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Volume 10, Number 4—April 2004

Dispatch

Human Challenge Pilot Study with Cyclospora cayetanensis

Edith M. Alfano-Sobsey*Comments to Author , Mark L. Eberhard†, John R. Seed‡, David J. Weber‡, Kimberly Y. Won†, Eva K. Nace†, and Christine L. Moe§
Author affiliations: *Office of Public Health Preparedness and Response, Raleigh, North Carolina, USA; †Centers for Disease Control and Prevention, Atlanta, Georgia, USA; ‡University of North Carolina, Chapel Hill, North Carolina, USA; §Emory University, Atlanta, Georgia, USA

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Table

Inoculum treament and challenge conditions from the Cyclospora human challenge studya

Volun-teer Oocysts source (no.) Oocysts ingested, mean ± SD (% sporulated) Inoculum disinfectionb,c Storage medium until dosing Total storage (mo)d Inoculum ingestion medium and conditions
1
Haiti (3)
647 ± 183 (82)
Bleach and thiosulfate (pre-storage)
Sterile water
6+
Sterile water, then light lunch
2
Haiti (3)
203 ± 22 (69)
Bleach and thiosulfate (pre-storage)
Sterile water
7+
Sterile water, then light lunch
3
Haiti (1)
884 ± 22 (96)
Bleach and thiosulfate (pre-storage)
Sterile water
10
Sterile water, then light lunch
4
MO, USA (1)
4,851 ± 545 (71)
Bleach only; wash on dosing day
Sterile PBS
6+
Sterile water, with a chicken salad meal
5
MO, USA (1)
1,815 ± 249 (67)
Thiosulfate only; wash on dosing day
Sterile PBS
7
Sterile water, with a chicken salad meal
6
MO, USA (1)
4,916 ± 1,153 (67)
Bleach and thiosulfate (pre-storage)
Sterile PBS
7+
Sterile water, with a chicken salad meal
7 GA, USA (1) 48,884 ± 15,345 (94) Bleach and thiosulfate 3 days predosing 2.5% dichromate 5 Raspberries, then light lunch

aMO, Missouri; GA, Georgia; PBS, phosphate-buffered saline.
bHousehold bleach (5.25% sodium hypochlorite) was used for disinfection, and sodium thiosulfate (0.01%–0.1%) was used to inactivate residual bleach in the inocula.
cFor safety testing laboratory details, contact corresponding author.
dTime in storage from stool collection until volunteer dosing date, includes time oocysts were exposed to potassium dichromate in stool until sporulation plus the time the oocysts were in storage media after they were extracted from the stool specimens.

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