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

July 2012
Human (Granulocytic) Anaplasmosis (HGA) & Babesiosis
Revised 08/07/2012
Linda Riley, MD
The milder than normal past winter suggests that there may be increased
incidence of tick-borne illnesses in the upper Midwest, including Minnesota,
during 2012. Lyme disease was discussed in a prior Best Practices in Laboratory
Testing article in July 2010. In the current issue, HGA and Babesiosis are
presented. Further data about these diseases or related diseases may be
obtained from Minnesota Department of Health (MDH) and Center for Disease
Control (CDC) web sites (see references below).
Health care providers are required to report to MDH (MDH Phone : 651-201-
5414) all confirmed or suspected cases of Lyme disease, Anaplasmosis,
Babesiosis, Rocky Mountain Spotted Fever, Ehrlichiosis and Powassan (POW)
Virus.
Human Granulocytic Anaplasmosis (HGA)
The Family Anaplasmataceae includes the genera Anaplasma and Ehrlichia,
which are tick-borne 0.5 micron obligate intracellular gram negative rickettsial
coccobacillary bacteria that reside in cytoplasmic vacuoles within white blood
cells.
The terms “Anaplasmosis” and “Ehlichiosis” are often used interchangeably,
including in the Allina Health laboratory system, which, although technically not
quite correct, serves well for our purposes. HGA was formerly known as Human
Granulocytic Ehrlichiosis but was renamed HGA in 2003. It is the second most
common tick-borne disease in Minnesota after Lyme disease. It is transmitted to
humans by ticks of Ixodes genus including Ixodes scapularis (also known as
deer tick or blacklegged tick, previously called Ixodes dammini), the same tick
that transmits Lyme disease and babesiosis. Co-infections with agents of Lyme
disease and/or babesiosis can occur from the same tick bite.

In 2010, there were 720 reported confirmed or probable cases of HGA in Minnesota (16.9
cases per 100,000 population), more than twice the number reported in 2009. 59% were in
males, the median age was 57 years, and the majority of cases were reported in May-July,
with a peak in June. 27% of patients were hospitalized (1-42 days) and there was one
reported death. 5% of HGA cases also had Lyme disease, and 1% also had confirmed or
probable babesiosis. The frequency of co-infection may be underestimated.
A disease related to HGA, called Human Monocytic Ehrlichiosis, is caused by Ehrlichia
chaffeensis. It is uncommon in Minnesota. It is found throughout much of the southeastern
and southcentral United States and is carried mainly by the Lone Star tick. However, a few
cases of Ehrlichia muris-like agent-related disease, carried by I. scapularis, have been reported
in Minnesota and Wisconsin since 2009. Ehrlichia ewingii, the agent of canine granulocytic
ehrlichiosis, may occasionally cause an ehrlichia-like illness in humans.
Anaplasma phagocytophilum (formerly known as Ehrlichia phagocytophilum) is the agent of
HGA. It has tropism for neutrophils (whereas E. chaffeensis has tropism for monocytes). The
incubation period is typically 7-10 days before development of overt symptoms, although onset
of illness may be 5-21 days after exposure. Disease transmission is usually from tick bite,
although other reported routes include blood inhalation/percutaneous blood exposure
following butchering of white-tailed deer, blood transfusion, and transplacental infection. Many
infections go undiagnosed because of the mild nonspecific symptomatology associated with
the majority of infections.
Symptoms typically include chills, fever, headache, myalgias and arthralgias. Less common
symptoms include nausea/anorexia and vomiting, weight loss, abdominal pain, cough,
diarrhea, and mental status changes. Rare patients will develop encephalitis, acute respiratory
distress syndrome, or shock-like illness with multiorgan involvement. Disease tends to be most
severe in elderly or immunocompromised individuals. The fatality rate is usually less than 1%,
although some sources state a 2-3% fatality rate, and may be associated with opportunistic
superimposed fungal or viral infection.
Laboratory Findings:
The majority of patients will have thrombocytopenia. Approximately 50% will have leukopenia.
Liver function tests (LFTs) may be elevated due to hepatocellular injury.
Pathology:
Intravacuolar bacterial microcolonies reside in neutrophils and may be seen by microscopic
evaluation when peripheral blood is smeared on a slide and stained by the Wright-Giemsa
method. These microcolonies resemble a mulberry and are therefore called morules or
morulae because the Latin word for mulberry is “morula.”
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Morules in neutrophils indicated by arrows
Other pathologic findings include infiltrates of foamy macrophages in reticuloendothelial organs,
multiorgan perivascular lymphohistiocytic infiltrates, and focal hepatocellular apoptosis
(reflecting the hepatocellular injury manifesting as elevated liver function tests (LFTs)).
Treatment:
The first-line treatment for adults and children of all ages, as recommended by the CDC, is
doxycycline. Treatment should be initiated immediately whenever HGA is suspected. For patients
who are allergic to doxycycline or have other contraindications, alternative antibiotic
treatment should be considered (see CDC for recommendations and doses). However,
prophylactic antibiotic treatment following a tick bite in an individual who has not developed
disease is not recommended, since there is no evidence that this is effective.
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Laboratory-based diagnostic methods:
Test
Turnaround
Time
Sensitivity
Comments
LAB 453/EHL
Ehrlichia Smear
Identification of
morulae in
neutrophils or
monocytes.
LAB 2780/EDP
Ehrlichia/Anaplasma
PCR
Detects and differentiates
DNA of
Anaplasma phagocytophilum,
Ehrlichia chaffeensis,
Ehrlichia
ewingii, and
Ehrlichia muris-like
Same day
Performed at
Allina Medical
Laboratories
1-3 days
Test Referred
to Mayo Medical
Labs
20-80% sensitivity
during the first
week of infection
60-70% sensitivity
during first week of
illness.
A positive test
result is helpful but
a negative test result
does not rule
out disease.
This is an insensitive
method (although dazzling
when it works).
A negative examination
should NOT dissuade you
from initiating treatment if
the clinical presentation
and routine laboratory
findings support the diagnosis
of HGA.
Test of choice for Ehrlichia
muris-like organisms.
Treatment should not be
withheld due to a negative
result. This test should not
be used to test
asymptomatic individuals.
LAB 2785/EHR
Ehrlichia Antibody
Panel
Detects IgG and
IgM antibodies to
Ehrlichia and Anaplasma.
1-3 days
Test Referred
to Mayo Medical
Labs
94-100% sensitivity
after 14 days.
Antibodies may not
be detectable during
the first week
of illness (when
patients typically
present for treatment).
A positive titer indicates
current or past infection.
Paired sera should be
collected 2-3 weeks apart.
A four fold rise in titer
confirms acute infection.
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BABESIOSIS
Babesiosis (originally called “Nantucket fever” due to its initially recognized occurrence in the
late 1960s on Nantucket Island) is a malaria-like illness caused by an apicomplexan protozoan.
These organisms are found worldwide. Although there are many species, only a few are identified
as causing human disease, including: B. microti, B. divergens, B. duncani (WA1 species),
and a strain designated MO-1. Like malaria, Babesia species infect erythrocytes, but unlike
malaria, babesiosis is transmitted by ticks, and the organism is found in a variety of animal
species that serve as reservoirs. Our previously mentioned “friend” Ixodes scapularis (deer
tick, blacklegged tick) is the usual tick vector.
Human infections in the United States of America occur mainly in the upper Midwest and
northeastern states due to infection by the rodent parasite Babesia microti (which infects the
white-footed mouse and other small mammals and which is the main species that infects people
in the United States). Tick larvae hatch in early summer from eggs laid in the spring by
adult female ticks, and become infected when they take a blood meal from infected whitefooted
mice. They molt into infected nymphs the following spring, and when they feed on
mice or humans in late spring or early summer, these hosts then also become infected. The
parasite is usually spread to humans by the young nymph stage of the tick (at which time the
tick is about the size of a poppy seed). In the fall, the nymphs molt into adults that feed on
white-tailed deer (that, according to some sources, do not become infected but nevertheless
support/amplify the tick population by providing the blood meals); if these infected adult ticks
feed instead on humans, they can infect humans at this time, as well. Thus, the main mode of
transmission to humans is through the bite of an infected tick (usually nymph, sometimes
adult), when humans engage in outdoor activities where Babesiosis is found.
In human infection, the sporozoites which are introduced into the bloodstream by the biting
tick attach to and enter the red blood cells (erythrocytes), where they mature into trophozoites
that eventually bud to form four merozoites (these stages are visible via light microscopy,
the four-merozoite stage sometimes characterized by the so-called “Maltese cross” formation
in infected red blood cells).
Babesia microti infection, Giemsa-stained thin smear
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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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Infected individuals may be asymptomatic. Symptoms/signs of the disease may include hemolysis,
high fever, chills, muscle aches/arthralgias, headache, fatigue, loss of appetite,
nausea and vomiting. More extreme expressions of disease include hypotension, hepatic
dysfunction, renal failure, disseminated intravascular coagulation, multiorgan failure and
death.
Supportive laboratory findings may include hemolysis, thrombocytopenia, and elevated LFTs.
Treatment:
According to the CDC, most patients who are asymptompatic do not require treatment. Early
diagnosis and treatment of symptomatic patients may reduce the length of illness and severity
of disease. CDC recommendations include assistance from infectious disease specialists
and antimicrobial drugs: Atovaquone + azithromycin for mild to moderate cases or
Clindamycin + quinine for severe cases, usually for 7-10 days, although repeat treatment or
monitoring of parasitemia may be necessary for some patients (immunocompromised, for
example). Please see CDC or MDH web sites for dosing recommendations.
Additionally, those patients with severe illness may require or benefit from supportive care
such as: vasopressors, antipyretics, blood transfusions, exchange transfusions, dialysis, and
mechanical ventilation.
Laboratory Diagnosis:
Bear in mind that some patients may be simultaneously infected with more than one tickborne
infection.
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MDH recommends at least two of the following three tests for diagnosis:
Test
LAB 6607/MAL
Malaria/Parasite Stain
Specially prepared
smear identifies parasites
within infected
red blood cells.
Turnaround
Time
Same day
Performed at
Allina Medical
Laboratories
Sensitivity
Highly sensitive during
acute illness.
Cannot differentiate
between Babesia species.
Comments
A negative examination
does not rule out the
diagnosis.
LAB 8076
Babesia microti PCR
Detects Babesia DNA
in whole blood.
1-3 days
Test Referred to
Mayo Medical
Laboratories
Highly sensitive
May be helpful in cases
of low parasitemia and
can differentiate between
species.
LAB 994/MSO
Babesia microti Abs
IgG, IgM
1-3 days
Test Referred to
Focus Labs via-
Mayo Medical
Laboratories
88-96% sensitivity for
B. microti
IgM antibody first appears
2 weeks after
the onset of illness.
IgG titers often exceed
1:1024 during the
first weeks of illness,
and then decline gradually
over 6 months to
titers of 1:16 to 1:256
Does not detect Babesia
WA1 species (B.
duncani) found on the
west coast.
A positive Babesia IFA
test for IgM is
insufficient for diagnosis.
If IgM is positive but
the IgG result is negative,
a follow-up blood
specimen drawn at
least one week after
the first should be tested.
If the IgG result remains
negative in the
second specimen, the
IgM result was likely a
false positive result.
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TRANSFUSION-TRANSMITTED DISEASE
Cases of transfusion-transmitted HGA and babesiosis do occur. Anaplasma can survive for
more than one week in refrigerated blood. Leukoreduction reduces but does not eliminate the
risk of transmission for HGA. Babesia organisms may also survive in refrigerated blood, and
the transfusion-transmitted rate of babesiosis, thought to be higher than that of transfusiontransmitted
HGA, may be as high as 1 in 1800 red cell units. American Red Cross reports that
50% of recipients receiving Babesia-infected cellular products will demonstrate seroconversion.
There is sharing of blood products nationally, so the packed red cells your patient receives
may theoretically have come from anywhere in the United States. Some of the reasons
why it is so hard to eliminate the risk of an infected blood product include: It is difficult
to identify those donors who are infected before they become symptomatic or if they have
subclinical infection; some donors infected with Babesia may harbor the parasite for months
without overt symptoms; deferring donors during peak tick activity as potentially infected just
because they are from disease-endemic areas would severely limit blood supply with little potential
gain; and PCR testing of donors for HGA is cost prohibitive and felt to be of low yield.
Transfusion-transmitted HGA and/or Babesiosis should be considered in patients who develop
fever and thrombocytopenia post-transfusion. The incubation period before manifestation of
symptoms in HGA appears to be 7-10 days, similar to that of HGA disease transmitted by tick
bites. Symptom onset for Babesiosis is 1-9 weeks following the instigating tick bite; symptom
onset for Babesiosis due to an infected blood product is also thought to be 1-9 weeks, although
it may be shorter than for tick bites, presumably because more organisms are being
introduced. Please contact the associated Blood Bank and MDH immediately about any suspected
cases so that investigation can be undertaken.
As always, please be vigilantly mindful of risks versus benefits when prescribing blood products,
and make sure that you obtain informed consent from your patients.
Also, be aware that the American Red Cross (ARC) is currently undertaking a look-back study
to evaluate by IFA and PCR representative blood donations from high, moderate and low endemic
areas. 10,000 total blood donations from Minnesota/Wisconsin/upper Midwest
(considered a moderately endemic area by ARC) are reportedly going to be evaluated this
year. Donors whose products test positive will be notified, and recipient tracing will be undertaken.
If your patient is a recipient of one of these positive blood products, expect notification
through ARC or via the blood bank/pathologist.
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Your Pets
A study from Austria showed no increased seroprevalence for Anaplasma phagocytophilum in
cat or dog owners compared to non-pet owners, suggesting that pets are not a likely source
of infection. In Europe and possibly in Washington state, transmission of Babesia divergens
by Ixodes ricinus to humans has been reported.
More About Ixodes scapularis (Deer Tick, Blacklegged Tick):
Reservoir hosts for HGA in the United States of America are the white-footed mouse
(transient bacteremia of 1-4 weeks), other small mammals, and the white-tailed deer
(persistent subclinical infection vs merely supplying the food source). Humans are infected
with tick-borne diseases when they come into contact with the tick vector in reservoir animal
habitats. Peak tick activity is April through September.
High risk counties in Minnesota include the eastern two-thirds of the state, in the
approximate mid-portion, in a swath oriented from northwest to southeast extending to the
St. Croix River region.
The ticks are found in wooded and brushy areas but may reside in your own back yard,
especially if you live adjacent to woods or have abundant brush or leaf litter in your yard.
Ixodes scapularis life cycle
Engorged Ixodes scapularis tick
Adult ticks are approximately 1/8 inch long. Nymphs are slightly less than 1/16 inch long.
Typically the tick must be attached for at least 12-24 hours in order to transmit the bacteria
(although this may be shorter for HGA). Not all ticks carry the culprit organisms. Additional
photographs of the deer tick are available on CDC and MDH web sites.
For information on preventing tick-borne disease and how to remove ticks, visit the MDH web
site
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REFERENCES
K. Annen, D.O., et al. Two Cases of Transfusion-Transmitted Anaplasma phagocytophilum.
Am J of Clin Path. 2012;137:562-565.
Skerget M, et al. Cat or Dog Ownership and Seroprevalence of Ehrlichiosis, Q Fever, and
Cat-Scratch Disease. Emerg Infect Dis. 2003;9:1337-1339.
McKechnie, D.B., et al. Survival of Ehrlichia chaffeensis in Refrigerated ADSOL-Treated
RBCs. Transfusion. 2000; 40:1041-1047.
Minnesota Department of Health web site: www.health.state.mn.us/
Mayo Medical Laboratories web site: MayoMedicalLaboratories.com
Personal Communication, American Red Cross, www.redcrossmn.org
Centers for Disease Control web site: www.cdc.gov/
Henry’s Clinical Diagnosis and Management by Laboratory Methods, 21 st Edition, 2007,
Publisher Saunders Elsevier, ISBN: 978-1-4160-0287-1
HGA: G. Woods M.D., D Walker M.D., “Chlamydial, Rickettsial, and Mycoplasmal Infections”,
pp. 1007-1008
Babesiosis: T. Fritsche, M.D. and R. Selvarangan, B.V.Sc., “Medical Parasitology”, pp.
1134-1135
E. Vannier and P. Krause, “Human Babesiosis”, New England Journal of Medicine June 21,
2012; 366;25, pp. 2397-2407
For questions, comments, or suggestions about this newsletter or other laboratory issues,
please contact Lauren Anthony, MD, Medical Director of Allina Medical Laboratories,
(612) 863-0409 or Lauren.Anthony@allina.com
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