No matter the species causing the infection, the signs and symptoms are similar. Some diseases may show no noticeable symptoms, while others can be severe and even life-threatening. Most cause an abrupt onset of illness with fever, chills, headache, and malaise (a general ill feeling). This usually starts around 12 days after the tick bite. Patients may also experience confusion, nausea, vomiting, and joint pain. Some patients develop a rash involving the trunk and limbs.

Very ill patients can develop low numbers of white blood cells and platelets, as well as kidney failure.

If you think you have ehrlichiosis, contact your healthcare provider and mention your exposure to ticks.

Ehrlichiosis spreads through the bite of an infected tick. Evidence suggests that the lone star tick transmits HME and that the deer tick transmits HGE.

Anyone can get ehrlichiosis, but the majority of known cases have been in adults. People who spend time outdoors in tick-infested areas have the greatest risk of exposure. This is usually from April until October. 

Aside from the southeastern and southcentral regions of the U.S., HME also exists in Europe and Africa. HGE is more common in Europe than HME. A rare, related illness called Sennetsu fever occurs in Malaysia and Japan.

Observe the usual tick precautions when participating in outdoor activities. Grassy or wooded areas (e.g., trekking, camping, or going on safari) are higher-risk areas.

Ehrlichiosis is difficult to diagnose. In the beginning, it is often confused with Rocky Mountain spotted fever (RMSF). The main difference is that the rash in ehrlichiosis occurs less often and is less pronounced than RMSF. Because diagnostic tests are not available everywhere, the diagnosis is usually based on symptoms and a history of exposure to ticks. Certain laboratory test results (such as low white blood cell count, low platelet count, and elevated liver enzymes) can suggest a diagnosis of ehrlichiosis.

With early antibiotic treatment, patients generally respond well.

No vaccine is available to protect humans against ehrlichiosis. You can reduce your risk by taking these precautions against tick bites:

• During outside activities, wear long sleeves and long pants tucked into socks. Wear a hat and tie your hair back.

• Use chemicals to repel or kill ticks. When using any of these chemicals, follow label directions carefully. Pay close attention to whether you must apply it to the skin or to clothing. Be especially cautious when using them on children.

• After outdoor activities, check yourself for ticks, with the help of a friend. Check body areas like behind the knees, between the fingers and toes, under the arms, in and behind the ears, and on the neck, hairline, and top of the head. Check places where clothing presses on the skin.

• Remove any attached ticks immediately. Use tweezers and grab as closely to the skin as possible. Do not remove ticks by squeezing them, coating them with petroleum jelly, or burning them with a match. If you remove attached ticks within 36 hours, the risk of infection is minimal.

Report ehrlichiosis within one week. Investigation Form

There are several laws in Texas (Tex. Health & Safety Code, Chapters 81, 84, and 87) that require doctors, hospitals, schools, and labs to inform the Texas Department of State Health Services (DSHS) if they think someone has a notifiable condition (25 Tex. Admin. Code §97.2).

In Texas, ehrlichiosis is a rare disease. Fewer than 10 cases of ehrlichiosis are reported each year. However, many people with ehrlichiosis infections have no symptoms and do not seek medical care. Some cases are also misdiagnosed, so it is difficult to know how common it is with certainty.

Human Ehrlichiosis in the United States
Centers for Disease Control and Prevention