Human granulocytic anaplasmosis

Human granulocytic anaplasmosis (HGA) is a tick-borne, infectious disease caused by Anaplasma phagocytophilum. These bacteria are spread to people by tick bites primarily from the blacklegged tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus).

Cause

Anaplasmosis is a tickborne disease caused by the bacterium Anaplasma phagocytophilum. Tick bites A. phagocytophilum is primarily spread to people by the bite of an infected tick. In the United States, the bacteria is carried by the blacklegged tick (Ixodes scapularis) in the Northeast and Midwestern United States and the western blacklegged tick (Ixodes pacificus) along the West Coast. Blood transfusion In rare cases, A. phagocytophilum has been spread by blood transfusion. Anaplasmosis is most commonly reported in the Northeastern and upper Midwestern states.

Risk factors

• The frequency of reported cases of anaplasmosis is highest among males and people over 40 years of age.
• People with weakened immune systems (such as those occurring due to cancer treatments, advanced HIV infection, prior organ transplants, or some medications) might be at increased risk of severe outcome.
• People who live near or spend time in known tick habitats might be at increased risk for infection.

Signs and Symptoms

Signs and symptoms of anaplasmosis typically begin within 1–2 weeks after the bite of an infected tick. Tick bites are usually painless, and many people do not remember being bitten. See your healthcare provider if you become ill after having been bitten by a tick or having been in the woods or in areas with high brush where ticks commonly live. Early Illness Early signs and symptoms (days 1-5) are usually mild or moderate and may include:

• Fever, chills
• Severe headache
• Muscle aches
• Nausea, vomiting, diarrhea, loss of appetite
• Late Illness

Rarely, if treatment is delayed or if there are other medical conditions present, anaplasmosis can cause severe illness. Prompt treatment can reduce your risk of developing severe illness. Signs and symptoms of severe (late stage) illness can include:

• Respiratory failure
• Bleeding problems
• Organ failure
• Death

Diagnosis

Your healthcare provider can order certain blood tests to look for evidence of anaplasmosis or other illnesses that cause similar symptoms. Test results may take several weeks. If your healthcare provider thinks you have anaplasmosis, or another tickborne infection, he or she may prescribe antibiotics while you wait for test results. PCR is very useful for diagnosis.

Treatment

Early treatment with the antibiotic doxycycline can prevent death and severe illness. Doxycycline is the recommended antibiotic treatment for anaplasmosis in adults and children of all ages. Doxycycline compromises dental enamel during development. Although rifampin is indicated for post-delivery pediatric and some doxycycline-allergic patients, it is teratogenic. Rifampin is contraindicated during conception and pregnancy.

Prevention

There is no vaccine to prevent anaplasmosis. Prevent illness by preventing tick bites, preventing ticks on your pets, and preventing ticks in your yard.

Epidemiology

Anaplasmosis is most frequently reported from the upper midwestern and northeastern United States. The number of anaplasmosis cases reported has increased steadily since the disease became reportable, from 348 cases in 2000, to a peak of 5,762 in 2017. However, cases reported in 2018 were substantially lower. The case fatality rate (i.e., the proportion of anaplasmosis patients that reportedly died as a result of infection) has remained low, at less than 1%.

Human granulocytic anaplasmosis Resources
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