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Oh Deer! A Tick Bite!

written by Marsha Seidelman, M.D.
on Sunday, 24th August ,2014

Although deer are beautiful animals, they bring to mind deer ticks … and Lyme disease, the most common tick-borne illness, first described in Lyme, Connecticut.

The infection (technically a spirochete, Borrelia burgdorferi) is carried by backlegged ticks, including the famous deer ticks which are common in New England, down to Maryland and in the northern midwestern states; a different tick carries it in the western US. The tiny nymphal form of deer ticks are most prevalent from May through September; they are the size of poppy seeds and difficult to see so can reside on us without being noticed.

The ticks feed on Lyme-infected animals, usually mice, chipmunks or other small animals or birds. When the tick, which may be carried by deer, then bites a human and becomes engorged with human blood, the Lyme organisms multiply and are injected into the human host. This generally takes 36 hours, which is why a non-engorged tick or one that is removed immediately is VERY unlikely to transmit Lyme, even if the tick itself is infected.

In areas where Lyme is endemic, the ticks usually land on those out in the woods and fields, including athletes and gardeners. After coming in from these areas, people should inspect each other for ticks. In children, the head and neck areas are most common; in general, the groin, underarm, waist, back and legs are the places to look. Dog ticks do not carry Lyme, but dogs may carry deer ticks that may then land on humans.

People can get Lyme without noticing a tick bite or the classic 'bull's eye' or 'target' lesion, called erythema migrans (EM). When present, EM usually starts as a red spot at the site of the tick bite a few days to a month after the actual bite, then enlarges. It may have blisters or lighter or darker areas in the middle, or it may be uniformly red. The clearing in the center often occurs when it becomes very large, sometimes a foot in diameter. It can itch - or not - or rarely hurt. There are many other reasons for large red spots, such as spider or other bug bites, infection, reaction to medications or foods, fungal infections, etc.

There may be no symptoms with this early localized Lyme lesion, or there may be fatigue, headache, achiness and occasionally fever. Multiple skin lesions may appear, after the organism spreads through the blood during early disseminated disease. This can also result in nerve changes, especially involving the face, meningitis signs and heart rhythm changes, weeks to months after the tick bite.

If untreated by this stage, late disseminated disease with other neurologic issues, subtle cognitive changes or arthritis in larger joints, especially the knees, may occur months to years later. These are less common now that Lyme is often detected and treated in its earlier stages.

Post-Lyme disease syndrome may include headache, fatigue and joint discomfort that may persist for months but usually fade by 6-12 months. It's not clear, but it may be due to an autoimmune response triggered by the infection. In any case, further use of antibiotics is not helpful.

'Chronic Lyme' is not recognized by the Infectious Disease Society or the American Academy of Neurology as an entity, although there is much written on the internet about it. When there are persistent generalized symptoms, work-up must be pursued regarding other causes; they suggest that fibromyalgia is common in the general population, produces the same symptoms, and is not treated with antibiotics. Prolonged antibiotic treatment for presumed 'chronic Lyme' may have minimal or no benefit and can be very expensive and have substantial side effects including blood clots and superimposed infections.

Lyme antibodies may remain elevated forever in some patients and do not represent ongoing disease. The CDC and FDA advise caution regarding physicians or labs that have their own standards for the Western Blot test or do urine tests or other tests that are not generally used. There was such a controversy about this issue that in 2009, a day long conference was held in Washington, DC in which a panel of 9 experts in the field, not involved in the previous guidelines, heard testimony from 150 people. They reviewed the information for a year. The outcome was that the panel supported the previous guidelines that have been summarized above.

Diagnosis: When EM is present, it is usually too early for a blood test to show Lyme disease. Sometimes, with appropriate early treatment, the blood tests might not show evidence later either. Lyme may be diagnosed without testing when a characteristic EM rash is seen in an endemic area, especially if an engorged tick was actually noticed. When blood testing for antibodies to Lyme is done, elevated levels are confirmed with a Western Blot test, which is considered the gold standard for diagnosis. It is NOT recommended that people be tested routinely or for nonspecific symptoms like fatigue because in that case a positive result is just as likely to be a false positive as a true positive, and not represent true disease. At least 5% of the population may test positive for the antibodies with other infections as diverse as Ebstein-Barr (mono virus) or malaria. Testing the tick itself is not helpful, since even if it carries Lyme, it may not have transmitted it. Particularly in certain areas of New England, ticks may be co-infected with babesiosis or less often anaplasmosis (previously ehrlichiosis). Patients with these may have more severe illness, fever or changes in their blood counts. There is most concern for the very young, very old or those without a spleen.

Treatment: Cure rates of Lyme are very high, about 90% with a standard course of doxycycline (not to be used in children, pregnant or breastfeeding patients or those expected to have high sun exposure) or amoxicillin (not if allergic to penicillin) or cefuroxime. If someone is unable to take these, various forms of erythromycin can be used with a slightly lower cure rate. No difference in cure has been shown with 14 days versus 21 days of treatment for early Lyme. More advanced forms involving joints or the heart may be treated differently. About 15% of people will have fever, muscle and joint pain in the first day or two of treatment, representing a reaction to the organisms being destroyed.

Prevention: Insect repellants with at least 20% DEET and/or using a hat and covering the skin with pants and long-sleeved shirts are the best prevention. Bathing within 2 hours of exposure may help because ticks take at least 2 hours to fully attach. Removing ticks promptly by examining the common sites (see above) reduces the overall risk of Lyme to 1-3%. The CDC recommends using a fine-tipped tweezer to grasp the tick as close to the skin as possible, and pulling upward with steady pressure.  Clean the site and your hands with rubbing alcohol, iodine scrub or soap and water.  Submerge the tick in alcohol or flush it - do not crush it with your hand!  When an engorged tick is removed, doxycycline 200 mg once can decrease the risk of Lyme, but is not routinely used. There is no evidence that Lyme can be spread by sexual contact, breastfeeding or sharing eating utensils with someone who has it.

Recurrence: Re-infection with another strain is possible. Usually those who had 'late' disease initially are protected against a recurrence because they have a more vigorous antibody response to the next exposure.

Enjoy the outdoors, but check for ticks, and see your doctor if you have concern about Lyme. The cdc.gov site has an excellent review and photos of ticks, EM and the procedure for tick removal.


REFERENCES:

1) Shapiro, E. Lyme Disease. NEJM 2014; 370:1724-31
2) http://www.cdc.gov/lyme/
3) http://www.idsociety.org/Lyme/
4) Hu, L. Clinical manifestations of Lyme disease in adults. www.uptodate.com. July 2014
5) Hu, L. Diagnosis of Lyme disease. www.uptodate.com. July 2014.

Tags: Lyme, tick bite

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