Tickborne anaplasmosis is on the rise this autumn

Deer ticks that carry Lyme disease may also carry the agent for anaplasmosis (Anaplasma phagocytophilum), a disease that’s increased more than tenfold since 2000 and continues to spread, according to the US Centers for Disease Control and Prevention.

Anaplasmosis cases have been escalating for more than a decade. In recent years, the number of cases reported to the CDC jumped from 2,800 in 2014 to 3,656 cases in 2015—a 31% increase.

Anaplasmosis is most frequently reported in the same geographic areas as Lyme disease, including the upper Midwest and the Northeastern United States. Reports of cases are concentrated most densely around the Atlantic coast from northern New Jersey to southern Maine, and all throughout Wisconsin and Minnesota. But sporadic cases have been reported in the South and as far west as coastal California.

In Vermont, health officials recently released an advisory about the continuing threat of anaplasmosis into the months of autumn, when adult ticks come out to feed before winter. The number of anaplasmosis cases in Vermont reached a high of 201 in 2016, a dramatic increase over 2010 when only 3 cases were reported. Health officials said the number of anaplasmosis cases in 2017 have already surpassed the number reached in 2016.

Reported Cases of Anaplasmosis in US, 2015

“We’re very concerned about the rate of anaplasmosis that we are seeing all over Vermont, and especially in the southern part of the state,” said Bradley Tompkins, MPH, an infectious disease epidemiologist with the Vermont Department of Health. “Even though it’s only October, we have already exceeded last year’s case count.”

In more than one-third of these cases, infected Vermonters were sick enough to be hospitalized.

Signs and symptoms

Anaplasmosis can be difficult to diagnose. Unlike Lyme disease, anaplasmosis doesn’t present with a telltale sign like the classic bullseye rash common to Lyme. Rash occurs rarely in anaplasmosis cases.

Typical signs and symptoms include fever, shaking, chills, severe headache, malaise, body aches, gastrointestinal symptoms (nausea, vomiting, diarrhea, anorexia), and cough. If not treated early, stiff neck and confusion may develop several days after initial symptoms. In rare instances, encephalitis or meningitis may occur.

Anaplasmosis is difficult to distinguish from a similar disease, ehrlichiosis, which is also transmitted by deer ticks (Ixodes scapularis, also called blacklegged ticks). Patients present with similar symptoms in both conditions.

Common lab findings for anaplasmosis include thrombocytopenia, leukopenia, mild anemia, increased hepatic transaminase levels, increased numbers of immature neutrophils and, in blood smears, visualization of morulae in the cytoplasm of granulocytes (although this is not conclusive).

The common confirmation method is serologic testing using indirect immunofluorescence assay (IFA) on paired samples, according to CDC guidance. Take the first sample within the first week of illness and take the second sample 2 to 4 weeks later. PCR amplification of DNA extracted from whole blood is also useful for diagnosing the infecting agent.

Don’t wait for test results to begin antibiotic treatment, the CDC advises, because a delay in treatment may result in severe illness and even death. Use doxycycline as first-line treatment in patients of all ages. Adults receive 100 mg of oral or IV doxycycline twice per day for 10 to 14 days. Children under 100 lbs. receive oral or IV doxycycline at 2.2 mg/kg per dose twice per day.

Check the pet

Pets can carry ticks into the house, which increases the risk for human exposure. Recommend that patients do a routine tick check on their dogs and other pets. On dogs, ticks are commonly found around and inside the ears, between the toes, and in the axillae and groin.