Cryptosporidium is a coccidian protozoan parasite, which
discovery is associated with E.E. Tyzzer, in 1907 but considered
medically unimportant to humans until the first cases of cryptosporidiosis in
humans were reported in 1976 by [1,2]. Electron microscopic examination of the
intestinal mucosa led to the discovery that Cryptosporidium was the
infectious species in humans. In the early 1980s, the strong association
between cases of cryptosporidiosis and immunodeficient individuals
brought Cryptosporidium to the head as a ubiquitous human
Cryptosporidium can infect several different hosts, can survive
most environments for long periods of time due to its "hardy cyst"
and inhabits all climates and locales . Cryptosporidium was first
recognized as a waterborne pathogen during an outbreak in Braun Station, Texas,
where more than 2,000 individuals were afflicted with cryptosporidiosis [4,5].
complete description of the morphological features of each life cycle stage
consists of oocyst, sporozoite, trophozoite, merozoite, microgametocyte,
macrogametocyte of Cryptosporidium is provided in the 1994 .
Cryptosporidium is taxonomically classified as a Sporozoa,
since its oocyst releases four sporozoites (its motile infectious agents) upon
The life cycle has both sexual and asexual cycles, and there are six distinct
developmental stages . After ingestion, the oocysts
excyst in the small intestine. They release sporozoites that attach to the
microvilli of the epithelial cells of the small intestine. From there they
become trophozoites that reproduce asexually by fission, a process known as
schizogony. The trophozoites develop into Type 1 meronts that contain 8 daughter cells . These daughter cells are Type 1 merozoites, which get
released by the meronts. Some of these merozoites can cause autoinfection by
attaching to epithelial cells. Others of these merozoites become Type II
meronts , which
contain 4 Type II merozoites . These
merozoites get released and they attach to the epithelial cells. From there
they become either macrogamonts or microgamonts . These are the female and male
sexual forms, respectively . This stage, when sexual forms arise, is called gametogony
formed by microgametes from the microgamont penetrating the macrogamonts. The
zygotes develop into oocysts of two types . 20% of oocysts have thin walls
and can re infect the host by rupturing and releasing sporozoites that start
the process over again . The
thick-walled oocysts are excreted into the environment . The oocysts are mature and infective
upon being excreted . They can
survive in the environment for months . The cycle begins anew when these oocysts are ingested by a
new host. Below is a visual representation of the Cryptosporidium life cycle .
The various symptoms
of cryptosporidiosis differ between immunocompetent and immunocompromised
individuals. In immunocompetent patients, cryptosporidiosis is an acute, yet
self-limiting diarrheal illness (1-2 week duration), and symptoms are: 
persons, the illness is much more severe:
Due to lack of tissue specificity, C.
parvum infection has also
been identified in the biliary tract and the respiratory system .
has been reported in six continents and identified in patients aged 3 days to
95 years old . Transmission is
usually fecal-oral route, often through water contaminated by livestock mammal
feces. Persons most likely to be infected by Cryptosporidium are: [2,3,6,12,13]
and younger children in day-care centers
whose drinking water is unfiltered and untreated
in farming practices such as lambing, calving, and muck-spreading
in sexual practices that brings a person into oral contact with feces of
an infected individual
in a nosocomial setting with other infected patients or health-care
who come in contact with farm animals
to areas with untreated water
in densely populated urban areas
of infected household pets (rare)
infection can consequently be transmitted from fecally contaminated food and
water, from animal-person contact, and through person-person contact .
Food and water
One most important
outbreak in Milwaukee in 1993 affected over 400,000 persons. Outbreaks such as
these usually result from drinking water taken from surface water sources such
as lakes and rivers .
Swimming pools and water park wave pools have also been associated with
outbreaks of cryptosporidiosis. Also, untreated groundwater or well water
public drinking water supplies can be sources of contamination.
The highly environmentally
resistant cyst of C. parvum allows the pathogen to survive a
variety of drinking water filtrations and chemical treatments such as
chlorination. All waterborne outbreaks of cryptosporidiosis have occurred in
commmunities where the local utilities met all state and federal drinking water
Food can also be a source of
transmission, when either an infected person or an asymptomatic carrier
contaminates a food supply . The oocysts do not survive cooking, but food
contamination can occur in beverages, salads, or other foods not heated or
cooked after handling.
Transmission of C.
parvum from household pets is
rare, but there is a definite association between calves and humans--approximately
50% of calves shed oocysts and the pathogen is present on upwards of 90% of all
dairy farms . Pets have not
often been implicated as a source of infection and are not considered a major
risk factor for acquisition of cryptosporidiosis .
Cryptosporidium transmission occurs at a high frequency
in day-care centers, where infants or younger children are clustered within
classrooms; share bathrooms and common play grounds, or necessitate frequent
diaper-changing . Day-care employees can
become easily infected by C.
parvum through careless
diaper-changing or through washing the laundry of infected children. Day-care
workers can then spread the pathogen to their families at home.
Nosocomial situations are
also a major medium for cryptosporidial transmission. There have been several
reports of both transmission from patients to health care staff and
patient-to-patient transmission . This "environmental contamination" raises the
possibility of aerosol transmission of C.
parvum from person-to-person.
Various routes of transmission such as aerosol infection is quite likely, since Cryptosporidium oocysts are shed in large numbers
during acute infection and are immediately infective to others .
excystation, four sporozoites are released which adhere their apical ends to
the surface of the intestinal mucosa . Below is a phase contrast photograph of sporozoite
release from the Cryptosporidium oocyst . A sporozoite-specific lectin
adherence factor has been identified as the agent of attachment to the
intestinal surface . After sporozoite attachment, it has been hypothesized
that the epithelial mucosa cells release cytokines that activate resident
phagocytes . These activated cells release soluble factors that
increase intestinal secretion of water and chloride and also inhibit
absorption. These soluble factors include histamine, serotonin, adenosine,
prostaglandins, leukotrienes, and platelet-activating factor, and they act on
various substrates, including enteric nerves and on the epithelial cells
themselves . Consequently, epithelial cells are damaged by one of two
death is a direct result of parasite invasion, multiplication, and
damage could occur through T cell-mediated inflammation, producing villus
atrophy and crypt hyperplasia
distortion of villus construction and is accompanied by nutrient malabsorption
and diarrhea .
When C. parvum was first identified as a human
pathogen, diagnosis was made by a biopsy of intestinal tissue . However, this method of testing can give false negatives
due the "patchy" nature of the intestinal parasitic infection .
Staining methods were then developed to detect and identify the oocysts
directly from stool samples. The modified acid-fast stain is usually used to
most reliably and specifically detect the presence of cryptosporidial oocysts . Immunologically, anti-cryptosporidial IgM, IgG, and IgA can be
detected by the enzyme-linked immunoabsorbent assay (ELISA) or by the antibody
immunofluorescence assay (IFA), but neither of these assays can provide a
direct diagnosis of cryptosporidiosis. Traditional enzyme immunoassays (EIA)
can provide rapid detection of oocysts with little tediousness. EIA can be used
to analyze environmental samples. 
reported a positive EIA detection of one oocyst.  reported EIA
sensitivity equal to microscopic examination in both environmental and human
Recently, new genetic
methods of detecting C. parvum have been developed, using PCR or
other DNA-based for
the detection of Cryptosporidium in drinking water. Oocysts were detected by PCR in wastewater, surface waters,
and drinking water, but the sensitivity of the PCR assay was inhibited by
"uncharacterized components in the samples"[18,23].
No protected and
effective therapy for cryptosporidial has been successfully developed. Since
cryptosporidiosis is a self-limiting illness in immunocompetent individuals,
general care is the only treatment for the illness. Oral or intravenous
rehydration and replacement of electrolytes may be essential for particularly
voluminous, watery diarrhea. Oral rehydration treatment can include Gatorade,
bouillon, or oral rehydration solution, containing glucose, sodium bicarbonate,
and potassium .
patients with cryptosporidiosis, quite a few antimicrobial agents have been
tested as treatments. Antibiotics such as spiramycin and dicalzuril sodium have
produced partial responses in patients, but have not reliable, reproducible
results . However, one
particular antimicrobial agent, paromomycin, has been shown to decrease the
intensity of infection and improve intestinal function and morphology .
serological antibodies do not provide any protection from cryptosporidial
infection, but more than a few studies have been done to show that antibodies
in the intestinal lumen may help clear or even prevent infection. The feeding
of bovine colostral immunoglobulin to patients has been shown to ameliorate
symptoms of Cryptosporidium infection
in humans, and it has also been shown that the release of intestinal IgA
accompanies this clearance of infection11. Additionally,
anti-sporozoite antibodies have blocked the infectivity of C. parvum sporozoites in mice by inhibiting
their ability to attach to the surface of the intestininal mucosa. A more
recent study by , reproduced the
inhibition of C. parvum infection by hyperimmune bovine
colostrum in vitro, providing an ideal system through which cryptosporidial
infection can be studied in the laboratory. The mean number of intracellular
parasites per host cell was reduced by 61% upon introducing HBC Ig antibodies
with a concentration of 1 mg/ml IgG. This investigation also purified
antibodies from HBC Ig on Western blots of Cryptosporidium
proteins and found that they, too, inhibited C. parvum infectivity in vitro .
WATER: PURIFICATION AND FILTERATION
Current data is not
adequate to advise all immunodeficient persons to boil or avoid tap water, but
the risks involved are high enough that, until the health risk of drinking
water containing small number of Cryptosporidium oocysts is clearly defined, it is
advised that these individuals boil all water intended for drinking for at
least one minute.
Household water filtration
system or drinking bottled water can reduce the risk of Cryptosporidium infection .
Municipal water utilities provide relatively good protection against
water-borne Cryptosporidium infection. Municipal drinking water is
purified two ways: through chemical treatments like, chlorination and through
filtration . Chlorine dioxide and monochloramine were also ineffective
in inactivating C. parvum oocysts in drinking water26.
Filtration is better for removing C.
parvum oocysts from municipal
drinking water. In recent years, ultra-fine membranes have been developed to
remove various contaminants from drinking water . Hence, C. parvum oocysts can be as small as 4 microns,
at least micro filtration is needed to reliably remove oocysts from the water
supply . Since Cryptosporidium oocysts are so resistant to chemical
disinfectants, ultra filtration or reverse osmosis would provide ideal
protection against waterborne outbreaks via drinking water. Clarify the
relationship between low numbers of oocysts in drinking water and the frequency
of cryptosporidial infection. Determine the asymptomatic carrier rate for Cryptosporidium in immunocompromised persons and the
chance that these individuals will develop cryptosporidiosis when their CD4
counts drop to a low level. Calculate the relative risks of infection from
drinking water, contact with animals, unsafe sexual practices, and nosocomial
contact to see where focus on preventative strategies should be placed. Improve
state and federal communication for reporting cases of cryptosporidiosis and
identifying outbreaks. Continue to develop more effective therapies for
ameliorating cryptosporidiosis symptoms.
According to the epidemiology, the cases of cryptosporidiosis
globally have been observed due to the consumption of contaminated water and
food as it’s a potential fecal oral pathogen. In the same way, poor hygiene is
also one of the alarming factors for the transmission of this parasite, so
there is a need to encourage the hand washing practices in our society and as
possibly avoid unfiltered and unclean water. Like many fecal-oral pathogens, it
can also be transmitted by contaminated food or poor hygiene. Proper and
frequent hand washing has to be promoted in order to break the chain of
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