develop after a
period of not having any symptoms. A whole range of symptoms have been
described in joints, nerves, brain and heart. The brain problems may
include mild confusion, and problems with memory, concentration, mood,
sleep, personality and/or language. There is controversy as to whether
Lyme disease may cause depression, anxiety, schizophrenic-like illness,
bipolar disorder and dementia.
How is Lyme disease diagnosed?
In most
cases, Lyme disease is diagnosed in stage one of the disease by the
typical symptoms. That is, the typical rash, sometimes also with a
flu-like illness, in someone who has been bitten by a tick. Other tests
are not needed in this situation and treatment is usually given. The
diagnosis of stage two or three is more difficult. Blood and urine
tests and skin tests are helpful (but not foolproof) in diagnosing the
disease if it is suspected from the symptoms.
What is the treatment for Lyme disease?
A
course of antibiotics will usually clear the infection. Most people are
diagnosed in stage one when treatment will clear the symptoms and
prevent the development into stages two or three.
Can Lyme disease be prevented?
The following will reduce your risk of developing Lyme disease:
- If possible, avoid areas where infected ticks live - particularly in the summer months.
- If living or visiting a tick prone area, when outdoors wear
appropriate clothing. That is: long-sleeved shirts and trousers and
tuck them in whenever possible. Inspect your entire body each day to
check for ticks and remove any that are on the skin.
- Consider using a tick repellent spray, cream, etc, on your skin that contains N,N-diethyl-m-toluamide (DEET).
What is the outcome (prognosis)?
If you are treated with antibiotics in stage one of the disease, you should expect a complete cure with no further problems.
If
you are not treated in stage one, about 8 in 10 develop some symptoms
of stage two or three. However, these are often mild and transient
symptoms such as a skin rash or mild joint pains. Some people develop
more severe symptoms if they progress to stage two or three. Treatment
with antibiotics during stage two or three is also usually curative.
However,
some people report ongoing symptoms that may be triggered by Lyme
disease even when the infection has been cleared by antibiotics. This
has been called 'Post-Lyme Disease Syndrome'. It may be due to a
reaction of the immune system that does not 'switch off' even when the
bacteria causing the infection have been cleared. Symptoms that have
been reported include: tiredness, joint or muscle pains, headaches,
hearing loss, vertigo, mood disturbances, pins and needles and
difficulty sleeping.
Further help and information
Lyme Disease Action
Web: www.lymediseaseaction.org.uk
References
-
Meyerhoff J. Lyme disease. eMedicine. Article dated January 4th 2007
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Wormser GP, Dattwyler RJ, Shapiro ED, et al;
The clinical assessment, treatment, and prevention of lyme disease,
human granulocytic anaplasmosis, and babesiosis: clinical practice
guidelines by the Infectious Diseases Society of America. Clin Infect
Dis. 2006 Nov 1;43(9):1089-134. Epub 2006 Oct 2. [abstract]
-
Lyme Disease - Health Protection Agency (2007)
© EMIS and PiP 2008 Updated: 19 Jun 2007
