Eva K. Nace

ATTEMPTS TO ESTABLISH EXPERIMENTAL CYCLOSPORA CAYETANENSIS INFECTION IN LABORATORY ANIMALS

Attempts were made to develop an animal model for Cyclospora cayetanensis to identify a practical laboratory host for studying human cyclosporiasis. Oocysts collected from stool of infected humans in the United States, Haiti, Guatemala, Peru, and Nepal were held in potassium dichromate solution to allow development of sporozoites. The following animal types were inoculated: 9 strains of mice, including adult and neonatal immunocompetent and immune-deficient inbred and outbred strains, rats, sandrats, chickens, ducks, rabbits, jirds, hamsters, ferrets, pigs, dogs, owl monkeys, rhesus monkeys, and cynomolgus monkeys. Most animals were inoculated by gavage, although some of the primates were fed oocysts on food items. The animals were examined for signs of infection, particularly diarrhea, and stool samples were examined for 4–6 wk after inoculation. None of the animals developed patent infections or signs of infection. We conclude that none of the animals tested is susceptible to infection with C. cayetanensis.

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.

Survey for Cyclospora cayetanensis in domestic animals in an endemic area in Haiti.

From January 1997 through July 1998, we examined stool samples from 327 domestic animals, including pigs, cattle, horses, goats, dogs, cats, guinea pigs, chicken, ducks, turkeys, and pigeons in Leogane, Haiti, for the presence of Cyclospora cayetanensis infection. No coccidian oocysts morphologically compatible with C. cayetanensis were detected in any of the animal samples, despite their living in, or near, households with infected individuals. These results suggest that domestic animals are not reservoir hosts for C. cayetanensis and that in this endemic area, humans are the only natural host for this parasite.

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.

A survey for Cyclospora spp. in Kenyan primates, with some notes on its biology

From March 1999 through August 2000, 511 stool samples collected from 11 different primate species in 10 geographically distinct locations in Kenya, East Africa, were screened for the presence of Cyclospora spp. oocysts. Positive samples (43/102, 42%) were identified in vervet monkeys (Cercopithecus aethiops) in 4 of 4 locations; 19/206 (9%) in yellow and olive baboons (Papio cynocephalus, P. anubis, respectively) in 5 of 5 locations; and 19/76 (25%) in black and white colobus monkeys (Colobus angolensis, C. guereza, respectively) from 2 of 3 locations. DNA sequences obtained from 18 S rRNA coding regions from respective subsets of these positive samples were typed as Cyclospora cercopitheci (samples from Cercopithecus aethiops), Cyclospora papionis (samples from Papio cynocephalus and P. anubis), and Cyclospora colobi (samples from Colobus angolensis and C. guereza). Cyclospora oocysts were not detected in samples collected from patas, highland sykes, lowland sykes, blue sykes, DeBrazza, or red-tailed monkeys. A coded map showing the geographic location of the collected samples is given. Stool samples from 1 troop of vervet monkeys were collected over a 12-mo period. Positive samples ranged between 21 and 63%. These results suggest that there is no strongly marked seasonality evident in Cyclospora infection in monkeys as has been noted in human infection. This is further confirmed by the recovery of positive samples collected from vervet monkeys, baboons, and colobus monkeys at all times of the year during this survey. This absence of seasonality in infection is especially notable because of the extreme weather patterns typical of Kenya, where marked rainy and dry seasons occur. A second noteworthy observation is that the striking host specificity of the Cyclospora species initially described was confirmed in this survey. Baboons were only infected with C. papionis, vervet monkeys with C. cercopitheci, and colobus monkeys with C. colobi, despite geographic overlaps of both the monkey and parasite species and wide geographic distribution of each parasite and monkey host.

A longitudinal study of Babesia microti infection in seropositive blood donors

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.

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.