Phylum -
Ciliophora
They are group of protozoa characterized by head like
structure called cilium which is important in A – movement
B - nutrition .
Genus -Balantidium
This parasite have two species :Balantidium suis
infect the pigs .
Balantidium coli
infect the human .
This disease is regarded as a zoonotic disease .
Disease : Balantidiosis
B.coli :- is the largest intestinal protozoa that effect
human and can be seen macroscopically .
Morphology :- the parasite is observed in two stages only which are
:A – trophozoite :1- Large size (40 µm to more than 70 µm) .
2- called the invasive stage .
3- ovoidal in shape .
4- covered by cilia & the anterior end are longer than the
posterior end .
5- in the anterior end there is mouth called cytosome .
6- the internal structures :A- have two nuclei , the macronucleus (the largest
one) & micronucleus (the smallest one ) .
B- the macronucleus is kidney or bean in shape .
C- the micronucleus is small spherical shape
located in the concavity of macronucleus .
D- have two secretory contractile vacuoles .
E- numerous food vacuoles .
B- Cyst :1- typically spherical in shape .
2- surrounded by thick wall (one or two layers ) by
encystation in small intestine to protect the parasite from
the host .
3- contain the macronucleus and contractile vacuoles are
visible in the cyst .
4- the cilia are undetectable , only the roots may present .
Multiplication :- occur by two method
1- Asexual type by binary fission .
2- Sexual type by conjugation .
Life cycle :- direct life cycle or simple life cycle that mean the parasite not
need for intermediate host .
Mature cysts are passed with feces.
Transmission :- by ingestion of contaminated food or water (NOT in
undercooked meat) with feces contain the mature cyst .
Excystation occurs in the small intestine, and the trophozoites colonize in
the large intestine.
Trophozoites undergo encystation to produce infective cysts.
Cysts are the infective stage of this parasite.
Life Cycle – B coli
Infective form: Cysts
Mucosal & submucosal
ulcers
Ingestion: Faeco-oral
No extra intestinal
invasion
Stomach: Resist acid
Diarrhoea / Dysentery
Small Intestine - excyst
Large intestine: encyst
Large intestine – trophozoites
(one cyst – one trophozoite)
Passed out in feces
30/03/08
Dr Ekta,Microbiology
Pathogenesis

Balantidium coli produces proteolytic enzymes
that break down and digest the intestinal
epithelium.
Colon ulceration develops which allows for
infiltration by lymphocytes and leukocytes.
Hemorrhaging and secondary bacterial
infections will develop next.
Perforation of the large intestine and appendix
will occur.
Clinical Signs
 Mild infections occur with diarrhea,
 Abdominal pain
 Alternating periods of constipation
 Ulceration of the gut wall
Diagnosis
 Cysts-formed stools
 Active trophs-diarrheic stools
Diagnosis
Microscopy –in saline preparation ,motile 
trophozoite -fresh diarrhoeic stool
Cyst-found occasionally in formed stool 
When stool examination is negative-scrapings or
biopsy specimens –sigmoidoscopy –useful in
suspected
cases

Laboratory diagnosis
Specimen:
Stool
Diarrhoeic- trophozoites, formed - cysts
Microscopy:
Trophozoites / cysts
Treatment:
Tetracycline 500mg four times a day for 10
days
Metronidazole / tinidazole also effective
Prevention:
30/03/08
Personal hygiene, avoid food & water
contamination, drink safe water
Dr Ekta,Microbiology
Treatement
Tetracycline -500 mg –four times -10 days
Metronidazole -750mg-three times-5 days
Prophylaxis-protection against contaminated food
and water with faeces containing cyst
CYCLOSPORA
CAYETANENSIS
Is a coccidian parasite 
Belongs to family Eimeriidae 
First case was reported in peru in 1985 
Causes disease –cyclosporiasis in man
Distribution –worldwide distribution-infects 
reptiles, birds and animals
Common cause of travellers diarrhoea 
Particular reports from nepal ,india and south 
America 
TRANSMISSION
By ingestion of sporulated oocyst from 
contaminated water
Morphology 
Oocyst are of medium size (8-10µm) 
Content-contains two sporocysts-each 
containing two sporozoites-which in turn
contain membrane bound nucleus and
micronemes –characteristic of apicomplexans
Life cycle
Unsporulated cysts are passed in faeces 
Sporulation occurs in 7-13 days
Complete sporulation leads to production of
sporocyts-each containing two crescent –shaped
sporazoites
Human-by ingestion of infective(sporulated)oocystcontaminated
After excystation in duodenum and jejunumSporozoites released from oocysts-penetrate
epithilium
Clinic disease
Incubation period ranges-2-11 days 
Malaise ,low grade fever, watery diarrhoea-7-8 
stool per day
In immunocompromised hosts-diarrhoea is (8- 
12) weeks
Lab diagnosis
Detection of cyclospora oocysts in stool 
Light microscopy 
Fresh saline wet mount of stool-sporocyst-nonrefractile ,spherical to ovoid body of 8-10µm
Formalin fixed stool smears stained with 
modified acid fast(kingoun)stain-cyclospora
oocysts stain acid fast variable

Diagnosis of Cyclospora & Isospora
Stool examination to detect unstained and stained oocysts
Unstained oocyst
Unsporulated
Isospora
Cyclospora
Stained oocyst by MZN stain
Cyclospora
Unsporulated
Isospora
Sporulated
Isospora
Sporulated
Isospora
Cyclospora cayetanensis
Oocysts in faeces
3-5 m
Cryptosporidium
8-10m
Autofluorescence 
Cyclospora fluoresce-when examined with 
ultraviolet fluorescent microscope
Concentration method-cyclospora oocyst in 
faeces –concentrated by modified zinc sulfate
Treatement –trimethoprim-sulfamethxazole 
Control-improve personal hygiene and 
sanitation
Cyclospora –appear resistant to chlorination- 
filtration of water is effective
Immunodiagnostic tests
Treatement –trimethoprim-sulfamethxazole 
Control-improve personal hygine and sanitation
Cyclospora –appear resistant to chlorination- 
filtration of water is effective

Microsporida
Belongs to phylum microspora
Sevengenera(Enterocytozoon,Encephalitozoon,Nose
ma,Pleistophora,Thelohenea,Trachiplestophora
and – Vittaforma-cause the disease
microsporidiosis-particularly in AIDS patients)
The Phylum Microspora was discovered in the 
late 1800s, but the first human case was described
only in 1959 in a Japanese child.
The rise in microsporidiosis is associated with the
arrival and spread of HIV; microsporidiasis is
primarily found in patients with AIDS or are
otherwise immuno-compromised (like organ
transplant patients).
However, at least three species of Nosema and one
of Brachiola have been documented in immunocompetent patients. Microsporidia are considered
casual, accidental or opportunistic agents in
humans.


Microsporidia are primitive eukaryotes with well 
defined nuclei and plasma membrane but lack
some typical organelles found in more typical
eukaryotes mainly mitochondria, stacked golgi
apparutus
Microsporidia spores are all round and oblong 
and those associated with human infection tend
to be about 1-4 µm in size (an important feature
for diagnosis as some species are often mistaken
for bacteria).
The life cycle involves a proliferative merogonic 
stage followed by sporogony, which results in
spores containing a tubular extrusion apparatus
(polar tubule) for injecting infective spore contents into the host cell
Infection occurs by ingestion of spores 
Sporoplasm with its nuclear material is injected 
through the polar tubule into the host cell
Transmission
By ingestion of food and drink contaminated by
spores
Clinical presentation 
Diarrhoea-intestinal infection caused- 
Encephalitozoon intestinalis and
Encephalitozoon bieneusi in AIDS
Keratoconjunctivitis, sinusitis, bronchitis 

Lab diagnosis
Detection of organism-biopsy material, CSF and 
urine
Electron microscopy-examination of tissue 
Other test- PCR ,cell culture and serologic test – 
under investigation
Treatment-no specific drug 
Metronidazole provides temporary improvement 