Ticks and Tickborne Diseases


Ehrlichiosis, is an acute disease of humans and animals caused by bacteria named Ehrlichia that attacks white blood cells. The bacteria are transmitted to humans by the bite of an infected tick. The ticks that spread ehrlichiosis are the deer tick, the dog tickLone Star tick. and the

Ehrlichiosis is found in almost any area of the United States and in many foreign countries as well. The first human case in the U.S. was reported in 1986. Since 1986, there have been as many as 13 cases reported in one year in MD-DC-VA.

One type of ehrlichiosis, caused by the bacterium Ehrlichia chaffeensis, infects a white blood cell called a monocytes. This species of Ehrlichia has been known to exist and cause human illness for several years. A newly recognized species of Ehrlichia (not yet named) infects another type of white blood cell known as a granulocyte.

The Symptoms

Most patients with ehrlichiosis report exposure to ticks 1 – 3 weeks before onset of symptoms. Symptoms include the sudden onset of moderate to high fever, headache and muscle aches. The infection also can cause chills, nausea, vomiting, joint pains, or loss of appetite. Unlike Lyme disease or Rocky Mountain spotted fever, a rash is not common. Blood tests may show a low white blood cell count or a low platelet count. Because diagnostic tests are not readily available, the diagnosis of ehrlichiosis should be made based on clinical symptoms and a history of exposure to ticks.

The Treatment

The disease responds well to treatment with doxycycline or other tetracyclines. Because these antibiotics can cause dental staining in children, physicians should consult with an infectious disease expert when treating children.


  • Avoid tick-infested areas such as tall grass and dense vegetation.
  • Walk in the center of mowed trails to avoid brushing against vegetation.
  • Keep grass cut and underbrush thinned in yards. Follow directions carefully if chemicals are used for tick control or hire a professional.
  • Eliminate the living places of small rodents.
  • Wear light-colored clothing so that ticks are easier to see and remove.
  • Tuck pant legs into socks and boots. Wear long-sleeved shirts buttoned at the wrists.
  • Conduct tick checks on yourself, your children and your pets every 4 to 6 hours.
  • Apply tick repellent to areas of the body and clothing that may come in contact with grass and brush. Select repellents specifically for ticks; ones containing 30 percent DEET or 0.5 percent permethrin are effective in repelling ticks. Follow directions carefully and do not overuse. Some tick repellents can cause toxic or allergic reactions. Permethrin products only work on clothing, not skin.
  • Ask your veterinarian to recommend tick control methods for your pets. Animals can get Lyme disease and Rocky Mountain spotted fever, but they do not transmit these diseases to humans.