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Parasitology > Intro to Nematodes > Flashcards

Intro to Nematodes Flashcards

(33 cards)

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1
Q

Helminths

A
  • Worms or “metzoa”
  • Multicellular eukaryotes
  • Kingdom Animalia
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2
Q

Helminth Phyla

A
  • Phylum Platyhelminthes (flatworms)
  • -Class Trematoda (flukes)
  • -Class Cestoda (tapeworms)
  • Phylum Nemathelminthes (roundworms)
  • -Class Nematoda
  • Phylum Acanthocephala (thorny-headed worms)
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3
Q

Platyhelminthes morphology

A
  • Flat, broad, long
  • Each segment has reproductive organs
  • Hermaphrodite
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4
Q

Nemathelminthes morphology

A
  • Cylindrical
  • Coelom (body cavity)
  • Sexual dimorphism
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5
Q

Acanthocephala morphology

A
  • Have thorny heads

- Do not need to know

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6
Q

Nematode developmental stages

A

Egg –> L1 –> L2 –> L3 –> L4 –> (L5) –> adult

may be male or female, undergoes molting

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7
Q

Trematode developmental stages

A

Egg –> miracidium –> sporocyst –> (redia) –> cercariae –> (metacercaria) –> many adults (asexual reproduction)
(4 stages after egg are found in the intermediate host)

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8
Q

Cestode developmental stages

A

egg –> metacestode (larval stage) –> adult

some asexual reproduction; may have one or many adults

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9
Q

Nematode adult morphology

A
  • Separate male/female sexes
  • -Females have a tapered tail
  • -Males have copulatory spicules (helps to hold the female during copulation), and bursa with rays
  • Sophisticated reproductive organs
  • Complete digestive system (mouth and anus)
  • Complex tegument
  • Simple nervous system
  • Simple excretory system
  • Every organ is tubular
  • Have a pseudocoelom filled with fluid
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10
Q

Complex tegument

A

Cuticle surface, which sometimes has ornamentation

–Bosses, cordons, alae, and vesicles

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11
Q

Nematode reproduction

A

Dioecious (separate sexes)

  • Males may/not have spicules for copulation
  • Males have bursa as clasping organs
  • Females have a uterus and vulva that may open at the front, middle, or caudal end of the body
  • End product is variable: oviparous, oviviparous, and viviparous
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12
Q

Oviparous

A

One celled or segmented egg released from female

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13
Q

Oviviparous

A

Larvated egg released from female

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14
Q

Viviparous

A

Living larvae released from female

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15
Q

Nematode excretion/secretion

A
  • Excretory function occurs through the intestine
  • Serves secretory and osmoregulatory functions
  • Glandular and tubular
  • Excretory-secretory proteins are important in host-parasite interaction
  • -Immunogens
  • -Vaccine and diagnostics development
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16
Q

Nematode nervous system

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A

Well-developed

17
Q

Parasite life cycles

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A
  • Definitive host (DH) carries adult parasite - reproduce/produce eggs
  • Intermediate host (IH) has larval stages of parasite - some degree of development (stops at L3)
  • Paratenic host (PH) accumulates and maintains parasite stages (no development required)
18
Q

Nematode life cycle patterns

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A
  • May or may not have environmentally resistant stage in life cycle
  • Egg –> L1 –> L2 –> L3 –> L4 –> (L5) –> adult
  • L1-L3 are still in the egg
  • L3 is free living and infective
  • L3 is found in the intermediate host
19
Q

Direct life cycle

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A

-Ingested
–Host A1 –> environment –> host A2
OR
–Host A1 –> host A2

20
Q

Indirect life cycle

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A
  • Transmitted via intermediate hose
  • -L1 - L3 (in intermediate host)
  • -L4 - adult (in definitive host)
  • Ex: heartworm (intermediate host is mosquito, definitive host is dog)
21
Q

Superfamily Ascaroidea

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A
  • Roundworms
  • Large, thick bodied worms
  • Direct/Indirect life cycle
  • Thick shelled, single-celled eggs passed in feces
  • Larvated eggs are infectious
  • Prepatent period is 2-2.5 months
  • Several members are zoonotic
  • Infective L3 develops within the egg
  • Millions of eggs are shed in the feces
  • Eggs are extremely resistant
  • L1-L3 can be found in the environment
  • Fecal floatation used
22
Q

Superfamily Oxyuroidae

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A
  • Pinworms
  • Direct life cycle
  • Prepatent period is 5 months
  • Perirectal deposition of eggs
  • Scotch tape test to trap eggs
  • Infective L3 develops within the egg
  • L1-L3 can be found in the environment or on the hosts skin
  • Common in equids, ruminants, reptiles, primates, rabbits, and rodents
  • Not found in cats or dogs
23
Q

Superfamily Trichonelloidea

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A
  • Adult worms have a whip-like morphology
  • Stichosome esophagus
  • Includes Trichuris, Trichinella, and capillarids (Eucoleus, Pearsonema, and Aonchotheca)
  • All lay eggs (bipolar plugs), except Trichinella (L1)
  • L1 within the egg is the infective stage (except Trichinella)
  • Trichinella is zoonotic
  • L1 can be found in the environment
  • Fecal floatation used
24
Q

Superfamily Rhabditoidea

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A
  • Threadworms
  • Includes Strongyloides species
  • Unusual life cycle
  • -Alternative parasitic and free-living generations (L1-L3)
  • -Only females are parasitic
  • Larvated egg – Strongyloides spp. of ruminants, swine, and horses
  • Larva in feces - S. stercoralis in dogs
  • Fecal floatation used for larvated eggs
  • Baermann test used for Strongyloidosis in dogs
25
Superfamily Strongyloidea
- Large and small strongyles of horses - Chabertia and Oesophagostomum of ruminants - Stephanurus dentatus of swine - Worms are stout 1-2.5 cm long - Large buccal cavity, +/- teeth, +/- leafcrowns - Males have well developed copulatory bursa, supported by bursal rays - Fecal floatation used - Egg - L3 develop in environment - L3 is the infective stage - L4 migrates in the tissues - Adult is found in the gut lumen
26
Superfamily Ancylostomoidea
- Hookworms - Adult worms lack corona radiata (leaf crowns) - Anterior end bent dorsally - Large buccal capsule - Presence of teeth or cutting plates - Ancystoma spp., Uncinaria sp. (dogs and cats) - Ruminants, wild canids, humans, pinnipeds, etc. - Routes of transmission: oral, skin penetration, paratenic host - Transmammary (certain members) - L3 arrested in tissues - Some members are zoonotic - Fecal floatation used - Egg - L3 develop in environment - L3 is the infective stage - L4 migrates in the tissues - Adult is found in the gut lumen
27
Superfamily Trichostrongyloidea
- Small to medium slender worms in GI tract - Buccal cavity is rudimentary or absent - Bursa, spicules, cuticular modifications help ID - Genera: Haemonchus, Ostertagia, Cooperia, Nematodirus, Trichostrongylus - Eggs look alike - genus/species ID based on larval morphology or molecular methods - Ollulanus tricuspis (dogs and cats) - exception to the life cycle pattern - Dictyocaulus (respiratory tract) - Egg - L3 develop in environment - L3 is the infective stage
28
Superfamily Spiruroidea
- Adult worms in mouth, stomach, or eye - Anterior cuticular ornamentation may be present - Male tail - coiled with alae and two spicules (unequal and dissimilar) - Indirect life cycle - intermediate (coprophagus beetles or arthropods) and paratenic hosts - Larvated eggs do not float well - Genera: Spirocerca, Habronema, Draschia, Thelazia, Gongylonema - L1-L3 found in intermediate host - L1 is passed into the environment - Once the intermediate host is ingested, L3 develops through L4 into the adult in the definitive host
29
Superfamily Physalopteroidea
- Morphologically distinct gastric parasites - Worms resemble ascarids - Morphologically distinct lips bearing teeth or tooth-like ridges - Eggs are thick shelled, larvated - Life cycle similar to members of Spiruroidea - -Coprophagus beetles are intermediate host - -Several paratenic hosts
30
Superfamily Metastrongyloidea
- Lungworms - Respiratory tract or blood vessels - Buccal cavity is reduced or absent - Copulatory bursa is reduced or absent - Usually larvated eggs hatch before reaching feces - Indirect life cycle - snail or slug intermediate host - Metastrongylus, Filaroides, Muellerius, Aleurostrongylus, Angiostrongylus, Parelaphostrongylus - L1-L3 - intermediate host, infective stages - L1 passed into environment - L4-adult - definitive host
31
Superfamily Dioctophymatoidea
- Medium to large sized nematodes - Digestive tract, kidney, and abdominal cavity - Rudimentary mouth encircled by one to three rings of papillae - Bell shaped bursa without rays and single spicule - Eggs in urine - sedimentation - Indirect life cycle - intermediate and paratenic host - Genus: Dioctophyme - L1 passed into environment/water - L3 - IH oligochate, inefective - L4-adult - DH dog/mink
32
Superfamily Dracunculoidea
- Long, slender worms - Subcutaneous tissues of vertebrate host - Rudimentary esophagus, intestine, and anus - Readily observable cephalic papillae - Females shed larve - Indirect lifecycle - copepod intermediate host - Genus: Dracunculus - L1 - passed into environment - L1-L3 - IH copepod - L3 - infective - L4-adult - DH dog/mammal
33
Superfamily Filaroidea
- Long, slender delicate worms - Buccal cavity is rudimentary - Body cavities, blood or lymph vessels, CT - L1 are called microfilaria - Species ID - morphological features of microfilaria - Indirect life cycle - blood sucking insects are intermediate host - Genera: Dirofilaria, Dipetalonema, Onchocerca, Wuchereria, Brugia, Loa, Elaeophora, Stephanofilaria, Setaria - No egg in environmental stage - L1 - ingested by IH vector - L1-L3 - intermediate host - L3 - infective stage - L3-adult - definitive host

Parasitology (8 decks)

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