A longitudinal study of Babesia microti infection in seropositive blood donors.

BACKGROUND: Babesia infection is caused by intraerythrocytic tick-borne parasites. Cases of transfusion-transmitted babesiosis have been increasingly recognized. To date, no Babesia test has been licensed for screening US blood donors. We conducted a longitudinal study to assess the course and markers of Babesia infection among seropositive donors identified in a seroprevalence study. STUDY DESIGN AND METHODS: Eligible donors had B. microti indirect fluorescent antibody (IFA) titers of 64 or greater. Enrollees were monitored up to 3 years, by IFA and three methods for evidence of parasitemia: B. microti nested polymerase chain reaction (PCR) analysis (at two laboratories), hamster inoculation, and blood-smear examination. RESULTS: Among 115 eligible donors, 84 (73%) enrolled. Eighteen enrollees (21%) had evidence of parasitemia for 30 total specimens (17% of 181), which were collected in 9 different months and tested positive by various approaches: PCR (25 specimens/16 persons), hamster inoculation (13 specimens/8 persons), and blood smear (one specimen positive by all three approaches). Overall, 14 persons had one or more specimen with positive PCR results at both laboratories (12 persons) and/or had parasitologically confirmed infection (eight persons). Three of nine persons who had more than one specimen with evidence of parasitemia had nonconsecutive positives. Several enrollees likely had been infected at least 1 year when their last positive specimen was collected. The final three specimens for seven persons tested negative by all study methods, including IFA. CONCLUSION: Seropositive blood donors can have protracted low-level parasitemia that is variably and intermittently detected by parasitologic and molecular methods. Donor-screening algorithms should include serologic testing and not solely rely on molecular testing.

Human challenge pilot study with Cyclospora cayetanensis.

We describe a pilot study that attempted to infect human volunteers with Cyclospora cayetanensis. Seven healthy volunteers ingested an inoculum of Cyclospora oocysts (approximately 200-49,000 oocysts). The volunteers did not experience symptoms of gastroenteritis, and no oocysts were detected in any stool samples during the 16 weeks volunteers were monitored.

Development of an immunohistochemical assay for the detection of babesiosis in formalin-fixed, paraffin-embedded tissue samples.

The hemoparasite Babesia can cause life-threatening infections to neonates, elderly and immunocompromised people, and people who have undergone splenectomy. By using pooled hamster serum samples collected 21 days after infection with Babesia microti, we developed an immunohistochemical assay for formalin-fixed, paraffin-embedded tissue (FFPET) samples and blood smears. By use of the immunohistochemical assay, parasites were detected inside erythrocytes present in the heart, spleen, and liver of experimentally and naturally infected animals. FFPET samples from 2 fatal and 1 nonfatal human cases demonstrated immunohistochemical assay-positive parasites in circulating erythrocytes in various organs, including lymph nodes and spleen. In addition, air-dried blood smears from 4 patients showed positive immunohistochemical staining inside the erythrocytes. The immunohistochemical assay showed cross-reactivity against the Babesia WA-1 strain but did not react against Babesia bigemina or Plasmodium falciparum. The immunohistochemical assay for Babesia microti successfully detected parasites in human and animal FFPET samples and blood smears. This technique will be useful for the diagnosis of clinically suspected cases and for differentiating Babesia microti infection from malaria. Application of this technique to animal models will better define pathogenic mechanisms, including the possible recognition of exoerythrocytic tissue stages.

Molecular and morphologic characterization of a Cryptosporidium genotype identified in lemurs.

This study reports the molecular and morphologic characterization of a Cryptosporidium sp., identified in stools of captive lemurs Propithecus verreauxi coquereli. Stool samples were collected from seven animals (n=7) presenting episodes of diarrhea. Bright-field light microscopy of stool smears stained with modified acid-fast technique revealed the presence of Cryptosporidium sp. oocysts in four of the stool samples analyzed. All microscopically positive samples were confirmed by PCR using primers designed to amplify DNA fragments from two independent loci, i.e. the Cryptosporidium oocyst wall protein (COWP) gene and the small subunit ribosomal RNA (ssrRNA) gene. Phylogenetic analysis based on the full-length ssrRNA gene placed this isolate within a clade that contains all currently known C. parvum species/genotypes, closely related to the C. parvum pig genotype. Comparison with partial ssrRNA sequences available in the GenBank revealed 100% sequence identity with the genotype previously identified in Canadian patients. This finding was confirmed further by comparison of the COWP gene partial sequences.

Baylisascaris procyonis in the metropolitan Atlanta area.

Baylisascaris procyonis, the raccoon roundworm responsible for fatal larva migrans in humans, has long been thought to be absent from many regions in the southeastern United States. During spring 2002, 11 (22%) of 50 raccoons trapped in DeKalb County, Georgia, had B. procyonis infection. The increasing number of cases highlight this emerging zoonotic infection.

Transmission of Babesia microti in Minnesota through four blood donations from the same donor over a 6-month period.

BACKGROUND: Babesiosis is a tick-borne zoonosis caused by intraerythrocytic protozoa. More than 40 US cases of Babesia microti infection acquired by blood transfusion have been reported. This report describes the identification of a transfusion-associated case of babesiosis and the subsequent identification of the infected blood donor and three other infected recipients of cellular blood components from three other donations by this donor. STUDY DESIGN AND METHODS: Serum specimens from the donors of blood that had been made into cellular components received by the index recipient and from other recipients of such components from the implicated donor were tested by the indirect fluorescent antibody (IFA) assay for antibodies to B. microti. Whole blood from IFA-positive persons was tested by PCR for B. microti DNA. RESULTS: IFA testing of serum from 31 of 36 donors implicated a 45-year-old man (titer, 1 in 256), whose donation had been used for RBCs. He likely became infected when bitten by ticks while camping in Minnesota in June 1999 and had donated blood four times thereafter. As demonstrated by PCR, he remained parasitemic for at least 10 months. Of the five other surviving recipients of cellular blood components from the implicated donor, three recipients (one for each of the three other donations) had become infected through either RBC or platelet transfusions. CONCLUSIONS: Babesiosis should be included in the differential diagnosis of posttransfusion febrile illness, and effective means for preventing transmission by blood transfusion are needed.