Cl. Chappell et al., CRYPTOSPORIDIUM-PARVUM - INTENSITY OF INFECTION AND OOCYST EXCRETION PATTERNS IN HEALTHY-VOLUNTEERS, The Journal of infectious diseases, 173(1), 1996, pp. 232-236
Data about human Cryptosporidium parvum infection have originated from
travelers, community and day care center outbreaks, and persons infec
ted with the human immunodeficiency virus, In addition, experimental i
nfection in 29 antibody-negative, healthy, adult volunteers generated
information on the dose-infection response of C. parvum (Iowa strain),
In that report, low inocula were sufficient to cause infection in 18
and illness in 7 persons, To further define the duration and intensity
of infection in this population, oocyst shedding patterns were invest
igated in the 18 subjects infected with C. parvum. Oocyst quantitation
revealed that volunteers with diarrheal illness (n = 7) excreted more
oocysts over the course of the infection than did volunteers without
diarrhea (n = 11; P < .05). Symptomatic subjects were more likely to s
hed oocysts on consecutive days, Further, a statistical nonsignificant
inverse trend (r(2) = .330, P = .136) was seen between challenge dose
and total excreted oocysts, This paradox may relate to receptor satur
ation or a toxic effect on cells, parasites, or both afforded by a hig
h inoculum.