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Lyme Disease
Basics
Beyond Lyme Disease
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Beyond Lyme Disease
Emerging tick-borne diseases create new reasons to be cautious.
Since the discovery of Lyme disease in the late 1970s, people have become wary of ticks — and with good reason. In the past 16 years, Americans in 48 states have contracted Lyme disease and other tick-transmitted diseases. In the years 2004 and 2005, more than 43,000 cases of Lyme disease were reported to the U.S. Centers for Disease Control and Prevention (CDC). A great number of cases have been attributed primarily to the spread of homes into wooded areas.
Though Lyme disease is the most common tick-borne illness, other diseases are passed this way as well.
Ehrlichiosis (air-LICK-ee-oh-sis) and babesiosis (buh-BEE-zee-oh-sis), two bacterial infections that are spread through tick bites, are still relatively rare. They are being diagnosed with increasing frequency, however, as physicians become more aware of them. And they are occurring in locations where they never existed before. For example, as farmland or forests are turned into housing developments, deer, mice and other small mammals migrate into those areas, carrying disease-laden ticks to pets and into closer proximity to humans.
Lyme disease, ehrlichiosis and babesiosis all can be spread by the same type of tick, so it is possible to acquire more than one of these infections from the same tick.
Ehrlichiosis
Ehrlichiosis was unknown in human beings until 1986, when one strain — human monocytic ehrlichiosis (HME) — was discovered. Since then, a second strain has been found, human granulocytic ehrlichiosis (HGE). Symptoms are similar, but the bacteria that cause these diseases infect different types of white blood cells (either monocytes or granulocytes, respectively).
There had been an estimated 900 cases by the end of 1996. But the true number may be higher, because many doctors are unfamiliar with this disease and may mistake its symptoms for those of the flu or another condition. Patients with mild forms of the disease may not seek medical attention. In addition, some patients have more than one tick-borne infection, such as ehrlichiosis and Lyme disease, at the same time, further complicating efforts to establish the diagnosis.
Symptoms: These include fever, headache and flu-like muscle aches. Nearly half of those infected then develop nausea, vomiting, diarrhea or cough. One-third of people with HME and less than 10 percent of people with HGE will develop a red skin rash that spares the palms and soles and may be raised or flat. Complications can include shock; lung, heart or kidney failure; and neurological damage. About 1 percent to 2 percent of patients die as a result of infection.
Treatment: All patients who are suspected of having ehrlichiosis should be treated with an antibiotic such as doxycycline for at least one week.
How detected: Unfortunately, ehrlichiosis can be difficult to diagnose. A simple blood test that looks for the bacteria in blood cells is abnormal in up to one-third of infected patients. A more sophisticated test called polymerase chain reaction, or PCR, can detect very small quantities of ehrlichia DNA in the blood of patients, but few physicians have easy access to this type of test. Most cases are detected several weeks after infection by identifying antibodies in the blood.
Who's at risk: HME has been found in at least 30 states and is carried by the lone star tick, whereas HGE has been found mainly in the upper Midwest, the Northeast United States and northern California and is carried by the deer tick — the same tick that hosts the bacteria that cause Lyme disease and babesiosis. All of these ticks are found on pets and other mammals, but they also live in backyards, golf courses and especially forests and other areas with tall grasses. Risk factors for infection include tick bites, golfing and exposure to wildlife.
Babesiosis
Carried by deer ticks — the same ticks that carry Lyme disease — babesiosis is a disease caused by a protozoa, similar to one that causes malaria, which infects human red blood cells. There are no reliable estimates of the number of people infected. In areas of the United States where infected ticks are common, up to 20 percent of people have antibody results suggesting exposure. Most of those exposed, however, have no evidence of the disease, babesiosis.
Most cases have been noted in the coastal United States, especially on islands off the coast, such as Martha's Vineyard or Shelter Island. Eighty percent of cases occur during summer months. Overall, about 6 percent of people with disease severe enough to require hospitalization die.
Symptoms: The tick bite is frequently unnoticed. Usual symptoms, which begin one to three weeks after the bite, include fever, headache and fatigue, symptoms that make it easy to confuse babesiosis with other diseases. Some patients also have chills, joint pain, neck stiffness, cough or sore throat. If the breakdown of red blood cells (hemolysis) is brisk, jaundice (yellowing of the skin) may develop. Kidney, heart or respiratory failure may lead to death in severe cases.
Treatment: Standard treatment includes a combination of quinine and an antibiotic called clindamycin. A combination of atovaquone and azithromycin is also effective and may cause fewer side effects.
How detected: Diagnosis is difficult because current laboratory tests are not sensitive enough to identify all cases. Examination of the red cells under the microscope will identify infection in 60 percent to 85 percent of cases; antibody tests have a higher accuracy rate but take at least one week to become abnormal. As with ehrlichiosis, PCR testing for minute amounts of the microbe's DNA is also available and is highly accurate.
Who's at risk: People with tick exposures who live in the coastal areas and islands off of Massachusetts (Cape Cod, Nantucket and Martha's Vineyard), New York (Long Island, Shelter Island and Fire Island) or Rhode Island (Block Island). Eighty percent of cases occur between May and August, when humans tend to enter tick-infested areas.
The disease is extremely serious for people who have had their spleens removed. Because the spleen filters out babesia-infected red blood cells, in those who lack the organ the parasites can grow uncontrolled. These patients can die unless treated immediately.
What To Do About Tick-Borne Illnesses
Despite the potential threat posed by these emerging illnesses, most tick bites don't contain infectious agents. In northern Maryland, for example, only 20 percent of deer ticks carry Lyme disease bacteria, and less than 2 percent carry the HGE bacteria.
Your best defense is prevention. Preventive measures can effectively reduce your chances of a tick bite; wearing long-sleeves and long pants tucked into socks, checking the skin for ticks after possible exposure, and using DEET-containing repellants are all appropriate measures to take if you must be in an area known to have ehrlichiosis or babesiosis during summer months. Do not donate blood within two months of fever or exposure to ticks.
If you do see a tick on your body:
Remove it quickly and clean the area with soap and water. The sooner the tick is removed, the better chance you have of preventing the transmission of any infectious agent. With a pair of tweezers, grasp the tick right at the point of the insertion of the tick's proboscis (its mouthpiece) and smoothly pull it out — don't jerk it out. This might be slightly uncomfortable because a small bit of skin will be pulled off along with the tick. If you don't remove the tick intact, don't try to dig it out. Instead, apply a triple antibiotic (such as Neosporin) to the area.
Preserve it. Save the tick in a small container with a little bit of rubbing alcohol to preserve it. If you get sick, the doctor can identify what kind of tick bit you and completely exclude certain classes of diseases. For example, if it's not a deer tick, Lyme disease is unlikely.
See what happens. Monitor the bite area for about two weeks. Tick bites normally look red and slightly inflamed for up to five days. If redness persists or the red area begins to increase in size, see a physician. Also see a doctor if you experience any disease symptoms (such as fever, headache, muscle or joint pain, or nausea) within a few weeks of the tick bite; if possible, bring the preserved tick with you. If you have a tick bite and live in an area where Lyme disease is particularly common, antibiotic therapy to prevent this disease may be recommended. However, if the tick is removed and is not attached or swollen (meaning it has not been attached for long), it is unlikely Lyme disease will follow.
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Last updated September 17, 2010
