So I was bitten by a tick, now what?
August 29, 2008
by Dr. Laurence Degelsmith
Just because we live in the Lyme capital of the world, there’s no need to panic.The risk of developing Lyme disease is very low, especially if the tick carrying Lyme disease is removed from its human host within 24 hours. Patients presenting with tick bites are a fairly common occurrence in our emergency department at Northern Westchester Hospital. When people are most likely to be out enjoying the weather, from late spring to early fall, ticks are most abundant and active.
At the same time, the “tick taxis,” the deer population who relocate the ticks, is thriving in Westchester County. These factors contribute to the preponderance of tick bites and Lyme disease in this area.
Although the lazy days of summer are past, it is important to remain vigilant against ticks until the temperature drops below 45 degrees. If you are new to the area, it’s time to learn the basics about Lyme disease.
Why is the risk of transmission low after a tick bite?
Lyme disease is actually the most common tick-borne infection in the United States as well as in Europe. It is caused by a microscopic organism called Borrelia burgdorferi, which is transmitted by the deer tick, Ixodes scapularis, to a human host. Borrelia burgdorferi is present in about 20-40 percent of deer ticks. It lives in the gut of the tick and must work its way to the salivary glands, through which it leaves the tick as the tick feeds and it enters the human host. This process takes about 36 hours at which time the tick may start to become engorged with the host’s blood.
Only about 20 percent of bitten patients will develop Lyme disease even after 72 hours of tick attachment, by which time the ticks are highly engorged. Therefore, it is very unlikely to develop Lyme disease from a tick that is not engorged, especially if it has been attached for less than 36 hours.
Interestingly, although the transmission rate of Lyme disease by adult ticks is much higher than by ticks in the nymph stage, the adults are much larger and often seen earlier and removed more quickly, thereby making Lyme transmission by adult ticks less common. The nymphs are the size of a pin head and are often overlooked, allowing longer attachment times. If a tick can be completely removed and the time of attachment can be reliably estimated to be less than 36 hours, no further treatment is recommended other than local disinfection of the skin and observation of the area for infection. Prophylaxis in this case against Lyme disease, which will be discussed later, is an option but not recommended routinely by infectious disease experts.
Lyme detection and treatment
Lyme disease usually begins as a circular “target-like” rash called “erythema migrans,” or EM, within 3 – 30 days at the site of the tick bite. The vast majority of patients, 70 - 80 percent, with Lyme disease start with this rash, but sometime it is missed or not there at all. The next stage is often a viral-like syndrome with fatigue, fever, chills, weakness, headache, swollen glands and joint aches.
The early diagnosis of Lyme disease is made clinically by identifying the EM rash, if present. We can also order a blood test for Lyme disease if the diagnosis is in doubt, but we often don’t if we see the typical rash. The results of the blood test also take a couple of days to come back from the lab, so we may treat until the results are in. The treatment of Lyme disease is either doxycycline, if the patient is over eight years old, or amoxicillin for any age. I’m not aware of any studies indicating that one is better for treating Lyme disease than the other. The usual course of treatment is 14-28 days depending on symptoms, fourteen days if caught early.
If left untreated, some people with Lyme disease will improve on their own, but up to 60 percent will go on to have chronic and recurrent joint pains. Up to 5 percent may develop chronic neurological symptoms, which may include numbness, tingling, shooting pains, headaches and problems with concentration. Although many of these manifestations merit concern, it needs to be stressed that they will resolve with a proper course of antibiotics.
Prevention of Lyme disease after a tick bite
Many studies have been done to determine if antibiotics can prevent Lyme disease after a tick bite, and the general conclusion is that a single dose of doxycycline (200mg) is about 85 percent effective in preventing Lyme disease from developing. There is no evidence for or against amoxicillin to prevent Lyme disease after a tick bite, so it is not generally recommended. This means than anyone under eight years of age can’t receive the prophylactic antibiotic doxycycline and must merely be monitored for signs of Lyme after a tick bite. If Lyme disease is indicated, then a full course of amoxicillin is recommended.
I will admit that most patients over eight that we see in the emergency department with a tick bite receive doxycycline for one dose even though the odds of getting Lyme are minimal. The health department and most infectious disease experts may not recommend this treatment strategy based on the evidence stated at the beginning of this article relating to the low risk of contracting Lyme from a quickly removed tick. But the risk of taking 200 mg of doxycycline is also pretty small as well. Therefore we dole out the drug quite often.
A word about “chronic Lyme disease:” there is no evidence that it exists. If a full course of antibiotics was taken after a diagnosis of Lyme disease was made, the Lyme disease will be successfully treated. There are a small percentage of patients that go on to have chronic symptoms after treatment, but no evidence, the presence of IgM antibodies to Lyme, of active Lyme is ever found. This chronicity of symptoms is thought to be from a chronic autoimmune response by the body to the original infection and not due to chronic, ongoing Lyme disease. There is much debate among various self-described Lyme disease “specialists” regarding this issue and I’ve run into many patients in the emergency department who have received months and months of antibiotics to treat “chronic Lyme.” However, there is no scientific evidence to support this treatment.
In rare cases, Lyme can affect the brain and nervous system causing muscle weakness, Bell’s palsy, shooting pains and even meningitis. Lyme also typically affects the large joints causing migrating arthritis. The heart may be affected as well. Lyme carditis is manifested by palpitations, dizziness, fatigue with exertion and sometimes passing out which is usually caused by heart rhythm changes.
Ticks can come bearing other diseases
Lyme disease, unfortunately, is not the only disease transmitted by deer ticks. Two additional creatures coexist with Borrelia burgdorferi in a tick’s gut and they cause the illnesses Ehrlichiosis and Babesiosis. These two infections can occur with or without Lyme disease. Ehrlichiosis isn’t usually much of an issue, since the treatment for Ehrlichliosis is the same as for Lyme disease, doxycycline.
Babesiosis, however, is treated with different medications. It is usually suspected when the typical treatment for Lyme or Ehrlichiosis fails to improve the patient’s symptoms after 48 hours. Those symptoms include severe flu-like symptoms: high fevers, severe headaches, muscle aches and weakness. Babesia attacks the red cells in the body much like the parasite malaria and can occasionally even cause death. Often the symptoms are very mild and go away without treatment.
I have seen a few healthy adults with Babesiosis and they generally look and feel as if they had a bad case of influenza. I saw an elderly man last month who almost died from Babesiosis. The laboratory saw the parasites in the blood smear and called us with this unexpected information. We were able to start treatment in time and he is doing well. He probably would have died if left untreated for one more day.
Diagnosis and treatment of Ehrlichiosis and Babesiosis
Ehrlichiosis and Babesiosis can be diagnosed immediately by looking at the patient’s blood on a microscope slide, which the lab in the hospital does routinely. Because I am seeing an occasional patient with Ehrlichiosis or Babesiosis, I generally order these tests on any patient suspected of having Lyme disease.
Ehrlichiosis is treated with doxycycline and not amoxicillin. Like Lyme disease, the usual course of treatment consists of 14-28 days depending on symptoms, 14 days for early stage Ehrlichiosis.
The preferred treatment for Babesiosis is an antiparasitic called atovaquone in combination with the antibiotic zithromax.
Laurence Degelsmith graduated from Horace Greeley High School in 1985, has an undergraduate degree from Washington University in Saint Louis, attended New York Medical College and did his residency in emergency medicine at the University of Michigan. He is an emergency department physician at Northern Westchester Hospital in Mt. Kisco and a member of the Chappaqua Volunteer Ambulance Corps.
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