Protozoa causing diarrhea

1. Benhafacultyof medicine
Departmentof parasitology
Protozoa causing
diarrhea
Under supervision of : DR. Ghada & DR. Heba

2. Entamoeba histolytica
Entamoeba histolytica is a worldwidespread protozoon that causes
amebiasis,especially in countries with poor sanitation wherebarriers
between human feces and food and water supplies are inadequate.
Entamoeba histolytica passes its life cycle only in one host , that is
man,whereit habitates mucosaland submucosallayers of the large
intestine.The infective form of the parasiteare the for nucleated cysts,
that are transmitted through contaminated food ingested by the
host.Trophozoitephaseof the parasiteis responsiblefor producing the
characteristic lesion of amoebiasis.
Although mostcases of amebiasis are asymptomatic , 10-20% of
infections develop to amoebiasis that in severecases may lead to
death.Minor symptoms areloose stools(diarrhea) , stomach pain and
cramping.Rarely,theparasiteinvades into the liver tissue and cause
liver abscess.Ithas also been shown to spread to other parts of the
body such as lung and brain , but is not very common .Ittakes about 2
to 4 weeks to develop its symptoms.
The diagnosis of Entamoeba histolytica is difficult , becauseits
morphologically identical to Entamoeba dispar and differentiation
must be based on isoenzymatic or immunologic analysis.However , E.
histolytica cystcan be found in stool, while the trophozoitein diarrheic
stool, but the examination is not beneficial becausemost trophozoites
die in 30 minutes.In addition, E.histolytica can be also identified by
aspirates or biopsy samples obtained during colonoscopy or

3. surgery.Severalimmunodiagnostic tests are used for detection of
antibodies , such as IHAT and EIA teststhatare more suitable for
laboratories.Antigen detection may be usefulas it has improved
sensitivity and specifity of fecal antigen essays wioth the use of
monoclonal antibodies which can distinguish between E.histolytica and
E. dispar.
To treat invasiveamebiasis,metronidazoleis recommended for
amoebic liver abscesses (up to 10 cm sized abscesses).Tinidazoleis for
treatment of both intestinal and extraintestinal amebiasis.
Giardia lamblia is a flagellated parasitethat causes an infection in the
small intestine called giardiasis.Its geographicaldistribution is
cosmopolitan in areas wheresoil, food or water has been
contaminated with feces from infected humans or animals .
Giardia lamblia
Giardia lamblia exists in two forms , an active form called a trophozoite
and an inactive formcalled a cyst. the active trophozoite attaches to
the linig of the intestine with a sucker and is responsiblefor causing
the signs and symptoms of giardiasis . When ingested the cystis
activated by the stomach acid into trophozoite.Later on , the
trophozoiteforms the cyst that exits the in feces to spread infection to
others .
The most common way to get giardiasis is to drink water that contain
G. lamblia . Contaminated water can be in swimming pools , spas and
lakes.Sources of infection include animal feces , diapers and
agricultural runoff.

4. Some people are carriers of giardiasis withoutany symptoms
.Symptoms generally show up after two weeks .Acute symptoms
include diarrhea , stomach or abdominak cramps , nausea , vomiting
and dehydration that results from diarrhea.
Giardia can be diagnosed by examination of stool under the
microscopefor cysts .The best bestfor diagnosing giardiasis is antigen
testing of stool .Other tests include examination of fluid from the
duodenum or biopsy.
Giardiasis is treated by metronidazolefor 5-10 days .Tinidazole is also
added.

5. Cryptosporidium parvum
Cryptosporidium parvum Cryptosporidium parvum is a protozoan and
an obligate intracellular parasite (a parasite that cannotsurvive
without a host) that commonly causes an opportunistic infection in
immunocompromised hosts. Distribution: Cosmopolitian ,
immunocompromised peole are more susceptible
Life cycle: Oocyst→trophozoite→aporogony Epidemology : Fecal-
oral route is the most common mode of transmission of the disease.
The parasite can survivein food, water, soil or in vertebratehosts.
INCUBATIONPERIOD : Notprecisely known; 1-12 days is the likely
range with a mean of 7 days.
Pathology & manifestation : Cryptosporidiasis, a diarrhealdiseaseis
characterized by watery diarrhea, nausea and vomiting, dehydration,
abdominal cramps and fever. Symptoms usually resolvein 2-4 weeks in
immunocompetent hosts. Cryptosporidiosiscan also manifest as
pulmonary or tracheal disease, causing cough and fever. However,
these patients also manifest with the intestinal component of the
disease. Diagnosis: Identification of cysts in fecal smears or by
intestinal biopsy. Treatment: Symptomatic treatment of the diarrhea
by administering plenty of fluids to preventdehydration is the primary
management. A new drug, Nitazoxanide has been approved for the
treatment of cryptosporidiosis.

6. ospora cyatenansisCycl
Geographic distribution: Cyclosporiasis has been reported in many
countries , but most common in tropical and subtropicalareas.
lifecycle & transmition
lifecycle intracellularly within the host's epithelial cells and
gastrointestinaltract. Infection is transmitted through the fecal-oral
route, and begins when a person ingests oocysts in fecally
contaminated food or water. Various chemicals in the host's
gastrointestinaltract causethe oocysts to excyst and release
sporozoites; generally, two are observed per oocyst. After these
sporozoites invadethe epithelial cells, they undergo merogony, a form
of asexual reproduction that results in many daughter merozoites.
These daughter cells may either infect new host cells and initiate yet
another round of merogony or take on a sexual track via gametogony:
Daughter merozoites become male macrogamonts—which form many
microgametes—and female macrogamonts. After fertilization has
occurred via male microgamete fusion with female macrogamont, the
zygotematures into an oocystand ruptures the hostcell, from which
point it is passed with the stool. The oocysts that are passed arenot,
however, immediately infectious. Sporulation can take from one to
severalweeks, meaning person-to-person transmission is nota likely
problem. This differentiates C. cayentanensis from Cryptosporidium
parvum—a closely related organism that causes a similar disease—
since C. parvum oocysts areimmediately infectious upon release from
the host.
symptoms

7. C. cayentanensis causes gastroenteritis, with the extent of the illness
varying based on age, condition of the host, and sizeof the infectious
dose. Symptoms include "watery diarrhea, loss of appetite, weight loss,
abdominal bloating and cramping, increased flatulence, nausea,
fatigue, and low-gradefever", though this can be augmented in more
severecases by vomiting, substantial weight loss, excessivediarrhea,
and muscle aches. Typically, patients with a persistent watery diarrhea
lasting over several days may be suspected of harboring the disease,
especially if they have traveled to a region where the protozoan is
endemic. The incubation period in the host is typically around a week,
and illness can last six weeks before self-limiting. Unless treated, illness
may relapse. The more severeforms of the disease can occur in
immunocompromised patients, such as thosewith AIDS.
Treatment
The specific drug treatment for disease caused by Cyclospora
cayetanensis is the combination of two antibiotics—trimethoprim and
sulfamethoxazole(co-trimaxazole).
Sarcocystis
Itis a protozoan genus of parasites , the majority of species infect
mammals and some infect reptiles and birds.
Disribution:In wild Africa , Europe, China , India
Life cycle:There are two hostspecies , definitive host and its predator ,
intermediate host is its prey . The parasite reproduces sexually in the gut of
the definitive host , then passes with and is ingested by intermediate host ,
there it enters the muscle tissue . When intermediate hostis eaten by the
definitive host, the cycle is completed.

8. Mode of infection: Eating raw meat from cattle and pig
Clinical picture: Symptoms appear 3-6 hours after eating . These
include anorexia , nausea , abdominal pain , distension , diarrhea ,
dyspnea and tachycardia.
Diagnosis: By biopsy of infected muscle . Sarcocysts areidentifiable by
the hematoxylin and eosin stain. Inflammatory cells can be found in
cases of myositis and vasculitis.
Treatment: Albendazole,Metronidazole and coatrimoxozolefor
myositis.Corticosteroids areused for symptomatic relief.Amprolium
and selinomycin is effective in preventing severe illness and death.
Done by
Sarah ElSayed Ahmed Gobba (Entamoeba histolytica &
Giardia lamblia)
Asmaa Mohamed ElShamy (Cryptosporidium parvum)
Mina Attallah Iskandar (Cyclospora Cyetanensis)
Doha Saber Abdelbaky (Sarcocystis)