Anaplasma phagocytophilum

Human Granulocytotropic Anaplasmosis (HGA)

Anaplasma phagocytophilum (Human Granulocytic Anapasmosis)

o Intracellular pathogen in granulocytes

o Synergistically suppresses host immune system with Bb infection

In addition to Lyme disease ticks can carry many other infections. Human granulocytic anaplasmosis (HGA- formerly called human granulocytic ehrlichiosis) is one of these infections. The HGA bacteria infects white blood cells. Anaplasma organisms can also be carried by mosquitoes.

The diagnosis of anaplasmosis must be made based on clinical signs and symptoms, and can later be confirmed using specialized confirmatory laboratory tests. Treatment should never be delayed pending the receipt of laboratory test results, or be withheld on the basis of an initial negative laboratory result. (CDC)


HGA symptoms usually appear within a few days to two weeks after being bitten by an infected tick. Symptoms include severe headaches, fever, chills and shaking, loss of appetite, joint aches, change in mental status, confusion and muscle pain. The patient may experience abdominal pain, vomiting, diarrhea, cough or a loss of appetite.

A rash may appear in a small percentage of patients. Difficulty breathing, hemorrhage, renal failure and neurological problems can also be seen in more severe cases. Symptoms of HGA may be very mild to quite severe and include multi-organ failure.


Blood tests for Anaplasma may be negative in the early stages, especially in the acute phase. 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 can be used to confirm the diagnosis of anaplasmosis.

Testing for Anaplasma



If Anaplasmosis is suspected immediately start treatment. Do NOT wait for blood test results, begin treatment immediately. (CDC)

Adults and children who show signs or symptoms of HGA should immediately be treated with an antibiotic (doxycycline is the recommended drug) to reduce the risk of severity and long term complications.

Rifampin is an option for pregnant women or patients allergic to doxycycline.

Blood Transfusion and Organ Transplant Risks

Associated with Anaplasma Species

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. Anaplasma 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. (CDC)

More Information on HGA (Pg. 1828 CDC)

"What is unclear from these data is whether the discrepancy between the seroprevalence and symptomatic rate results from underdiagnosis of infection, asymptomatic serologic reactions, or even infections that produce cross- reactive serologic responses. In any case, symptomatic infection can occur often in tick-endemic regions and varies in severity from mild, self-limited fever to death.

Severity sufficient for hospitalization is observed in half of symptomatic patients and is associated with older age, higher neutrophil counts, lower lymphocyte counts, anemia, the presence of morulae in leukocytes, or underlying immune suppression (5). Approximately 5%–7% of patients require intensive care, and at least 7 deaths have been identified (2,4,5,7,19), in which delayed diagnosis and treatment were risk factors.

Severe complications include a septic or toxic shock–like syndrome, coagulopathy, atypical pneumonitis/acute respiratory distress syndrome (ARDS), acute abdominal syndrome, rhabdomyolysis, myocarditis, acute renal failure, hemorrhage, brachial plexopathy, demyelinating polyneuropathy, cranial nerve palsies, and opportunistic infections.

At least 3 of the deaths resulted from opportunistic fungal or viral infections or hemorrhage that occurred immediately after HGA."

Source Located Here

Additional Selected Studies

2017- Tick-Borne Emerging Infections: Ehrlichiosis and Anaplasmosis

2017- Detection of Borrelia miyamotoi and other tick-borne pathogens in human clinical specimens and Ixodes scapularis ticks in New York State, 2012-2015

2016- Extensive genetic diversity of Rickettsiales bacteria in multiple mosquito species

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Last Updated- April 2019Lucy