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Parasitology
Review
2017
MARGIE MORGAN
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
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
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
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
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
Protozoa Found in Stool: Amebae
pathogen
Intestinal amoeba
Entamoeba coli
Entamoeba histolytica/dispar
Entamoeba hartmanni
Endolimax nana
Iodamoeba butschlii
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
Entamoeba histolytica/dispar
Cysts @10-12 um
In diameter
Up to 4 nuclei in
the cyst
Peripheral
chromatin is evenClean chromatin
Bulls-eye nucleoli
Entamoeba histolytica/dispar
Trophozoites & Cysts
Trophozoite with ingested rbcs
Elongated
chromatoid
body
Amebic abscess
Flask-shaped ulcer of intestinal amebiasis
Amebic liver abscess
Entamoeba histolytica
Serology – high %
positive in extra-
intestinal cases
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
Entamoeba coli – important to
differentiate from the pathogen E. histolytica
Trophozoites & Cysts
Cysts usually
15-25µm, with 5
or more nuclei
visible.
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
Iodamoeba butschlii cysts, 10 – 12 µm in
size with starch inclusion (glycogen mass)
Iodine preparation – glycogen
inclusion stains with iodine
Flagellates
Giardia lamblia
Dientamoeba fragilis
Trichomonas vaginalis
Protozoa Found in Stool: Flagellates
Pathogen
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
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
Giardia lamblia cysts
Clearing between the cell
wall and the cell membrane
Giardia lamblia cysts
Giardia lamblia
only invades intestinal tissue
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
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)
Trichomonas vaginalis
Urogenital protozoan
Scant, watery vaginal
discharge
Four flagella, short
undulating membrane
Protozoa Found in Stool:
Ciliates, Coccidia, Blastocystis
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
Intestinal Sporozoa
(coccidia)
Isospora (Cystoisospora)
Cryptosporidium
Cyclospora
Sarcocystis
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
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
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
Direct Fluorescence Antibody stain –
Cryptosporidium spp
Molecular assays (PCR) and
Enzyme immunoassay for antigen
available.
Giardia
Cryptosporidium
Combo stain for Cryptosporidium
and Giardia lamblia
Cryptosporidia
in intestine
Cryptosporidia in the
intestine - located
just below the
plasma membrane
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
Cyclospora cayetanensis
Modified acid fast positive
8-10 microns
UV autofluorescence
Also positive on Calcofluor
white stain
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
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
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
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
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
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
Trypanosoma cruzi –
Trypomastigote
Peripheral blood – Giemsa stain
Reduvid
bug
Amastigote of T. cruzi in cardiac
tissue
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
TRYPANOSOMA BRUCEI GAMBIENSE
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
Leishmania
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
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
Leishmania amastigotes
◦Macrophages filled with amastigotes (arrows),
several of which have a clearly visible nucleus and
kinetoplast
Nucleus
Kinetoplast
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
Babesia
Maltese cross forms
MALARIA
Protozoan parasite
Transmitted by the anopheles mosquito
Endemic in tropical areas
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
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
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
MALARIA
Life Cycle of Plasmodium Species
Progression of the RBC forms
of Malaria
Ring form  Trophozoite Schizont
Gametocyte
Merozoites
(ruptured schizont)
Plasmodium species
Plasmodium falciparum
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi – primates only
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
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 (%)
Parasitology Review 2017
Schuffner’s
granules
P. ovale
Fimbriated
edge
“Rosette” schizont
P. malariae
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
• P. falciparum
-multiple ring forms
per cell
-accolade forms(ring
forms on the edge of
cell.
-Banana gametocyte
Malignant tertian malaria
Black water fever
P. falciparum
High % parasitism
Accolade form
Banana gametocyte
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
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
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
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
Toxoplasma gondii
Toxoplasma gondii cyst Toxoplasma
in brain tissue stained tachyzoites
with hematoxylin and eosin
Free-living Amoeba
Naegleria fowleri
Acanthamoeba
Balamuthia
Parasitology Review 2017
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
Parasitology Review 2017
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
HELMINTHS
Nematodes (roundworms)
Trematodes (flukes)
Cestodes (tapeworms)
Nematodes
Enterobius
Ascaris
Trichuris
Necator and Ancylostoma (Hookworm)
Microfilaria – Wucheria, Brugia, Loa loa,
Mansonella, and Onchocerca
Parasitology Review 2017
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
Enterobius vermicularis (pinworm) eggs
Asymmetrical eggs
Pinworm larvae -
may be seen in stool
specimens examined for
pinworm
Eggs
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
Ascaris lumbricoides
Parasitology Review 2017
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
Trichuris trichiura
tail
Head
Necator americanus,
Ancylostoma duodenale
(Hookworms)
Soil transmitted
2nd
most common helminth infection
Enter via exposed skin
Necator or Ancylostoma – Hookworm egg
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
Strongyloides stercoralis
Can be found in intestines or stools
In real sick can go to lung and cause
pneumonia
Trichinella spiralis
-Tissue nematode
-All stages occur in single
host
-usually an incidental finding
in muscle
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
Parasitology Review 2017
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.
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
Wucheria bancrofti
Brugia malayi
Loa loa
Mansonella perstans
Onchocerciasis
Black fly
Onchocerciasis
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
Intestinal and liver flukes
Fasciolopsis buski Fasciola hepatica
The two most common intestinal flukes
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
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.
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.
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.
Schistosoma mansonii
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).
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
Diphyllobothrium latum
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
Diphyllobothrium latum
Sucking plate
Diphyllobothrium latum
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
Taenia
species
Taenia eggs
Identical eggs for the two species
Taenia saginata
Proglottid > 12 uterine
branches
Parasitology Review 2017
Taenia solium
Proglottis – fewer uterine branches
(<=12 uterine branches)
Scolex - Ring of thorns
Cysticercosis
Caused by the ingestion of T. solium eggs
Not by eating infected pork
Hymenolepis nana
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
Hymenolepis diminuta
Uncommon tapeworm
Big egg @ 80 microns in
diameter
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.
Echinococcus – hydatid cyst
Short tapeworm
Sand like material
contained in the
Cyst, due to inverted folded
tapeworms
Relative size of Helminth
eggs
http://www2.bc.cc.ca.us/bio16/pal/Parasitology.htm
Additional Insects of interest
Maggots
House fly larvae
Bot fly larvae
Bot fly bites human,
Larvae develops and
extrudes from the skin
Ticks of
importance
Soft tick -
Expands with blood
engorgement
Hard Ticks
Black Widow spider
Hour glass
On tummy
Flea
Body louse
Crab louse
Hair nit
Scabies
Tinyeggsunderskin
Mite

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Parasitology Review 2017

  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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 (%)
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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.
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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

Editor's Notes

  1. Particularly difficult to differentiate from falciprium
  2. Hallmark of babesiosis is the tetrad (Maltese cross; cruciform body)
  3. Blackwater fever (falciprium and think black pee)
  4. Microscopic examination
  5. Exception for non-falcirpium is P. vivax where chlorquine resistance is seen in Papua New Guinea and Indonesia
  6. The malaria parasite life cycle involves two hosts.  During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host.  Sporozoites infect liver cells and mature into schizonts, which rupture and release merozoites.  (Of note, in P. vivax and P. ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later.)  After this initial replication in the liver (exo-erythrocytic schizogony ), the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony ).  Merozoites infect red blood cells .  The ring stage trophozoites mature into schizonts, which rupture releasing merozoites.  Some parasites differentiate into sexual erythrocytic stages (gametocytes).  Blood stage parasites are responsible for the clinical manifestations of the disease. The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal .  The parasites’ multiplication in the mosquito is known as the sporogonic cycle .  While in the mosquito&amp;apos;s stomach, the microgametes penetrate the macrogametes generating zygotes .  The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts .  The oocysts grow, rupture, and release sporozoites , which make their way to the mosquito&amp;apos;s salivary glands.  Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle . 
  7. Presence of absence of various stages in the blood Morphology of the gametocyte Size of the infected RBC
  8. Most prevalent Widest geographical distribution
  9. Enlarged RBC; fimbriated/ragged rbc
  10. Fever cycle every 72 hours (quartan), can remain dormant in the blood for years. Untreated infections may last as long as 20 years
  11. P