CLS08 - Helminths

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  1. Types of helminths w/ alt name (3)
    • Trematodes: flukes (flatworms)
    • Cestodes: tapeworms
    • Nematodes: roundworms
  2. General transmission of helminths
    • Direct ingestion of eggs
    • Ingesting larvae in intermediate host
    • direct penetration of skin/membrane
    • *adults do not multiply in human body
  3. T. gondii 3 lifecycle names/stages
    • Oocysts: env, animals
    • bradyzoites: tissue of animals (encysted)
    • tachyzoites: sexual phase (goes to fetus in preggos)
  4. Tissue nematodes (roundworms) - stages, transmission
    • stages: adult male, female
    • Larval - rhabditiform (non-infective), filariform (infective)
    • transmission: biting arthropods
    • ingestion of freshwater crustaceans
    • ingestion of contaminated meat
  5. Trichinella spiralis - transmission, life cycle, disease, lab ID
    • transmission: encysted larvae are ingested from undercooked meat
    • *larve encyst in striated muscle
    • life cycle: ingest encycsted larvae -> cyst digested -> larve mature/mate in upper intestine -> female worms penetrate mucosa w/ larvae -> larvae carried to muscles and encyst
    • disease: trichinosis
    • encysted larvae disease the muscle 
    • adults reside in the intestine
    • *larve can migrate to brain and heart (won't encyst)
    • ID: muscle biopsy
  6. Toxocara - spp, ID, disease (incl transmission)
    • spp: T. canis (intestinal ascarid of dogs)
    • T. cati (intestinal ascarid of cats)
    • ID: biopsy of tissue, serology in ocular larval migrans (OLM)
    • *OLM is migration and death seen on skin
    • disease: toxocariasis, OLM
    • ingestion of eggs -> larvae released and migrate to tissues -> adults can't mature
    • 70+ people blinded each year
    • *14% has been exposed
  7. Flukes (flatworms) - general lifecycle, ID, egg morph
    • Eggs must reach water to mature
    • Snail is intermediate host, release organisms into water where they attach to vegetation or fish
    • Humans infected when they ingest them
    • Infects liver, lung, and blood
    • ID: concentrated wetmount w/ visible eggs
    • egg morph: include knob, lateral spine, operculum
  8. Liver flukes - adult site, intermediate host, spp, reservoir hosts, basic lifecycle, disease
    • site: live in biliary ducts
    • int: freshwater snail
    • spp: Clonorchis sinensis (Chinese liver fluke)
    • Opisthorchis viverrini (Southeast Asian liver fluke)
    • Fasciola (sheep liver fluke)
    • reservoir: dogs, pigs, rabbits
    • lifecycle: adult worms in humans -> eggs in feces/sputum -> reach water -> miracidium larvae penetrate snail -> cercariae emerge from snail -> metacercariae encyst on vegetation, fish, crabs, or crayfish -> ingested by humans
    • disease: Clonorchis sinensis and Opisthochis viverrini - mostly asymptomatic, light infections
    • heavy infections cause fever, abdominal pain, jaundice
    • severe infections cause biliary obstruction
    • Fasciola - light infections cause fever, diarrhea, jaundice
    • larvae may migrate to intestinal walls, lungs, heart, brain
  9. Describe clonorchis sinensis adult worms and eggs
    • adult: narrow and transparent reddish-yellow
    • eggs: shouldered opercula, small knob opposite, yellow-brown, embryonated
  10. Lung flukes - spp, site of adult, hosts, disease, ID, egg morph
    • spp: Paragonimus westermani (most common)
    • Paragonimus mexicanus
    • site: adults in lungs
    • eggs in sputum or feces
    • hosts: intermediate host - freshwater snail
    • 2nd int host - crab/crayfish
    • reservoir hosts - dogs and cats (Westermani), pigs (mexicanus)
    • disease: light infections asymptomatic
    • metacercariae migration may cause tissue damage
    • worms encapsulate in a granuloma and cause chronic cough
    • ID: eggs isolated in sputum
    • lesions in lungs via X-Ray
    • morph: unembryonated, otherwise similar to chlonorchis sinensis
  11. Cestodes (tapeworms) - basic lifecycle, sexual repr, ID, spp
    • cycle: adult in human produces eggs (released via proglottids) which are infective to intermediate host
    • humans infected after ingesting meat with larval stage
    • repr: adults are hermaphroditic
    • ID: eggs in concentrated wet mount, proglottids
    • spp: Diphyllobothrium latum, Taenia solium
  12. Diphyllobothrium latum - AKA, unique, lifecycle, disease, ID (morph), hosts
    • AKA freshwater broadfish tapeworm (reservoir)
    • unique: largest human tapeworm
    • lifecycle: adult in human intestine -> eggs in feces -> eggs hatch in fresh water -> copepod ingests larvae -> fish ingests copepod -> human ingests fish
    • disease: mild GI symptoms, may cause megaloblastic anemia (competition for vitamins)
    • ID: eggs are ovoid, operculated, and yellow-brown
    • proglottids are wider than long w/ rosette-shaped central uterus
    • hosts: fish (intermediate), human (definitive)
  13. Taenia solium - AKA, hosts, ID (morph)
    • AKA: pork tapeworm
    • hosts: Pigs (intermediate), human (definitive)
    • ID: proglottids in stool 7-13 uterine branches
    • Eggs - round and oval w/ thicky straited shell and six oncospheres
  14. Taenia saginata - AKA, hosts, ID (incl morph)
    • AKA: beef tapeworm
    • hosts: cattle (intermediate), Humans (definitive)
    • ID: proglottis in stool 15-18 lateral branches
    • Eggs in stool
  15. Taenia - life cycle, disease,
    • life: adult in human small intestine -> eggs in feces -> cattle/pigs ingest eggs -> oncospheres hatch -> become cysicerci in muscle -> ingested by humans
    • disease: intestinal cysticercosis (diarrhea)
    • extraintestinal cysticercosis (cysticerci develop in muscles, eyes, brain, spinal cord)
    • *in muscles does not usually cause symptoms
    • Neurocysticercosis = worst outcome.  (seizures, headaches, confusion, hydrocephalus, death)
  16. Nematodes (roundworms) - physical characteristics, sexual characteristics, transmission
    • phys: nonsegmented
    • elongated, cylindrical
    • sex: separate sexes
    • eggs found in stool samples
    • transmission: ingestion of eggs or direct penetration of skin by larvae (varies with spp)
    • *most common of all US helminth infectons
  17. Enterobius vermicularis - AKA, basic info, egg morphology
    • AKA: pinworm
    • basic: children <14
    • eggs fecal/oral
    • night cycle
    • scotch tape prep
    • *eggs rarely present in stool
    • egg: flat on one side
  18. What are the most common soil-transmitted helminths w/ AKA and morph.  Why are they a problem
    • Trichuris trichiura: whipworm
    • very small adult, egg has bipolar regions
    • Ascaris lumbricoides: mostly in children
    • egg has THICK shell and dark middle space
    • Necator Americanus: Hookworm
    • *#2 helminth in US
    • egg is plate of cookies
    • problem: major cause of worldwide chronic infections (esp children) that can affect physical and mental development
  19. Which worms transmit via DIRECT SKIN PENETRATION?
    • Necator Americanus (Hookworm)
    • Stronglyoides stercoralis (threadworm)
    • *plate on media and look for tracks (migration in humans as well)
    • *only adults are diagnostic.
Card Set:
CLS08 - Helminths
2016-04-25 08:09:15
CLS08 Helminths
CLS08 - Helminths
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