Babesiosis: Problems in Diagnosis Using Autoanalyzers
DAVID A. BRUCKNER, Sc.D., LYNNE S. GARCIA, M.S.,., CLS(NCA), ROBYN Y. SHIMIZU, MT(ASCP),
ELLIE J. C. GOLDSTEIN, M.D., PATRICIA M. MURRAY,, M.D., AND GARY S. LAZAR, M.D.
A 76-year-old white man previous diagnosed as having
Waldenstrom's macroglobulinemia continued with persistent
fevers and sweats for two and a half years. Recently, repeated
automated differentials during 11 days of hospitalization failed
to note any intracellular inclusions in the RBCs. Blood sent to
the Microbiology Laboratory was noted to contain Babesia
species. A review of the hematology slides revealed that
Babesia species was present on all the slides the analyzer had
screened. This failure to note infected RBCs may pose serious
diagnostic problems. (Key words: Waldenstrom's macroglobulinemia; Babesia; Ixodes dammini; Parasites) Am J Clin
Pathol 1985; 83: 520-521
THE FIRST CASE of babesiosis in humans was reported
in 1957,10 and the first case identified in the United
States occurred in 1966.9 Before this time, the disease
was thought to be primarily of zoologic interest, infecting
wild and domestic animals. The majority of the human
cases in the United States have been reported from
Nantucket Island, Shelter Island, and Long Island.3 The
spectrum of disease varies from asymptomatic to acute
febrile illness, with the most severe symptoms and death
occurring in splenectomized patients. 38
Babesiosis is caused by a blood parasite transmitted
to humans by the bite of a tick, Ixodes dammini, and
occasionally by transfusion.4,7 Diagnosis of babesiosis is
primarily made by finding characteristic intraerythrocytic
ring forms in peripheral blood smears.5
This report summarizes a case of babesiosis where
the patient had a history of fever and whose recent
hospital stay and diagnosis may have been prolonged
by the repeated inability of new rapid automated differential blood analyzers to distinguish inclusions within
the red blood cells (RBCs).
Report of a Case
This 76-year-old white man, living in South Hampton, Long Island,
New York, was in good health until approximately two and a half
years ago. At that time, fevers and drenching sweats had developed for
approximately two weeks, after which he had a spontaneous splenic
rupture of unknown etiology. The patient was diagnosed as having
Waldenstrom's macroglobulinemia. He was started on chlorambucil
and prednisone every other day and released from the hospital. The
Clinical Microbiology, Department of Pathology, and
Department of Medicine, UCLA Medical Center,
Los Angeles, California
patient moved to Los Angeles two years ago and continued having
persistent fevers and sweats. Three months ago, the patient again had
spiked fevers of approximately 104 °F every other day, on days when
prednisone was not taken. Tests done at this time were unremarkable,
and he was started on Indocin® to control his fevers. He stopped
taking Indocin after one month, and the fever and sweats reappeared.
He was admitted to a community hospital for examination and then
transferred to University of California, Los Angeles, for further workup
of his Waldenstrom's macroglobulinemia syndrome.
Upon admission he was well nourished and did net appear acutely
ill. His physical examination was unremarkable except for his healed
abdominal surgery scar and an enlarged liver, which was not tender
on palpation.
Laboratory blood chemistries were unremarkable except for creatinine
levels of 2.2 mg/dL (normal: 0.7-1.3 mg/dL), urea nitrogen 85 mg/dL
(normal: 8-12 mg/dL); iron 23 mg/dL (normal: 50-150 mg/dL; iron
binding capacity 180 /ug/dL (normal: 280-400 Mg/dL), and IgM level
532 mg/dL (normal: 50-271 mg/dL). CBC was 2.1 X 103 WBC (normal
7.8 ± 3 X 103), 2.89 X 106 RBC (normal: 5.4 ± 0.8 X 106), 10.4 g/dL
hemoglobin (normal: 16.0 ± 2 g/dL), and 29.8% hematocrit (normal
47 ± 5%). Sedimentation rate was 55 mm/hour (normal: 0-23 mm/
hour), and platlet count was 73 X 103 (normal range: 150-350 X 103).
Blood sent for bacterial and fungal cultures were negative, and sputum
cultures were negative for bacterial and mycobacterial pathogens.
After 11 days postadmission, the Infectious Disease Service was
consulted. Because of persistent fevers, blood smears were requested
to rule out malaria or babesiosis. RBCs contained intracellular parasites
on thin blood films stained with Giemsa. The organisms were present
on both thick and thin blood films and were seen as small malarialike ring stages, measuring 0.8-1.8 nm in diameter, containing a redstaining nucleus with a thin rim of blue-staining cytoplasm. Additional
blood films were requested six hours later, however, no advanced
developmental stages were noted, and the diagnosis of Babesia species
was made.
Upon additional questioning, it was found that the patient had
owned marshlands in Long Island, where he frequently hiked. The
patient recalled being bitten numerous times by ticks while walking
through these areas.
Treatment was begun with quinine (600 mg tid) and clindamycin
(600 mg tid). Because of complications on the third day of therapy,
the quinine dosage was reduced to 300 mg tid. The patient was treated
for 12 days. Follow-up blood smears were negative when examined by
the technologists, and the patient remained afebrile.
Received May 25, 1984; received revised manuscript and accepted
for publication June 26, 1984.
Address reprint requests to Dr. Bruckner: Clinical Microbiology,
Room A2-250, UCLA Medical Center, Los Angeles, California 90024.
520
Discussion
The diagnosis of babesiosis was made when blood
was sent to the parasitology laboratory. Organisms were
Vol. 83 • No. 4
CASE REPORTS
noted on both thick and thin peripheral blood smears
stained with Giemsa. Differentiating Babesia species
from malaria, particularly Plasmodium falciparum, is
difficult because the young trophozoites resemble each
other.5'6 During the early stages of P. falciparum infection,
when gametocytes are not present, it may be difficult to
speciate the organisms without an adequate patient
history. The trophozoite stage of Babesia species is pear
shaped, round, or oval and varies in size from 1.0 to
5.0 nm. The cytoplasm is thin and wispy, and the
nucleus may consist of one to two chromatin masses.
The characteristic tetrad form (Maltese Cross) of Babesia
species is found infrequently in human blood smears.
One can distinguish Babesia species from Plasmodium
species by the absence of gametocytes and schizonts in
the blood smears containing the former. Also, the RBCs
are not enlarged and there is absence of pigment deposits
in erythrocytes parasitized with Babesia species in contrast to that found in erythrocytes parasitized by Plasmodium species. The diagnosis of babesiosis also may
be accomplished by animal inoculation and serology.2'7'8
In most patients, babesiosis is a self-limited febrile
illness, and recovery occurs with only supportive care.
However, immunocompromized patients may have an
acute more fulminant illness.1 This patient, even though
splenectomized and on immunosuppressive therapy,
appears to have had undiagnosed babesiosis for an
extended period of time. The parasitemia was fairly low,
one infected red blood cell per every 15-20 oil objective
fields. After the diagnosis was made, all hematology
differential reports and slides were reviewed. Only one
of seven hematology request slips had a working diagnosis
listed. Differential reports are generated by new automated methods, thus, only a minimal number of oil
objective fields are reviewed by a licensed medical
technologist (10 fields per slide). Differentials were performed seven different times over a period of 11 hospitalized days before the diagnosis was made using nonautomated methods. A review of all previously prepared
slides scanned by the auto-analyzer revealed infected
red blood cells (one infected RBC per 15-20 oil objective
521
fields). If the laboratory had been notified by the physician that this patient had persistent fevers of unknown
origin and if a more careful history had been obtained,
the slides would have been reviewed more carefully and
perhaps a diagnosis made sooner.
The inability of the automated blood analyzers to
discriminate between uninfected RBCs and those infected
with protozoan pathogens may pose serious diagnostic
problems. Rapid analyzers sort cells based upon size
and density of cytoplasmic inclusions. In this particular
case, the analyzer was not able to distinguish the Babesia
species infected cells. The first reports based on peripheral
blood examination in many laboratories are generated
in the hematology section, not in microbiology, therefore,
laboratories will have to develop effective review procedures and make the physician aware of this potential
problem. An adequate history and inclusion of a presumptive diagnosis and symptoms on the laboratory
request form always are recommended, particularly when
an infectious etiology is suspected.
References
1. Bredt AB, Weinstein WM, Cohen S: Treatment of babesiosis in
asplenic patients. JAMA 1981; 245:1938-1939
2. Filstein MR, Benach JL, White DJ, et al: Serosurvey for human
babesiosis in New York. J Infect Dis 1980; 141:518-520
3. Gombert MD, Goldstein EJC, Benach JL, et al: Human babesiosis:
Clinical and therapeutic considerations. JAMA 1982; 248:
3005-3007
4. Grabowski EF, Giardina PJV, Goldberg D, et al: Babesiosis
transmitted by a transfusion of frozen-thawed blood. Ann
Intern Med 1982; 96:466-467
5. Healy GR, Ruebush TK: Morphology of Babesia microti in
human blood smears. Am J Clin Pathol 1980; 73:107-109
6. Hoare CA: Comparative aspects of human babesiosis. Roy Soc
Trop Med Hyg Trans 1980; 72:143-148
7. Jacoby GA, Hunt JV, Kosinski KS, et al: Treatment of transfusion
transmitted babesiosis by exchange transfusion. N Engl J Med
1980;303:1098-1100
8. Ristic M, Healy GR: Babesiosis, vol. 1, CRC Handbook in
Zoonoses: Sec C, Parasitic Zoonoses. Edited by LN Jacobs, P
Arambulo. 1982, pp 151-165
9. Scholtens RG, Braff EH, Healy GR, Gleason NN: A case of
babesiosis in man in the United States. Am J Trop Med Hyg
1969; 17:810
10. Skrabalo Z, Deanovic Z: Piroplasmosis in man. Report of a case.
Doc Med Geogr Trop 1957; 9:11