Parasitology Exam 2 Flashcards by Luke Morton-Yates

eggs can be mamalated (bumpy) or smooth when fertilized
eggs are barrel-shaped when unfertilized
requires both male and female worm present to fertilize

Ascaris lumbricoides

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Ascaris lumbricoides: Diagnostic and Infective

Diagnostic: eggs
Infective: eggs

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eggs have “flat football” appearance (one flat side)
eggs collected from the peri-anal area with a sticky-sided spatula

Enterobius vermicularis (Pinworm)

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Enterobius vermicularis: Diagnostic and Infective

Diagnostic: eggs
Infective: eggs

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eggs have distinctive “polar plugs” and are barrel-shaped
light amber color on bile stain

Trichuris trichuria (Whip worm)

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Trichuris trichuria: Diagnostic and Infective

Diagnostic: eggs
Infective: eggs

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eggs have granular cluster of larvae with visible space between them and the cell wall
two organisms have the same egg morphology

Ancylostoma duodenale (Old World Hookworm)
Necator americanus (New World Hookworm)

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Hookworm: Diagnostic and Infective

Diagnostic: eggs
Infective: filariform larva penetrates skin

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“Worm burden”

a measure of how many hookworms are in the gut, can relate to the severity of iron deficiency anemia that may develop from chronic bleeding

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Differences in adult hookworm morphology

Ancylostoma duodenale has 2 pairs of teeth for attachment
Necator americanus has two cutting plates for attachment

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Differences between strongyloides and hookworm rhabditiform larvae

Strongyloides has short buccal cavity
Hookworm has long buccal cavity

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Which nematode can cause autoinfection?

Strongyloides stercoralis

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Strongyloides stercoralis: Diagnostic and Infective

Diagnostic: rhabditiform larvae
Infective: filariform larva penetrates skin

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Usually obtained from infected animal tissue, especially raw pork. “Wood knots” appearance in tissue

Trichinella spiralis

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Trichinella spiralis: Diagnostic and Infective

Diagnostic: Larvae in tissue
Infective: encysted larvae in undercooked meat

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Adult worm releases larvae from a blister on the leg or foot. Eliminated by slowly winding on a stick.

Dracunulus medinensis

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Dracunulus medinensis: Diagnostic and Infective

Diagnostic: Blister bursting
Infective: ingesting copepods in water

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Causes elephantiasis of the lower extremities
Microfilariae in the blood have a sheath, but no nuclei in the tip of the tail

Wucheria bancrofti

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Wucheria bancrofti: Diagnostic and Infective

Diagnostic: microfilaria in blood
Infective: skin penetration of microfilariae by insect vector (Anopheles)

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Causes elephantiasis of the lower extremities
Microfilariae in the blood have a sheath and 2 terminal nuclei in the tail

Brugia malayi

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Brugia malayi: Diagnostic and Infective

Diagnostic: microfilaria in blood
Infective: skin penetration of microfilariae by insect vector (Anopheles)

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Microfilariae in the blood have a sheath and nuclei are continuous to tip of the tail

Loa Loa (eye worm)

Loa Loa: Diagnostic and Infective

Diagnostic: Calibar swelling (nodules), seeing worm migrate
Infective: Larvae are spread by insect vector (sandfly, deerfly, chrysops)

Causes “River blindness”
Subcutaneous nodules known as “ochocercoma” where the adult lives
Microfilariae in the blood have NO sheath, nuclei do NOT extend to tip of tail

Onchocerca volvulus

Onchocerca volvulus: Diagnostic and Infective

Diagnostic: biopsy skin snips of nodule Infective: larvae spread by bite of gnat

- Cause largely asymptomatic filarial roundworm infections - Inhabit body cavities - Spread by insect vector

- Mansonella ozzardi (unsheathed, no nuclei to tip of tail) - Mansonella perstands (unsheathed, nuclei extend to tip of tail)

- Eggs have a "ruffled edge" appearance - Eggs are almost circular - Eggs are thick-walled, have 3 pairs of hooklets for attachment

Taenia (saginata and solium, egg can't be distinguished)

Taenia: Diagnostic and Infective

Diagnostic: Egg or proglottid in stool Infective: Encysted larva in undercooked meat

Taenia saginata morphology

- Proglottids are longer than wide - Proglottids have15-20 uterine branches/side - Adult scolex has 4 suckers, no hooks (unarmed)

Taenia solium morphology

- Proglottids are longer than wide - Proglottids have <13 uterine branches/side - Adult scolex has 4 suckers, with hooks (armed)

Which cestode can encyst in other parts of the body (cysticercosis)?

Taenia solium

- Egg is 30-50 um - Egg has hooked oncosphere - Egg has polar filaments

Hymenolepis nana (dwarf tapeworm)

- Egg is 60-80 um - Egg has hooked oncosphere - Egg has NO polar filaments

Hymenolepis diminuta (rat tapeworm)

- Tapeworm commonly infects dogs and cats - Forms characteristic egg packets (8-15 eggs) - Egg packets measure 25-40 um

Dipylidium caninum

- adult has spoon-shaped scolex - Proglottids are wider than long, central uterine pore - Egg has lidded operculum, terminal knob on avoperculum

Diphyllobothrium latum (fish tapeworm)

Diphyllobothrium latum: Diagnostic and Infective

Diagnostic: egg Infective: cysts in undercooked fish

What cestode can lead to megaloblastic anemia due to B12 deficiency?

Diphyllobothrium latum

- normal life cycle involves dogs and sheep - forms hydatid cysts filled with hydatid sand in tissues of humans

Echinococcus granulosus

What happens if a hydatid cyst bursts during surgical removal?

Dissemination of the daughter cells within, possible anaphylaxis if cyst leakage has previously stimulated an IgE response

Echinococcus granulosus: Diagnostic and Infective

Diagnostic: Cyst Infective: Egg

- Self-resolving itchy skin after contact with water

Schistasome Dermatitis, aka "swimmer's itch". Caused by avian schistosomes that can't penetrate deeper than the skin

- Egg shows a terminal spine - Leading cause of bladder cancer in Egypt - Lives in blood vessels supplying the bladder

Schistosoma haemotobium (bladder fluke)

Schistosoma haemotobium: Diagnostic and Infective

Diagnostic: Eggs found in URINE Infective: Cercariae penetrates skin

- Intestinal schistosome - Egg has large lateral spine - Egg is large (160x80 um)

Schistosoma mansoni

Schistosoma mansoni: Diagnostic and Infective

Diagnostic: egg in stool Infective: Cercariae penetrates skin

- Intestinal schistosome - Egg has small lateral spine (can be hard to see) - Egg is small (80x90 um)

Schistosoma japonicum (Oriental Blood Fluke)

Schistosoma japonicum: Diagnostic and Infective

Diagnostic: egg in stool Infective: Cercariae penetrates skin

- Large operculated egg (55x85 um) - Shouldered operculum

Paragonimus westermanni (Oriental Lung Fluke)

Paragonimus westermanni: Diagnostic and Infective

Diagnostic: egg seen in SPUTUM Infective: eating cysts in undercooked crayfish

- Very large operculated egg (150x90 um) - Densely granulated egg, amber color

Fasciola hepatica (Sheep Liver Fluke) or Fasciolopsis buski (Intestinal Fluke)

Fascioloa hepatica: Diagnostic and Infective

Diagnostic: egg in stool Infective: Eating cysts in contaminated watercress

Fasciolopsis buski: Diagnostic and Infective

Diagnostic: egg in stool Infective: Eating cysts in contaminated water chestnuts

- tiny egg (30x16 um) with shouldered operculum - egg has terminal knob (not always visible) - smallest fluke

Clonorchis sinensis (Chinese Liver Fluke)