Cryptosporidium parvumBenjamin Harris1Cousins, Grandpa,
EpidemiologyFound on all six continents.
Distributed through fecal-oral route from infected hosts.
Most commonly transmitted through contaminated
water.HostsDefinitive Host: non-specific (terrestrial mammals)
Intermediate Host: None
Infects:HumansLivestockPetsAlmost any domesticated mammal.First
confirmed human case was 3-year-old girl from rural Tennessee in
1976LifecycleSporulated oocyst (containing four sporozoites) are
ingested or inhaled by infected host.Excystation occurs and
sporozoites are released attaching to intestinal or respiratory
walls.Undergo asexual multiplication (schizogony or merogony) or
sexual multiplication (gametogony).
Lifecycle ContinuedSexual multiplication yields:Microgamonts
Upon fertilization of zygote, two types of oocysts can be
produced.Thick-walled (typically excreated)Thin-walled (primarily
TransmissionFecally contaminated food and waterSwimming pools,
public drinking water, lakes, rivers.Animal-person
(zoonotic)Approximately 50% of calves discrete
oocysts.Person-PersonHigh frequency in day-care centers, bathrooms,
urban.Fecal-oral route.Small contamination required:Infective dose
(132 oocysts for healthy persons)
SymptomsNauseaVomitingAbdominal CrampsLow-grade feverFrequent
Much more severe in all respects for immunocompromised persons