Lyme disease and related tick-borne infections
Description
An in-depth report on the causes, diagnosis, treatment, and prevention of Lyme disease.
Alternative Names
Babesiosis; Human granulocytic anaplasmosis (HGA)
Prevention
Everyone should avoid specific tick-infested areas, including tall grass, woods, and bushes where ticks tend to congregate. If this is not possible, then people should take additional preventive measures. The CDC also recommends:
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Use of tick repellant
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Routine tick checks -- removal of infected ticks within 48 hours of attachment substantially reduces the likelihood of transmission.
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Prompt antibiotic prevention for tick bites -- although this method is controversial, the CDC concludes that it is probably beneficial.
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Removing brush and leaves -- such landscaping measures can reduce transmission rates by 50 - 90%.
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Applying pesticides to yards once or twice per year, which can decrease the number of ticks by 68 - 100%
Protecting Property from Tick Infestation
Mowing the grass regularly, clearing away leaves, and placing wood chips as a barrier around a lawn can help greatly reduce the tick population.
Permethrin for the Lawn.
Insecticides can reduce tick infestation by 90%. Insecticides should be applied in late spring or early fall in a strip a few feet wide along the perimeter of the lawn where small animals are likely to enter or live.
The most commonly used insecticides are pyrethrins, which are compounds derived from the Chrysanthemum family. They are available as natural products or in synthetic forms (permethrin). They are poisons that affect the nerve system of insects. They are safe, particularly the natural products, for humans and pets. All pyrethrins are highly toxic for certain fish and slightly toxic for birds, such as mallard ducks. Some people do experience an allergic reaction to them. As with all insecticides, there is some concern about the possible consequences of long-term exposure, but to date there is no evidence of any harm.
Damminix, available in hardware stores, consists of cardboard tubes stuffed with permethrin-treated cotton. The tubes are placed where mice can find them (dense, dark brush) and collect the cotton for lining their nests. The pesticide on the cotton kills any immature ticks that are feeding on the mice. Best results are obtained with regular applications early in the spring and again in late summer. As many neighbors as possible should use it to be effective.
Other Pesticides.
Other tick-killing spray pesticides that have been used include those containing diazinon, chlorpyrifos, and carbaryl. Animal studies have reported severe toxic effects associated with these chemicals. Some of these chemicals are being phased out for home use. Parents should balance the effects of a very negligible risk for a highly treatable infection versus excessive use of possibly harmful chemicals.
Eliminating Risk from Deer
Fencing.
Deer fencing, a wire fence about 3 - 4 yards high, or electrified fencing can be helpful, but it is costly to put up and maintain.
Ivermectin.
Corn that is laced with the anti-parasite medication ivermectin (Ivomec and others) and then eaten by deer helps prevent ticks from feeding on them. Ivermectin is present in a number of products used by veterinarians to control parasites, such as heartworm. It has potential toxic effects in collie or collie mixed breeds, however.
Protective Clothing in the Woods
Hiking and camping in the Northeastern woods carries a significant risk for tick bites and Lyme disease (3% in one study). Anyone out in the woods during tick season should wear protective clothing, including:
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Light-colored clothing -- makes it easier to spot ticks
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Long-sleeved shirts and long pants with cuffs tucked into shoes or socks
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High boots, preferably rubber boots
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Tick-collars for small dogs -- can be worn around a person's ankles over socks or pants
Simply washing clothes will not kill ticks. After venturing outdoors, people should run their clothes through a dryer at high temperature for a half hour. Spraying clothes with solutions containing permethrin (Permanone, Duranon, Permakill) affords additional protection. Keep in mind that these sprays should not be applied to the skin. Clothes should not be retreated with permethrin for 48 hours unless they are washed.
Insect Repellent
DEET.
Most insect repellents contain the chemical DEET (N,N-diethyl-meta-toluamide), which remains the gold standard of currently available mosquito and tick repellents. DEET has been used for more than 40 years and is safe for most children when used as directed. Comparison studies suggest that DEET preparations are the most effective insect repellents now available.
Concentrations range from 4% to almost 100%. The concentration determines the duration of protection. Experts recommend that most adults and children over 12 years old use preparations containing a DEET concentration of 20 - 35% (such as Ultrathon), which provides complete protection for an average of 5 hours. (Higher DEET concentrations may be necessary for adults who are in high-risk regions for prolonged periods.)
DEET products should never be used on infants younger than 2 months. According to the Environmental Protection Agency, DEET products can safely be used on all children age 2 months and older. The EPA recommends that parents check insect repellant product labels for age restrictions.
If there is no age restriction listed, the product is safe for any age. The American Academy of Pediatrics recommends that children use concentrations of 10% or less; 30% DEET is the maximum concentration that should be used for children. In deciding what concentration is most appropriate, parents should consider the amount of time that children will be spending outside, and the risk of mosquito bites and mosquito-borne disease.
When applying DEET, the following precautions should be taken:
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Do not use on the face and apply only enough to cover exposed skin on other areas.
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Do not over apply and do not use under clothing.
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Do not apply over any cuts, wounds, or irritated skin.
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Parents or an adult should apply repellent to a child and not let the child apply it. They should first put DEET on their own hands and then apply it to the child. They should avoid putting DEET not only near the child's eyes and mouth, but also on the hands (since children frequently touch their faces).
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Wash any treated skin after going back inside.
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If using a spray, apply DEET outdoors -- never indoors. Spray repellents should not be applied inside or directly on anyone's face.
Other Insect Repellent Products
. In 2005, the U.S. Centers for Disease Control (CDC) added two new mosquito repellents to its list of recommended products:
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Picaridin. Picaridin, also known as KBR 3023 or Bayrepel, is an ingredient that has been used for many years in repellents sold in Europe, Latin America, and Asia. A product containing 7% picaridin is now available in the United States. Picaridin can safely be applied to young children and is also safe for women who are pregnant or breastfeeding. According to the CDC, insect repellents containing DEET or picaridin work better than other products.
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Oil of lemon eucalyptus. In scientific tests, oil of lemon eucalyptus, also known as PMD, worked as well as low concentrations of DEET. However, oil of lemon eucalyptus is not recommended for children under the age of 3 years.
Self-Inspection and Tick Removal
Self-Inspection.
The tick is unlikely to transmit the infection within 3 days of the bite, but prompt removal is still important. The following tips are important for self-inspection:
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Ticks responsible for Lyme disease are very small and may resemble freckles or scabs.
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People spending time in tick-infested locations should inspect themselves several times a day, including at bedtime.
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Check nonexposed areas, such as the back of the knee, as well as exposed areas. Someone else should check the scalp, back of the neck, and other difficult to reach areas.
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Check clothing as well as skin. A tick on can be hidden in folds or creases.
Tick Removal.
If an attached tick is discovered, there is no reason to panic. Do not put a hot match to the tick or try to smother it with petroleum jelly, nail polish, or other noxious substances. This only prolongs exposure time and may cause the tick to eject the Lyme organism into the body.
The safest and most effective way to remove an attached tick is:
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Grasp the tick's mouth area with clean tweezers as close to the skin as possible. (Take care not to handle it with bare fingers as this can also spread infection.)
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Next, pull upward with a steady even pressure. Do not twist, crush, or squeeze the body area of the tick, because this region contains the infectious organism. In fact, do not be alarmed if some of the mouth parts remain in the skin. They are not infectious.
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Put the tick in a jar or container of alcohol, which will kill it. Some people lay a piece of adhesive tape to the top of the tick and fold it over, without touching the insect. Then they simply throw it away. Tape is also effective for trapping a tick that has not yet attached to the skin.
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Once the tick is removed, wash the bite area with soap and water or with an antiseptic to destroy any contaminating microorganisms. Wash hands as well.
Vaccines
The LYMErix Vaccine.
The LYMErix vaccine, previously approved, was taken off the market because of poor sales and because of problems encountered with its use. A primary limitation was that the vaccine was effective only in about 75% of cases and the effects were not long lasting. There were also reports of arthritic and neurologic symptoms in a few vaccinated people; however there is no definitive evidence that the vaccine was responsible for these symptoms.
Other Vaccines.
Deer ticks lay their eggs on mice and other small rodents. These eggs develop into larvae that feed on these small animals. When the larvae develop into nymphs, they seek a larger host like a deer or human. Scientists are exploring the idea of vaccinating mice and other rodents against
B. burgdorferi
. Inserting an oral vaccine into these animals’ food supply helps reduce the number of nymph ticks and may be a more effective preventive strategy than vaccinating humans. Recent studies suggest that vaccination of mice produces 89 -- 100% protection from
B. burgdorferi
infection.
Protecting Pets
Since dogs, cats and even horses can get Lyme disease, pets should be inspected for ticks regularly. Symptoms in animals include lameness and lethargy. Dogs are much more likely to get Lyme disease than cats, but both are susceptible. In dogs, symptoms occur 2 - 5 months after a tick bite and include fever, lameness, and lack of appetite. In rare cases, Lyme disease can cause kidney damage in dogs if it is left untreated.
Preventive Products.
Products containing permethrin (Bio Spot, EXspot), amitraz (Preventic), or fipronyl (Frontline) can be used safely on dogs. Not all of these products are safe in cats. Only permethrin is also effective against fleas. Some veterinarians suggest that the combination of BioSpot and Preventic is very effective. (Another product-- selamectin [Revolution] --is sold for flea and tick control, but it appears to have very limited effect against ticks.)
Pet Vaccines.
Lyme disease vaccines are available for dogs, but they do not offer total protection. Veterinarians vary in their use of the vaccines.
Treatment
. As with people, antibiotics almost always cure the infection in animals.
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Review Date: 1/18/2007
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Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital
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