INTESTINAL PROTOZOA

-Balantidium coli
-Cryptosporidium
-Cyclospora
-Isospora
-Sarcocystis
-Microsporidia

FREE LIVING AMOEBAE

-Naegleria
-Acanthamoeba
 CLASSIFICATION OF PROTOZOA
Phylum Genus Species Habitat Pathogenic effect

Sarcomastigophora Entamoeba E.histolytica Large Dysetery, liver abscess

intestine
Intestinal flagellate Giardia G.intestinalis Small Diarrhoea
intestine
Genital flagellate Trichomonas T.vaginalis Vagina Vaginitis
Blood and tissue Trypanosoma T.brucei Blood, Sleeping sicknesss
flagellates lymph node, (African trypanosomiasis)
C.N.S

T.cruzi Heart, Chagas ’ disease

nervous
system

Leishmania L.donovani R.E.system Kala azar& dermal

leishmanoid
L.tropica Skin Oriental sore
L.brasiliensis Oronasal Espundia
mucosa
Phylum Genus Species Habitat Pathogenic effect
Ciliophora Balantidium B.coli Large intestine Dysentery

Apicomplexa Plasmodium RBC Malaria

Toxoplasma T.gondii R.E system Encephalomyelitis

choroidoretinitis
Cryptosporidium C.parvum Large intestine cryptosporidiosis

Cyclospora C.cayentanensis Epi cells of intestine Cyclosporiasis

Isospora I.belli Epi cells ofintestine Diarrhoea

Sarcocystis S.hominis, Large intestine Sarcocystosis

S.suihominis
Microspora Enterocytozoon E. bieuneusi Epi cells of intestine Microsporidiasis

Encephalitozoon E. intestinalis Epi cells of intestine Microsporidiasis

Balantidium coli
Introduction

• Balantidium coli is the largest protozoan and the only ciliate

that infects human beings

• Balantidiasis /ciliate dysentery- type of dysentery which

cannot be distinguished from amoebic dysentery clinically.

• Balantidiasis is a zoonosis, the principal reservoir being pig

Geographical distribution : worldwide

Habitat : large intestine of man/pigs/monkeys

Morphology:
Occurs in two forms
- Trophozoite/vegetative form
- Cyst stage
Trophozoite
• Shape-oval
• Size-60-70μ x 40-50μ
• Motile –cilia
• Nuclei-large kidney shaped
macronucleus and one small
micronucleus
• Ant. end-narrow, cytostome and
cytopharynx
• Post end-broad,small pore(cytopyge)
• Two contractile vacuoles
• Many food vacuoles/tissue
debris/WBCs/RBCs in the cytoplasm
Cyst stage
• Oval
• 50-60μm diameter
• Nucleus-2nuclei (macro/micro)
• Cyst wall- double
layered/thick/transparent
Life cycle
Definitive host - pig is the natural host/man-accidental host

Infection occurs by ingestion of cyst

Cyst hatches out into trophozoite in small intestine

Multiply in intestine by binary fission and form large number of

trophozoites

When conditions become unfavorable for the survival of

trophozoites, encystment occurs in large
intestine

Mature cysts are passed in the feces

Pathogenesis
SOI - pigs/infected persons
MOT - ingestion
SOE - trophozoites can invade the mucosa of the large
intestine (caecum and colon)
- The parasite secretes a substance called
hyaluronidase enzyme, which helps degrade
intestinal tissue and facilitates penetration of the
mucosa and cause ulcerations resembling the
lesions
of amoebiasis.
C/F
-resembles amoebiasis
• Diarrhoea/frank dysentery
• Abdominal colic
• Tenesmus
• Nausea
• Vomiting

Complications
• Intestinal perforation
• Peritonitis
• Note : no hepatic involvement
Lab diagnosis
• Demonstration of trophozoite/cyst in stool sample by saline
and iodine preparation

Prophylaxis
• Protection of food and drink from contamination with human
and animal feces
• Personal hygiene

Treatment
• Tetracycline 500mg qdsx10 days
• Metronidazole
• Nitroimidazole
Apicomplexa

-Cryptosporidium
-Cyclospora
-Isospora
-Sarcocystis
Complex life cyle
• Asexual schizogony inside the epi. cells of intestine-
• Trophozoite
• Schizont
• Merozoite

• Sexual cycle
• Merozoites sexual differentiation into male/female
forms(microgametocyte and macrogametocyte male
and female gametes fertilization
 Cryptosporidium
• C.parvum causes cryptosporidiosis, a parasitic disease of bird,
fish, reptiles
• 1976- reported in humans
• The disease was found in immuno compromized, causing
severe diarrhoea.

Geographical distribution: world wide

Habitat : the parasite is intracellular

: found in jejunum/ileum
Morphology
• Oocyst is the infective form
• Exists in 2 forms
• Thick walled and thinwalled oocysts
• Spherical/ oval/colourless/1.5-5μ diameter
• Highly refractile
• Four elongated sporozoites are present in
both the oocysts(sporulated)
• Thick walled oocysts are excreted in the
stool
• Thin walled oocysts cause autoinfection
Life cycle
 Life Cycle

parasite lab.4 by l.wafaa

21
menawi
Life cycle in host
 Clinical Features
- Wide range of manifestations, from asymptomatic infections to
severe, life-threatening illness.

- Incubation period is from 2 to 10 days.

- Watery diarrhea, accompanied by dehydration, and malabsorption

syndrome.

- In immunocompetent persons, symptoms are usually short lived

(1 to 2 weeks).

- In immunocompromised it can be chronic and more severe

patients, especially those with CD4 counts <200/µl. 

- Infections in other organs including:

the lungs, liver, gall bladder and possibly conjunctiva.
• Laboratory diagnosis
 Demonstration of oocysts in the feces/sputum/duodenal aspirate
 Concentration techniques

 Staining methods
• Modified Z N staining
• IF staining

 IF staining :for greatest sensitivity and specificity, it is the method of

choice (followed closely by ELISA for Ag detection).

 Molecular methods are mainly a research tool (PCR).

 Source:http://biology.kenyon.edu

Phase contrast photograph of sporozoite release

from the Cryptosporidium oocyst
 Giardia cyst
C. parvum

Source: http://www.dpd.cdc.gov

Oocysts of C. parvum (upper left) and cysts of Giardia intestinalis (lower

right) labeled with immunofluorescent antibodies
Treatment
Infection in healthy, immunocompetent persons is self-limited.

•  Nitazoxanide has been approved for treatment of diarrhea

caused in immunocompetent patients.

  *The effectiveness of nitazoxanide in immunosuppressed

persons is unclear.
 
*For persons with AIDS, anti-retroviral therapy, which improves
immune status, will also reduce oocyst excretion and decrease
diarrhea associated with cryptosporidiosis.
 Cyclospora

• Cyclospora cayetanensis causes cyclosporiasis

• World wide distribution
• Life cycle similar to Cryptosporidium
• Man is infected by ingestion of contaminated food/water
• Unsporulated oocyst in feces sporulates outside the host
Morphology of Oocyst :
Spherical/8-10μm in diameter
It contains 2 sporocysts
Each sporocyst contains 2 sporozoites(semilunar in shape)
C/F:
• IP - one week
• watery diarrhea, anorexia, weight loss, abdominal pain,
nausea and vomiting, myalgias, low-grade fever, and fatigue.
•   untreated infections typically last for 10-12 weeks and may
follow a relapsing course ( AIDS patients).
Laboratory diagnosis
• Detection of oocyst in stool(concentration technique by
flotation method)
• Modified ZN staining

Treatment
- cotrimoxazole
 Isospora

• Isosporiasis – cause d by I.belli particularly in patients with

AIDS
• Geographic Distribution:
Worldwide, especially in tropical and subtropical areas. 
Morphology of Oocyst:

• Elongated, 25x15μm

• Cyst wall has 2 layers

• In human feces immature oocyst is passed-contains 2 sporoblasts

• Mature into sporocysts ( each sporocyst contain 4 sporozoites-

crescent shaped)
Life Cycle
of
Isospora
belli
C/F:

IP: 7-11 days

Infections are asymptomatic and self-limited.

Symptomatic Infection include;

- acute, non bloody diarrhea
- malabsorption syndrome (Villous atrophy)
- Severe diarrhea/death in AIDS patients
 Laboratory Diagnosis
Stool microscopy
• Repeated stool examinations and concentration procedures
are recommended.
• Examination of duodenal specimens by biopsy or string test
(Enterotest®) may be needed.

 - They can also be stained by modified acid-fast procedure or

auramine-rhodamine stains.
-The modified acid-fast procedure is especially useful.
 Isospora oocysts

Mature oocyst Immature oocyst Stained oocyst

Treatment

• Trimethoprim-sulfamethoxazole combination is the drug of

choice in immunosuppressed person- every 6 hours for 10
days, followed by the same dose twice daily for 3 weeks.

• Combined pyrimethamine and sulfadiazine has also been

shown to be an effective treatment.
Cryptosporidium
• 4-5 mm oocysts
• 4 sporozoites
• no sporocysts

Cyclospora
• 8-10 mm oocyts
• 2 sporocysts
• 2 sporozoites each

Isospora belli
• 30 x 12 mm oocyts
• 2 sporocysts
• 4 sporozoites each
Sarcocystis
Phylum Genus Species Habitat Pathogenic effect
Ciliophora Balantidium B.coli Large intestine Dysentery

Apicomplexa Plasmodium RBC Malaria

Toxoplasma T.gondii R.E system Encephalomyelitis

choroidoretinitis
Cryptosporidium C.parvum Large intestine cryptosporidiosis

Cyclospora C.cayentanensis Epi cells of intestine Cyclosporiasis

Isospora I.belli Epi cells ofintestine Diarrhoea

Sarcocystis S.hominis, Large intestine Sarcocystosis

S.suihominis
Microspora Enterocytozoon E. bieuneusi Epi cells of intestine Microsporidiasis

Encephalitozoon E. intestinalis Epi cells of intestine Microsporidiasis

Sarcocystis

Sarcocystis is a parasite which forms the cyst in the muscle

Geographical distribution - world wide/ comparatively low

incidence in man

Three species
• S.hominis
• S.suihominis - intestinal sarcocystosis

• S.lindemanni - muscular sarcocystosis

Morphology
There are three morphological forms

Oocyst
contains two sporocysts and four sporozoites are present in
each sporocyst
• Thin walled/colourless
• Size :
S.hominis - 13-19μm in diameter
S.suihominis - 10-13 μm in diameter
Sporocyst
• Oval
• 8-10 μm in diameter
• Contains four banana shaped sporozoites
• Passed in human feces and is infective form of parasite
Sarcocysts/muscular cyst
• Spindle shaped structures with thick striated wall and found
along the length of muscle fibres of cattle, pig
• Divided into many compartments containing bradyzoites
Life cycle of S.hominis and S.suihominis

Two hosts are required

Definitive host : man

Intermediate host : cattle and pigs
Diagnosis
- Demonstration of mature sporocysts/ occassionally oocysts

in human feces
- Two species of sarcocyst-difficult to differentiate on the basis

of sporocyst examination
(IHA,IFA,ELISA to differentiate)
The oocysts of Sarcocystis spp. sporulate within the host's intestine and then
rupture, releasing the sporocysts, which are thus found on a flotation of the feces.
Muscular sarcocystosis
It is caused by S.lindemanni and man is rarely infected

Lifecycle
Definitive host - cats/dogs/carnivorous animals
Intermediate host - man

• Ingestion of food/drink contaminated by sporocysts of

S.lidemanni
• Sporocyst liberates sporozoites which invade intestinal wall
and then disseminate d to skeletal muscle to cause
subcutaneous and muscular inflammation
• Similar life cycle, differs only from the pattern of hosts
C/F:
• Asymptomatic
• Localized painful muscular swelling

Diagnosis
• Muscle biopsy-shows sarcocysts
• Radiology-faint shadows in the muscles

Treatment
• No specific treatment
• Avoidance of ingestion of raw/undercooked beef/pork
• Avoidance of contamination of food/drink with feces of cat, dog
and other carnivorous animals
 Microsporidia

• Belong to the phylum Microspora

• They are minute unicellular obligate intracellular spore forming
protozoa
• Enterocytozoon bieneusi
• Encephalitozoon intestinalis

- frequently infect intestinal cells causing

• chronic diarrhoea
• abdominal cramps
• nausea
• malabsorption in AIDS patients
Morphology:
• The spore is oval/ cylindrical in shape
• 0.5x4μm in size
• Thick double layered wall
• Within the cytoplasm there is coiled polar tube
Life cycle
• Infection is acquired by ingestion of spore
• In the intestine they extrude the polar tube and penetrates the
enterocytes
• Successive cycles of merogony followed by sporogony occurs and
several spores are formed and these spores infect other cells
C/F:
• Causes intestinal microsporidiosis in AIDS patients
• Persistent diarrhoea, nausea, anorexia, abdominal pain
• Encephalitozoon intestinalis – eye, kidney(Interstitial nephritis)

Diagnosis
• Detection of spore by light microscopic or electron microscopic
examination of small intestinal biopsy material
• Detection of spore in stool, urine, duodenal or jejunal contents
• Immunodiagnosis –indirect immunofluoroscent Ab test
Modified ZN stain Trichrome stain
Immunofluoroscent Ab Technique
Treatment:

• No effective treatment has been developed against

Enterocytozoon bieneusi

• Albendazole - Encephalitozoon intestinalis

 Pathogenic
free living
amoebae
you are NOT immune to Naegleria infection!
Pathogenic free living amoebae

• Found in fresh water, mud, moist soil and may infect man
• Genus Naegleria - species N.fowleri
• Genus Acanthamoeba
Naegleria fowleri

Geographical distribution - world wide (in warm fresh water)

Exists in three forms

• Trophozoite /amoeboid form- surface of vegetation/mud
• Free swimming flagellate form-found on surface layer of water
• Cyst/resting form- surface of vegetation/mud
Trophozoite form
• 6-15μm indiameter
• Slug shaped with one broad
and one pointed extremity
• Single large nucleus-2 μm,
large nucleolus, perinuclear
hallow
Flagellate form
• Pear shaped cells with 2 flagella
• Flagellate form can revert to
the trophozoite form for its
multiplication

Cysts
• Uninucleated and possess
double cyst wall
• Life cycle
Pathogenicity
Primary Amoebic Meningo encephalitis
• Caused by the free living amoebae of the genus Naegleria
• Found in fresh water, mud, moist soil, polluted warm lake
water, streams, ponds, indoor swimming pools

Human infection
 nasopharyngeal route, during swimming in contaminated
water
 inhalation of particles of decaying animal manure
C/F

• Incubation period:5-7days

• The amoebae are neurotropic and cerebral invasion takes

place through olfactory nerve

• Symptoms of URTI followed by signs of meningitis

Diagnosis
• Unstained preparations to demonstrate trophozoites
• CSF staining with Wright/Giemsa stain
• Fluoroscent Ab staining of CSF
• Culture –non nutrient agar seeded with E.coli

Treatment
DOC : large dose of antifungal agent Amphotericin B/Ketoconazole
 brain section
Trophozoite of N. fowleri in CSF
 Acanthamoeba
Geographical distribution –worldwide

Morphology:
Two forms,
Trophozoite :
• 20-50μm
• Acanthopoda – rough exterior with several spine like projections
• Single nucleus with large, central, dense nucleolus surrounded by
halo

Cyst
• spherical, 15μm
• Wrinkled outer surface with smooth inner wall with several spores
Life cycle

Man acquires infection by

• inhalation of dust containing trophozoites/cysts or
• by direct invasion of traumatized skin or eye
• The trophozoites invade the CNS through blood stream

 Granulomatous Amoebic Encephalitis

 Chronic Acanthamoeba Keratitis

• Infection of brain is not associated with swimming

Pathogenicity and Clinical Features:

Granulomatous Amoebic Encephalitis

: occurs in debilitated/chronically ill patients having
immunosuppressive therapy or immunocompromized patients
such as AIDS

• IP-7days, insidious onset with prolonged clinical course

• Characterized by granulomatous lesion in the brain

 Chronic Acanthamoeba Keratitis
• contact lens users
• due to direct inoculation of amoebic trophozoites or cysts into
cornea during insertion of contaminated lens
Diagnosis-
• Wet mount preparation of CSF or corneal scraping - motile

trophozoites
• Culture on agar plates seeded with E.coli
• Indirect fluoroscent Ab test
• HPE of brain tissue/corneal tissue to demonstrate
trophozoite and cyst

Treatment
No effective treatment for GAE
Ocular lesions- enucleation of ulcer and corneal transplant
Cyst

Trophozoite
 Naegleria Acanthamoeba encephalitis
meningoencephalitis-PAM GAE & CAK
Children & Debilitated
young adults Chronically ill
low immunity

• Diffuse meningoencephalitis. • Focal, granulomatous, space-

• Runs rapidly fatal course occupying lesion.
(death within 3-6 days) • Runs sub-acute or chronic
course (lasts for weeks, months
• History of swimming in natural or years)
water or swimming pools. • Not strongly associated with
• Infection occurs through: swimming.
The nasal route olfactory • Infection occurs in:
nerve brain. Lower respiratory tract,
ulcerated skin or mucosa
blood stream CNS
Life cycle of sarcocystis
Definitive host : man

Man becomes infected by ingesting undercooked/raw beef/pork

containing sarcocysts

Sarcocysts bursts in small intestine and liberates numerous

bradyzoites which penetrates the intestinal epithelium

In the sub epithelial space they undergo development forming

microgametes and macrogametes

Fertilization occurs to form zygotes

 An oocyst develops from the zygote

Sporulation

Sporulated oocysts are shed into the lumen of the small intestine and

rupture to release sporocysts in the feces of man

(infective to intermediate host)

Contaminated food/water containing sporocysts are ingested by

cattle/pig and they become infected
Intermediate host:
Sporozoites are released from sporocyst in the small intestine
and enter the blood stream and produce 2 generation of
schizonts

Merozoites are released from schizonts

Merozoites migrate to skeletal and cardiac muscles to develop

into sarcocyst containing numerous bradyzoites

The raw/ undercooked beef/pork containing this sarcocyst is

ingested by man and cycle repeats.