Los Angeles County West Vector & Vector-Borne Disease Control District

Lyme Disease

What is Lyme Disease?

                           Lyme disease is an infection caused by the corkscrew-shaped bacteria Borrelia burgdorferi (see picture at left) that is transmitted by the bite of deer (Ixodes scapularis) and western black-legged (Ixodes pacificus) ticks. The deer tick, which normally feeds on the white-footed mouse, the white-tailed deer, other mammals, and birds, is responsible for transmitting Lyme disease bacteria to humans in the northeastern and north-central United States. On the Pacific Coast, the bacteria are transmitted to humans by the western black-legged tick.LymeDi1.jpg (10332 bytes)

    The western black-legged tick is much smaller than common dog and cattle ticks.  In their larval and nymphal stages, they are no bigger than a pinhead. Adult ticks are slightly larger.   Larvae and nymphs take in spirochetes as they feed on infected mice.  Infected larvae molt to infected nymphs and infected nymphs molt to infected adults.  

LifeCycle.gif (19495 bytes)More cases of people infected with Lyme disease are the result of the feeding of infected nymphs rather than infected adults.  Ticks will attach anywhere on the body, but prefer body creases such as the armpit, groin, back of the knee, and nape of the neck.  Most cases of Lyme disease occur between late spring and early fall when people are outdoors and ticks are most active.  Ticks feed on blood by inserting their mouth parts (not their whole bodies) into the skin of a host animal. They are slow feeders: a complete blood meal can take several days. As they feed, their bodies slowly enlarge.

Risk

    Thewpe10.gif (20911 bytes) number of annually reported cases of Lyme disease in the United States has increased about 25-fold since national surveillance began in 1982, and a mean of approximately 12,500 cases annually were reported by states to the Centers for Disease Control and Prevention (CDC) from 1993-1997.   In the United States (click on map), the disease is mostly localized to states in the northeastern, mid-Atlantic, and upper north-central regions, and to several counties in northwestern California .  
    Most B. burgdorferi infections are thought to result from exposure to infected ticks during property maintenance, recreation, and leisure activities.  Thus, individuals who live or work in residential areas surrounded by woods or overgrown brush infested by vector ticks are at risk of getting Lyme disease.  In addition, persons who participate in recreational activities away from home such as hiking, camping, fishing and hunting in tick habitat, and persons who engage in outdoor occupations, such as landscaping, brush clearing, forestry, and wildlife and parks management in endemic areas may also be at risk of getting Lyme disease.

Symptoms

    The early symptoms of LD can be mild and easily overlooked. People who are aware of the risk of LD in their communities and who don't ignore the sometimes subtle early symptoms are most likely to seek medical attention and treatment early enough to be assured of a full recovery.

    The first symptom is usually an expanding rash (called erythema migrans, or EM, in medical terms) which is thought to occur in only about 50-60% of all LD cases.  Although a majority of infected persons develop the classic red rash, many do not.

     MISC.S2.jpg (5765 bytes)                            An EM rash generally has the following characteristics:

Usually (but not always) radiates from the site of the tickbite
Appears either as a solid red expanding rash or blotch, 
OR a central spot surrounded by clear skin that is in turn ringed 
by an expanding red rash (looks like a bull's-eye)
Appears an average of 1 to 2 weeks (range = 3 to 30 days) 
after disease transmission
Has an average diameter of 5 to 6 inches (range = 2 inches to 2 feet)
Persists for about 3 to 5 weeks
May or may not be warm to the touch
Is usually not painful or itchy

    EM rashes appearing on brown-skinned or sun-tanned patients may be more difficult to identify because of decreased contrast between darker skin tones and the red rash. A dark, bruise-like appearance is more common on dark-skinned patients.

    Around the time the rash appears, other symptoms such as joint pains, chills, fever, and fatigue are common, but they may not seem serious enough to require medical attention. These symptoms may be brief, only to recur as a broader spectrum of symptoms as the disease progresses.

    As the LD spirochete continues disseminating through the body, a number of other symptoms including severe fatique, a stiff, aching neck, and peripheral nervous system (PNS) involvement such as tingling or numbness in the extremities or facial palsy (paralysis) can occur.

    The more severe, potentially debilitating symptoms of later-stage LD may occur weeks, months, or, in a few cases, years after a tick bite. These can include severe headaches, painful arthritis and swelling of joints, cardiac abnormalities, and central nervous system (CNS) involvement leading to cognitive (mental) disorders.

Diagnosis

    There is no test that can determine if a patient is infected with the LD bacterium and then demonstrate that the patient has become bacterium-free. Therefore, LD is clinical diagnosis, based on signs and symptoms, with the patients travel history to endemic areas and test results being additional pieces of information in the complete picture. No test can "rule-out" Lyme disease.

What Laboratory Tests Aid in the Diagnosis?

INDIRECT TESTS (Antibody Tests)

Antibodies are the immune system's response to "fight off" infection. Tests strive to be both sensitive (detecting any LD antibodies) and specific (detecting just LD antibodies).

Test Interpretation
False Negative tests occur due to defects in test sensitivity; too low an antibody level to detect (e.g. they are bound to the bacteria, with too few free-floating; the patient taking antibiotics or other drugs; naturally low antibody production); the bacterium has changed, limiting recognition by the immune system; or bacterial strain variations.
False positive tests occur due to test failure or cross-reacting antibodies (e.g. syphilis, periodontal disease, ANA or RF).

Types of Tests
Titer (ELISA, EIA, IFA) - These tests measure the level of Bb antibodies in
 fluid. Laboratories use different detection criteria, cut-off points, types of 
measurements, and reagents.
Western blot - This test produces bands indicating the immune system's 
reactivity to Bb. Laboratories differ in their interpretation and reporting of 
these bands.

DIRECT DETECTION TESTS
Antigen detection - These tests detect a unique Bb protein in fluid (e.g. urine) of patients. This may be useful for detecting LD in patients taking antibiotics or during symptom flare-up.
Polymerase chain reaction (PCR) - This test multiplies the number of Bb DNA to a detectable measurable level.
Culturing - Growing the bacterium in culture is difficult and can take months.
Staining - Staining of tissue is time consuming and has low yield. The problem is that in Lyme disease there are too few of the Lyme spirochete in the body, and could result in the biopsy having no bacteria.

Treatment

    Treatment varies and depends on how early a diagnosis is made and the organ system(s) involved. No definitive treatment regimens have been determined, and failures occur with all protocols.

    Oral antibiotics may be sufficient for early stages of non-disseminated infection.

    Long-standing or Disseminated Lyme Disease responds best to one or several courses of either oral or intravenous antibiotics.

    Physicians and researchers agree that it is unethical not to treat people with demonstrated, persisting infection. Therefore, some people receive retreatment or longer treatment.

 

Prevention

Avoidance of tick habitat
    
Whenever possible, persons should avoid entering areas that are likely to be infested with ticks, particularly in spring and summer when nymphal ticks feed. Ticks favor a moist, shaded environment, especially that provided by leaf litter and low-lying vegetation in wooded, brushy or overgrown grassy habitat.  Sources for information on the distribution of ticks in an area include state and local health departments, park personnel, and agricultural extension services. 

 You can greatly reduce your chances of contracting Lyme disease if you remove a tick within 24 hours after it embeds in your skin. 

Personal protection
   
Individuals Tuck pants into sockswho are exposed to tick infested areas should wear light-colored clothing so that ticks can be spotted more easily and removed before becoming attached. Wearing long-sleeved shirts and tucking pants into socks or boot tops may help keep ticks from reaching the skin. Ticks are usually located close to the ground, so wearing high rubber boots may provide additional protection. Application of insect repellents containing DEET (n,n-diethyl-m-toluamide) to clothes and exposed skin, and permethrin (which kills ticks on contact) to clothes, should also help reduce the risk of tick attachment. DEET can be used safely on children and adults but should be applied according to Environmental Protection Agency guidelines to reduce the possibility of toxicity.

Reducing  ticks on your property

Reduce the humidity in your property.
Ticks are suscecptible to dehydration. You can reduce humidity in property by:
pruning trees
clearing brush
removing litter
mowing grass short, and
letting it dry thoroughly between waterings.
Move shubbery and overgrowth farther away from areas frequented by people.
You can do this by frequently mowing and landscaping such areas.
Make your property unattractive to animals that are hosts to ticks.
Accomplish this by:
eliminating birdfeeders, birdbaths, and salt licks;
erecting fencing around the property;
clearing away wood, garbage, and leaf piles;
removing stonewalls that provide homes to wildlife.
Have your property chemically treated.
You can kill ticks on your property by applying the following chemicals: cyfluthrin, chlorpyrifos, and carbaryl. Seek profession advice before application from either your local agricultural station or lawn & garden center.

 

Lyme Disease in Pets

    Lyme disease can affect individual pets differently. Some animals may display no symptoms. Other animals may develop fever, loss of appetite, painful joints, lethargy, and vomiting. If left untreated, the spirochete may damage the eyes, heart, kidneys, and nervous system. Lyme disease has been diagnosed in humans, dogs, cats, horses, goats, and cattle. Other species may also be at risk.

Cats
    Cats may show lameness, fever, loss of appetite, fatigue, eye damage, unusual breathing, or heart involvement. Many cats do not show noticeable symptoms, despite being infected.

Dogs
    Infected dogs may be lethargic, have a poor/loss of appetite, or a fever (103 - 105 F). Dogs may also experience lameness shifting from one joint to another, fatigue, kidney damage or failure, heart disorders, or neurologic involvement (e.g. aggression, confusion, overeating, seizures). Dogs can be infected with the Lyme bacterium but not exhibit any noticeable symptoms. Dogs appear to have the same expression of disease as humans, therefore, humans have been considered an animal model for dogs. Transplacental transmission has occurred in dogs.

Cattle
    Many cattle do not display signs of Lyme disease; those that do may have lameness, painful or swollen joints, fever, laminitis, or weight loss. A skin rash may be present on the udder of infected cows. Bb has been found to exist in urine and colostrum of infected cattle; therefore, the possibility of transmission between cows should be considered. The Lyme bacterium has also been found in blood, milk, synovial fluid, and spontaneously aborted fetal tissue. Bb can survive in frozen milk, but is killed during pasteurization.

Horses
    Infected horses generally do not have a fever, but may have lame or stiff joints, laminitis, depression, or refuse to eat. This bacterial infection may be a cause of moon blindness or loss of vision. There have been reports of spontaneous abortion and encephalitis in horses infected with Bb. Neurologic signs include head tilt, difficulty swallowing, or aimless wandering. Transplacental transmission occurs. Colts born to infected mares have displayed birth defects. Many horses may be infected with the spirochete, but display no symptoms.

PROTECTING YOUR PET
Apply tick-killing chemicals to your animals in order to protect them from disease spreading ticks. Sprays and dips containing permethrins and pyrethrins kill ticks on dogs, cats, and horses. Precautions should be taken when applying insecticides as some animals may be sensitive to the chemicals. Follow the manufacturer's instructions.
It is a good idea to wear rubber gloves during application. Tick collars will help discourage ticks from attaching to your pet(s). Never apply multiple repellents on your pet. A mixture of different chemicals on your pet could make the animal very sick.
Take precautions to guard against ticks when entering tick habitat, such as grassy, shrubby, wooded, or beach grass areas. Cut/mow grassy areas regularly to reduce tick habitation.
Treat the environment with insecticides designed specifically for ticks. To avoid contaminating water, experts recommend spraying at least 75 feet away from a well.
Conduct frequent Tick-Checks! Examine animals closely in order to detect embedded ticks.
Remove attached ticks properly and promptly to reduce the chance of transmission of the LD bacterium. Place fine point tweezers around the tick's mouthparts (the place where the tick is attached) and gently pull upwards until the tick detaches. Do not use your bare fingers!
Disinfect the bite site and tweezers after removal. Wash your hands. Place the tick, along with several blades of grass, into a small container (e.g. a clean screw-cap pill bottle or a zip-lock bag) for later examination. Call your veterinarian to determine if there is a local place where the tick can be tested. Label the container with: the date, name of pet, type of animal, owner's name, address and phone number.
Have your animal(s) examined as soon as possible if you notice any symptoms of disease; the sooner a disease is diagnosed, the easier it is to treat.
Vaccines are available for dogs.

 

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