Anaplasmosis is a tickborne disease that is caused by the bacterium Anaplasma phagocytophilum and primarily spread by an infected deer tick bite. It impacts over 5,000 people across the United States every year and is most commonly reported in Northeastern and upper Midwestern states.
What is Anaplasmosis?
Anaplasmosis is transmitted by the blacklegged (deer) tick (Ixodes scapularis). This tick also transmits the agents that cause Lyme disease and babesiosis.
The number of anaplasmosis cases reported to the United States Centers for Disease Control and Prevention (CDC) have increased steadily the disease become reportable, going from 348 cases in 2000 to 5,655 cases in 2019.
The reservoir for A. phagocytophilum, the bacteria that causes anaplasmosis, is primarily small mammals such as the white-footed mouse. In humans, reported anaplasmosis cases is highest among males and people over the age of 41.
People who live or spend time in known tick habitats have an increased risk of infection. The peak incidence of disease transmission is during June and July.
Anaplasmosis Symptoms
Anaplasmosis symptoms usually present during the first week after a tick bite, between four and nine days.
The clinical presentation of the tickborne disease generally includes:
- Fever
- Headache
- Leukopenia (reduction of white cells in the blood)
- Thrombocytopenia (low platelet count)
- Elevated liver enzymes
Rash is uncommon with anaplasmosis. This disease is very similar to ehrlichiosis, but milder. It also can present similarly to Borrelia miyamotoi infection.
Approximately 5-7% of patients with anaplasmosis require intensive care. Inflammatory markers such as C-reactive protein and procalcitonin (PCT) are usually elevated in these cases.
Diagnosis
The diagnosis of anaplasmosis requires both a compatible clinical history and laboratory evidence of infection. Antibodies, specifically the IgM antibody, may be negative at the beginning of the infection because not enough time has passed for the patient’s immune system to develop them. Thus, the best test for an early diagnosis is the detection of bacteria DNA in the blood using a PCR test. After two to three weeks of disease, laboratory evidence of infection includes a single IgG antibody titer of at least 256.
Anaplasmosis Treatment
Patients usually respond well to a seven-to-ten-day course of doxycycline, 100 milligrams orally, twice a day. Doxycycline should be taken with one to two glasses of water, in an upright position to prevent esophagitis (inflammation of the esophagus) and other gastrointestinal symptoms. Doxycycline is usually well-tolerated.
For tickborne disease prevention, immediate and complete removal of attached ticks is critical.
