Cryptosporidium parvum
Jennifer E. Dumaine,1
Jayesh Tandel,1
and Boris Striepen1,
*
1
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 380 South University Avenue, Philadelphia, PA 19104, USA
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Cryptosporidium is a leading cause of diarrheal disease in young children and untreated AIDS patients in resourcelimited
countries worldwide. Transmission occurs via the fecal–oral route, and sources of Cryptosporidium infection
include contaminated water or food, or contact with infected people or animals. Upon ingestion of the infective parasite
oocysts, motile sporozoites emerge and invade epithelial cells of the small intestine where they develop in an
intracellular but extracytoplasmic niche. Cryptosporidium completes its complex life cycle in a single host, with both
asexual and sexual stages present in the intestine. Replication of the parasite, and the resulting immune response
contribute to the development of severe, watery diarrhea in infected individuals. Currently, there is no vaccine, and
only one drug (nitazoxanide), which has limited efficacy in those most susceptible.
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KEY FACTS:
Human infections are caused by
C. parvum and Cryptosporidium hominis
but transmission of multiple additional
species occurs locally.
Zoonotic C. parvum strains appear
genetically distinct from anthroponotic
strains.
C. parvum invasive stages resemble
those of other apicomplexans, but invasion
and intracellular development show
important differences.
C. parvum has a minute genome
(9.1 Mbp encoding 4020 genes), lacks
an apicoplast and mitochondrial DNA,
has greatly reduced metabolic capabilities,
and relies on host metabolism.
Recent advances: genetic engineering,
cryopreservation, culture in organoids,
tractable life cycle, phenotypic screens delivered
potent drug leads, a natural mouse
model to study protective immunity.
DISEASE FACTS:
Cryptosporidiosis is a major cause of
global child mortality, particularly under
the age of two.
With advanced water treatment, outbreaks
are still frequent due to oocyst resistance
to water chlorination.
The main disease symptoms are severe
watery diarrhea, nausea, vomiting, and
wasting.
Chronic infection causes villus blunting, nutrient
malabsorption, and stunted growth.
Infection results in protective immunity, albeit
not sterile and not in a single infection.
T cells are required to clear the infection,
and interferon-γ is a key mediator of parasite
restriction.
TAXONOMY AND CLASSIFICATION:
SUPERPHYLUM: Alveolata
PHYLUM: Apicomplexa
CLASS: Conoidasida
ORDER: Cryptogregarinorida
FAMILY: Cryptosporidiidae
GENUS: Cryptosporidium
SPECIES: C. parvum
*Correspondence:
striepen@upenn.edu (B. Striepen).
Trends in Parasitology, May 2020, Vol. 36, No. 5 © 2019 Elsevier Ltd. All rights reserved. https://doi.org/10.1016/j.pt.2019.11.003 485
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Acknowledgment
Our work on Cryptosporidium is supported by grants from the National Institutes of Health and the Bill and Melinda Gates Foundation to B.S. and a National Institute of Allergy and
Infectious Diseases (NIAID) T32 fellowship to J.E.D.
Resources
www.cdc.gov/parasites/crypto/index.html
https://cryptodb.org/cryptodb/
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