Ehrlichiosis is a broad term applied to three different bacterial infections transmitted through a tick bite. Ehrlichia chaffeensis and Ehrlichia Ewingii are transmitted through the Lone Star Tick and typically found in patients living or traveling in the south central and southeast United States. Ehrlichia Muris is found in patients in the upper Midwest, more specifically in Minnesota and Wisconsin, the tick carrying these bacteria is undetermined. The American dog tick, Deer tick, and Lone Star tick are all common carriers. A bacteria belonging to the Rickettsiae family cause Ehrlichiosis. Rickettsiae bacteria can cause several serious diseases including Rocky Mountain Spotted Fever and Typhus.
Ehrlichiosis was first recognized in the late 1980’s. It officially became a reportable disease in 1999. The number of cases reported has increased steadily since the disease was first recognized. In 2000 there were 200 cases of Erhlichiosis reported, in 2008 the number of cases reported increased to 961.
The typical incubation period between tick bite and appearance of symptoms is between 7-14 days. Patients exhibit flu-like symptoms including chills, fever, headache, muscle aches, nausea, rash, and general malaise. Rash-like symptoms may occur resembling that of Rocky Mountain Spotted Fever making diagnosis based on clinical signs difficult. Symptoms of rash occur in 60% of children and 30% of adult patients.
Diagnosis must be made from clinical signs and initial blood work with treatment commencing immediately. Early blood work indicators of Ehrlichiosis are low platelet count, low white blood cell count, and elevated liver enzyme levels. Identification of the Ehrlichia bacterium requires specialized laboratories; a routine culture in a hospital emergency room will not expose the bacterium. Antibiotic treatment with tetracycline or doxycycline should be started immediately upon diagnosis. Further testing of the blood is required to confirm the diagnosis of Ehrlichiosis. A serologic test known as indirect immunofluorescence assay (IFA) is the preferred test to confirm existence of the Ehrlichia bacterium and is available in a few commercial laboratories.
Prognosis for those treated early is typically good. Fatality is rare occurring in only 1.8% of those diagnosed. Fatality rates are higher in individuals with compromised immune systems from immunosuppressive therapy, HIV, or splenectomy. For patients diagnosed early, a 7-14 day antibiotic treatment will typically suffice. Within 24-48 hours of early treatment symptoms will usually subside. However, full recovery may take several weeks with headaches, weakness, and malaise persisting long after the termination of antibiotics. Patients that go undiagnosed, or patients with more severe courses, may require intravenous antibiotics and hospitalization. Complications associated with Ehrlichiosis include coma, death, kidney damage, lung damage, and seizure.
With occurrences of Ehrlichiosis rising and geographic infection areas becoming more widespread, prevention is the best measure to ensure you avoid contracting this disease.
- Always wear long-sleeved shirts and pants when walking in wooded areas or in long grasses.
- Use insect repellants when possible.
- Check your body for ticks immediately after exposure to wooded or grassy areas.
Ticks hide in dark, moist areas of the human body. Removal of the tick within 24 hours is essential to reduce the risk of contracting Ehrlichiosis. If you do find a tick on your body, be sure and document when and where the tick came from. If possible, save the tick in case you develop symptoms.
References:
www.ncbi.nlm.nih.gov/pubmedhealth/pmh0002357/
