Lyme Disease Contagious
What is Lyme Disease?
Lyme disease, also known as Lyme
borreliosis, is an infectious disease caused by bacteria of the Borrelia type.
The most widespread sign of infection is an expanding area of redness, known as
erythema migrans, that begins at the site of a bite about a week after it has
occurred. The rash is normally neither itchy nor painful. About 25% of people
do not develop a rash. Other early symptoms may include fever, headache, and
feeling tired. If untreated, symptoms may include loss of the ability to move
one or both sides of the face, joint pains, and severe headaches with neck
stiffness, or heart palpitations, among others. Months to years later, repeated
episodes of joint pain and swelling may occur. Occasionally, people develop
shooting pains or tingling in their arms and legs. Despite appropriate
treatment, about 10 to 20% of people also develop joint pains, have problems
with memory, and feel tired much of the time.
What is Lyme Disease?- Video
How is Lyme Disease Transmitted?
Lyme disease is transmitted to
humans by the bite of infected ticks of the Ixodes genus. Usually, the tick
must be attached for 36 to 48 hours before the bacteria are spread. In North
America, the only bacterium involved is Borrelia burgdorferi sensu stricto,
while in Europe and Asia, the bacteria Borrelia afzelii and Borrelia garinii
are also causes of the disease. The disease does not appear to be transmissible
between people, by other animals, or through food. Diagnosis is based upon a
combination of symptoms, history of tick exposure, and possibly testing for
specific antibodies in the blood. Blood tests are often negative in the early
stages of the disease. Testing of individual ticks is not typically useful.
While Lyme spirochetes have been
found in insects, as well as ticks, reports of actual infectious transmission
appear to be rare. Lyme spirochete DNA has been found in semen and breast milk,
but transmission has not been known to take place through sexual contact.
According to the CDC, live spirochetes have not been found in breast milk,
urine, or semen. However, more recent studies published in 2014, suggest a link
might exist.
How Lyme Disease can be Prevented?
Prevention includes efforts to
prevent tick bites such as by wearing long pants and using DEET. Using
pesticides to reduce tick numbers may also be effective. Following a bite,
antibiotics are typically only recommended if the removed tick was full of
blood. In this situation, a single dose of doxycycline may be recommended.
Ticks can be removed using tweezers. If an infection develops, a number of
antibiotics are effective, including doxycycline, amoxicillin, and cefuroxime.
Treatment is usually for two or three weeks. Some people develop a fever and
muscle and joint pains from treatment which may last for one or two days. In
those who develop persistent symptoms, long-term antibiotic therapy has not
been found to be useful.
Signs and Symptoms of Lyme Disease
This "classic"
bull's-eye rash is also called erythema migrans. A rash caused by Lyme does not
always look like this. Around 20% to 30% of persons who are infected with Lyme
disease may have no rash.
Raised, red borders around
indurated central portion.
Lyme disease can affect multiple
body systems and produce a broad range of symptoms. Not all patients with Lyme
disease have all symptoms, and many of the symptoms are not specific to Lyme
disease, but can occur with other diseases, as well. The incubation period from
infection to the onset of symptoms is usually one to two weeks, but can be much
shorter (days) or much longer (months to years).
Symptoms most often occur from
May to September, because the nymphal stage of the tick is responsible for most
cases. Asymptomatic infection exists, but occurs in less than 7% of infected
individuals in the United States. Asymptomatic infection may be much more
common among those infected in Europe.
Early localized infection
Early localized infection can
occur when the infection has not yet spread throughout the body. Only the site
where the infection has first come into contact with the skin is affected. The
classic sign of early local infection with Lyme disease is a circular,
outwardly expanding rash called erythema chronicum migrans (EM), which occurs
at the site of the tick bite three to 30 days after the tick bite. The rash is
red, and may be warm, but is generally painless. Classically, the innermost
portion remains dark red and becomes indurated (is thicker and firmer), the
outer edge remains red, and the portion in between clears, giving the
appearance of a bull's eye. However, partial clearing is uncommon, and the
bull's-eye pattern more often involves central redness.
The EM rash associated with early
infection is found in about 80% of patients and can have a range of appearances
including the classic target bull's-eye lesion and nontarget appearing lesions.
The 20% without the EM and the nontarget lesions can often cause
misidentification of Lyme disease. Patients can also experience flu-like
symptoms, such as headache, muscle soreness, fever, and malaise. Lyme disease
can progress to later stages even in patients who do not develop a rash.
Early disseminated infection
Within days to weeks after the
onset of local infection, the Borrelia bacteria may begin to spread through the
bloodstream. EM may develop at sites across the body that bear no relation to
the original tick bite. Another skin condition, apparently absent in North
American patients, but found in Europe, is borrelial lymphocytoma, a purplish
lump that develops on the ear lobe, nipple, or scrotum. Other discrete symptoms
include migrating pain in muscles, joints, and tendons, and dizziness.
Various acute neurological
problems, termed neuroborreliosis, appear in 10–15% of untreated patients.
These include facial palsy, which is the loss of muscle tone on one or both
sides of the face, as well as meningitis, which involves severe headaches, neck
stiffness, and sensitivity to light. Radiculoneuritis causes shooting pains
that may interfere with sleep, as well as abnormal skin sensations. Mild
encephalitis may lead to memory loss, sleep disturbances, or mood changes. In
addition, some case reports have described altered mental status as the only
symptom seen in a few cases of early neuroborreliosis. The disease may also
have cardiac manifestations such as atrioventricular block.
Late disseminated infection
After several months, untreated
or inadequately treated patients may go on to develop severe and chronic
symptoms that affect many parts of the body, including the brain, nerves, eyes,
joints, and heart. Many disabling symptoms can occur, including permanent
impairment of motor or sensory function of the lower extremities in extreme
cases. The associated nerve pain radiating out from the spine is termed
Bannwarth syndrome, named after Alfred Bannwarth.
The late disseminated stage is
where the infection has fully spread throughout the body. Chronic neurologic
symptoms occur in up to 5% of untreated patients. A polyneuropathy that
involves shooting pains, numbness, and tingling in the hands or feet may
develop. A neurologic syndrome called Lyme encephalopathy is associated with
subtle cognitive problems, such as difficulties with concentration and
short-term memory. These patients may also experience fatigue. Other problems,
however, such as depression and fibromyalgia, are no more common in people with
Lyme disease than in the general population.
Chronic encephalomyelitis, which
may be progressive, can involve cognitive impairment, brain fog, migraines,
balance issues weakness in the legs, awkward gait, facial palsy, bladder
problems, vertigo, and back pain. In rare cases, untreated Lyme disease may
cause frank psychosis, which has been misdiagnosed as schizophrenia or bipolar
disorder. Panic attacks and anxiety can occur; also, delusional behavior may be
seen, including somatoform delusions, sometimes accompanied by a
depersonalization or derealization syndrome, where the patients begin to feel
detached from them or from reality.
Lyme arthritis usually affects
the knees. In a minority of patients, arthritis can occur in other joints,
including the ankles, elbows, wrists, hips, and shoulders. Pain is often mild
or moderate, usually with swelling at the involved joint. Baker's cysts may
form and rupture. In some cases, joint erosion occurs.
Acrodermatitis chronica
atrophicans (ACA) is a chronic skin disorder observed primarily in Europe among
the elderly. ACA begins as a reddish-blue patch of discolored skin, often on
the backs of the hands or feet. The lesion slowly atrophies over several weeks
or months, with the skin becoming first thin and wrinkled and then, if
untreated, completely dry and hairless.
Cause
Borrelia bacteria, the causative
agent of Lyme disease, magnified
Ixodes scapularis, the primary
vector of Lyme disease in eastern North America
Lyme disease is caused by
spirochetal bacteria from the genus Borrelia. Spirochetes are surrounded by
peptidoglycan and flagella, along with an outer membrane similar to other
Gram-negative bacteria. Because of their double-membrane envelope, Borrelia
bacteria are often mistakenly described as Gram negative despite the
considerable differences in their envelope components from Gram-negative
bacteria. The Lyme-related Borrelia species are collectively known as
Borrelia burgdorferi sensu lato, and show a great deal of genetic diversity.
Transmission
Lyme disease is classified as a
zoonosis, as it is transmitted to humans from a natural reservoir among rodents
by ticks that feed on both sets of hosts. Hard-bodied ticks of the genus Ixodes
are the main vectors of Lyme disease (also the vector for Babesia). Most
infections are caused by ticks in the nymphal stage, as they are very small and
may feed for long periods of time undetected. Larval ticks are very rarely
infected. Although deer are the preferred hosts of deer ticks, and the size of
the tick population parallels that of the deer population, ticks cannot acquire
Lyme disease spirochetes from deer. Rather, deer ticks acquire Borrelia
microbes from infected rodents, such as the white-footed mouse, Peromyscus
leucopus.
Within the tick midgut, the
Borrelia's outer surface protein A (OspA) binds to the tick receptor for OspA,
known as TROSPA. When the tick feeds, the Borrelia downregulates OspA and
upregulates OspC, another surface protein. After the bacteria migrate from the
midgut to the salivary glands, OspC binds to Salp15, a tick salivary protein
that appears to have immunosuppressive effects that enhance infection.
Successful infection of the mammalian host depends on bacterial expression of
OspC.
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.
However, transmission is quite rare, with only about 1% of recognized tick
bites resulting in Lyme disease. Transmission may occur within 24 hours of the
tick bite.
In Europe, the vector is Ixodes
ricinus, which is also called the sheep tick or castor bean tick. In China,
Ixodes persulcatus (the taiga tick) is probably the most important vector. In
North America, the black-legged tick or deer tick (Ixodes scapularis) is the
main vector on the East Coast.
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 spirochaetes, 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 of the United
States, the main vector is the western black-legged tick (Ixodes pacificus).
The tendency of this tick species to feed predominantly on host species such as
lizards that are resistant to Borrelia infection appears to diminish
transmission of Lyme disease in the West.
Transmission across the placenta
during pregnancy has not been demonstrated, and no consistent pattern of
teratogenicity or specific "congenital Lyme borreliosis" has been
identified. As with a number of other spirochetal diseases, adverse pregnancy
outcomes are possible with untreated infection; prompt treatment with
antibiotics reduces or eliminates this risk.
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