1. Fall 2022
Microbiology II course
Parasitology- Week 10 (Intestinal & Urogenital Protozoa)
By
Dr. Khawaja Shakeel Ahmed
2. The Gastrointestinal Systems
• The gastrointestinal system enables the body to DIGEST
complex food substances which need to be broken down into
simpler forms so that they can be utilized by the body's cells.
The gastrointestinal system must also remove WASTE
together with the urinary system.
• The alimentary canal is a continuous tube from mouth to
anus, sometimes known as the DIGESTIVE TRACT.
• There are three main sections:
• The mouth cavity, pharynx, oesophagus and stomach
• The small intestine (duodenum, jejunum, and ileum)
• The large intestine (caecum, colon, and rectum)
3. The Urinary Systems
• The urinary system removes waste from the body.
It is also important for keeping the body in
homeostasis (balance) by controlling the
composition and volume of blood.
• The organs of the urinary system are:
•
•
•
•
Two kidneys
The two ureters
The bladder
The urethra.
4. Intestinal & Urogenital PROTOZOA
• Numerous protozoa inhabit the gastro-intestinal tract of humans.
• The majority of the protozoa are non-pathogenic commensals, or only
result in mild disease.
• Some of these organisms can cause severe disease under certain
circumstances. For example, Giardia lamblia can cause severe acute
diarrhea which may lead to a chronic diarrhea and nutritional disorders.
• Entamoeba histolytica can become a highly virulent and invasive
organism that causes a potentially lethal systemic disease.
• Trichomonas vaginalis It infects the urogenital tract and causes
a sexually-transmitted disease.
4
5. Protozoology
• The major protozoan pathogens are grouped according to the location in the
body where they most frequently cause disease:
A. Within the intestinal tract, there are three common organisms—
1. The flagellate: Giardia lamblia
2. Amoeba: Entamoeba histolytica
3. Sporozoan: Cryptosporidium parvum
4. Ciliata: Balantidium coli
B. In the urogenital tract, the flagellate Trichomonas vaginalis is the important
pathogen.
6. The intestinal parasite life cycle:
The fecal Oral Life Cycle
Intestinal protozoa are transmitted
by the fecal-oral route and tend to
exhibit similar life cycles consisting of
a cyst stage and a trophozoite stage.
Fecal-oral transmission involves the
ingestion of food or water
contaminated with cysts.
After ingestion by an appropriate host, the cysts transform into trophozoites
which exhibit an active metabolism and are usually motile.
• The parasite takes up nutrients and undergoes asexual replication during the
trophic phase. Some of the trophozoites will develop into cysts instead of
undergoing replication.
7. The fecal Oral Life Cycle
• Cysts are characterized by a
resistant wall and are excreted
with the feces.
• The cyst wall functions to protect the organism from desiccation in the
external environment as the parasite undergoes a relatively dormant period
waiting to be ingested by the next host.
• Factors which increase the likelihood of ingesting material contaminated
with fecal material play a role in the transmission of this intestinal protozoa.
In general, situations involving close human-human contact and unhygienic
conditions promote transmission.
8. Intestinal and Urogenital tract
Major protozoa
Location
Species
Giardia lamblia
Intestinal tract Entamoeba histolytica
Disease
Giardiasis
Amebiasis
Cryptosporidium Parvum Cryptosporidiosis
Balantidium coli
Urogenital tract Trichomonas vaginalis
balantidiasis
Trichomoniasis
9. Intestinal Protozoa
1- Giardia lamblia
• Giardia lamblia (also known as G. duodenalis)
is a protozoan parasite that colonizes the upper
portions of the small intestine and cause
giardiasis. It has a worldwide distribution and
is the most common protozoan isolated from
human stools. The incidence is estimated at 200
million clinical cases per year.
• Giardiasis is especially prevalent in children and particularly those children in
institutions or day-care centers.
10. Disease
• Typically Giardia is non-invasive and often
results in asymptomatic infections.
• Symptomatic giardiasis is characterized by
acute or chronic diarrhea and/or other gastro-
intestinal manifestations.
• Giardia lamblia causes giardiasis. The trophozoite causes inflammation of the
duodenal mucosa, leading to malabsorption of protein and fat.
11. Intestinal & Urogenital Protozoa
Giardia
The life cycle consists of two stages:
A- The cyst: The oval cyst is thick-walled with four nuclei and several internal
fibers. Each cyst gives rise to two trophozoites during excystation in the intestinal
tract.
B- The trophozoite : Is pear-shaped with two nuclei, four pairs of flagella, and a
suction disk with which it attaches to the intestinal wall.
12. Transmission
• Giardia occurs worldwide. Transmission is via
ingestion of contaminated water or food, or direct
person-to-person spread via the faecal- oral route.
• Hikers who drink untreated stream water are
frequently infected.
• Many species of mammals as well as humans act as
the reservoirs.
• They pass cysts in the stool, which then
contaminates water sources.
• The zoonotic transmission of Giardia is
controversial and has not been unambiguously
13. Treatment:
• The treatment of choice is metronidazole (Flagyl).
Prevention:
• Prevention involves drinking boiled, filtered water in endemic areas and while
hiking. No prophylactic drug or vaccine is available.
14. 2- Entamoeba histolytica
Important Properties
• Habitat: Large intestine
• Disease: Amoebic dysentery, amoebic liver abscess (Hepatic Amoebiasis)
The life cycle has two stages:
A- The nonmotile cyst: Infective stage (and diagnostic stage).
B- The motile amoeba (trophozoite): Feeding stage.
• Usually, the cysts have 4 nuclei. They are not highly resistant and are readily killed by
boiling but not by chlorination of water supplies. They are removed by filtration of
water.
• The trophozoite is found within the intestinal and extraintestinal lesions and in diarrheal
stools. The cyst predominates in nondiarrheal stools.
15. Transmission
• The organism is acquired by ingestion of
cysts that are transmitted primarily by the
fecal–oral route in contaminated food
and water.
• There is no animal reservoir. The ingested
cysts differentiate into trophozoites which
colonize the cecum and colon.
• Top blue arrow shows cysts being ingested. Within the intestine, the cyst produces
trophozoites that cause amebic dysentery in the colon and can spread to the liver (most
often), lung, and brain (Boxes A and B).
• Bottom blue arrow shows cysts and trophozoites being passed in the stool and entering the
environment. Red arrow indicates survival of cysts in the environment.
16. Diseases
• Entamoeba histolytica causes amebic dysentery and
liver abscess (Hepatic Amoebiasis).
• It is the third leading parasitic cause of mortality, after malaria and
schistosomiasis.
• The incubation period is highly variable from 1–4 months.
• The clinical course is characterized by prolonged latency, relapses and
intermissions.
• The majority of infected humans (80–99%) are asymptomatic, invasive
amoebiasis causes disabling illness in an estimated 50 million of people
and causes 50,000 deaths annually, mostly in the tropical belt of Asia,
Africa, and Latin America.
17. Diseases
• Cysts pass through stomach, and
trophozoite release from the effect of
gastric acid.
• Trophozoites cause necrosis
• Invasion into the deep mucosa and
peritoneal cavity may occur.
• By far the most frequent site of
systemic disease is the liver, where
abscesses containing trophozoites
form, but sometimes other organs
like lungs, brains, and heart can be
infected.
18. • Entamoeba histolytica. flask-shaped ulcer forms in colonic mucosa resulting in
bloody diarrhea.
• Liver abscess damage – tube of “chocolate puss” from abscess
19. Treatment
• The treatment of choice for symptomatic intestinal amebiasis or hepatic
abscesses is metronidazole (Flagyl) or tinidazole.
• Asymptomatic cyst carriers should be treated with iodoquinol or
paromomycin.
Prevention
• Prevention involves avoiding fecal contamination of food and water and
observing good personal hygiene such as handwashing.
20. 3- Cryptosporidium
❑is worldwide in distribution.
❑Its importance as a pathogen causing diarrohea in animals
and human.
❑Cryptosporidium has assumed great importance that can
cause of intractable diarrohea, in AIDS patients, and
immunocompromised subjects.
❑species of cryptosporidium, C. hominis and C. parvum
mostly cause human infections
❑infective form and diagnostic form of the parasite is
oocyst, which 4 crescent shaped sporozoites
❑can survive chlrorinated water and remain viable in the
environment for long periods, as it is very hard and resistant to
most disinfectants and temperature upto 60°C.
20
Oocysts of cryptosporidium
parvum. A. Thickwalled
oocyst; B. Thin walled
oocyst
21. Cryptosporidium Parvum
• Habitat
C. parvum inhabits the small intestine. It may
also be found in stomach, appendix, colon,
rectum, and pulomonary tree.
• Life Cycle
The parasite complete its life cycle, sexual and
asexual phases in a single host
• Reservoirs:
Man, cattle, cat, and dog.
.
22. Cryptosporidium Parvum
Mode of transmission:
Man acquires infection by:
• Ingestion of food and water
contaminated with feces containing
oocysts (human or animals)
• Infective form: Sporulated oocysts.
• The oocyst contains 4 sporozoites, which
are released in the intestine.
23. Pathogenicity and Clinical Features
• Humans get infection either by ingestion of contaminated
food and water with feces or by direct contact with
infected animals.
• Human to human transmission can also occur. Incubation
period is 2–14 days.
• Clinical manifestations of c. parvum infection vary
depending upon the immune status of the host.
• Infection in healthy immunocompetent persons may be asymptomatic or cause a self-limiting
febrile illness, with watery diarrhea in conjunction with abdominal pain, nausea, and weight
loss. It can also cause childhood and traveler's diarrhea, as well as waterborne outbreaks.
• In immunocompromised hosts, especially those with AIDS can be chronic, persistent, and
remarkably profuse, causing significant fluid and electrolyte depletion, weight loss,
23
24. • Laboratory Diagnosis
Stool Examination
• Treatment
No chemotherapeutic agent effective against cryptosporidium has been
identified, although nitazomamide may be partially effective in few patients
with AIDS.
24
25. Balantidium coli
• It is the only ciliate parasite of humans
• Largest protozoan parasite residing in large
intestine.
It occurs in 2 stages: trophozoite and cyst.
• Trophozoite live in the large intestine, it is oval shaped with a slightly pointed
anterior end with a groove and rounded posterior end has a small anal pore,
cytopyge and has a large kidney- shaped macronucleus and small micronucleus.
• Cyst: It is the infective stage of the parasite. Macronucleus and micronucleus are
present .
• Habitat: B. coli resides in the large intestine of man, pigs, and monkeys.
• The motility of trophozoite is due to the presence of short delicate cilia over the
25entire surface of the body.
26. Mode of transmission:
• Balantidiasis is a zoonosis. Human beings
acquire infection by ingestion of food and water
contaminated with feces containing the cysts
of B. coli.
• Infection is acquired from pigs and other
animal reservoirs or from human carriers.
• From each cyst, a single trophozoite is
produced which migrates to large intestine
• Unlike E. histolytica, B. coli does not invade liver
or any other extraintestinal sites.
26
27. Treatment
• Tetracycline is the drug of choice, Metronidazole has also been reported to be useful in some
cases.
Clinical features:
• Most infections are asymptomatic.
• Symptomatic disease or balantidiasis resembles amoebiasis causing diarrhea or frank
dysentery with abdominal colic, nausea, and vomiting.
Prevention:
• Avoiding contamination of food and water and treatment of infected pigs and persons.
27
28. Urogenital Protozoa
Trichomonas vaginalis
• T. vaginalis is likely the most common non-viral sexually
transmitted infection (STI) in the world. It is as an
important source of reproductive morbidity, a facilitator
of HIV transmission and acquisition, and thus it is an
important public health problem
• Trichomonas vaginalis exists only as a trophozoite; there is no cyst form. Trophozoite
inhabits the vagina in female while it inhabits the prostate, seminal vesicles and urethra in
male.
• The trophozoites of Trichomonas have a single nucleus, four anterior flagella and a single
lateral flagellum attached to body to form an undulating membrane. They are actively motile,
pear-shaped.
30. Disease
• Trichomonas vaginalis causes trichomoniasis
which is a sexually transmitted disease (STD).
• T. vaginalis, despite its name, infects both men
and women. In females the organism primarily
inhabits the vagina, and in males it is usually
found in the urethra, prostate or epididymis.
• Infection in men is usually asymptomatic, but
about 10% of infected men have urethritis
31. Symptoms
• Many people who suffer from Trichomonas do not exhibit any signs or symptoms.
• The symptoms may be mild itching to severe inflammation.
• Pregnant women who are infected with trichomoniasis are at risk of their membranes rupturing
prematurely, thereby delivering children prematurely with low birth weight
• Women who exhibit symptoms display characteristics that include irritation/burning/redness in
the genital area, pain during sexual intercourse or urination, and vaginal discharge that has a bad
odor (severe vaginitis).
• The vaginal discharge may be of different colors such as yellow, gray, white, or green.
Transmission
• The organism is transmitted by sexual contact. It is found only in humans; there is no animal
reservoir. Trichomoniasis is one of the most common infections worldwide. Asymptomatic
infections are common in both men and women.
32. Treatment:
• The drug of choice is metronidazole (Flagyl).
Prevention:
• The prevention involves avoidance of unhealthy relationships. No prophylactic
drug or vaccine is available.
33. Organism Mode of transmission Diagnosis Treatment
Entamoeba Ingestion of cysts in
food
Trophozoites or
cysts in stool;
serology
Metronidazole or
tinidazole
Giardia Ingestion of cysts in
food
Ingestion of cysts in
food
Trophozoites or cysts in Metronidazole or
stoolstinidazole
Cysts on acid-fast stain
Nitazoxanide in
immunocompetent;
paromomycin may be
useful in AIDS patient
Cryptosporidium
Trichomonas Sexual Trophozoites in wet
mount
Metronidazole or
tinidazole
