Tickborne Disease 

Healthcare Professionals: Common Ticks | Anaplasmosis | Ehrlichiosis | Lyme Disease | Rocky Mountain Spotted Fever | STARI | Tularemia


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Anaplasmosis is a tickborne disease caused by the bacterium Anaplasma phagocytophilum. It was previously known as human granulocytic ehrlichiosis (HGE) and has more recently been called human granulocytic anaplasmosis (HGA). In Arkansas, Anaplasmosis is transmitted to humans by tick bites primarily from the black-legged tick (Ixodes scapularis). Of the four distinct phases in the tick life-cycle (egg, larvae, nymph, adult), nymphal and adult ticks are most frequently associated with transmission of anaplasmosis to humans.

Anaplasmosis has been reported year round in Arkansas, but typically increases in the spring and again in the fall of the year.


Anaplasmosis was first recognized as a disease of humans in the United States in the mid-1990’s, but did not become a reportable disease until 1999. The Arkansas Department of Health conducts surveillance and investigates cases of Anaplasmosis reported in Arkansas.

  • Anaplasmosis is the fourth most prevalent tickborne disease in Arkansas, and is found statewide.
  • Anaplasmosis has been found year round in Arkansas.

Clinical Description

The first symptoms of anaplasmosis typically begin within 1-2 weeks after the bite of an infected tick. A tick bite is usually painless, and some patients who develop anaplasmosis do not remember being bitten. The following is a list of symptoms commonly seen with this disease. However, it is important to note that few people with the disease will develop all symptoms, and the number and combination of symptoms varies greatly from person to person.

  • Fever 
  • Headache
  • Muscle pain 
  • Malaise 
  • Chills 
  • Nausea / Abdominal pain 
  • Cough 
  • Confusion 
  • Rash (rare with anaplasmosis)

Anaplasmosis can be a serious illness that can be fatal if not treated correctly, even in previously healthy people. Severe clinical presentations may include difficulty breathing, hemorrhage, renal failure or neurological problems. The estimated case fatality rate (i.e., the proportion of persons who die as a result of their infection) is less than 1%. Patients who are treated early may recover quickly on outpatient medication, while those who experience a more severe course may require intravenous antibiotics, prolonged hospitalization or intensive care.

Rash is rarely reported in patients with anaplasmosis and the presence of a rash may signify that the patient has a co-infection with the pathogen that causes Lyme disease or another tickborne disease, such as Rocky Mountain Spotted Fever.

The severity of anaplasmosis may depend in part on the immune status of the patient. Persons with compromised immunity caused by immunosuppressive therapies (e.g., corticosteroids, cancer chemotherapy, or long-term immunosuppressive therapy following organ transplant), HIV infection, or splenectomy appear to develop more severe disease, and case-fatality rates for these individuals are characteristically higher than case-fatality rates reported for the general population.

Because A. phagocytophilum infects the white blood cells and circulates in the blood stream, this pathogen may pose a risk to be transmitted through blood transfusions. A. phagocytophilum has been shown to survive for more than a week in refrigerated blood. Several cases of anaplasmosis have been reported associated with the transfusion of packed red blood cells donated from asymptomatic or acutely infected donors. Patients who develop anaplasmosis within a month of receiving a blood transfusion or solid organ transplant should be reported to state health officials for prompt investigation. Use of leukoreduced blood products may theoretically decrease the risk of transfusion-associated transmission of these pathogens. However, the filtration process does not remove all leukocytes or bacteria not associated with leukocytes from leukoreduced blood. Therefore, while this process may reduce the risk of transmission, it does not eliminate it completely.

There are several aspects of anaplasmosis that make it challenging for healthcare providers to diagnose and treat. The symptoms vary from patient to patient and can be difficult to distinguish from other diseases. Treatment is more likely to be effective if started early in the course of disease. Diagnostic tests based on the detection of antibodies will frequently appear negative in the first 7-10 days of illness. For this reason, healthcare providers must use their judgment to treat patients based on clinical suspicion alone. Healthcare providers may find important information in the patient’s history and physical examination that may aid clinical diagnosis. Information such as recent tick bites, exposure to areas where ticks are likely to be found, or history of recent travel to areas where anaplasmosis is endemic can be helpful in making the diagnosis.

The healthcare provider should also look at routine blood tests, such as a complete blood cell count or a chemistry panel. Clues such as a low platelet count (thrombocytopenia), low white blood cell count (leukopenia), or elevated liver enzyme levels are helpful predictors of anaplasmosis, but may not be present in all patients. After a suspect diagnosis is made on clinical suspicion and treatment has begun, specialized laboratory testing should be used to confirm the diagnosis of anaplasmosis.

Case Definition

The Arkansas Department of Health utilizes the Centers for Disease Control and Prevention (CDC) case definition for Anaplasmosis. Current case definitions for all tickborne diseases can be found on the National Notifiable Diseases Surveillance System (NNDSS) website.


Doxycycline is the first line treatment for adults and children of all ages and should be initiated immediately whenever anaplasmosis is suspected. The clinical presentation for anaplasmosis can resemble other tickborne diseases, such as Rocky Mountain spotted fever and ehrlichiosis. Similar to anaplasmosis, these infections respond well to treatment with doxycycline. Healthcare providers should order diagnostic tests for additional agents if the clinical history and geographic association warrant.

  • Use of antibiotics other than doxycycline or other tetracyclines has been associated with a higher risk of fatal outcome for some rickettsial infections.
  • Doxycycline is most effective at preventing severe complications from developing if it is started early in the course of disease. Therefore, treatment must be based on clinical suspicion alone and should always begin before laboratory results return.
  • If the patient is treated within the first 5 days of the disease, fever generally subsides within 24-72 hours. In fact, failure to respond to doxycycline suggests that the patient’s condition might not be due to anaplasmosis.
  • Severely ill patients may require longer periods before their fever resolves. Resistance to doxycycline or relapses in symptoms after the completion of the recommended course has not been documented.
  • In cases of life threatening allergies to doxycycline and in some pregnant patients for whom the clinical course of anaplasmosis appears mild, physicians may need to consider alternate antibiotics. Although recommended as a second-line therapeutic alternative to treat RMSF, chloramphenicol is not recommended for the treatment of anaplasmosis, as studies have shown a lack of efficacy.
  • Rifampin has been used successfully in several pregnant women with anaplasmosis, and studies suggest that this drug appears effective against Anaplasma species. However, rifampin is not effective in treating RMSF, a disease that may be confused with anaplasmosis.
  • Healthcare providers should be cautious when exploring treatments other than doxycycline, which is highly effective in treating both.
  • Broad spectrum antibiotics are not considered highly effective against A. phagocytophilum
  • The use of sulfa drugs during acute illness may worsen the severity of infection.

Recommended Dosage

Doxycycline is the first line treatment for adults and children of all ages:
Adults: 100 mg every 12 hours

  • Children under 45 kg (100 lbs.): 2.2 mg/kg body weight given twice a day
  • Patients should be treated for at least 3 days after the fever subsides and until there is evidence of clinical improvement. Standard duration of treatment is 7 to 14 days.
  • Some patients may continue to experience headache, weakness and malaise for weeks after adequate treatment.


Avoiding being bit by a tick is the best prevention for Anaplasmosis. Antibiotic treatment following a tick bite is not recommended as a means to prevent anaplasmosis. There is no evidence this practice is effective, and this may simply delay onset of disease. For more in-depth information about prevention of tickborne disease, please visit our Prevention of Mosquito and Tickborne Disease section. Additional information on tickborne disease can be found at CDC’s Division of Vector-Borne Diseases (DVBD) webpage.