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Compendium Microbiology > Parasitology > Flashcards

Parasitology Flashcards

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1
Q

stool for ova and parasites

  • timing
  • components
A
  • 3 specimens at least 24 hours apart
  • Components:
    • fresh: should be examined within 1 hour, otherwise use fixative
    • concentration with examination of wet prep
    • permanent preparation
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2
Q

most common parasites in blood

A

RBCs:

plasmodium and babesia

WBCs:

leishmania and toxoplasma gondii

whole blood/plasma:

trypanosoma and microfilariae

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3
Q

most common parasites in CNS

A

BATTTMEN

  1. Taenia solium
  2. Echinococcus
  3. Naegleria fowleri
  4. Acanthamoeba
  5. Balamuthia mandrillaris
  6. Toxoplasma gondii
  7. Microsporidia
  8. Trypanosoma brucei
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4
Q

most common parasites in bone marrow

A

leishmania and plasmodium

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5
Q

most common parasites in cutaneous ulcer

A

leishmania and acanthamoeba

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6
Q

most common parasites in liver and spleen

A
  1. echinococcus
  2. entamoeba histolytica
  3. leishmania
  4. microsporidia
  5. schistosoma mansoni and japonicum (eggs only)
  6. fasciola hepatica
  7. clonorchis sinensis

ME CLEFS

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7
Q

most common parasites in muscle

A

trichinella, taenia solium, trypanosoma cruzi, and microsporidia

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8
Q

most common parasites in lungs

A
  1. cryptosporidium
  2. echinococcus hooklets
  3. paragonimus eggs
  4. toxoplasma gondii
  5. strongyloides stercoralis larvae
  6. microsporidia
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9
Q

most common parasites in skin and subcutaneous ulcer

A
  1. leishmania
  2. microfilariae
    1. onchocerca volvulus
    2. loa loa (adult worm)
  3. sarcoptes scabei
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10
Q

most common parasites in GU system

A
  1. trichomonas vaginalis
  2. schistosoma (eggs only)
  3. microsporidia
  4. microfilariae
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11
Q

most common parasites in eyes

A
  1. acanthamoeba
  2. toxoplasma gondii
  3. loa loa
  4. onchocerca volvulus
  5. microsporidia
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12
Q

Protozoa that are likely to be missed on routine O&P

A
  1. cryptosporidium
  2. cyclospora cayetanensis
  3. cystoisospora (formerly isospora) belli

These require modified acid fast (Kinyoun, DMSO, auramine-O) or modified safranin stains

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13
Q

Technique used to collect duodenal contents for parasite exam

A

Beale string technique or aspiration during endoscopy

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14
Q

Blood parasites and stain used

A
  1. Plasmodium and babesia in RBCs
  2. Leishmania mastigotes and toxoplasma gondii tachyzoites in leukocytes
  3. Extracellular trypanosoma
  4. Extracellular microfilariae
    • wuchereria bancrofti
    • brugia malayi
    • loa loa
    • mansonella

Giemsa stained on thin and thick blood films for plasmodium and babesia

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15
Q

serology in parasitology

A

(limited role)

used in prenatal and postnatal toxoplasmosis screening and diagnosis of amebic liver abscess due to E histolytica

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16
Q

Parasites that can be cultured

A
  1. free living amebae (use tap water agar on bed of E coli)
    1. acanthamoeba
    2. naegleria fowleri
  2. Leishmania and trypanosoma (Novy-MacNeal-Nicolle (NNN) medium)
  3. Trichomonas vaginalis (diamond media)
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17
Q

Protozoa

A
  1. amebae (sarcodina): unicellualar organisms, motile by pseudopodal extension
    • intestinal
      • entamoeba
      • endolimax nana
      • iodamoeba butschlii
    • free living
      • naegleria fowleri
      • acanthamoeba
      • balamuthia mandrillaris
  2. Flagellates
    • giardia intestinalis
    • dientamoeba fragilis
    • trichomonas vaginalis
    • leishmania
    • trypanosoma
  3. Ciliates
    • balantidium coli
    • microspora (microsporidia)
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18
Q

Entamoeba histolytica

  • resemble
  • forms
  • diagnosis
  • transmission
  • geographic distribution
  • clinical disease
A
  • morphologically the same as nonpathogenic E dispar
  • morphology similar to E coli and E hartmanni
  • Trophozoites
    • 15-20 um
    • small central karyosome in nucleus with fine chromatin along inner nuclear membrane
    • ground glass cytoplasm, may contain RBCs (only feature that distinguishes from dispar)
    • wet mounts have progressive unidirectional motility
  • Cysts have up to 4 nuclei, may contain chromatoidal bodies with smooth rounded ends
  • Stool EIA better than micro for dx
  • acquired through ingestion of cysts in poopy water/food
  • worldwide
  • Clinical:
    • asymptomatic to bad diarrhea
    • does not invade intestines
    • disseminates to liver
    • abscesses contain “anchovy” paste
    • intestinal flask shaped ulcer, often cecum
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19
Q

Entamoeba coli

A
  • larger than E histolytica
  • nondirectional motility
  • larger eccentric karyosome than histolytica
  • clumped peripheral nuclear chromatin
  • frayed chromatoidal bodies
  • up to 8 nuclei in cyst form
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20
Q

Entamoeba hartmanni

A
  • smaller than histolytica (5-10 um)
  • nondirectional motility
  • small, central karyosome
  • fine chromatin along membrane
  • up to 4 nuclei in cyst
  • chromatoidal bars have rounded ends
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21
Q

Endolimax nana

A

large, knobby “ball and socket” central karyosome

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22
Q

Iodamoeba butschlii

A

prominent iodine staining vacuole

large “ball and socket” central karyosome

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23
Q

Naegleria fowleri

  • clinical disease
  • morphology
  • diagnosis
A
  • primary amebic meningoencephalitis
    • children who have been swimming/diving in warm stagnant fresh water sources
    • enters via olfactory nerve running through cribriform plate
    • fatal
  • trophozoites found in CSF or in meninges (10-35 um), small nucleus with large dense central karyosome
  • cultured on lawn of bacteria (E coli)
  • CSF specimens should NOT be refrigerated
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24
Q

Acanthamoeba

  • clinical diseases
  • morphology
A
  • granulomatous amebic encephalitis (along with balamuthia mandrillaris)
    • cutaneous or pulmonary source
    • hematogenous dissemination to brain; organisms found in perivascular spaces
  • amebic keratitis in contact lens wearer
  • Cysts have 2 walls, 1 nucleus, large karyosome
  • Trophozoites are pleomorphic, small nucleus with large central karyosome
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25
Q

giardia intestinalis

  • morphology
  • similar to
  • dx
  • geographic distribution
  • associations
A
  • trophozoites
    • 10-20 um
    • stool or small bowel bx
    • comma shaped from the side
    • flagella
    • falling leaf motility
    • similar in appearance to chilomastix mesnili: nonpathogenic (lacks central axoneme, rotary motion; cyst lemon shaped with a single nucleus)
  • cysts (10-14 um) oval and contain 4 nuclei along central axoneme
  • EIA dx
  • worldwide
  • associated with daycare centers, ski resorts, and backcountry hiking/camping
  • Associated with B cell humoral immunodeficiency
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26
Q

Dientamoeba fragilis

  • morphology
  • geographic distribution
  • coinfection with ___
A
  • Trophozoites round, binucleate; nuclei with fragile (“fractured”) central karyosome
  • internalized flagellum
  • worldwide: diarrhea and anal pruritis
  • coinfection with enterobius vermicularis
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27
Q

Trichomonas vaginalis

  • transmission
  • morphology
A
  • sexually transmitted
  • trophozoites pear shaped with large nucleus at the anterior end of central axostyle
  • undulating membrane that extends about halfway down the organism
  • jerky nondirectional motility
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28
Q

leishmania

  • dx
  • morphology
  • transmission
  • geographic distribution
  • clinical diseases
A
  • best diagnosed on biopsy, but may be cultured using NNN medium
  • morphology:
    • 2-5 um intracellular amastigotes within histiocytes
    • oval
    • small nucleus adjacent to distinct rod shaped kinetoplast (kinetoplast also found in trypanosoma)
  • transmitted from sandfly
  • Algeria, Afghanistan, Saudia Arabia, Syria, Pakistan, Peru, Brazil
  • Clinical disease:
    • mucocutaneous
      • L braziliensis complex
      • oral/nasal persistent and highly destructive
    • visceral (kala azar)
      • L donovani
      • liver, spleen, bone marrow infection
    • chiclero ulcer of the ear lobe: L mexicana
    • Solitary cutaneous lesions: L tropica and L major
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29
Q

DDX for multiple 2-5 um intracellular organisms

A
  1. Leishmania (amastigotes with barlike kinetoplast in histiocytes, GMS-)
  2. histoplasma (small oval with pseudocapsule in histiocytes, GMS+)
  3. toxoplasma gondii (tachyzoites in multiple cell types, GMS-)
  4. trypanosoma cruzi (heart muscle, GMS-)
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30
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39
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40
Q
A

Only ciliated protozoa to infect humans

Diarrhea

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41
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44
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45
Q

Trypanosoma species

  • morphology
  • dx
  • organs affected
A
  • T cruzi: 20 um and C shaped with a large posterior kinetoplast
  • T brucei: 30 um and delicately curved with a small posterior kinetoplast
  • more likely to be in buffy coat
  • can be found in heart or other tissue in chronic phase
  • DX:
    • cultured using NNN medium
    • serology
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46
Q

Trypanosoma cruzi

  • disease
  • transmission
A

Disease

  • Chagas disease
    • distal esophageal muscularis involvement causes achalasia
    • myocardium (leading cause of heart failure in South and Central America)
  • reduvid bug
    • inoculation site (chagoma) on face
    • Romana sign (palpebral and periocular swelling) is a type of chagoma
    • mud, adobe, and/or thatch homes
  • can be transmitted from mother to child, ingestion, transfusion
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47
Q

T brucei

  • disease
  • transmission
A
  • African sleeping sickness
  • tsetse (glossina) fly
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48
Q

Balantidium coli

  • disease
  • type of protozoa
A
  • bloody diarrhea
  • Ciliate
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49
Q

Microsporidia

  • species type
  • name species
  • diagnosis
A
  • spore forming unicellular organisms, now thought to be fungi, instead of a ciliate
  • Species:
    • Enterocytozoon bieneusi (intestinal and hepatobiliary)
    • Encephalitozoon hellem (ocular)
    • Encephalitozoon intestinalis (intestinal and disseminated)
  • Diagnosis
    • small intestine biopsy: numerous oval intracellular organisms in apical aspect of RBCs
    • stool sample: 1-3 um spores that stain dark red with trichrome
    • PCR
50
Q

Apicomplexa (same level as protozoa)

  • name species
A
  • Coccidia
    • Cryptosporidium parvum
    • Cryptosporidium hominis
    • Cyclospora cayetanensis
    • Cystoisospora (formerly isospora) belli
    • Sarcocystis
    • Toxoplasma gondii
  • Plasmodium
    • P falciparum
    • P vivax
    • P ovale
    • P malariae
  • Babesia
51
Q

Cryptosporidium parvum and hominis

  • disease
  • diagnosis
A
  • watery diarrhea in immunocompromised
  • Diagnosis
    • small intestinal bx (small blue dots at luminal surface; located in an extracytoplasmic apical vacuole on brush border)
    • stool sample: 4-6 um oocysts visible with modified acid fast
    • stool EIA
52
Q

Cyclospora cayetenensis

  • diagnosis
  • disease
A
  • watery diarrhea in Nepal, Peru, Haiti, Guatemala, and US from imported soft fruits and vegetables
  • Diagnosis
    • small bowel biopsy: different stages of the organisms are inside enterocytes
    • stool sample: modified acid fast or autofluorescence
53
Q

Cystoisospora belli

  • diagnosis
  • disease
A
  • watery diarrhea
  • daignosis
    • small intestinal bx: oval structures within enterocytes (interdigitates??)
    • stool: oocysts, 25-30 um, with typical ellipsoidal shape and 1 or 2 sporocysts visible with modified acid fast
54
Q

Sarcocystis

  • disease
  • diagnosis
A
  • infects intestine or striated muscle causing diarrhea and/or myositis
  • diagnosis:
    • stool: 15-20 um long by 15-20 um wide oocysts containing 2 sporocysts; will autofluoresce under UV light and are weakly acid fast
    • skeletal or cardiac muscle bx: bradyzoites seen
55
Q

Toxoplasma gondii

  • disease
  • host
  • diagnosis
  • transmission
A

Disease

  • mono-like syndrome with posterior cervical LAD
  • can cause fetal loss in 1st trimester
  • risk of fetal CNS infection in 3rd trimester (periventricular calcification and chorioretinitis)
  • immunocompromised can develop CNS infection

Cat is the host

Diagnosis:

  • biopsy: tachyzoites are 3-5 um curved structures with large eccentric nucleus; no kinetoplast; bradyzoites are the intraceullar replicative form
  • DDX with bradyzoites, which are within histiocytes:
    • leishmania
    • histoplasma
    • Trypansoma
    • Coccidiodes
  • Serology: IgM positive in congenital and acute infection; rising IgG titer (>1:1024) (low IgG suggests prior infection so pregnant woman not at risk)
  • PCR

Transmission:

  • by ingestion of cat oocyst from feces or from undercooked meat from animals containing tissue cysts
  • transplacental
  • blood/organ transplant
56
Q

P ovale located where

A

western Africa

57
Q

transmission of plasmodia

A

Anopheles mosquito

  • sporozoite injected into host go to the liver and proliferate (exoerythrocytic schizogony)
  • schizonts rupture and release merozoites into blood
  • infect red cells to intitiate RBC schizogony
  • Hypnozoites maintain latent infection in the liver
58
Q

Clinical features of malariae

  • who is at risk
  • initial symptoms
  • frequency of fever spikes
  • lethality
  • nephrotic syndrome ___
  • CNS involvement in ___
  • hemosiderinuria, hemoglobinuria, and renal failure in ____
  • true relapse/recurrence in ____
  • Recrudescence in ____
A
  • immunity develops in children who survive the disease in endemic areas
  • outside of endemic areas, all age groups are susceptible (otherwise kids and pregnant at greatest risk)
  • Vague symptoms at first during erythrocyte schizogony initial stages
  • within weeks schizogony becomes synchronized and produces fever cycles
  • symptoms become paroxysmal with symptomatic periods lasting 6-12 hours and correlating with intermittent intravascular hemolysis

Fever spikes:

  • 48 hours: ovale, falciparum, vivax
  • 72 hours: malariae

lethality: falciparum

nephrotic syndrome: malariae

CNS involvement: falciparum

hemosiderinuria, etc.: falciparum

Relapse: vivax, ovale (reinvasion of RBCs by liver merozoites from hepatic hypnozoites occurs after complete clearing of blood stream by therapy)

Recrudescence: all (parasitemia rendered low by treatment or immunity increases again)

59
Q

Plasmodium infection in

young red cells:

old red cells:

all red cells:

A

young red cells: vivax, ovale

old red cells: malariae

all red cells: falciparum

60
Q

Effect of inherited red cell anomalies on malaria susceptibility

  • hemoglobin S
  • thalassemia, HbC, HbE, hereditary persistence of HbF
  • Duffy negative blood type
  • G6PD deficiency
  • Hereditary ovalocytoses
A
  • hemoglobin S: protective against falciparum
  • thalassemia, HbC, HbE, hereditary persistence of HbF: protective
  • Duffy negative blood type: protective against vivax
  • G6PD deficiency: protective against all
  • Hereditary ovalocytosis: protective against cerebral malaria
61
Q

Diagnosis of plasmodium

A
  • wright stains or fluorescent stains (acridine orange and rhodamine)
  • thick blood film for screening
  • thin blood film for species ID
  • best to obtain specimen preceding next anticipated fever spike
  • need to examine > 100 oil immersion thick film fields or 300 thin film fields to achieve reported sensitivity (5 parasites/ uL)
  • single negative smear insufficient to exclude malaria (need 2-3 smears over 24 hours)
  • flow cytometry
  • antigen detection
  • antibody detection
62
Q

Plasmodium forms found in blood

A
  • Early trophozoites (ring forms): occupy < 1/2 the red cell with 1 or 2 nuclei
  • Trophozoites: divide into multiple merozoites which make up the schizont stage, where multiple nuclei are seen
  • Schizont ruptures and releases merozoites to infect other RBCs
  • Some trophozoites also form a gametocyte ( a solid mononuclear structure occupying >1/2 the red cell that is infective stage for mosquito)
  • Mature stages may contain hematin pigment (coarse in malariae and delicate in other species)
  • Inclusions: Schuffner dots in vivax and ovale and Maurer clefts in falciparum
63
Q

Rosette schizont

A

6-12 merozoites surround a clump of hematin in P malariae

64
Q

P falciparum

  • forms seen in blood
  • infects what organs
A
  • only ring and gametocyte (banana shaped) forms in blood
  • Applique forms
  • headphone forms (ring forms that have double chromatin dots)
  • maurer clefts (round to comma shaped red cytoplasmic dots)
  • RBCs with intermediate forms are in capillaries of brain, heart, kidneys, liver
65
Q

P vivax and ovale

  • morphology
  • number of merozoites
A

Morphology

  • found in enlarged RBCs
  • RBCs in ovale are more oval and may be fimbriated
  • vivax has more ameboid forms (filling RBC)
  • Schuffner dots
  • all stages present

Merozoite number:

  • 6-14 in ovale
  • 12-24 in vivax
66
Q

P malariae

  • size of RBCs
  • morphology
A
  • small to normal size RBCs
  • all stages present
  • 6-12 merozoites in schizonts
  • occasional band, basket, and bird’s eye form trophozoites
67
Q

Mixed infections of plasmodium

A

falciparum and vivax usually (mixed occur in 5%)

68
Q

Degree of parasitemia most important in what Plasmodium species

A

Falciparum

> 2% parasitemia is severe

after treatment started there is a transient increase in parasitemia

69
Q

Babesia diagnosis

A
  • Direct observation on blood smear
    • trophozoites often multiple in red cells; may form tetrads; light blue ring forms with red chromatin dots
    • extraerythrocytic ring forms
    • no pigment or nonring forms seen
  • Antibabesial antibodies may be misleading
    • Antibody titer, by IFA, >=1:1024 indicates active infection
    • remote infection has titer <= 1:64
  • PCR
70
Q

Babesia location

A

US (northeast - B microti)

Europe (Babesia divergens)

Asia

Africa

71
Q

Babesia transmission

A
  • Northeastern US: Ixodes scapularis
  • White tailed deer and white footed mouse (the latter also harbors Borrelia burgdorferi and anaplasma phagocytophilum (human granulocytic anaplasmosis))
    • I scapularis tick transmits (also transmits Borrelia burgdorferi and anaplasma phagocytophilum)
    • coinfection with flavivirus
  • Ixodes ricinus transmits in Europe
72
Q

Babesia disease

A
  • Fatal disease occurs in splenectomized and immunodeficient
  • Nonperiodic fever and hemolysis
73
Q

Metazoa Types

A
  1. Nematodes
  2. Trematodes (flukes)
  3. Cestodes (tapeworms)
74
Q

Nematode species

A

Intestinal

  1. Enterobius vermicularis
  2. Trichuris trichiura (whipworm)
  3. Ascaris lumbricoides (round worm)
  4. Necator americanus and ancylostoma duodenale
  5. Strongyloides stercoralis (thread worm)

Filarial

  1. Wuchereria bancrofti
  2. Brugia malayi
  3. Loa loa
  4. Mansonella perstans
  5. O volvulus (not found in blood)
  6. Dirofilaria immitis (not found in blood)

Zoonotic

  1. Trichinella spiralis
  2. Toxocara canis/cati
  3. Anisakiasis
75
Q

Enterobius vermicularis

  • morphology
  • eggs
  • transmission
  • disease
A
  • Morphology: adult female has bent and pointed tail and has lateral alae on cross section
  • Mature females inhabit cecum and appendix and nocturnally lay eggs perianally
  • Eggs: 30-50 um oval with 1 side flattened and not found in stool
  • Transmission: ingestion of eggs
  • Anal pruritis, vaginitis, and/or enuresis
  • Appendicitis is an occasional complication
76
Q

Trichuris trichiura

  • morphology of worm
  • eggs
  • disease
A
  • worm measures up to 5 cm and has a whiplike anterior end
  • eggs are 50 x 25 um, brownish thick shells, barrel shaped with bilateral polar plugs
  • Dysenterylike; rectal prolapse in children
77
Q

Ascaris lumbricoides (roundworm)

  • worm morphology
  • eggs
  • transmission
  • disease
A
  • 35 cm worm in intestine
  • egg 60 um, bile stained, thick hyaline shell and round mammillated surface (fertile and infertile forms)
  • Transmission:
    • ingest eggs that hatch to produce larvae that penetrate mucosa, enter bloodstream and go to lungs (Loffler syndrome with eos)
    • Expectorated and swallowed, mature into adults that infest duodenum
  • Asymptomatic or complicated by bowel obstruction, cholangitis, or appendicitis
78
Q

Necatur americanus & ancylostoma duodenale

  • worm morphology
  • eggs
  • geographic distribution
  • disease
A
  • adult hookworm 1 cm; mouth parts differ
    • N americanus: cutting plates (on the right in the picture)
    • A duodenale: “teeth” (on the left)
  • Eggs: thin translucent wall encloses morulalike cluster of spherical embryos
  • Found in Asia and sub Saharan Africa, especially coastal regions
    • N americanus found in southeastern US
  • Infection results from penetration of skin by larvae
    • localized pruritis
    • larvae pass through lungs (Loffler) and are expectorated and swallowed
    • adults infest small bowel and may produce iron deficiency anemia
79
Q

Strongyloides stercoralis (thread worm)

  • adult worm morphology
  • eggs
  • diagnosis
  • geographic distribution
  • Disease
A
  • adult worm ~ 3 mm; burrow into intestinal crypts
  • egg identical to hookworm egg but usually not found in stool
    • eggs hatch in bowel and feces contain rhabditoid larvae
    • larvae similar to hookworm larvae but have short buccal groove and prominent genital primordium
  • Duodenal aspirate string test
  • Tropical and subtropical regions, southeast US
  • Penetrate skin, migrate through lungs, expectorated and swallowed resulting in duodenal infection
    • in malnourished host larvae penetrate bowel wall, circulate through lungs (autoinfection)
    • in immunocompromised host autoinfection can lead to hyperinfection where larvae disseminate widely
80
Q

W bancrofti and B malayi

  • disease
  • transmission
  • morphology
A
  • adults infect the lymphatics (elephantiasis)
  • shed into blood at night
  • highest likelihood of detection is between 10 pm and 2 am
  • bancrofti has no nuclei in the tail and it has a sheath
  • malayi has 2 separated nuclei in the tail and it has a sheath
81
Q

Loa loa

  • transmission
  • disease
  • morphology
  • periodicity
A
  • adults migrate through subcutaneous and conjunctival locations
  • transient migratory edema (calabar swellings)
  • diurnal
  • nuclei in tail and it has a sheath
  • Chrysops species flies (deer fly and mango fly)
82
Q

Mansonella perstans

  • morphology
  • disease
  • vector
A
  • inhabit body cavities
  • No sheath
  • biting midge (culicoides)
83
Q

O volvulus

  • transmission
  • disease
  • diagnosis
A
  • Simulium black fly
  • adults ball up in a subcutaneous nodule and release microfilariae into surrounding skin which migrate to the eye
  • River blindness in central Africa and Central America
  • Diagnose by identifying larvae in skin snips
84
Q

Dirofilaria immitis

  • transmission
  • disease
A

Dog heartworm

Mosquito

presents as subcutaneous or pulmonary granulomatous nodule surrounding a degenerating worm

85
Q

Trichinella spiralis

  • transmitted
  • disease
  • diagnosis
A
  • Consumption of undercooked meat, especially pork and wild game
  • infection of skeletal muscle by encysted larvae producing myositis and weakness
  • can be seen on histologic sections of infected skeletal muscle
  • serology diagnosis
86
Q

Toxocara canis and cati

  • disease
A
  • visceral larva migrans (VLM) and ocular larva migrans
  • organism wanders throughout various organs
  • syndrome of hypereosinophilia, HSM, pneumonitis
87
Q

Anisakiasis

  • transmission

diagnosis

A
  • ingestion of raw or undercooked fish
  • biopsy shows eos + granuloma containing the nematode
88
Q

Trematodes (flukes)

A
  1. Fasciolopsis buski (intestinal fluke)
  2. Fasciola hepatica (liver fluke)
  3. Clonorchis sinensis/Opisthorchis species (liver fluke)
  4. Paragonimus westermani (oriental lung fluke)
  5. Schistosomiasis
89
Q

Fasciolopsis buski

  • transmission
  • geographic distribution
  • disease
  • diagnosis
A
  • ingestion of freshwater plants (e.g., water chestnuts)
  • Asia and Indian subcontinent
  • infection of duodenum
  • Diagnosis
    • adult has pointed cephalad
    • egg
      • 100-150 um
      • oval with thin shell
      • unshouldered operculum
      • abopercular knob (identical to F hepatica)
90
Q

Clonorchis sinensis

  • transmission
  • geographic distribution
  • disease
  • diagnosis
A

Liver fluke

  • ingestion of undercooked freshwater fish
  • Asia
  • chronic biliary infection leading to biliary fibrosis; risk factor for cholangiocarcinoma
  • diagnosis:
    • adults have a snoutlike cephalad
    • egg -
      • oval 30 um
      • shouldered operculum
      • small abopercular knob
91
Q

Paragonimus westermani

A

Oriental lung fluke

  • acquired by ingestion of undercooked crustaceans
  • lung infection with pneumonitis
  • Diagnosis:
    • egg -
      • 90 um
      • oval
      • shouldered operculum
      • sputum or stool
92
Q

Schistosomiasis (bilharziasis, blood flukes)

  • transmission
  • disease
  • diagnosis
A

Transmission

  • fork tailed cercariae penetrate skin (snails), migrate through blood to mesenteric and pelvic blood vessels, release eggs which lodge in small capillaries, some of which penetrate bowel or bladder

Clinical

  • acute stage mediated by circulating immune complexes (Katayama fever)
  • Chronic stage reflects local tissue reaction to eggs
  • S mansoni
    • ​South America, Caribbean, Africa, Middle East
    • affects portal and inferior mesenteric distribution
    • resulting portal fibrosis, cirrhosis, colitis
    • eggs in rectal biopsy
  • S japonicum (Far East) - cirrhosis and rarely CNS disease
  • S haematobium (Africa, Middle East) - bladder with hematuria and irritation leading to SCC (eggs in urine or bx)
  • S intercalatum - resembles S haematobium but infects intestine

Diagnosis

  • eggs - 75-150 um have a single spine
  • S haematobium - terminal spine
  • S mansoni - lateral spine
  • S japonicum - small, knoblike spine
93
Q

Cestodes (tapeworms)

A
  1. Taenia saginata (beef tapeworm)
  2. Taenia solium (pork tapeworm)
  3. Diphyllobothrium latum (fish tapeworm)
  4. Hymenolepsis nana (dwarf tapeworm)
  5. Dipylidium caninum (double pored dog tapeworm)
  6. Echinococcus
94
Q

Taenia saginata

  • diagnosis
  • geographic distribution
  • transmission
A

Diagnosis

  • egg (same as solium) - 30-40 um, spherical with thick radially striated wall and 3 pairs of hooks
  • scolex has 4 suckers and a smooth surface (unarmed rostellum…rostellum = “crown of the scolex”)
  • proglottid longer than it is wide, with > 13 lateral uterine branches

South and Central America (not US)

Transmission:

  • Acquired by ingestion of encysted organisms in beef
  • small bowel infection by adult worm
  • eggs not infectious (unlike solium); thus cysticercosis (larval form of disease in humans) does not occur
95
Q

Taenia solium (pork tapeworm)

  • Diagnosis
  • Geographic distribution
  • Disease
  • Transmission
A
  • Diagnosis
    • Egg identical to T saginata
    • 1 cm cyst has invaginated scolex with 4 suckers and double row of hooklets (acid fast and birefringent)
    • proglottid longer than it is wide
  • occasional in US
  • *intestinal infection** results from ingestion of encysted organisms (cysticerci) in “measly” pork
  • cysticercosis results from ingestion of eggs shed in feces of person with intestinal infection; pork ingestion not required
96
Q

Diphyllobothrium latum

  • diagnosis
  • geographic distribution
  • transmission
  • complication
A
  • Diagnosis
    • egg
      • 60 um
      • oval with smooth shell
      • unshouldered operculum
      • small abopercular knob
    • scolex almond shaped with 2 longitudinal sucking grooves
    • proglottid wider than it is long, with coiled uterus in the shape of a rosette
  • Scandinavia, Russia, Canada, northern US, and Alaska
  • Ingestion of poorly cooked freshwater fish, resulting in intestinal infection
  • may be complicated by B12 deficiency
97
Q

Hymenolepsis nana

  • diagnosis
  • geographic distribution
  • transmission
  • interesting facts
A

Dwarf (smallest tapeworm to infect humans) tapeworm

  • Diagnosis
    • egg has thin inner and outer shells; space in between contains 2 pairs of polar filaments; inner shell contains embryo with hooklets
  • Relatively common in US
  • ingestion of infected beetles
  • person to person spread can occur
  • Only tapeworm that can complete life cycle in a single host
98
Q

Dipylidium caninum

  • diagnosis
  • disease
A
  • egg - resembles H diminuta, except occurs in packets of 5-15 eggs
  • proglottid has double genital pore, one exiting out of each side of proglottid
  • infects cats, dogs, and may infect humans after accidental ingestion of fleas
99
Q

Echinococcus

  • morphology
  • transmission
A
  • hydatid cysts have daughter cysts with protoscoleces and hooklets (which are refractile)
  • acquired from food contaminated with eggs from stool of infected dog, the definitive host
  • sheep and cattle raising areas
100
Q

Dual infections involving parasites

A
  1. ascaris and trichuris
  2. pinworm and dientamoeba fragilis
  3. babesia, lyme, and anaplasma
  4. lepromatous leprosy or HTLV1 and strongyloides hyperinfection
101
Q

Parasitic oculocutaneous infections

A

Loa loa (worm)

Onchocerca volvulus (larvae)

102
Q

parasitic infections capable of person to person spread

A

enterobius

hymenolepsis nana

103
Q
A
104
Q
A
105
Q
A
106
Q
A
107
Q
A
108
Q
A
109
Q
A
110
Q
A
111
Q
A
112
Q
A
113
Q
A
114
Q
A
115
Q
A
116
Q
A
117
Q

Fasciola hepatica

  • transmission
  • geographic distribution
  • disease
  • morphology
A

Liver fluke

  • ingestion of freshwater plants (e.g., water cress)
  • Asia and Middle East
  • Definitive host is sheep or other herbivore that ingests aquatic plant
  • Infection of bile ducts and hepatic parenchyma with resulting fibrosis/cirrhosis
  • Morphology
    • cephalic cone on adult
    • egg is same as F buski
  • Drug for trematodes is praziquantel

Compendium Microbiology (15 decks)

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