Ehrlichiosis and Anaplasmosis

Clinical features of ehrlichiosis and anaplasmosis are generally similar. Although some infections are asymptomatic, most cause abrupt onset of a nonspecific febrile illness with fever, chills, myalgias, weakness, nausea, vomiting, cough, headache, and malaise, usually beginning approximately 9 days (range 5 to 14 days) after the tick bite (1).

Rash is uncommon in anaplasmosis. Some patients infected with E. chaffeensis develop a maculopapular or petechial rash on the trunk and extremities. Eschar is typically absent in both infections, in contrast to rickettsial diseases.

Central nervous system and gastrointestinal manifestations are less frequent in anaplasmosis (1).

Ehrlichiosis and anaplasmosis may result in disseminated intravascular coagulation, multiorgan failure, seizures, and coma. Central nervous system involvement is more common in ehrlichiosis.

• Molecular diagnostic testing (polymerase chain reaction [PCR]) of a blood sample

• Sometimes serologic tests

• Sometimes immunohistochemistry

• Laboratory tests to assess for systemic effects (eg, complete blood count, comprehensive metabolic panel)

PCR testing of whole blood for pathogen-specific DNA is sensitive and specific for the detection of both E. chaffeensis and A. phagocytophilum and can result in rapid diagnosis (1, 2).

Serologic tests are available but require comparison of serial titers over time, thus confirmation of infection can be time-consuming. Serology is frequently negative in the first 10 days of illness and is therefore not useful in the acute setting (1).

Peripheral blood smear microscopic examination may reveal cytoplasmic inclusions in monocytes (ehrlichiosis) or in neutrophils (anaplasmosis). Cytoplasmic inclusions are more commonly seen in anaplasmosis.

Immunohistochemistry of biopsied skin, tissue, or bone marrow may also aid in diagnosis (1). 

Blood and liver tests may detect hematologic and hepatic abnormalities, such as anemia, leukopenia, thrombocytopenia, and elevated aminotransferase levels.

(See also the CDC's video Rickettsial Disease Diagnostic Testing and Interpretation for Healthcare Providers.)

Ehrlichia chaffeensis morulae

Image

This immunohistochemical stain shows E. chaffeensis morulae (red) within monocytes in the kidney of a patient with ehrlichiosis.

Morulae are microcolonies of Ehrlichia in the cytoplasm of white blood cells (arrows). If these morulae are identified, ehrlichiosis should be strongly suspected. Morulae may also be identified in a peripheral blood smear.

CDC

• DoxycyclineDoxycycline

For patients with characteristic symptoms and signs in endemic areas, particularly those with a known recent tick bite, empiric treatment of ehrlichiosis and anaplasmosis is best initiated before laboratory results return. When treatment is started early, patients generally respond rapidly and well.

Doxycycline is the first-line treatment for both ehrlichiosis and anaplasmosis in patients of all ages, including children. Treatment with this medication is administered until improvement is noted and the patient has been afebrile for 24 to 48 hours. Duration of therapy is 5 to 7 days for ehrlichiosis; for anaplasmosis, the United States Centers for Disease Control and Prevention (CDC) recommends 10 to 14 days of treatment to cover possible coinfection with Doxycycline is the first-line treatment for both ehrlichiosis and anaplasmosis in patients of all ages, including children. Treatment with this medication is administered until improvement is noted and the patient has been afebrile for 24 to 48 hours. Duration of therapy is 5 to 7 days for ehrlichiosis; for anaplasmosis, the United States Centers for Disease Control and Prevention (CDC) recommends 10 to 14 days of treatment to cover possible coinfection withBorrelia burgdorferi (a causative agent of Lyme disease) (1, 2).

For patients who cannot tolerate doxycycline, desensitization is recommended (3). Chloramphenicol is ineffective and not an acceptable alternative for the treatment of either ehrlichiosis or anaplasmosis.

Although some tetracyclines can cause tooth staining in children < 8 years of age, the CDC advises that a course of doxycycline is warranted (Although some tetracyclines can cause tooth staining in children doxycycline is warranted (1, 2). Research indicates that short courses of doxycycline (5 to 10 days, as used for rickettsial disease) can be used in children without causing tooth staining or weakening of tooth enamel (4).

Some patients continue to have headache, weakness, and malaise for weeks after adequate treatment.

With treatment, the case fatality rate for patients with anaplasmosis is approximately < 1% and for patients with ehrlichiosis is approximately 3% (3). A delay in treatment may lead to serious complications, including viral and fungal superinfections and a significantly increased risk of death.

No vaccine is available to prevent ehrlichiosis or anaplasmosis.

Measures can be taken to prevent tick bites (1).

Preventing Tick Bites

Preventing tick access to skin includes: Staying on paths and trails Tucking trousers into boots or socks Wearing long-sleeved shirts Applying repellents including diethyltoluamide (DEET), picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone to skin surfacesApplying repellents including diethyltoluamide (DEET), picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone to skin surfaces Treating clothing, shoes/boots, and gear with permethrinTreating clothing, shoes/boots, and gear with permethrin To avoid potential toxicity, DEET should not be used in infants under 2 months of age, and DEET concentrations ≤ 10% should be used in children under 12 years of age (2). OLE and PMD should not be used in children under 3 years of age (3). Permethrin on clothing effectively kills ticks. Frequent searches for ticks, particularly in hairy areas and on children, are essential in endemic areas.). Permethrin on clothing effectively kills ticks. Frequent searches for ticks, particularly in hairy areas and on children, are essential in endemic areas. Engorged ticks should be removed with care and not crushed between the fingers because crushing the tick may result in disease transmission. The tick’s body should not be grasped or squeezed. Gradual traction on the head with a small forceps dislodges the tick. The point of attachment and the person's hands should be disinfected with soap and water, rubbing alcohol, or hand sanitizer. Petroleum jelly, lit matches, and other irritants are not effective ways to remove ticks and should not be used. Complete elimination of tick populations is often not practically possible over large areas, but they may be reduced in certain zones (eg, residential) within endemic areas. To create a tick-safe residential environment, it is necessary to eliminate tick habitats and restrict host entry by clearing brush, tall grasses, and accumulated debris from around homes and lawn edges (1). Regular lawn maintenance, including frequent mowing and the installation of a 3-foot wide barrier of wood chips or gravel between lawns and wooded areas, is recommended to restrict tick migration into recreational zones. To reduce the presence of disease-carrying rodents (eg, rats, mice) and wildlife (eg, deer, raccoons), firewood may be stacked in dry, elevated areas. Physical fencing can also be installed. Recreational equipment and outdoor seating should be removed from shaded yard edges as should accumulated yard clutter to eliminate the potential for tick harborage.