This document summarizes gastrointestinal protozoal infections. It discusses various protozoa including Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum, Balantidium coli, and Isospora belli. It covers the morphology, life cycles, clinical manifestations, diagnosis, and treatment of these protozoa. Risk factors for infection include developing countries, poor sanitation, homosexuality, and immunocompromised states like HIV/AIDS. Protozoal infections commonly cause diarrhea but can also lead to more severe complications in vulnerable groups. Diagnosis involves microscopic examination of stool samples, and treatment consists of antimicrobial agents like metronidazole and nitazox

1. GASTROINTESTINAL PROTOZOAL
INFECTIONS
Chair person: Prof Dr Nagappa H
Co-chair person: Dr Narayanaswamy
Presenter: Dr Yashavanth H S
Date: 21/01/2014
Time: 2.15pm

2. Introduction:
• Protozoan
• Greek: protos- first, and zoon- animal
• Protozoology
• A protozoan can be defined as a motile
eucaryotic unicellular organism
• Entamoeba histolytica infects all age groups but
has its most profound effects in adults.
• Giardia lamblia and Cryptosporidium parvum
have their major impact in childrens

3. Protozoa
• Moisture is necessary protozoa because they
are susceptible to desiccation.
• Most protozoa are free living and inhabit
freshwater or marine environments.
• Many terrestrial protozoa can be found in
decaying organic matter, in soil, and even in
beach sand
• Some are parasitic in plants or animals.

4. Nutrition of protozoa
• Holozoic nutrition : bacteria are acquired by
phagocytosis and the subsequent formation of
phagocytic vacuoles.
• Saprozoic nutrition: soluble nutrients such as
amino acids and sugars cross the plasma
membrane by pinocytosis, diffusion, or carrier
mediated transport
• Significant role in the food web of nature

5. Morphology

6. Y

7. Cysts
• They protect against adverse changes in the
environment
• They are sites for nuclear reorganization and
cell division (reproductive cysts)
• They serve as a means of transfer between
hosts in parasitic species.

8. E histolytica G lambia
Isospora oocyst Cryptosporidium oocysts
CYSTS
B. coli cyst

9. Protozoans causing intestinal infection
• Entamoeba
• Giardia
• Cryptosporidium
• Isospora
• Balantadium
• Cyclospora
• Microsporidia

10. Epidemiology
• Race – not associated
• Sex – no association ( except in amoebic liver
abscess M:F= 10:1 )
• 53.8% school children are infected
• 36.8% of pregnant women are infected
• In rural southern India: 23.1% was infected by
one variety and 74.3% are infected by more
than 1 group

11. Poor
personal
hygiene
Developing
countries
Water-
borne
epidemics
Male
homosexuality
Zoonosis
RISK
FACTORS

12. In HIV
• Diarrhoea is the most common GI manifestation
• The diagnosis and management of diarrhoea in a PLHIV is a
major challenge.
• There are multiple reasons for the high occurrence of
diarrhoea:
• Immune dysfunction of the intestinal epithelial cells.
• Reduced IgA levels.
• Poor gastric acid secretion and nutritional deficiencies.

13. • Protozoa isolated from the stools of PLHIV
without any symptoms, although the isolation of
parasites was shown to be more common in
patients with diarrhoea.
• The most common pathogen identified in those
with diarrhoea was Isospora belli.
• In asymptomatic patients were more likely to
shed Giardia in their stools

14. • Enteric pathogens in stool:
– 57.4% of diarrhoeal patients
– 40% without diarrhoea (P >0.05)
• Protozoal pathogens 71.8%
• Most commonly isolated pathogens:
– Chronic diarrhoea: Isospora belli (25%)
– Controls: Giardia lamblia (16%)
• In patients with acute diarrhoea, there is no definite
prominent pathogen

15. Common Enteric Pathogens in HIV

16. Differential diagnosis
• Irritable bowel syndrome
• Inflammatory bowel disease (Crohn's,
microscopic colitis)
• Gallbladder or pancreatic disease
• Malignancy (amoeboma)
• HIV Enteropathy

17. Diagnosis of Intestinal Protozoa
•Suspect: acute or chronic GI symptoms
•Confirmed: detection of parasite in feces
•3 non-consecutive days (inconsistent excretion)
•copro-antigens or molecular probes
•Cryptosporidium
•acid-fast stain
•Giardia
•duoenal aspirates or biopsy
•presumptive treatment in chronic cases
•Entamoeba
•sigmoidoscopy (lesions, aspirates, biopsy)
•extra-intestinal disease

18. • Sometimes even after repeated stool testing, no
pathogen can be isolated.
• May not be related to technique, but due to fact that
the shedding of pathogens may be intermittent.
• The relationship between the pathogen and diarrhoea is
unclear.
• Many of the pathogens have been isolated from stools
of asymptomatic PLHIV.

19. • Stool cultures
• Endoscopic studies
• Biopsies and histo-pathological studies
• Electron microscopy and other special studies

20. Diagnosis of Extraintestinal Disease
• Symptoms associated with
specific organ
• History of dysentery
• Hepatic
• right upper quadrant pain
• enlarged liver
• Serology
• Imaging (CT, MRI, ultrasound)
• Abscess aspiration
• only select cases
• reddish brown liquid
• trophozoites at abscess wall

21. Non specific treatment
• Maintaining adequate hydration
• Adequate nutritional supplements and
specific vitamins and minerals replacement
are essential.
• Initiate ART : Initiation of ART is important in
controlling diarrhoea especially in conditions
where diarhhoea due to cryptosporiodia,
isospora and microspora.

22. Giardiasis
Salient features
• First observed by Leeuwenhoek
in 1681 and described by Vilem
dusan lambl in 1859
• Giardiasis intestinalis /
G lamblia / G duodenalis
• Worldwide distribution
• Cross infectivity between animals
and humans
• Largely devoid of cytoplasmic
organelles (including
mitochondria)
• First organism to emerge from
the prokaryotic to the eukaryotic
state.

23. Risk factors
• Hypogammaglobulinemia
• AIDS
• Cystic fibrosis

24. Pathogenesis
Epithelial damage
• villus blunting
• crypt cell hypertrophy
• cellular infiltration
Malabsorbtion
Enzyme deficiencies
• lactase (lactose intolerance)

25. Role of bile and bile salts
• Bile has been shown to promote growth of Giardia
both in vivo and in vitro
• The final stage of the life cycle, encystation, can also be
completed following exposure of trophozoites to high
concentrations of conjugated bile salts at neutral pH.
• Thus, bile and bile salts may have a dual role in the
parasite life cycle.
• On one hand promoting growth and multipli cation,
while at the same time ensuring that the parasite
completes its life cycle by encystation

26. Range of Outcomes
Asymptomatic/latent
Acute short-lasting
diarrhea
Chronic/nutritional
disorders

27. Acute Symptoms
• 1-2 week incubation
• Sudden explosive, watery diarrhea
bulky, frothy, greasy, foul-smelling stools
no blood or mucus
• Upper gastro-intestinal symptoms
• Usually clears spontaneously (undiagnosed),
but can persist or become chronic

28. Subacute / Chronic
• Recurrent diarrheal
episodes
• Cramps uncommon
• Sulfuric belching, anorexia
and nausea
• Can lead to weight loss and
failure to thrive
Extraintestinal manifestations
• Urticaria
• Anterior uveitis
• Arthritis

29. SYMPTOMATOLOGY

30. Complications
• Dehydration
• Weight loss
• Malnutrition
• Malabsorption
• Arthritis
• “Salt and pepper" retinal changes

31. Diagnosis
• The traditional diagnosis for giardiasis consists
of performing an ova and parasite (O+P) exam
of one to three stool specimens on non-
consecutive days (sensitivity: 85-90%)
• Several days of specimen collection are
needed to improve sensitivity
• Stool microscopy is relatively inexpensive, but
it does require a skilled technician and may be
a time consuming process

32. • These alternative diagnostic methods should
only be used when stool examination is
repeatedly negative and there is a high clinical
suspicion of infection
• Duodenal aspirate biopsy and collection of
duodenal fluid with the string test

33. Enterotest
• This test requires the patient to swallow a
gelatin capsule containing a string. The
proximal end of the string is taped to the
patient's cheek and the distal end in the
capsule moves to the duodenum after the
capsule dissolves in the stomach. Several (4-6)
hours later, the string is removed and
microscopically examined for trophozoites.

34. Treatment
• Metronidazole 400 mg TID for 5 days OR
2 g OD for 3 days
• Tinidazole 2 g stat dose
• Nitazoxanide 500 mg BD for 3 days
• Furazolidone 100 mg QID for 7-10 days
• In refractory cases
Metronidazole 750 mg TID for 21 days

35. Amoebiasis
• Amoebiasis : has been defined by WHO as the
condition of harbouring the protozoan parasite
E.histolytica with or without clinical
manifestations
• Entamoeba histolytica
• Entamoeba dispar
• Symptomatic infection occur in <10% of infected
individuals and 1% develops invasive or
extraintestinal amebiasis

36. • Feco-oral route
• Oro-anal route
• No animal reservoirs
• World-wide distribution with major problem
in China, south east and west Asia and Latin
America
• Affects about 15% of the Indian population.

37. Risk factors
• People who have traveled to tropical places
that have poor sanitary conditions
• Immigrants from tropical countries that have
poor sanitary conditions
• People who live in institutions that have poor
sanitary conditions
• Men who have sex with men

38. Life Cycle

39. Colonization
Asymptomatic
cyst passer
Non-dysenteric
diarrhea
Abdominal
cramps, other GI
symptoms
NON-INVASIVE

40. INVASIVE
necrosis of
mucosa  ulcers,
dysentery
ulcer enlargement
 dysentery,
peritonitis
metastasis 
extraintestinal
amebiasis
Hepatic abscess
Empyema
Rupture into
pericardium
Cerebral abcess Cutaneous
amebiasis

41. Symptoms and findings in acute colitis

42. Intestinal amoebiasis
• Abdominal discomfort, loose motions or frank
diarrhoea
• Constitutional symptoms are not prominent
• Tenesmus occurs in half of the patients and is
always associated with rectosigmoid
involvement
• Tenderness may be localized anywhere in the
lower abdomen but is usually over the
caecum, transverse colon or sigmoid

43. • The disease may involve the terminal ileum
rarely.
• Rarely occasions involvement of the blood
vessels at the base of the ulcer may produce
brisk bleeding.
• Fulminant colitis clinical picture is virtually
indistinguishable from that of fulminant
ulcerative colitis

44. Flask shaped
ulcer
•
Intestinal
lesions

45. Amoeboma or amoebic granuloma
• Amoeboma is non-fibrotic and contains granulation tissue
with lymphocytes, plasma cells, eosinophils and giant cells.
There is remarkably little inflammation and most of the
swelling is due to oedema.
• Repeated invasion of the colon by E. histolytica,
complicated by pyogenic infection.
• Lesions are usually single and involve a short segment of
the colon.
• Occurs commonly in caecum (40%) and rectosigmoid
junction (20%).

46. Amoebic liver abscess
• Most common extraintestinal form
• 10 times more frequent in adults than in children
• Frequent in males than in females
• Common in the poorest sectors
• 20% of patients have a past history of dysentery
• Parasite can be detected in faeces in less than
50% of cases
• Onset of symptoms is usually abrupt

50. 1. Peritoneal amoebiasis
2. Pericardial amoebiasis
• most serious complication
• necessary to perform open drainage
3. Pleuropulmonary amoebiasis
• 15% of patients with liver abscess.
4. Cerebral amoebiasis
• Metronidazole- immediate use will improve the prognosis

51. 5. Genitourinary amoebiasis
• Renal amoebiasis usually respond well to
aspiration and medical therapy
• Genital lesions are usually caused by fistulas from
a liver abscess or rectocolitis & they are painful,
punched-out ulcers with profuse discharge.
Medical treatment is usually sufficient
6. Cutaneous amoebiasis
• Perforation of an abscess or surgical

52. Diagnosis
• Stool or rectal smears for cyst and trophozoite
(within 30 min)
• Rectosigmoidoscopy and colonoscopy of mild or
moderate cases usually reveals the presence of small
ulcers (3–5 mm in diameter)
• Serology can be useful in the diagnosis of amoebiasis,
particularly in non-endemic areas. Antibody response
is present in 85–95% of patients with invasive disease.

54. Tissue amebicides
Metronidazole
• 500mg TID IV for 7-10 days
(for extraintestinal)
• 400mg TID orally for 7-10
days
Tinidazole: 2 g/day for 3 days
Ornidazole : 1.5 g/ day for 3
days
Secnidazole : 2g single dose
Luminal infection
• Paromomycin 30mg/kg qid
PO in 3 divided doses
• Diloxanide furate: 500mg
TID for 10 days
• Iodoquinol 500mg PO BD
for 10 days

56. Complications
• Extensive inflammatory polyposis
• Peritonitis
• Hypovolaemia and electrolyte imbalance
• Amoeboma

57. Cryptosporidium
Tyzzer in 1907, was the first to describe Cryptosporidium
(c.muris) in the gastric mucosa of laboratory mice.
Currently 13 species are present
2 species infecting humans
•C. parvum: cattle and other mammals
•C. hominis: only humans
Self-limiting diarrhea in immunocompetent persons
Profuse, watery diarrhea associated with AIDS (life
threatening)

59. The Milwaukee Outbreak
NEJM 331:161 (1994)
•Massive cryptosporidiosis outbreak following
spring thaw
• >400,000 people may have been affected
• based on clinical symptoms (acute watery diarrhea)
• ~100-fold higher prevalence of Cryptosporidium oocysts
in stools than normal
•Treated water had high levels of turbidity

60. • Substantial outbreaks of water-borne
diarrhoea in the immunocompetent, and for
diarrhoea in travellers and in children.
• Cryptosporidiosis is an important contributor
to childhood diarrhoea, with a prevalence
among children with diarrhoea of 1–3% in the
industrialized world and 4–17% in developing
countries.

61. • Recognized to represent a threat to HIV-
infected individuals, with a lifetime risk of
infection of around 10%
• AIDS-related cryptosporidiosis, the dominant
site of infection was the distal small intestine
and right side of the colon.

63. Diagnosis and treatment
• Conventional stool examination for ova and
parasites does not detect Cryptosporidium (4-6
µm round in shape).
• Nitazoxanide : 500 mg twice daily for 3 days
and for 2 weeks in PLHIV
• Biliary tract obstruction may
require papillotomy or
T-tube placement.

64. Balantidium coli
• Reported in tropical and subtropical regions,
particularly Central and South America, Iran,
Papua New Guinea and the Philippines.
• Prevalence is usually <1%
• Higher rates are reported in hyperendemic
areas and some residential institutions.
• Swine - important animal reservoir
• Closely resembles amoebic colitis

66. B. coli
Invade
Distal ileal and colonic mucosa
penetrate
hyaluronidase
Mucosa and submucosa, and muscle layers
inflammation products of parasite
inflammatory cells
Inflammation

67. Iron hematoxylin stain Bailenger’s stain
Mayer’s hematoxylin Phase contrast microscopy
Iodine stain
Wet mount preparation

68. Diagnosis
• Large motile trophozoites can be detected
using hand lens
• Serology : specific antibody can be detected
Management
• Tetracycline 500 mg four times daily for 10
days

69. Isospora belli
• Faecal-oral spread
• Associated with mild to a subtotal villous
atrophy
• Inflammatory cells and eosinophils are seen in
the lamina propria.
• Watery diarrhoea, cramping abdominal pain
and nausea.
• Associated with wasting and dehydration

70. • Stool examination using
wet preparations and
modified Ziehl–Neelsen
acid-fast stained smears
• Co-trimoxazole QID for 10
days and then 1 DS tablet
three times daily for three
weeks

71. Cyclospora
• Cyclospora cayetanensis
• Single host to complete its entire life cycle
• History of foreign travel and those infected with
HIV.
• 4–7% has been reported in foreign residents in
Nepal( as seasonal outbreak)
• In 1996, a major outbreak of cyclosporiasis was
investigated in the USA, which was found to be
due to the ingestion of Guatemalan raspberries

72. • Responsible for persistent diarrhoea in both
immunocompetent and immunocompromised
individuals.
• Abdominal gas , bloating and weight loss are
also commonly associated features.
• Guillain–Barré syndrome.
• Cyst concentration techniques
• TMP-SMX 160–800 mg twice dailyfor 7 days

73. Microspora
• Found since the outbreak of the HIV
• Enterocytozoon bieneusi
• No mitochondria
• Sclerosing cholangitis like syndrome
indistinguishable from cryptococcus induced
• Diagnosis : gold standard is the electron
microscopy of intestinal epithelial cells
• Detection of spores using chromotope in stool

74. Treatment :
• No effective therapy
• Albendazole 7.5mg/kg/dose (max 400mg) bid 2-4
weeks
• Nitazoxanide :
• For Children aged 1-3 years: 100 mg bid 3 days
• For Children aged 4-11 years: 200 mg bid 3 days

75. Dientamoeba fragilis
• Most cases are asymptomatic. D. fragilis is a
small (6–12 mm) cosmopolitan parasite.
• Only trophozoites are known
• Presence of two nuclei in the majority of them.
• Detection : Trichrome stain
Culture
PCR

76. Examination: Assess for perforated Viscous
Investigation: CBC, MP, Widal Test, Stool Examination for routine & for leucocytes
Advice, if culture is available
Abdominal pain?
Fever?
Check: Hypotension, Pain Abdomen, Nausea, Vomiting
Treat for salmonella typhi, shigella, sepsis
Give Ceftrixone ig IV 2 g X 5-7 days
Provide hydration and evaluate for surgery
Provide oral
Rehydration and
observe
Stool Evaluation: Positive for ova
or parasites?
Tenesmus or Bloody stools Bloating / Flatulence?
Treat for
Giardiasis
Treat for
Amoebiasis
Treat Empirically for
Cyclosporiasis and
Giardiasis
Treat for Shigella sp,
Yersinia sp and
Salmonella sp.
NoYes
NoYes
Yes NoYes
Yes No
No
Give Specific Treatment

77. Problems with Diagnosis
and Management
• Failure to detect pathogens
• Relationship between enteric pathogens and
chronic diarrhoea is uncertain
• Pathogens may not have effective /
convenient treatment
• Laboratory facilities and expertise are needed
• Quality of life and functional status have
received little attention

78. • In PLHIV, Very often the episodes of diarrhoea are recurrent
and severely compromise the quality of life.
• Frequent absence from work and need to access medical
care.
• This has not been well studied.
• Although the initial evaluation is quite simple, if no
pathogen is isolated, then further testing may be required
and this is expensive.
• Lab facilities and expertise of this nature is not available in
most institutions.
• Finally, the cost needs to be considered.
• These include cost to the health care, to the patient- both
direct and indirect (due to loss of wages).

79. Approach in a resource poor settings
Management Approach
• Treat empirically with cotrimoxazole or quinolones first for
a period of 5-7 days
• If no improvement, treat with metronidazole for 7
days
• Cotrimoxazole DS 2 bid for three weeks and ciprofloxacin
750 mg bid for 1 week as empirical regimen is quite
effective
• May be combined with metronidazole or albendazole
• Investigate for the pathogen separately

80. Prevention
• Areas commonly missed in
hand washing

81. Effective Hand Washing

82. Prevention
1. Sanitation : safe disposal of human excreta
coupled with washing hands after defecation
and before eating
2. Water supply: protecting the water supplies
from fecal contamination cysts are not killed by
chlorination
3. Uncooked vegetables can be disinfected with
acetic acid or full sterngth vinegar
4. Education periodical examination and treatment
of food handlers

83. Safe to drink:
• Bottled water
• Tap water that has been boiled for at least 1
minute
• Carbonated (bubbly) water from sealed cans
or bottles
• Carbonated (bubbly) drinks (like soda) from
sealed cans or bottles

84. Filters that are designed to remove the parasite
should have one of the following labels:
• Reverse osmosis,
• Absolute pore size of 1 micron or smaller,
• Tested and certified by NSF Standard 53 for
cyst removal, or
• Tested and certified by NSF Standard 53 for
cyst reduction

85. References
• API medicine update 2013
• Harrison's Principles of Internal Medicine – 18th edition
• Davidson's Principles and Practice of Medicine 21st edition
• Manson's Tropical Diseases 22nd ed. - G. Cook, et. al., (Saunders,
2009)
• Parasitology in relation to clinical medicine by K D Chatterjee
• Park’ textbook of preventive and social medicine, 21st edition
• Parasitology Research journal, October 2005, Volume 97, Issue 4,
pp 270-273

86. References:
• Gastrointestinal Manifestations in PLHIV, NACO guidelines-
September 2013
• www.dpd.cdc.gov
• Enteric pathogens in southern Indian HIV-infected patients
with & without diarrhoea, Mukhopadhya A. Indian Journal
of Medical Research 1999; 109: 85-90.
• Attili SV, Gulati AK, Singh VP, Varma DV, Rai M, Sundar S.
Diarrhea, CD4 counts and enteric infections in a hospital -
based cohort of HIV-infected patients around Varanasi,
India. BMC Infect Dis. 2006 Mar 1;6:39.