Differences and similarities between culture-confirmed human granulocytic anaplasmosis and early lyme disease.

Lyme disease is transmitted by the bite of certain Ixodes ticks, which can also transmit Anaplasma phagocytophilum, the cause of human granulocytic anaplasmosis (HGA). Although culture can be used to identify patients infected with A. phagocytophilum and is the microbiologic gold standard, few studies have evaluated culture-confirmed patients with HGA. We conducted a prospective study in which blood culture was used to detect HGA infection in patients with a compatible clinical illness. Early Lyme disease was defined by the presence of erythema migrans. The epidemiologic, clinical, and laboratory features of 44 patients with culture-confirmed HGA were compared with those of a convenience sample of 62 patients with early Lyme disease. Coinfected patients were excluded. Patients with HGA had more symptoms (P = 0.003) and had a higher body temperature on presentation (P < 0.001) than patients with early Lyme disease. HGA patients were also more likely to have a headache, dizziness, myalgias, abdominal pain, anorexia, leukopenia, lymphopenia, thrombocytopenia, or elevated liver enzymes. A direct correlation between the number of symptoms and the duration of illness at time of presentation (rho = 0.389, P = 0.009) was observed for HGA patients but not for patients with Lyme disease. In conclusion, although there are overlapping features, culture-confirmed HGA is a more severe illness than early Lyme disease.

Dissociation between inhibition and killing by levofloxacin in human granulocytic anaplasmosis.

Human granulocytic anaplasmosis (HGA) is a potentially fatal tick-borne infection caused by Anaplasma phagocytophilum. Treatment options are limited for this entity, with doxycycline being the drug of choice. Certain fluoroquinolones such as levofloxacin are active against A. phagocytophilum in vitro. We report a hospitalized patient with HGA who improved coincident with a 13-day course of levofloxacin therapy, but clinically and microbiologically relapsed 15 days after completion of treatment. Relapse of infection after levofloxacin therapy was reproduced in a severe combined immune-deficient (SCID) mouse infection model. Quinolone therapy should not be considered curative of HGA.

Seroprevalence of antibodies that react with Anaplasma phagocytophila, the agent of human granulocytic ehrlichiosis, in different populations in Westchester County, New York.

We determined the frequencies of antibodies to Anaplasma phagocytophila, the agent of human granulocytic ehrlichiosis (HGE), in different groups of adults and children from Westchester County, New York. The groups included 159 adult blood donors and 215 children who were seronegative for Borrelia burgdorferi antibodies, 118 adult patients and 57 children who were seropositive for B. burgdorferi antibodies, and 42 adult patients with culture-confirmed erythema migrans. Eighteen (11.3%) of the blood donors and 11 (5.1%) of the B. burgdorferi-seronegative children were found to have A. phagocytophila antibodies by indirect immunofluorescent-antibody assay (IFA). Nine of 42 (21.4%) patients with culture-confirmed erythema migrans tested at the baseline visit, 42 of 118 (35.6%) adults, and 3 of 57 (5.3%) children whose sera were reactive for B. burgdorferi antibodies also tested positive for A. phagocytophila antibodies. The geometric mean titer ranged from 219 to 315 for all groups, and the differences in titers among the groups were not statistically significant. Only one-third of the healthy blood donors reactive by IFA were confirmed to be positive by immunoblotting. We conclude that a significant proportion of adults and children without clinical evidence of HGE will test positive for A. phagocytophila antibodies when the conventional cutoff titer of 80 is used in the IFA. This information must be considered in interpretation of test results.