Volume 9, Number 8—August 2003
Molecular Characterization of a Non–Babesia divergens Organism Causing Zoonotic Babesiosis in Europe
|Characteristics||Italian patient||Austrian patient|
|Residence and outdoor activities
||Lived in northern Italy, in a small town in the district of Romagna, on ~1 hectare of land; often hunted moles in his garden, even after he started chemotherapy
||Lived in northeastern Austria, in a small town in the district of Krems Land, in the province of Lower Austria; had an off-site garden; often hunted in the Dunkelsteinerwald forest (usually wild boars, sometimes foxes and badgers)
|Clinical illness and general laboratory data
|Initial clinical manifestations
||Fever (39°C) and chills developed on October 14, 1998; hospitalized on October 18 because of fever, headache, confusion, jaundice, and dark urine (discharged on November 6)
||Marked fatigue developed on July 23, 2000; dark urine, without dysuria, developed on July 24; hospitalized on July 25 (discharged on August 2)
||15e (13.2 on July 27, 2000)
|Leukocyte count (x109/L)
||7.3 (7.8, with 5% atypical lymphocytes, on July 26)
|Platelet count (x109/L)
||15 (8 on July 27)
|Values of serum chemistriesd
||7,877 (normal range 230–460)
||994 (July 26, 2000) (normal range 120–240)
|Total bilirubin (mg/dL)
||3.2 (normal range 0.2–1.10)
||3.27 (July 26) (normal range 0.2–1.0)
|Indirect bilirubin (mg/dL)
||2.4 (normal range 0.2–0.85)
||2.36 (July 26) (normal range 0.0–1.0)
||0.8 (normal range 0.0–0.25)
||0.91 (July 26) (normal range 0.0–0.25)
||2.5 (normal range 0.50–1.20)
||1.04 (normal range 0.5–1.3)
|Diagnosis of Babesia infection
|Parasitemia level (% of erythrocytes that were infected) on first blood smear examined
||~30% (October 24, 1998)
||1.3% (July 25, 2000) (Figure 2)
|Antibody titers in IFA testing for reactivity to B. divergens antigensf
||Titers of 1:64 (specimen from October 28, 1998) and 1:256 (February 15, 1999) in testing at both CDC and the Clinical Institute of Hygiene of the University of Vienna
||Titers of 1:256 (July 31, 2000) and 1:1,024 (August 8, 2000) in testing at CDC and titers of 1:64 (July 31) and 1:1,000 (August 8) in testing at the Clinical Institute of Hygiene of the University of Vienna
|Therapy for babesiosis
||Clindamycin (600 mg thrice daily, by intravenous infusion) and quinine sulfate (650 mg thrice daily, by mouth) for 15 days, from October 24, 2000 (i.e., 10 days after onset of fever), through November 7
||Clindamycin (600 mg thrice daily), by intravenous infusion, for 8 days, from July 25, 2000 (i.e., 2 days after onset of symptoms), through August 1, and by mouth, for 15 days thereafter (through August 15)
||11 U packed erythrocytes, from October 19–31, 1998c,g
|Response to therapy
||Fever resolved by day 3 of therapy; no parasites found by blood-smear examination after day 6 of therapy; negative PCR analysis of blood from February 15, 1999
||Blood from August 8, 2000, negative by blood-smear examination but positive by PCR analysis; negative PCR analysis of blood from November 7, 2000, and February 8, 2001
|Long-term follow-up||Non-Hodgkin’s lymphoma remitted during hospitalization in 1998, but the lymphoma relapsed in February 2000; no parasites were found on blood smears during subsequent chemotherapy||Remained well|
aIFA, indirect fluorescent antibody; PCR, polymerase chain reaction; CDC, Centers for Disease Control and Prevention.
bNon-Hodgkin’s lymphoma developed in the Italian patient (diagnosis: June 1998). Chemotherapy, begun on September 23, 1998, was stopped prematurely on October 14, after he became febrile. His chemotherapeutic regimen included daily prednisone (75 mg) and weekly administration of various drugs in rotation. He received 4 of the intended 12 weeks of therapy, which included doxorubicin and cyclophosphamide during odd-numbered weeks (weeks 1 and 3) and vincristine and either methotrexate (week 2) or bleomycin (week 4) during even-numbered weeks.
cAlthough the possibility that he became infected by blood transfusion could not be excluded because he had been transfused before blood smears were examined, his febrile illness and hemolytic anemia preceded the transfusions.
dLaboratory values were from hospital admission (October 18, 1998, for the Italian patient, and July 25, 2000, for the Austrian patient), unless otherwise specified. Values for the Austrian patient are from testing performed at the hospital to which he was transferred after a brief (<24-hour) stay at a local hospital.
eEarlier on July 25, at a local hospital, his hemoglobin value was 16.2 g/dL, which had been his approximate baseline value during the previous 10 months.
fIFA testing of serum specimens from both patients was negative for antibodies to B. microti. A specimen from the Italian patient (February 15, 1999) was negative for antibodies to WA1.
gPlasma exchange was performed on October 23, when he mistakenly was thought to have thrombotic th
1The issue of what constitutes a new or newly described species requires periodic reevaluation as the techniques for characterizing microbes improve. Although the advent of molecular biology/phylogeny has made it possible to characterize organisms more precisely, the issue of how large a genetic difference in a particular gene(s) constitutes a new or different species is controversial. Bacterial taxonomy is a much more active and advanced field (26,27) than that for characterizing protozoa, in part because of the increasingly large numbers of bacteria being proposed as new species and the challenges posed by such possibilities as genetic rearrangements. In the recommendations published in 2002 by an ad hoc committee that reevaluated the species definition for bacteria (26), scientists were encouraged to use the “Candidatus” concept (i.e., to propose candidates for newly described bacterial species) for organisms that had been well-characterized, including the sequencing of the small subunit RNA gene, but had not yet been cultured. As noted above, we have referred to the protozoan we characterized as EU1. We have not claimed it as a newly identified species, despite having complete, identical, and novel 18S rRNA sequences for the organism from two patients, who were separated in time and space, and having done the sequence analysis for the two cases in different countries. However, although the Candidatus concept per se does not formally exist now for protozoa, on the basis of the precedent from the field of bacterial taxonomy, we propose that EU1 be considered a candidate species. If additional evidence supports the conclusion that the organism indeed constitutes a newly described species of the Babesia genus, we would favor the name Babesia venatorum, which now does not constitute an official name. We chose this name because the patients whose cases we reported were avocational hunters; “venator” is the Latin word for “hunter” (“venatorum,” the plural genitive case, means “of the hunters”).