Article that gives complete idea of Zoonotic parasite cryptosporidium , its life cycle, morphology, mitigation and prophylactic measures.

1. Topic:
Cryptosporidium
By: Hooria Parvez

2. Cryptosporidium:
 Cryptosporidium is a single-celled parasite that belongs to the phylum
Apicomplexa.
 It is a protozoal parasite that causes Cryptosporidiosis, a disease of the
Gastrointestinal tract and Respiratory tract that causes diarrhea, acute
gastroenteritis (GIT), swelling of the nasal mucosa, and coughing.
 It was discovered by Tyzzer in 1907.
 Today more than 30 species of Cryptosporidium have been identified.
 Many species of Cryptosporidium are host specific.
 It is a zoonotic parasite that can be transferred from animals to
humans.

3. Classification:
KINGDOM Animalia
PHYLUM Apicomplexa
CLASS Conoidacida
ORDER Eucoccidiorida
FAMILY Cryptosporidiidae
GENUS Cryptosporidium
SPECIES C.parvum, C.hominis, etc.

4. Cryptosporidium species:
Cryptosporidium has a wide variety of species and most of them are host
specific having a specific location such as:
Species Host Site of infection
C.parvum/C.bovis Humans, mammals Small intestine
C.meleagridis Birds, mammals Intestine
C.suis Pigs Small intestine
C.tyzzeri Mice Small intestine
C.molnari Sea bream Intestine
C.muris Rodents Stomach
C.serpentis Reptiles Stomach
C.wrairi Ginea pigs Small intestine
C.varanii Reptiles Intestine

5. Morphological features:
 It has three developmental stages that are mironts, gamonts, and oocyst.
 Infective stage is oocyst which is a round or oval body that is 4µm to 6µm in
diameter.
 They have a smooth outer wall and contain four sporozoites (an invasive form of
the parasite).
 These sporozoites are arranged in pairs, one pair at each pole of the oocyst.
 Under EM the oocyst appear to have two layers:
• Electron-lucent
• Reflects light
Outer layer
• Electron-dense
• Does not reflect light
Inner layer

6. Structure of Cryptosporidium:
 Mature Cryptosporidium is a crescent-shaped cell possessing cellular
organelles along its length.
 On the posterior end there is a crystalloid body having salts and
water-soluble molecules.
 Have micronemes that are characteristic secretory organelles of
Phylum Apicomplexa (secrete proteases).
 Have a reduced form of mitochondria called mitosomes and are not
involved in energy production. They assemble cofactors for cellular
functions.
 Subpellicular microtubule helps to maintain structure and provide
support to the body.
 Conoid helps in invasion.
 Polar body detaches sporozoite from host cell

7. Transmission:
 Cryptosporidium is transmitted through contact with
infected faeces.
 It has no intermediate host.
 Parasite shed by the host remains in the environment and
waits for the contact with other host.
 It has an oral-faecal route of transmission.
 It is transmitted through drinking contaminated water or
eating contaminated food.
 By drinking unpasteurized milk.
 Swallowing Cryptosporidium by touching oocyst-
contaminated surfaces, doorknobs, toys, tables, or animal
skin.
Host
sheds
oocyst in
faeces
Settle in
environ-
ment
Again taken
up by host
through
oral cavity
Cause
disease
Oral-fecal
Route

8. Transmission:
 It can also be transmitted through
recreational water while swimming in pools,
lakes, or rivers.
 Day-care centers are another source of
infection in young children.
 Children below 5 years and elderly people
above 75 are more susceptible to the
disease.

9. Signs and Symptoms:
Signs and Symptoms of Cryptosporidium vary from person to person. But in GIT infection some of them are:
 Watery diarrhea
 Abdominal pain
 Weight loss
 Nausea
 Loss of appetite
If it infects the Respiratory tract then symptoms may be:
 Coughing
 Nasal discharge
 Voice change
 Inflamed trachea causing pain

10. Life Cycle:
1) Ingestion of Oocyst:
When a host ingests an oocyst, the parasite reaches GIT and starts its excystation
process.
2) Invasion of Epithelium:
Through excystation, sporozoites are released and infect epithelial cells of the GIT
and sometimes also affect respiratory epithelium. These sporozoites develop into
trophozites.
3) Asexual Reproduction:
In these cells, the trophozoites undergo asexual reproduction and develop into
Shizonts and then into meronts.

11. Life Cycle Cont.
4) Gametogamy:
Meronts change into merozoites. After that, gametogony occurs and two types of gametes are produced.
Male gametes are called microgamonts and female gametes are called macrogamonts.
5) Sexual Reproduction:
These two gametes fuse (sexual reproduction) and produce oocysts. The oocysts are of two types
 Thick-walled (They are commonly excreted by the infected host)
 Thin-walled (They are involved in autoinfection)
In autoinfection, oocysts develop into adult forms without ever leaving the body, they may excyst and begin
the cycle inside the host again).
6) Oocysts in Environment:
After excretion, the eggs (oocysts) become infective. They wait to be ingested by another host.

13. Pathogenicity:
Pathogenicity of Cryptosporidium varies in Immunocompetent and Immunocompromised patients.
People with weaker immune systems are at greater risk to get infected and Cryptosporidium can be fatal in
them.
 IN IMMUNOCOMPETENT PATIENTS:
 The disease is generally asymptomatic.
 Cause watery diarrhea, abdominal pain and weight loss.
 Does not require treatment with medicines.
 IN IMMUNOCOMPROMISED PATIENTS:
 Diarrhea can be chronic, persistent, and may last for several months, with severe coughing.
 The fluid and electrolyte level falls dangerously low.
 Severe dehydration can be life threatening.

14. Factors affecting Pathogenicity:
[1] Health Status:
 Individuals having a history of cancer, an organ
transplant, a stem cell transplant, HIV/AIDS, any
medical therapy that suppresses immune system
activity, and hormonal therapies are at greater risk
to develop cryptosporidiosis, due to a weakened
immune system.
 Underlying health conditions like malnutrition (i.e.
anorexia) can also reduce the ability to fight
infection.

15. Factors affecting Pathogenicity:
[2] Genetic Factors:
 The genetic background also plays its part in the elevated
infection of Cryptosporidium.
 For example, sometimes variation occurs in TLR4 and CD14
genes. Pathogens bind to these receptors and induce a
cytokine release.
 But at times pathogens like Cryptosporidium, having a small
infectious dose, enter in larger numbers. They bind to these
receptors and cause the immune system to respond violently,
resulting in an excessive cytokine release. This condition is
called a ‘cytokine storm’ and is life-threatening.

16. Factors affecting Pathogenicity:
[3] Age of host:
 This factor has been an area of interest for many researchers.
Cryptosporidium has been categorized using the age of the host
and its occurrence in them.
 According to it, C.parvum is predominant in suckling calves,
C.bovis and C.ryanae are predominant in post-weaned calves
and C.andersoni causes disease mostly in adults.
 Further studies revealed that Cryptosporidium prevalence
reduces with age due to immunity and exposure. But modern
studies have shown that these patterns are not consistent and
exceptions are always there. Humans under the age of 5 and
above the age of 75 are at greater risk.

17. Factors affecting Pathogenicity:
[4] Environmental conditions:
 Different environmental conditions can affect
the survival and transfer of pathogens like
temperature, humidity, and sanitation
practices.
 Moreover, it’s highly chlorine tolerant and can
tolerate chloramines and chlorine dioxide
which means that even after disinfecting
water by chlorination, the survival of
Cryptosporidium is a high chance.

18. Laboratory Diagnosis:
 Cryptosporidium is diagnosed by Faecal examination.
 A thin faecal smear with special staining is done to identify
the presence of eggs.
 The irregular oocyst-shedding pattern of the host requires at
least three different samples to be studied to prevent false
negative results.
 PCR technique is also used to diagnose Cryptosporidium as it
can also detect it up to species level.
 Other techniques like ELISA/EIA are also used to check the
presence of antibodies in the host against the specific
parasite.
C.Parvum

19. Laboratory Diagnosis:
 For diagnosis of Respiratory
Cryptosporidiosis, the sample is
taken from the sputum.
 Another method called DFA (Direct
fluorescent antibody) is used. This
method involves the use of
fluorescent-labeled antibodies that
when attach to the parasitic oocyst
make it glow and illuminate it under
a fluorescent microscope.

20. Treatment:
o To treat both GIT and RT Cryptosporidium a drug
called “Nitazoxanide” is used. Its dose varies for
people of different age groups and it is given for three
days.
o Mild Cryptosporidium can be treated by drinking
plenty of water to prevent dehydration.
o By taking a balanced diet and avoiding alcohol,
caffeine, tea, and soft drinks.
o For infants, doctors recommend Fluid-replacement
therapy.
o For people with AIDS, anti-retroviral therapy is used to
cure it.
Age Dose
Adults 500mg twice a day
1-3 years 100mg twice a day
4-11 200mg twice a day

21. Prevention:
 No disinfecting method has been proven much effective
against Cryptosporidium.
 It has high chlorine tolerance and even after chlorinating
drinking water or boiling it, Cryptosporidium can still be
present, keeping the water contaminated.
 Therefore, water should be filtered properly multiple times
before use.
 As Cryptosporidium spreads through recreational water,
therefore swimming pools should be disinfected properly.
 Milk should be pasteurized before drinking.
 Hands should be properly washed after contact with animals.

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