Parasitology Review 2017

1. Parasitology
Review
2017
MARGIE MORGAN

2. Clinical presentation
Travel history or poor sanitation put you at the
highest risk for parasitic infection
Infections associated with sporadic symptoms
Poor immune status higher risk
Dysentery not common (amebiasis)
Most usual symptoms:
◦Abdominal pain, cramping, long term nausea, and
malaise, mucous in stool, and +/- fever

3. Laboratory Diagnosis
Currently based on microscopic exam,
and molecular panels for the most
common (select) parasites
◦Stool (PCR applicable)
◦Non-stool
◦ Perianal specimen
◦ Sigmoidoscopic specimen
◦ Duodenal aspirates
◦ Liver abscess
◦ Sputum
◦ Urine
◦ Urogenital
◦Blood
◦Tissue
Alternative methods:
◦Serology
◦Fluorescent stains

4. Two-vial collection kit for
Stool
10% formalin
Concentration with ethyl
acetate to eliminate fecal
debris
Wet mount, DFA staining and
NAAT
Helminth eggs, larvae,
microsporidia, and protozoan
cysts
PVA with fixative
Polyvinyl alcohol
Permanent stained smear
◦Trichrome stain
Protozoan trophozoites and
cysts
Mercury based fixatives
phased out for safety – Zinc
fixatives are now used

5. Most Common Pathogens
Protozoa
◦Intestinal & urogenital
◦ E histolytica, Blastocystis hominis, Giardia lamblia, Dientamoeba fragilis,
Balantidium coli, Cryptosporidium sp., Cyclospora sp, Cyclospora,
Cytoisospora(Isospora) belli, and Microsporidia
◦Blood & tissue
◦ Plasmodium, Babesia, Trypanosomes
◦ Toxoplasma gondii, Leishmania
◦ Naegleria, Acanthamoeba, Balamuthia
Helminths
◦Nematodes
◦ Ascaris, Trichuris, hookworm, pinworm, and Strongyloides
◦Cestodes
◦ Taenia, Hymenolepis, Diphyllobothrium
◦Trematodes
◦ Fasciola, Fasciolopsis, Schistosoma, Paragonimus, Clonorchis

6. PROTOZOA
Amebae (found in stool)
◦ Entamoeba coli
◦ Entamoeba histolytica
◦ Endolimax nana
◦ Iodamoeba butschlii
◦ Dientamoeba fragilis
Flagellates (found in stool)
◦ Giardia lamblia
◦ Chilomastix mesnili
Ciliates, Coccidia, Blastocystis
◦ Balantidium
◦ Cryptosporidium
◦ Cystoisospora (Isospora) belli
◦ Sarcocystis
◦ Cyclospora
◦ Microsporidium
◦ Blastocystis hominis
Blood-Borne Protozoa
◦ Babesia
◦ Leishmania
◦ Trypanosoma brucei
◦ T. cruzi
◦ Plasmodium
Other
◦ Toxoplasma
◦ Naegleria fowleri
◦ Acanthamoeba

7. Protozoa Found in Stool: Amebae
pathogen

8. Intestinal amoeba
Entamoeba coli
Entamoeba histolytica/dispar
Entamoeba hartmanni
Endolimax nana
Iodamoeba butschlii

9. Entamoeba
histolytica/dispar
E. histolytica is a pathogen and E. dispar is a nonpathogenic
species that can also occur in the large intestine.
Morphologically indistinguishable
◦Antigen testing or molecular methods to distinguish the two species
E histolytica
◦Cysts = infectious form
◦Trophozoites = invasive form
◦Cysts found in contaminated water and poor sanitation
◦Colon biopsy shows “flask-shaped” ulcer with Trophs
◦Non-intestinal disease = extra-intestinal amebiasis (liver
abscess) with Trophs
◦Serology can be useful

10. Entamoeba histolytica/dispar
Cysts @10-12 um
In diameter
Up to 4 nuclei in
the cyst
Peripheral
chromatin is evenClean chromatin
Bulls-eye nucleoli

11. Entamoeba histolytica/dispar
Trophozoites & Cysts
Trophozoite with ingested rbcs
Elongated
chromatoid
body

12. Amebic abscess
Flask-shaped ulcer of intestinal amebiasis
Amebic liver abscess
Entamoeba histolytica
Serology – high %
positive in extra-
intestinal cases

13. Entamoeba coli cyst and trophozoite
Considered a commensal in the
intestine
Cyst @ 20 – 25µm
Up to 8 nuclei
Shed from host
Lives in environment
Trophozoite is the
invasive form that
invades the
intestine
Single nucleus with a large
karyosome located eccentrically
irregular chromatin ring.
The cytoplasm appears dirty and
vacuolated

14. Entamoeba coli – important to
differentiate from the pathogen E. histolytica
Trophozoites & Cysts
Cysts usually
15-25µm, with 5
or more nuclei
visible.

15. Endolimax nana trophozoite
Cysts – 8-10 µm in size, one nucleus
Mostly thought to be a non-pathogen, seen in stool
specimens from HIV/AIDS patients, some literature
suggesting it can cause intermittent or chronic diarrhea

16. Iodamoeba butschlii cysts, 10 – 12 µm in
size with starch inclusion (glycogen mass)
Iodine preparation – glycogen
inclusion stains with iodine

17. Flagellates
Giardia lamblia
Dientamoeba fragilis
Trichomonas vaginalis

18. Protozoa Found in Stool: Flagellates
Pathogen

19. Giardia lamblia
Contaminated water,
undercooked foods
Mild diarrhea to severe
malabsorption
Foul, watery diarrhea
Day-care center outbreaks
reported, traveler’s diarrhea
Cysts/trophozoites may be seen in
stool, but can be hard to find;
Fluorescent stains and NAAT for
more sensitive detection
Duodenal aspirations can be used
if stool specimens are negative
TROPHOZOITE
“falling leaf” motility
CYSTS

20. Giardia lamblia trophozoite
Waxing and waning
symptoms
Can be irregularly
shed in stool material
making antigen
and molecular methods
necessary for detection
Russia & Mexico
-Hot beds of infection
Confined to intestine
Flagyl (Metronidazole)
is drug of choice

21. Giardia lamblia cysts
Clearing between the cell
wall and the cell membrane

22. Giardia lamblia cysts

23. Giardia lamblia
only invades intestinal tissue

24. Chilomastix mesnili cyst
Nonpathogen
Mimics Giardia lamblia cyst –
except for clear space at end of
cyst
Internal structure looks like
“shepherd’s crook” or safety pin
C. mesnili trophozoite

25. Dientamoeba fragilis
Diarrhea, anal pruritus
Only a trophozoite stage 5 – 15 µm (No cyst)
Usually two nuclei visible in the trophozlite
Can occur in Co-infection with Enterobius (pinworm)

26. Trichomonas vaginalis
Urogenital protozoan
Scant, watery vaginal
discharge
Four flagella, short
undulating membrane

27. Protozoa Found in Stool:
Ciliates, Coccidia, Blastocystis

28. Ciliates
Balantidium coli
◦Mainly in swine
◦Contact with swine & poor hygiene
◦Only ciliate that’s pathogenic to humans
◦Similar disease as amebiasis, but extraintestinal invasion
rare
◦Largest (50-200 um) trophozoite; surface covered with
cilia; macronucleus
◦Cyst 40-60 um
◦Readily identified in fresh, wet mounts
◦Can cause flask shaped ulcer in intestine

29. Intestinal Sporozoa
(coccidia)
Isospora (Cystoisospora)
Cryptosporidium
Cyclospora
Sarcocystis

30. Isospora(Cystoisospora)
belli
Contaminated food/water, oral-anal
Found most commonly in HIV/AIDS
Infects intestinal epithelium
Malabsorption syndrome mimicking giardiasis
Positive
Modified acid fast stain

31. Cryptosporidium spp
C. parvum and C. hominis
Contaminated water
Resistant to usual water-purification procedures
(chlorination, ozone)
Daycare center outbreaks (fecal-oral), swimming
pools
Watery diarrhea; more severe in AIDS

32. Cryptosporidiosis: Diagnosis
Partial Acid Fast Stain Positive
Not detected in routine O & P exams (left)
Requires modified acid-fast stains for detection, oocysts measure
4-6 µm , Antigen, DFA and Molecular assays aid detection.
PAF stain Positive

33. Direct Fluorescence Antibody stain –
Cryptosporidium spp
Molecular assays (PCR) and
Enzyme immunoassay for antigen
available.
Giardia
Cryptosporidium
Combo stain for Cryptosporidium
and Giardia lamblia

34. Cryptosporidia
in intestine
Cryptosporidia in the
intestine - located
just below the
plasma membrane

35. Cyclospora cayetanensis
Contaminated fruits and vegetables – particularly ones with plant
hairs
Watery diarrhea; fatigue, anorexia, weight loss, flu like
symptoms. More severe in immune suppressed, can last for
months
Infects upper small bowel
Treatment Oral Trimethoprim/sulfamethoxazole
Found in vacuoles in cytoplasm of jejunal epithelium, villous
atrophy, crypt hyperplasia

36. Cyclospora cayetanensis
Modified acid fast positive
8-10 microns
UV autofluorescence
Also positive on Calcofluor
white stain

37. Microsporidia
Obligate intracellular fungal parasite
Enterocytozoon and Encephalitozoon species most
common genera
Primitive eukaryotic organism (fungi)
Infection by ingestion of spores
Chronic diarrhea in AIDS patients
Myositis, hepatitis, peritonitis, keratitis,
gastrointestinal and biliary tract

38. Microsporidia
-Diagram of detailed internal spore
structures
Positive on modified Trichrome
and Calcofluor white stains
-Longer staining times will eventually
allow for it to work its way into the spore

39. Blastocystis hominis (algae)
Small #s: can be commensal
Large #s: may be pathogenic
Contaminated food and H20  Traveler’s diarrhea
Iodine wet mount
Nuclear blobs
Around the periphery Trichrome
stain

40. None;None;
self resolving.self resolving.
Maltese cross in rbcMaltese cross in rbcHemolytic anemia,Hemolytic anemia,
Jaundice, fever,Jaundice, fever,
hepatomegalyhepatomegaly
Ixodes tickIxodes tickBabesia microtiBabesia microti
Pentosam;Pentosam;
PentamidinePentamidine
isethionate.isethionate.
IntracellularIntracellular
(macrophages)(macrophages)
leishmanial bodiesleishmanial bodies
with kinetoplastwith kinetoplast
Visceral leishmaniasisVisceral leishmaniasis
(Kala-azar),(Kala-azar),
granulomatous skingranulomatous skin
lesionslesions
Iraq/Iran/AfghanistanIraq/Iran/Afghanistan
Phlebotomine sandflyPhlebotomine sandflyLeishmania donovaniLeishmania donovani
CNS:CNS:
melarsoperolmelarsoperol
Nifurtimox andNifurtimox and
Benzonidazole.Benzonidazole.
Hemoflagellate inHemoflagellate in
blood or tissue.blood or tissue.
C- or comma-shapedC- or comma-shaped
AmericanAmerican
trypanosomiasis;trypanosomiasis;
Chagas disease:Chagas disease:
megacolon, cardiacmegacolon, cardiac
failure.failure.
Reduvid (kissing) bugReduvid (kissing) bugT. cruziT. cruzi
Blood stage:Blood stage:
Suramin orSuramin or
petamidinepetamidine
isethionateisethionate
Hemoflagellate inHemoflagellate in
blood or lymph nodeblood or lymph node
AfricanAfrican
trypanosomiasis;trypanosomiasis;
Sleeping sicknessSleeping sickness
Encephalitis; cardiacEncephalitis; cardiac
failurefailure
Tsetse flyTsetse flyTrypanosoma bruceiTrypanosoma brucei
TreatmentTreatmentDiagnosisDiagnosisDisease/SymptomsDisease/SymptomsTransmissionTransmissionOrganismOrganism
BLOOD BORNE PROTOZOA

41. Trypanosomes
2 Diseases
◦Chagas disease (American trypanosomiasis)
◦Trypanosoma cruzi
◦Vector: Reduviid / Triatome (kissing) bug
◦African sleeping sickness (African trypanosomiasis)
◦T. brucei (gambiense and rhodesiense)
◦Vector: Tsetse fly

42. Trypanosoma cruzi  Chagas
(American trypanosomiasis)
Vector: Reduvid/Triatoma (kissing) bug
Trypomastigotes are the only stage found in the blood of an
infected person; may be seen in CSF in CNS infections
Motile circulating trypomastigotes are readily seen on slides of
fresh anticoagulated blood in acute infection but are rarely
detectable by microscopy in chronic T. cruzi infection.
A typical trypomastigote has:
◦ A large, subterminal or terminal kinetoplast,
◦ A centrally located nucleus,
◦ An undulating membrane, and
◦ A flagellum running along the undulating membrane, leaving the body
at the anterior end.
◦ 12 to 30 µm in length.
Amastigote stage parasite may be seen in histopathology
specimens from affected organs.
C-shape

43. Trypanosoma cruzi –
Trypomastigote
Peripheral blood – Giemsa stain
Reduvid
bug
Amastigote of T. cruzi in cardiac
tissue

44. Trypanosoma brucei 
Sleeping sickness (African
trypanosomiasis)
The two T. brucei species that cause African
trypanosomiasis are indistinguishable morphologically
◦ T. brucei gambiense
◦ T. brucei rhodesiense
A typical trypomastigote has:
◦ A small kinetoplast located at the posterior end
◦ A centrally located nucleus
◦ An undulating membrane, and
◦ A flagellum running along the undulating membrane, leaving
the body at the anterior end
◦ 14 to 33 µm in length
Trypomastigotes are the only stage found in patients. kinetoplast
nucleus

45. TRYPANOSOMA BRUCEI GAMBIENSE

46. Leishmania
Obligate intracellular parasite
Vector: female sand fly bite
Two forms of disease
◦Visceral leishmaniasis (kala azar)
◦L. donovani
◦Cutaneous leishmaniasis
◦L. tropica
◦L. braziliensis

47. Leishmania

48. Leishmania – Clinical
Disease
Cutaneous
◦Single or few chronic, ulcerating lesions;
many species
◦Latin America, southern Europe, Middle east,
southern Asia, Africa
◦Mucocutaneous in Latin America
Visceral
◦primarily L. donovani complex (Asia), L.
infantum/chagasi (Africa and Latin America),
others
◦Hepatosplenomegaly, anemia, cytopenias,
systemic symptoms
◦India, Bangladesh, Nepal, Sudan, and Brazil
◦Important OI in HIV infection

49. Leishmania
Diagnosis
◦Biopsy of infected tissue (skin, bone marrow)
◦Multiple, tiny 2-5 um amastigotes within histiocytes
◦Distinct kinetoplast (bar-like structure adjacent to nucleus)
◦PCR methods
◦Urinary antigens (visceral)
DDx of multiple tiny intracellular organisms
◦Leishmania – kinetoplast
◦Histoplasma – budding
◦Toxoplasma – somewhat curved, mostly extracellular

50. Leishmania amastigotes
◦Macrophages filled with amastigotes (arrows),
several of which have a clearly visible nucleus and
kinetoplast
Nucleus
Kinetoplast

51. Babesia
Protozoan: B. microti, B. divergens
Zoonosis (deer, cattle, rodents; humans accidental host)
Transmission vector: Ixodes tick bite
Infects red blood cells
Found world-wide
B. microti along the Northeast US
◦ Nantucket Island, Martha’s vineyard, Shelter Island
Malaria-like syndrome
◦ Fever but without periodicity, “B-symptoms”, hemolytic anemia,
hemoglobinuria, renal failure
Dx:
◦ Blood smear examination
◦ Ring form only (mimics P. falciparum)
◦ Tetrads (unlike P. falciparum)
Maltese cross
(tetrads)
Ixodes tick

52. Babesia
Maltese cross forms

53. MALARIA
Protozoan parasite
Transmitted by the anopheles mosquito
Endemic in tropical areas

54. Malaria Symptoms
Fever pattern
ParasiteParasite DiseaseDisease
PlasmodiumPlasmodium
falciparumfalciparum
MalignantMalignant tertiantertian
malariamalaria
P. vivaxP. vivax BenignBenign tertiantertian malariamalaria
P. ovaleP. ovale BenignBenign tertiantertian malariamalaria
P. malariaeP. malariae QuartanQuartan malariamalaria
Tertian = q 48 hours (every other day)
Quartan = q 72 hours

55. Malaria
Physical exam findings
◦Fever
◦Splenomegaly
◦P. falciparum - most pathogenic species
◦Jaundice
◦Hepatomegaly
◦Increase in respiratory rate
◦CNS involvement
◦Blackwater fever – hemolysis, renal failure
Diagnosis: peripheral blood smear
Antigen screen (EIA) and NAAT

56. Malaria
Primary distinction is P. falciparum and non-falciparum
disease
◦P. falciparum = rapidly progressive and LETHAL (malignant
tertian fever), often chloroquine-resistant
◦Non-falciparum = rarely cause severe manifestations, often
chloroquine sensitive
Relapsing malaria
◦Dormant hepatic phase can recur from liver
◦Occurs only with P. vivax and P. ovale

57. MALARIA
Life Cycle of Plasmodium Species

58. Progression of the RBC forms
of Malaria
Ring form  Trophozoite Schizont
Gametocyte
Merozoites
(ruptured schizont)

59. Plasmodium species
Plasmodium falciparum
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi – primates only

60. ovaleovale
VectorVector MosquitoMosquito MosquitoMosquito MosquitoMosquito Ixodes tickIxodes tick
RBCRBC Any RBCAny RBC Young RBC;Young RBC;
enlargedenlarged
Mature RBC;Mature RBC;
Not enlargedNot enlarged
RingRing Multiple canMultiple can
be seen;be seen;
delicate;delicate;
“appliqu锓appliqué”
Rarely >1;Rarely >1;
thickenedthickened
1-121-12
TetradsTetrads
((MalteseMaltese
crosscross))
DelicateDelicate
Rings onlyRings only
SchizontSchizont Rarely seenRarely seen Commonly seenCommonly seen ““rosette”rosette” nonenone
GametocyteGametocyte Banana-Banana-
shapedshaped
RoundRound nonenone
Extra-RBCExtra-RBC
formform
NoneNone NoneNone PresentPresent
Schüffner dotsSchüffner dots NoNo YesYes NoNo
PigmentationPigmentation BrownBrown NoNo
Infection rateInfection rate >2%>2% <2%<2% 5-10%5-10%
ProtectiveProtective
polymorphismpolymorphism
ss
Hemoglobin S,Hemoglobin S,
C,E, alpha andC,E, alpha and
beta thal, G6PDbeta thal, G6PD
Duffy negativeDuffy negative
(P. vivax)(P. vivax)
DormantDormant
hepatic phasehepatic phase
(relapse)(relapse)
NoNo YesYes NoNo

61. Malarial Preparations
Thick smear
Drop of blood on slide
Water rinse to eliminate rbc’s
Stain with Giemsa stain (not
Wright-Giemsa) proper pH
Need the proper pH to stain
the Schuffner’s granules
Concentrated to spot malaria
parasites
Thin smear
Feather edge smear
For optimal morphology, stain
with Giemsa (not Wright-
Giemsa) stain with proper pH
Speciation of malaria
Parasitemia (%)

63. Schuffner’s
granules

64. P. ovale
Fimbriated
edge

65. “Rosette” schizont

66. P. malariae

67. P. vivax
Amoeboid ring form
P.vivax – benign tertian malaria (fever every 48 hours),
Duffy negative Red blood cell protects from Plasmodium invasion-
African natives lack Duffy rbc antigen and this prevents them from P. vivax.
Untreated infections last several years remaining dormant in the liver.
Patients can survive years without treatment, but recurrent and chronic infection can
lead to brain, kidney and liver damage

68. • P. falciparum
-multiple ring forms
per cell
-accolade forms(ring
forms on the edge of
cell.
-Banana gametocyte

69. Malignant tertian malaria
Black water fever
P. falciparum
High % parasitism
Accolade form
Banana gametocyte

70. P. falcipriumP. falciprium Non-Non-
FalciparumFalciparum
BabesiaBabesia
VectorVector MosquitoMosquito MosquitoMosquito Ixodes tickIxodes tick
RBCRBC All RBCAll RBC Young RBCYoung RBC
RingRing 1-31-3
delicatedelicate
Rarely >1Rarely >1
thickenedthickened
1-121-12
TetradsTetrads
DelicateDelicate
Rings onlyRings only
GametocyteGametocyte Banana shapedBanana shaped roundround nonenone
Extra-RBCExtra-RBC
formform
NoneNone NoneNone PresentPresent
PigmentationPigmentation BlackBlack brownbrown nonenone
InfectionInfection
raterate
>2%>2% <2%<2% 5-10%5-10%
ProtectiveProtective
polymorphispolymorphis
msms
Hemoglobin S,Hemoglobin S,
C,E, alpha andC,E, alpha and
beta thal, G-6-beta thal, G-6-
PDPD
Duffy negativeDuffy negative

71. OrganismOrganism TransmissionTransmission Disease/SymptoDisease/Sympto
msms
DiagnosisDiagnosis TreatmentTreatment
ToxoplasmaToxoplasma
gondiigondii
Oral from cat fecalOral from cat fecal
materialmaterial
or meator meat
Adult: flu like;Adult: flu like;
congenital:congenital:
abortion, neonatalabortion, neonatal
blindness andblindness and
neuropathiesneuropathies
Intracellular (inIntracellular (in
macrophages)macrophages)
tachyzoitestachyzoites
SulphonamidesSulphonamides
,,
pyemethaminepyemethamine
, possibly, possibly
spiramycinspiramycin
(non-FDA)(non-FDA)
Other Protozoa - Toxoplasma

72. Toxoplasma gondii
Coccidian protozoan
House cat (kittens) = definitive host
Infection from:
◦Ingestion of infective oocysts from contaminated cat feces
◦Ingestion of improperly cooked meat from animals that serve as
intermediate hosts
Symptoms
◦Predilection for lung, heart, lymphoid organs, CNS/eye
◦Infectious mono-like; lymphadenitis, hepatitis, rash, encephalomyelitis,
myocarditis, chorioretinitis
◦Transplacental infection
◦ 1st
trimester  spontaneous abortion, stillbirth or severe disease
◦ 2nd
/3rd
trimester  CNS infections (epilepsy, encephalitis, intracranial
calcifications, MR, chorioretinitis, blindness, hearing loss), jaundice, rash
◦AIDS - Encephalitis; mass lesions in brain

73. Toxoplasma gondiiDiagnosis
◦Serology EIA
◦Anti-toxo IgM – congenital and acute infection; may persist
for months
◦Anti-toxo IgG – common; if positive, gestations safe from
intrauterine toxoplasmosis infection
◦PCR

74. Toxoplasma gondii
Toxoplasma gondii cyst Toxoplasma
in brain tissue stained tachyzoites
with hematoxylin and eosin

75. Free-living Amoeba
Naegleria fowleri
Acanthamoeba
Balamuthia

77. Amoebic
meningoencephalitis
Most common cause: Naegleria fowleri
Granulomatous amoebic encephalitis or brain
abscess: Acanthamoeba and Balamuthia
Clinical scenario: swimming or diving into fresh-
water pools

79. Contact-lens keratitis
Caused by Acanthamoeba
Can be cultured on a “lawn of E. coli”
◦Take corneal scrapings
◦Visible trail of ameba moving across plate ingesting
E. coli
Wright’s stain

80. HELMINTHS
Nematodes (roundworms)
Trematodes (flukes)
Cestodes (tapeworms)

81. Nematodes
Enterobius
Ascaris
Trichuris
Necator and Ancylostoma (Hookworm)
Microfilaria – Wucheria, Brugia, Loa loa,
Mansonella, and Onchocerca

83. Enterobius vermicularis
(pinworm)
Humans considered only host
Females 8-13mm, males 2-5 mm
Dwell in the cecum
¼-1/2 inch in thickness, white, lloks like string in
stool
Lay up to 15,000 eggs
◦Oval with a flattened side: 50-60um by 20-30um
Diagnosis- Scotch tape test or anal swab
Most common helminth in US

84. Enterobius vermicularis (pinworm) eggs
Asymmetrical eggs

85. Pinworm larvae -
may be seen in stool
specimens examined for
pinworm
Eggs

86. Ascaris lumbricoides
(roundworm)
1-1.2 billion people infected
◦More common in children
20,000 death
Largest helminth to affect humans
Females 20-35cm long, males 15-30cm with a
curved tale
◦Can cause intestinal obstruction

87. Ascaris lumbricoides

89. Trichuris Trichiura
(whipworm)
Soil transmitted
Disease can can be similar to amebiasis
PVA preserved samples inferior to formalin
Adults attach to large intestine and are rarely
recovered – diagnosis by detecting egg in stool
specimens
Thinnest part- head
Males are smaller than females

90. Trichuris trichiura
tail
Head

91. Necator americanus,
Ancylostoma duodenale
(Hookworms)
Soil transmitted
2nd
most common helminth infection
Enter via exposed skin
Necator or Ancylostoma – Hookworm egg

92. Strongyloides stercoralis
Soil transmitted
Larval form only
Presence of internal structures can separate from
artifact
In immune suppressed - massive intestinal infection and
migration to the respiratory tract (eosinophilic
pneumoniae) possible
Strongyloides
larvae

93. Strongyloides stercoralis
Can be found in intestines or stools
In real sick can go to lung and cause
pneumonia

94. Trichinella spiralis
-Tissue nematode
-All stages occur in single
host
-usually an incidental finding
in muscle

95. Microfilariae
Sheathed
◦Wucheria bancrofti and Brugia malayi
◦Elephantiasis (lymphangitis/lymphedema)
◦Loa loa
◦Calabar swellings & migrating worms in the conjunctiva
Not sheathed
◦Onchocerca volvulus
◦Mansonella species
◦Allergic skin reactions, edema, Calabar swellings

97. Identification of microfilariae is based on the presence of a sheath covering the larvae, as
well as the distribution of nuclei in the tail region
A, W. bancrofti. B, B. malayi. C, L. loa. D, O. volvulus. E, Mansonella perstans. F, Mansonella
streptocerca. G, Mansonella ozzardi.

98. Filaria
Identification
a. W. bancrofti
◦ Sheathed, nuclei stop short
of end of tail
a. B. malayi
◦ Sheathed, two small nuclei
in tail
a. O. volvulus
◦ Unsheathed, from skin, not
blood
a. Loa loa
◦ Sheathed, nuclei to continue
to end of tail

99. Wucheria bancrofti

100. Brugia malayi

101. Loa loa

102. Mansonella perstans

103. Onchocerciasis
Black fly

104. Onchocerciasis

105. Trematodes (Flatworms)
Intestinal and Liver flukes
◦Fasciolopsis buski
◦Fasciola hepatica
Liver flukes
◦Clonorchis sinensis (Chinese liver fluke)
Paragonimus westermani – oriental lung fluke
Schistosomes
◦S mansoni – intestinal bilharziasis
◦S haematobium - urinary
◦S japonicum – blood fluke, found in intestines

106. Intestinal and liver flukes

107. Fasciolopsis buski Fasciola hepatica
The two most common intestinal flukes

108. Fasciola hepatica
Distinct nose
Fascioliasis is a parasitic infection typically caused by Fasciola hepatica,
also known as "the common liver fluke" or "the sheep liver fluke.
Fascioliasis is found in all 5 continents, especially where sheep or cattle
are reared. Infected by eating raw watercress or other water plants
contaminated with immature parasite larvae. The immature larval
flukes migrate through the intestinal wall, the abdominal cavity, and
the liver tissue, into the bile ducts, where they develop into mature
adult flukes, which produce eggs. The pathology typically is most
pronounced in the bile ducts and liver. Fasciola infection is both
treatable and preventable

109. Intestinal fluke Fasciolopsis buski, causes fasciolopsiasis, is the
largest intestinal fluke of humans. Prevented by cooking aquatic
plants well before eating them. Found in south and southeastern
Asia. Fasciolopsiasis is treatable. Many people do not have
symptoms from Fasciolopsis infection. However, abdominal pain
and diarrhea can occur 1 or 2 months after infection. With heavy
infections Fasciolopsis flukes can cause intestinal obstruction,
abdominal pain, nausea, vomiting, and fever.

110. Clonorchis sinensis
knobbin
Shoulders
operculates
Clonorchis is a
liver fluke that can
infect the liver,
gallbladder and
bile duct. Found
across parts of
Asia, it is also
known as the
Chinese or oriental
liver fluke.

111. Egg is operculate, not
embryonated, thick shell,
asymmetrical and large
Paragonimus westermani
Paragonimus is a parasitic lung fluke (flat
worm). Infections occur after a person
eats raw or undercooked infected crab or
crayfish. The illness is known as
paragonimiasis. Paragonimus infection
also can be very serious if the fluke
travels to the central nervous system,
where it can cause symptoms of
meningitis.

112. Schistosoma mansonii

113. Schistosomiasis, also known as bilharzia, more than 200 million
people are infected worldwide. In terms of impact this disease is
second only to malaria as the most devastating parasitic disease.
The parasites that cause schistosomiasis live in certain types of
freshwater snails. The infectious form of the parasite, known as
cercariae, emerge from the snail, hence contaminating water. You
can become infected when your skin comes in contact with
contaminated freshwater. Most human infections are caused by
Schistosoma mansoni, S. haematobium, or S. japonicum.
Stool or urine samples can be examined microscopically for parasite
eggs (stool for S. mansoni or S. japonicum eggs and urine for S.
haematobium eggs).

114. Cestodes (Tapeworms)
Examples
Diphyllobothrium latum
Taenia saginata
Taenia solium
Hymenolepis nana
Hymenolepis diminuta
Echinococcus granulosis
Flattened dorsoventrally, segmented
Head with armed or unarmed scolex
Proglottids immature, mature (sex organs)
Gravid (with eggs)
Internal structure of proglottids
Hermaphroditic-ovary, testes, vitellaria,
uterus, genital pore and ducts
Lateral excretory and nervous system
No gut-tegument absorbs nutrients
Muscles-longitidinal and horizontal

115. Diphyllobothrium latum

116. Diphyllobothrium latum
Poorly-cooked fresh-water fish (salmon)
Scandinavian, Russia, Canada, N. USA, Alaska
Broad fish tapeworm
Longitudinal sucker
Eggs have non-shouldered operculum and knob
◦They are not embryonated
Infection causes VitaminB12 deficiency

117. Diphyllobothrium latum

118. Sucking plate
Diphyllobothrium latum

119. Taenia saginata
 Beef tapeworm
 4 suckers on scolex
 >13 uterine branches in
proglottids
Ingestion of cysticerci in
beef
Intestinal infestation
Ingestion of eggs ->
Non-human pathogen
Taenia Solium
Pig tapeworm
Ring of thorns/crown on
scolex
<13 uterine branches in
proglottids
Ingestion of cysticerci in pork
Intestinal infestation
Ingestion of eggs ->
Cysticercosis
Taenia Species – two species
Outstanding characteristics

120. Taenia
species

121. Taenia eggs
Identical eggs for the two species

122. Taenia saginata
Proglottid > 12 uterine
branches

124. Taenia solium
Proglottis – fewer uterine branches
(<=12 uterine branches)
Scolex - Ring of thorns

125. Cysticercosis
Caused by the ingestion of T. solium eggs
Not by eating infected pork

126. Hymenolepis nana

127. Hymenolepis nana
Most common cestode recovered in USA
Worm is 2-4 cm
Egg has inner & outer shell separated
space
Water /food contaminated by rodent
droppings
Hooklets inside
Larger outer shell
No radial striations

128. Hymenolepis diminuta
Uncommon tapeworm
Big egg @ 80 microns in
diameter

129. Echinococcus – hydatid cyst disease
found in Africa, Europe, Asia, the Middle East, and
Central and South America. Highest prevalence is found
in populations that raise sheep. Infection ingestion of
egg found in animal feces.

130. Echinococcus – hydatid cyst
Short tapeworm
Sand like material
contained in the
Cyst, due to inverted folded
tapeworms

131. Relative size of Helminth
eggs
http://www2.bc.cc.ca.us/bio16/pal/Parasitology.htm

132. Additional Insects of interest

133. Maggots
House fly larvae
Bot fly larvae
Bot fly bites human,
Larvae develops and
extrudes from the skin

134. Ticks of
importance
Soft tick -
Expands with blood
engorgement
Hard Ticks

135. Black Widow spider
Hour glass
On tummy

136. Flea
Body louse
Crab louse
Hair nit

137. Scabies
Tinyeggsunderskin
Mite