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HELMINTHS. Helminth Helminths Helminthology: Study of parasitic worms and their effect on their hosts. A division of parasites living inside their host. Parasitic, worm-like organisms that live & feed off living hosts, receiving nutrition & protection

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slide2
Helminth
  • Helminths
  • Helminthology:
    • Study of parasitic worms and their effect on their hosts
slide3
A division of parasites living inside their host.
  • Parasitic, worm-like organisms that live & feed off living hosts, receiving nutrition & protection
  • Disrupt hosts' nutrient absorption, causing weakness & disease
  • Those inside the digestive tract: intestinal parasites
  • They can live inside humans as well as other animals.
slide4
Includes 2 phyla:
  • The Flatworms (Platyhelminthes)
    • Cestodes (or Tapeworms),
    • Trematodes (or Flukes).
  • The Roundworms (Nemathelminthes)
1 flatworms
1. FLATWORMS
  • Adult worms have flattened bodies
  • Have a HEAD
  • Bilaterally symmetrical bodies
  • Specialized organ systems (nervous, excretory & reproductive)
  • Have a digestive tract with a single opening through which food enters and waste leaves.
  • Some absorb nutrients via their outer covering.
1a tapeworms
1a. TAPEWORMS
  • In the intestines of animals incl. humans
  • Can grow upto 30 feet
  • Flat, segmented body has of 3 parts:
    • A scolex with hooks / suckers to attach the worm to intestinal lining,
    • Necklike germinal center where new segments are formed,
    • Segments (Proglottids) - Egg-making machines
slide7
Hermaphrodite: Each segment has both male & female reproductive organs
  • Fertilization occurs within the segment.
  • The larger & older segments are packed with fertilized eggs
  • Finally, shed in the feces.
  • Life cycle:
    • Larval Form: Develop in muscle, brain, eye, liver, or heart tissue. They displace surrounding tissue, causing serious damage.
    • Adult Form
taenia saginata beef tapeworm
Taenia saginata – Beef tapeworm
  • Humans parasitized by the adult form
  • Cattle carry Taenia saginata larvae
  • Encysted in their muscle as Cysticerci.
  • Humans get this by eating undercooked infected meat
  • Larvae hatch in human intestine
  • Develop into tapeworm in their intestines.
  • Proglottids containing eggs, excreted in their feces.
  • If this is on a grazing land, cattle might get infected, eggs hatch in cow’s intestine, larvae penetrate the intestinal wall and encyst in cow muscle
echinococcus granulosus
Echinococcus granulosus
  • Grazing animals & humans carry larval form.
  • Dogs carry adult form – relatively harmless
  • Larvae damage muscles of liver & lungs.
1b trematodes flukes
1b. TREMATODES / FLUKES
  • Flattened bodies, but NOT segmented.
  • Small, but deadly.
  • Size: From a few mm to a few cm
  • Have a ventral SUCKER to attach firmly to the host.
  • Larval & Adult forms
  • Humans carry adult forms in lung, liver & blood vessels
  • Aquatic animals & plants carry larvae: Intermediate hosts
    • Snails / Clams
    • Fish / Aquatic plant.
paragonimus westermani lung fluke
Paragonimus westermani - Lung fluke
  • Adult fluke develops in human lung.
    • Fever and cough producing blood-tinged sputum.
  • Hermaphrodite – Produces eggs
  • Hatch in water bodies & release free-swimming larvae: MIRACIDIA
  • Penetrates snail and multiplies: REDIA
  • Develops into a free-swimming form: CERCARIA
  • Penetrates crabs / crayfish, forms cysts: METACERCERIAE
  • Human consumption of undercooked crabs, etc  Larvae hatch from cysts, burrow through intestine and mature in the lung
2 roundworms
2. ROUNDWORMS
  • Cylindrically shaped bodies
  • Bilaterally symmetrical, tapered at both ends
  • Have a complete digestive, reproductive & nervous system
  • Separate male and female individuals
  • Larval & Adult forms
trichinella spiralis
Trichinella spiralis
  • Causative agent of Trichinosis
  • Larvae form cysts in animal muscles
  • Meat-eating animals ingest these cysts
  • Larvae hatch in the small intestine
  • Develop into adult worms
  • Produce more larvae
  • Some larvae, into blood via intestinal wall
  • Reach muscle and form cysts.
diseases caused in humans
Diseases caused in humans
  • Ascariasis
  • Dracunculiasis
  • Elephantiasis
  • Lymphatic filariasis
  • Onchocerciasis
  • Schistosomiasis
  • Trichuriasis