Human (Granulocytic) Anaplasmosis (HGA ... - Allina Health

Infection with Babesia
The merozoites escape by causing rupture of the host erythrocyte, and are then free to invade
other red cells. Multiplication of the parasites and rupture (hemolysis) of the red cells are
responsible for the clinical manifestations of the disease. For practical purposes, humans are
dead-end hosts; there is thought to be little, if any, subsequent transmission from infected
humans to feeding ticks (although human to human transmission has been reported in the
setting of transfusion of cellular blood products (see below), and possibly during pregnancy/
delivery).
Other infecting species (MO-1, B. duncani) have been reported in the western United States,
thought to be transmitted by the western black-legged tick Ixodes pacificus. In Europe,
infection of humans by B. divergens, transmitted by the sheep tick Ixodes ricinus, has been
reported.
In Minnesota in 2010, a record number of confirmed or probable cases (56, or 1.1 per
100,000 population) were reported, compared to 31 cases the year before. 59% of reported
patients were male, with median age 61 years (range 5-84 years). Onset of illness was elevated
from June through August with a peak in July comprising 40% of cases. 46% of patients
were hospitalized (range: 2 days – more than one month). One patient died. 14% of patients
also had confirmed Lyme disease, and a different 14% had confirmed or probable HGA.
Symptom onset after infection is usually 1-4 weeks (usually 1-9 weeks after infection resulting
from transfusion).
The spectrum of disease ranges from latent/subclinical to fulminant with hemolysis, multiorgan
failure and death. The most severely affected tend to be those individuals who are asplenic,
elderly or immunocompromised (i.e., HIV positive, underlying malignancy, corticosteroid
treatment).
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