Cryptosporidiosis
Etiology: Cryptosporidium spp.
Several Cryptosporidium species can cause severe acute
diarrhea in humans and animals . Human cryptosporidiosis is
usually
self-resolving
within
a
few
days,
but
immunocompromised patients can develop life-threatening
complications.
Outbreaks due to drinking water contamination continue to
occur, and there is no effective treatment, making
cryptosporidiosis a major public health issue and economic
problem.
Cryptosporidium parvum: an emerging
pathogen
•Cryptosporidium is a coccidian protozoan parasite( Sporozoa)
• Associated with diarrea in 1976 in a 3-year-old girl in the intestinal
epithelium
• Increasing population of immunocompromised persons and waterborne
outbreaks of cryptosporidiosis
•Little is known about the pathogenesis of the parasite
•Cryptosporidium can infect several different hosts, can survive most
environments for long periods
 Morphology:

C. parvum is a small round parasite measuring 3 to 5 micrometers which is
found in the gastrointestinal tract of many animals and causes epidemics of
diarrhea in humans via contaminated food and water.
Cryptosporidium
Occysts (eggs) travel in surface water, thus most common pathway of

contamination is by ingesting contaminated water.
 Sources of contaminated water include Agriculture (animal waste), Urban
(human waste through surface runoff),
 Largest Risk is for humans directly or indirectly ingesting contaminated
water from water supplier or from recreational activities
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Transmission:
Transmission of Cryptosporidium parvum occurs mainly through contact
with contaminated water (e.g., drinking or recreational water).
Occasionally food sources, such as chicken salad, may serve as
vehicles for transmission.
Zoonotic transmission of C. parvum occurs through exposure to
infected animals or exposure to water contaminated by feces of infected
animals.
Life cycle:
Cryptosporidium species live inside the epithelial cells of enterocytes within the intestinal tract
of a variety of vertebrates, but some species can infect the respiratory tract.
Humans are infected by ingestion of C. parvum sporulated oocysts, containing 4 sporozoites,
which excreted by the infected host through feces and possibly other routes such as respiratory
secretions.
The sporozoites are released in the upper GI tract attach to the gut mucosal then parasitize
epithelial cells of the gastrointestinal tract or other tissues such as the respiratory tract where they
divide to produce merozoites.
The merozoites invade other mucosal cells and further multiply asexually (schizogony or
merogony).
Some of the merozoites differentiate into male and female gametocytes.
Upon fertilization of the macrogamets by the microgametes the oocysts are developed and
sporulate in the infected host.
Two different types of oocysts are produced, the thick-walled, which is commonly excreted
from the host and the thin-walled oocyst which is primarily involved in autoinfection.
Oocysts thick-walled are infective upon excretion, thus permitting direct and immediate fecaloral transmission.
The mature oocyst is excreted with fecal material and infects other individuals.
Clinical manifestations
In immunocompetent patients
Cryptosporidiosis is an acute, yet self-limiting diarrheal illness
(1-2 week duration), and symptoms include .
Frequent, watery diarrhea
Nausea
Vomiting
Abdominal cramps
Low-grade fever
For immunocompromised persons
Illness is much more severe .
Debilitating, cholera-like diarrhea (up to 20 liters/day)
Severe abdominal cramps
Malaise
Low-grade fever
Weight loss
Anorexia
C. parvum infection has also been identified in the biliary tract
(causing thickening of the gallbladder wall) and the respiratory
system.
 Symptoms:
 When a large number of humans in a community have diarrhea, the most





likely cause is C. parvum.
A small bolus of infection may cause mild diarrhea, whereas a larger intake
of organisms may cause more pronounced symptoms including
1- Copious watery diarrhea,
2- Cramping abdominal pain,
3- Flatulence and weight loss.
4- Severity and duration of symptoms are related to immuno-competence. In
AIDS patients, the organism may cause prolonged, severe diarrhea and the
organisms may invade the gallbladder, biliary tract and the lung
epithelium.

Pathogenesis
Upon oocyst excystation, four sporozoites are released which adhere
their apical ends to the surface of the intestinal mucosa
A sporozoite-specific lectin adherence factor has been identified
Following attachment cytokines are released from Epithelial cells which
activates macrophages
Activated macrophages release
histamine, serotonin, adenosine,
prostaglandins, leukotrienes, and platelet-activating factor which
induce loss of fluid and electrolytes
Epithelial cells are damaged
1. Cell death is a direct result of parasite invasion, multiplication.
2. Cell damage could occur through T cell-mediated inflammation,
producing villus atrophy and crypt hyperplasia
Either model produces distortion of villus structural design results in
nutrient malabsorption and diarrhea
Detection and Diagnosis
Staining methods were then developed to detect and identify
the oocysts directly from stool samples.
The modified acid-fast stain is traditionally used to most
reliably and specifically detect the presence of cryptosporidial
oocysts
ELISA or IFA, has recently been described in diagnosis of
cryptosporidiosis
PCR (Polymerase Chain Reaction) has been used for C.
parvum
Source: http://medlib.med.utah.edu
C. parvum - Cysts in stool Acid fast
 The following 13 Cryptosporidium species are currently accepted, on the basis of
host specificity, pathogenesis, morphology and genotyping :
 Cryptosporidium hominis, Cryptosporidium parvum, Cryptosporidium wrairi,
Cryptosporidium felis, Cryptosporidium canis, Cryptosporidium and ersoni, and
Cryptosporidium muris as infecting mammals;
 Cryptosporidium baileyi, Cryptosporidium meleagridis, and Cryptosporidium galli
as infecting birds;
 Cryptosporidium serpentis and Cryptosporidium saurophilum as infecting reptiles;
and Cryptosporidium molnari as infecting fish

Recent phylogenetic analyses based on sequencing of the small
subunit rRNA gene (18S rRNA) ,the hsp 70 gene ,or other housekeeping
or structural genes show a complex multispecies organization of the
genus Cryptosporidium.
The C. parvum complex includes subspecies that specifically infect cattle
(former genotype 2), pigs, kangaroos, ferrets, or monkeys
Treatment
No safe and effective therapy for cryptosporidial
enteritis has been successfully developed.
Since cryptosporidiosis is a self-limiting illness in
immunocompetent individuals, general, supportive
care is the only treatment for the illness.
Oral or intravenous rehydration and replacement of
electrolytes may be necessary