Balantidium coli is the largest protozoan pathogen of humans. It causes a potentially life-threatening infection of the large intestine called balantidiasis. Transmission occurs through ingestion of food or water contaminated with the cyst form of B. coli from infected pig, monkey, or human feces. Symptoms include diarrhea or dysentery. Diagnosis involves identification of the trophozoite or cyst forms in stool samples under the microscope. Treatment involves antibiotics like tetracycline. Prevention focuses on avoiding contact with infected animal or human waste.

1. BALANTIDIUM COLI
By, Leyon Selvin Raj,
Tutor,
BN Patel institute of paramedical & Science, (Paramedical Division).

2. Blantidium coli
• Largest and least common protozoan pathogen of
humans.
• Caused life threatening colitis.
• Avoidable by antibiotic therapy.
• Fatalities are due to diagnostic imprecision.

3. Epidemiology
• Most commonly reported in
• Tropical and sub tropical
• Particularly central and south America
• Iran, Papu New Guinea and Philippines

4. • Prevalence is less than 1%
• Found in many mammals other than humans
• Pigs and monkeys- especially
• Swine- imp. Animal reservoir
*The largest reported balantidiasis, involves 110
persons, resulted from gross contamination of ground
and surface water supplies by pig feces after a severe
typhoon.

5. Morphology
• B. coli occurs in two stages
• Trophozoite
• Cyst

6. Trophozoite
• Lives in large intestine.
• Feeding on cell debris, bacteria, starch grains, and
other particles.
• Motile – found in dysenteric stool.
• Large ovoid cell. 60-70µm in length and 40-50µm in
breath. (200µm-large one)

8. Trop. Morp.
• At the anterior end, there is
a groove (peristome)
• leading to the mouth
(cytostome), and a short
funnelshaped gullet
(cytopharynx).
• Posteriorly, there is a small
anal pore (cytopyge).
• The cilia around the mouth
are larger (adoral cilia).

9. Trop. Morp.
• The cell has 2 nuclei—a
large kidney-shaped
macronucleus
• and lying in its concavity
a small micro nucleus.
• The cytoplasm has 1 or 2
contractile vacuoles
• And several food
vacuoles.

10. Cyst Morp.
• spherical in shape and
measures 40–60 μm in
diameter.
• It is surrounded by a thick and
transparent double layered
wall.
• The cytoplasm is granular.
Macronucleus, micro nucleus,
and vacuoles are also present
in the cyst.
• The cyst is the infective
stage of B. coli.
• It is found in chronic cases
and carriers.

11. Life cycle
• B. coli passes its life cycle in one host only
(monoxenous).
• Natural host: Pig
• Accidental host: Man.
• Reservoirs: Pig, monkey, and rat.
• Infective form: Cyst.

12. 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.

13. Mode of transmission
• Infection is acquired from pigs and other animal
reservoirs or from human carriers.
• Once the cyst is ingested, excystation occurs in
the small intestine.
• From each cyst, a single trophozoite is produced
which migrates to large intestine
• Liberated trophozoites multiply in the large
intestine by transverse binary fission. Sexual
union by conjugation also occurs infrequently,
during which reciprocal exchange of nuclear
material takes place between 2 trophozoites
enclosed within a single cyst wall.
• Encystation occurs as the trophozoite passes
down the colon or in the evacuated stool. In this
process, the cell rounds up and secretes a tough
cyst wall around it.
• The cysts remain viable in feces for a day or 2
and may contaminate food and water, thus it is
transmitted to other human or animals.

14. Pathogenesis
• In Healthy individual, B. coli lives as lumen commensal
and is asymptomatic.
• Clinical disease occurs only when the resistance of host
is lowered.
• Trophozoites burrow into the intestinal mucosa, set up
colonies, and initiate inflammatory reaction.
• Leads to mucosal ulcers and submucosal abcesses,
resembling lesions in amoebiasis.
• They don’t invade liver, like E. histolytica,

15. Clinical Features
• Most infections are asymptomatic.
• Symptomatic disease (balantidiasis) resembles
amoebiasis causing diarrhea or frank dysentery with
abdominal colic, tenesmus, nausea and vomiting.
• Balantidium ulcers may be secondarily infected by
bacteria.
• Occasionaly, intestinal perforation peritonitis and even
death may occur.

16. Laboratory Diagnosis
• Stool Examination
• Demonstration of trophozoites and cysts in feces.
• Trophozoites- diarrheic feces
• Large in size, macronucleus, and motile
• Cysts- formed stool
• Round shape and large macronucleus.

17. • Biopsy
• Scrapings from intestinal ulcers can be examined for presence
of tropozoites and cysts.

18. • Culture
• B. coli – Locke’s egg albumin medium or NIH polyxenic
mrdium
• *rarely needed

19. Treatment
• Tetracycline- 500mg 4times/day for 10 days
• Alternative
• Doxycycline

20. Prevention (prophylaxis)
• Avoidance- Contamination of food and water with
animal and human feces
• Prevention of human-pig contact
• Treatment of infected pigs

22. Reference
• Farrar, J., Hotez, P., Junghanss, T., Kang, G., Lalloo, D.
and White, N.J., 2013. Manson's Tropical Diseases E-
Book. Elsevier Health Sciences.
• Paniker, C.J., 2007. Textbook of medical
parasitology (No. Ed. 6). Jaypee Brothers Medical
Publishers (P) Ltd.