Ehrlichia Infection (Ehrlichiosis)

Signs & Symptoms

Most people will develop symptoms within 7-14 days after exposure to an infected tick. Early symptoms are non-specific and include:

• Chills
• Confusion
• Conjunctival injection
• Fever
• Gastrointestinal symptoms (nausea, vomiting, diarrhea, anorexia)
• Headache
• Malaise
• Muscle pain
• Rash (in up to 60% of children, less than 30% of adults)

It is important to note that few people will develop all symptoms and the number and combination of symptoms vary greatly from person to person.

Diagnosis

Antibodies to Ehrlichia are detectable 7-10 days after illness onset. The gold-standard serologic test looks for a four-fold change in IgG-specific antibody titers using immunofluorescence assay (IFA) on paired samples. The first sample should be taken within the first week of illness and the second should be taken 2 to 4 weeks later.

• Demonstration of a four-fold change in IgG-specific antibody titer by immunofluorescence assay (IFA) test in paired serum samples; or
• Detection of DNA by PCR on whole blood. This method is most sensitive within the first week of illness; may decrease in sensitivity after administration of antibiotics.

Note: IgM antibodies are less specific than IgG antibodies and are more likely to generate false positive results. IgM results alone should not be used for laboratory diagnosis.

Note: Antibody titers are frequently negative in the first 7-10 days of illness, thus serologic tests may be falsely negative during this time period. For accurate testing of suspect cases an acute and convalescent serum are necessary.

Common laboratory findings suggestive of RMSF include: thrombocytopenia (reduced platelet count), hyponatremia (reduced sodium levels), and elevated liver enzyme levels.

Treatment

Use doxycycline as first-line treatment for suspected ehrlichiosis in patients of all ages. The use of doxycycline to treat suspected ehrlichiosis in children is recommended by both the CDC and the American Academy of Pediatrics Committee on Infectious Diseases. Use of antibiotics other than doxycycline increases the risk of patient death. At the recommended dose and duration needed to treat ehrlichiosis, no evidence has been shown to cause staining of permanent teeth, even when five courses are given before the age of eight.

In Maricopa County

Although Ehrlichiosis is not present in Arizona, there are still cases in residents who have traveled to an endemic area or relocated to Arizona from an endemic area. From 2005 and 2011, there were 8 probable or confirmed cases of Ehrlichiosis reported to Maricopa County.