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1. Miscellanous protozoa
Dr. Himanshu Khatri
E-mail: himanshubkhatri@yahoo.co.in

2. • Blastocystis hominis
• Cystoisospora spp.
• Cryptosporidium spp.
• Cyclospora spp.
• Microsporidia
• Toxoplasma gondii
• Balantidium coli
• Sarcocystis spp.
• Babesia spp.

3. Blastocystis hominis
• Lives in human intestine
• Some may develop diarrhoea (especially
immunocompromised like HIV patients)
• Morphologic forms:
1. vacuolated
2. granular
3. amoeboid
4. cyst
• Transmission: faeco-oral
• Treatment: Iodoquinol, Metronidazole

5. Cystoisospora belli
• Previously Isospora belli
• Worldwide distribution
• More common in tropics/subtropics
• Common in AIDS patients

6. Organism characteristics and life cycle
• Simple life cycle
• Completes in one host
• Transmission is faeco-oral
• Infective form is mature (sporulated) oocyst
• Oocystexcystation8 sporozoitesinvade intestinal
epithelial cellsschizogony and gametogony
 Schizogonymerozoites infect other enterocytes
 Gametogonymacrogametes and
microgametessyngamyoocyst with 1 sporoblastoocyst
with 2 sporoblast (unsporulated) exit forms

7. Organism characteristics and life cycle…
cont’d
• Unsporulated oocyst (containing sporoblast)
matures in the environment to form
sporulated oocyst (containing sporocyst which
contain sporozoites)
 1 sporoblast2 Sporoblast 2 sporocysts,
each containing 4 sporozoites
Double layered cell wall

9. Oocyst
• Elliptical
• 22-33 microns x 10-15 microns

10. Pathology and clinical features
• Damage to intestinal mucosa
• Watery diarrhoea without blood and pus
• Abdominal cramps
• Malabsorptionweight loss
In immunocompetent: self limiting
In immunocompromised, infants and
children:chronic and relapsing formweight
loss

11. Laboratory diagnosis
• C.belli oocysts
• Oocysts are transparent. Hence difficult to see in
saline preparation, and only seen in iodine
• Modified acid-fast stain
• Fluorescent auramine stain
• Oocyst appear intermittently
 Concentration techniques
 Multiple specimen collection

15. Treatment
• Trimethoprim (160mg) and
sulphamethoxazole (800mg)
4 times a day
For 1 week

16. Cryptosporidium parvum
• More common in AIDS
• Infects humans and cattle
• Total 20 species of which 19 species do not
infect humans

17. Organism characteristics and life cycle
• Differentiating features:
Oocyst are spherical and 2-5 microns in
diameter
Thin walled (infect same host) and thick
walled (exit forms)
Sporozoites trophozoites which multiply in
vacuole between outer membrane and
cytoplasm

20. Pathology and clinical features
• Differentiating features
Profuse diarrhoea
Severe dehydration
Severe electrolyte imbalance
Higher hospitalization rates

21. Laboratory diagnosis
• Modified Ziehl-Neelsen staining
• Staining with diamidinophenylindole (DAPI):
stains sporozoites
• Concentration technique: Sheather’s sugar
floatation technique
• Intestinal biopsy
• Enterotest

23. Treatment
• No effective treatment
• Only supportive care

24. Cyclospora
• Differentiating features
Oocyst are spherical but 7-10 microns in
diameter
Oocyst contains 2 sporocysts each with 2
sporozoites
• Treatment: Cotrimoxazole

27. Microsporidia
• Around 15 species are known
• Microsporidia are more
commonly seen in AIDS
patients
• Are obligatory intracellular
parasites
• Produce spores by
sporogony, which are small
(2-3 μm in diameter), acid
fast, and highly
environmentally resistant
• Cause diarrhoea,
keratoconjunctivitis, and
myositis in AIDS patients

28. Laboratory diagnosis
• Diagnosis can be made by staining like Gram’s
(Gram positive), Ziehl-Neelsen (acid-fast),
periodic acid-Schiff or Giemsa of biopsy
sectionstiny intracytoplasmic spores are seen
• Spores can also be detected in stool samples
• Species identification can be done by electron
microscopy
• Other methods of diagnosis include culture,
immunofluorescence, serology and PCR

29. Toxoplasma
• Obligate intracellular parasite
• Phylum-Apicomplexa, Class-Coccidia
• Worldwide distribution
• Infects mammals and birds
• Congenital or acquired
• Acute or chronic
• Symptomatic or asymptomatic

30. Life cycle
Involves three distinct yet interlinked cycles
• 1st
: definitive host (feline cycle)
• 2nd
: definitive and intermediate host
(felinenon-feline cycle)
• 3rd
: 2 intermediate hosts (non-felinenon-
feline cycle)

31. Formation of oocysts in definitive host
(cat)
• Product of sexual multiplication
• Produced only in the intestine of cats
• Sperical or ovoid 10-15 microns x 8-12
microns
• Reach the external environment throught
faeces
• Contains 1 sporoblast

32. Maturation of oocysts
• Takes 2-3 days
• 1 sporoblast2 sporoblasts2 sporocysts each
sporocyst contains 4 sporozoites i.e. 2 sporocysts will
contain 8 sporozoites (similar C. belli)
• Oocysts can infect
 Cats (feline-feline cycle)
 Other intermediate hosts (feline-non feline cycle)

33. • OocystsSporozoites are liberated on reaching
intestine of cats/other mammals penetrate
intestinal mucosal cells multiply asexually

34. • Sporozoitesendozoites or tachyzoites (similar to
merozoites in malaria)on reaching a threshold
numberinfected cell ruptures to release
endozoites
• Many endozoites infect other intestinal cells
• Some endozoitesenter extraintestinal tissues
convert to cystozoites (bradyzoites) tissue cysts
particulary in brain and muscle
• These tissue cysts are also infective forms like the
oocysts

35. • In cats, in addition to the above:
endozoitesgametogonymicro-
gametocytes and
macrogametocytessyngamy
zygoteoocyst

36. • Feline-non feline cycle:
when a cat feeds on the
mouse/birdcystozoitesliberate in the intestine
of catschizogony and gametogony
• Non feline-non feline cycle:
when an intermediate host feeds on another
intermediate hostcystozoitesliberate in the
intestine only schizogony

39. Tissue cyst in muscle

40. Tissue cyst in brain

41. Infective forms
• Oocysts
• Tissue cysts
• Endozoites in blood

42. Infection in humans
• Accidental intermediate host
• Infective stages:
Oocysts: through food, water, unwashed
hands after handling cats
Tissue cysts: undercooked pork, beef or meat
from another animal, transplantation
Endozoites: blood transfusion, needle stick
injury, transplacental infection

43. Clinical features
• Asymptomatic in 80-90% immunocompetent
children and adults
• Symptomatic infection is generally mild
 Most common: cervical
lymphadenopathyasymptomatic tissue cysts
persist lifelong
 In immunosuppuressed eg. AIDS with CD4+ counts
<100 cells/cummdisseminated disease especially
encephalitis

44. Congenital toxoplasmosis
• Depends on period of infection in relation to
conception (i.e. if infection is > 6 months prior to
conceptionno risk)
• 1/3 of infected women transmit infection
• Risk depends on trimester:
lowest i.e.15% in 1st
semester
highest i.e. 65% in 3rd
semester
• Disease is most severe in 1st
semester and least
severe in 3rd
semester

45. Congenital toxoplasmosis (pathology)
• Hydrocephaly
• Microcephaly
• Intracerebral calcifications
• Microphthalmos
• Chorioretinitis
• Optic nerve atrophy
• Hepato-splenomegaly

46. Hydrocephaly

47. Intracerebral calcifications

48. Chorioretinitis

49. Laboratory diagnosis
• Important in:
pregnant women
newborns
AIDS patients

50. Laboratory diagnosis
• Animal inoculation- time consuming
• Demonstration of parasites in biopsies-time
consuming
• Serology-most widely used

51. Serology
• Sabin-Feldman dye test
• Immuno-fluorescent antibody (IFA)
• Indirect haemagglutination (IHA)
• Complement fixation test (CFT)
• ELISA
Positive titres 1:10 as early as 2-3 weeks

52. Treatment
• Sulfadiazine+pyrimethamine
 In immunocompetent: treatment only if persistent or severe
symptoms
 In pregnant women: pyrimethamine is contraindicated, but
spiramycin can be used
 Ocular toxoplasmosis: treatment for 1 month
 In immunocompromised: sulfadiazine+pyrimethamine+folinic
acid (to prevent bone marrow toxicity of pyrimethamine)
atovaquonepromising for encephalitis in AIDS
 Congenital: above+spiramycin+prednisolone

53. Prevention
• Washing hands before meals
• Washing fruits/vegatables
• Properly cooked meat

54. Balantidium coli
• It is the largest protozoal parasite of humans
(upto 152 microns x 123 microns)
• It lives in large intestines of humans, pigs,
monkeys and rodents

55. Organism characteristic
• It exists in two forms:
1. Trophozoite
2. Cyst

56. Trophozoite
• They are ovoid
• They taper anteriorly
• The anterior end has a depression called
‘periostoma’
• The entire trophozoite is covered with cilia
• They are the organ of locomotion
• They contain two nuclei:
-The bigger one is kidney shaped and called
‘macronucleus’
-The smaller one is round and is situated inside the
concavity of macronucleus

60. Cyst
• They are infective forms
• They are found in the feces of humans and
other animals

63. Life cycle (similar to EH)
• Transmission is either fecal oral or person to person
• Excystation occurs in intestine
• One trophozoite comes out of the cyst
• The trophozoite live in the large intestine
• It can invade the gut mucosa till the submucosa
• It lives on bacteria and can engulf RBCs
• They divide by binary fission
• Hematogenous spread to other organs does not occur
• After a period of growth and multiplication, encystation
occurs
• Cysts pass in the feces

64. Clinical features
• Most are symptomatic
• In symptomatic patients, diarrhoea occurs
• The diarrhoea varies in severity
• Fulminant dysentery may occur in some
patients
• In these patients, gross and microscopic
pathology is similar to amoebiasis

65. Laboratory diagnosis
• Cysts are present in formed stools
• Trophozoites can also be seen in stools, but
are more readily seen in biopsy of ulcers

66. Treatment
• Tetracycline is the treatment of choice
• Metronidazole is also effective

67. Self directed learning
• Sarcocystis
• Babesia

68. Sarcocystis
• Worldwide distribution
• Infects numerous animals
• Frequency of human infection is low
• Complex life cycle:
Definitive host: carnivore (dog, cat etc.)
Intermediate host: herbivore (cow, pig etc.)

69. Humans as host for Sarcocystis
• Definitive: S. hominis, S. suihominis
• Intermediate: S. lindemani

70. Humans as definitive host
• Life cycle very similar to Toxoplasma with some differences:
 Sarcocysts (equivalent to tissue cysts in Toxoplasma) are
infective forms for humans; oocysts are not infective
 Only gametogony takes place inside intestinal epithelial cells
(in Toxoplasma: endopolygeny and gametogony in cats;
endodyogeny in humans)
 Oocysts mature inside the definitive host i.e.humans (in
Toxoplasma:maturation in the environment)
 Oocysts rupture and sporocysts appear in faeces (in
Toxoplasma: oocysts appear in faeces of cats)

71. Intermediate host (cows, pigs)
• Sporozoitesendothelial cell2 generations of
asexual reproductionmerontsenter
mononuclear cells endodyogenymultiplyflow
down streamenter muscles round up to form
metrocytesincrease in number and initiate
sarcocyst formationalso metrocytes mature to
form crescent shaped bradyzoitesinfective form
for humans

72. Sarcocysts of S.hominis and
S.suihominis
• Located in
striated muscle of cows
Heart muscle of pigs
• 1-2 mm x < 1 c.m.
• Contain bradyzoites
• Humans are infected by consuming infected
beef or pork

73. Sporocysts of S.hominis and
S.suihominis
• Appear in human faeces
may appear cemented as a pair or singly
10-18 microns x 8-15 microns (very similar to
C.belli, but smaller)
Acid fast by modified ZN staining
• Infective to cows and pigs

74. Humans as intermediate host for S.
lindemani
• Infective forms for humans: sporocysts
• Sporocyst invade bowel wallvascular endothelial
cellsmultiply:merozoites
(tachyzoites)striated and heart muscle to devleop
into sarcocysts (100-325 microns)
• Sarcocysts in humans are dead end for S.lindemani

77. Clinical features
• Diarrhoea: S.hominis and S.suihominis
• Rarely: myositis, lymphadenopathy when
humans are intermediate host

78. Treatment
• No treatment available

79. Babesia
• > 70 species
• 2 species cause most of human infections:
B.microti
B.divergens
• Symptomatic human infections are rare and
accidental

80. Babesia Vs Malaria
• More common in N.America and Europe
• Ixodid ticks are vectors and reservoirs
• No liver stage
• Do not form pigment
• Tetrads: four daughter cells attached by strand of cytoplasm
• No schizogony or schizonts
• No gametogony (tick ingest merozoites containing RBC
merozoites form isogametes zygote)
• No sexual reproduction. Therefore no definitive or
intermediate host
• No fever at regular intervals

82. • Treatment
Quinine sulphate + clindamycin for 7-10 days
Chloroquine is not effective
• Prevention
Avoidance of tick bites

83. Thank you