Anaplasmosis is a disease caused by the bacterium 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).
People with anaplasmosis will often have fever, headache, chills, and muscle aches. Doxycycline is the drug of choice for adults and children of all ages with anaplasmosis.
Figure 1: Estimated geographic distribution of blacklegged ticks (above) and western blacklegged ticks (below)
Anaplasmosis is a tickborne disease caused by the bacterium Anaplasma phagocytophilum.
- Tick bites
- 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.
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 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
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
Risk factors for severe illness:
- Delayed treatment
- Age: being older puts you at risk
- Weakened immune system: People with weakened immune systems (such as those receiving some cancer treatments, individuals with advanced HIV infection, prior organ transplants, or people taking some medications) are at risk for severe illness
Diagnosis and Testing
- 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.
- 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.
- There is no vaccine to prevent anaplasmosis. Prevent illness by preventing tick bites, preventing ticks on your pets, and preventing ticks in your yard.
- Ticks live in grassy, brushy, or wooded areas, or even on animals, so spending time outside camping, gardening, or hunting will bring you in close contact with ticks. Protect yourself, your family, and your pets. Here’s how:
- Ticks can be active year-round, but ticks are most active during warmer months (April-September).
Tick exposure can occur year-round, but ticks are most active during warmer months (April-September). Know which ticks are most common in your area.
Before You Go Outdoors
- Know where to expect ticks. Ticks live in grassy, brushy, or wooded areas, or even on animals. Spending time outside walking your dog, camping, gardening, or hunting could bring you in close contact with ticks. Many people get ticks in their own yard or neighborhood.
- Treat clothing and gear with products containing 0.5% permethrin. Permethrin can be used to treat boots, clothing and camping gear and remain protective through several washings.
- Use Environmental Protection Agency (EPA)-registered insect repellents containing DEET, picaridin, IR3535, Oil of Lemon Eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone. EPA’s helpful search tool can help you find the product that best suits your needs. Always follow product instructions.
- Do not use insect repellent on babies younger than 2 months old.
- Do not use products containing OLE or PMD on children under 3 years old.
- Avoid Contact with Ticks
- Avoid wooded and brushy areas with high grass and leaf litter.
- Walk in the center of trails.
After You Come Indoors
Check your clothing for ticks. Ticks may be carried into the house on clothing. Any ticks that are found should be removed. Tumble dry clothes in a dryer on high heat for 10 minutes to kill ticks on dry clothing after you come indoors. If the clothes are damp, additional time may be needed. If the clothes require washing first, hot water is recommended. Cold and medium temperature water will not kill ticks.
Shower soon after being outdoors. Showering within two hours of coming indoors has been shown to reduce your risk of getting Lyme disease and may be effective in reducing the risk of other tickborne diseases. Showering may help wash off unattached ticks and it is a good opportunity to do a tick check.
Check your body for ticks after being outdoors. Conduct a full body check upon return from potentially tick-infested areas, including your own backyard. Use a hand-held or full-length mirror to view all parts of your body. Check these parts of your body and your child’s body for ticks:
- Under the arms
- In and around the ears
- Inside belly button
- Back of the knees
- In and around the hair
- Between the legs
- Around the waist
Examine gear and pets. Ticks can ride into the home on clothing and pets, then attach to a person later, so carefully examine pets, coats, and daypacks.
Epidemiology and Statistics
- Anaplasmosis is a disease caused by the bacterium Anaplasma phagocytophilum.
- This organism was previously known by other names, including Ehrlichia equi and Ehrlichia phagocytophilum, and the disease was previously known as human granulocytic ehrlichiosis (HGE).
- However, a taxonomic change in 2001 identified that this organism belonged to the genus Anaplasma, and resulted in a change in the name of the disease to anaplasmosis.
- In the United States, anaplasmosis was first recognized as human disease in the mid-1990s, but did not become nationally notifiable until 1999.
- CDC compiles the number of cases reported by state and local health departments and reports national trends.
- The number of anaplasmosis cases reported to CDC has increased steadily since the disease became reportable, from 348 cases in 2000, to 4,151 cases in 2016.
- The incidence (the number of cases for every million persons) of anaplasmosis has also increased, from 1.4 cases per million persons in 2000 to 6.1 cases per million persons in 2010.
- 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%.
Figure 1 – Number of U.S. anaplasmosis cases reported to CDC, 2000–2016
The graph displays the number of human cases of anaplasmosis reported to CDC annually from 2000 through 2016. *From 2000 to 2008, anaplasmosis was included in the reporting category “human granulocytic ehrlichiosis” in reports to NNDSS. **Since 2008, anaplasmosis has been reported to NNDSS in its own reporting category called “Anaplasma phagocytophilum”. Cases of anaplasmosis have generally increased from 350 cases in 2000, when the disease became nationally notifiable, to 1,163 cases in 2009, and 4,151 cases in 2016. The number of cases increased 14% between 2015 and 2016.
- Although cases of anaplasmosis can occur during any month of the year, the majority of cases reported to the CDC have an illness onset during the summer months and a peak in cases typically occurs in June and July.
- This period is the season for increased numbers of nymphal blacklegged ticks, which is the primary life stage of this tick that bites humans and can transmit the pathogen.
- A second, smaller peak occurs in October and November and corresponds with the period of adult blacklegged tick activity.
Figure 2 – Number of reported anaplasmosis cases by month of onset, 2000–2016
The figure shows the number of cases reported from 2000 through 2016 by month of onset to give the seasonality of cases. There are cases reported in each month of the year, however most are reported in June and July. More than 50% of all cases occur in June and July.
- Anaplasmosis is most frequently reported from the upper midwestern and northeastern United States.
- These areas correspond with the known geographic distribution of the blacklegged tick (Ixodes scapularis), the primary tick vector of A. phagocytophilum.
- This tick also transmits the agents of Lyme disease (Borrelia burgdorferi) and other human pathogens; co-infections with these organisms have occasionally been reported.
- The geographic range of anaplasmosis appears to be increasing, which is consistent with the blacklegged tick’s expanding range.
- Increasing ranges for the blacklegged tick have been documented along the Hudson River Valley, Michigan, and Virginia.
- Eight states (Vermont, Maine, Rhode Island, Minnesota, Massachusetts, Wisconsin, New Hampshire, and New York) account for 90% of all reported cases of anaplasmosis.
- Occasionally, anaplasmosis cases are reported in other parts of the United States, including southeastern and south-central states where the organism has not been commonly found.
- Some of these cases might be due to patient travel to states with higher levels of disease, or misdiagnosis of anaplasmosis in patients actually infected with another closely related tickborne disease, ehrlichiosis.
Figure 3 – Annual reported incidence (per million population) for anaplasmosis – United States, 2016. (NN= Not notifiable)
The figure shows the incidence of anaplasmosis cases by state in 2016 per million persons. Anaplasmosis was not notifiable in Alaska, Colorado, the District of Columbia, Hawaii, Idaho, or New Mexico in 2016. The incidence rate was zero for Arizona, Georgia, Indiana, Louisiana, Mississippi, Montana, Nevada, South Carolina, Utah, Washington, and West Virginia. Incidence ranged from > 0 to 3.0 cases per million persons in California, Kentucky, Oregon, Florida, Ohio, Illinois, Michigan, Oklahoma, Nebraska, Alabama, Maryland, South Dakota, Kansas, North Carolina, Wyoming, Tennessee, Virginia, Missouri, and Iowa. Incidence ranged from > 3 to 26 cases per million persons in Delaware, Pennsylvania, Arkansas, New Jersey and North Dakota. Incidence ranged from > 26 to 130 cases per million persons in Connecticut, New York, New Hampshire, Wisconsin, and Massachusetts. The highest incidence rates, greater than 130 cases per million persons, were found in Minnesota, Rhode Island, Maine, and Vermont.
- 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.