1. HELMINTHS

2. Helminth Helminths Helminthology:
Study of parasitic worms and their effect on their hosts

3. 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.

4. The Flatworms (Platyhelminthes)
Includes 2 phyla:
The Flatworms (Platyhelminthes)
Cestodes (or Tapeworms),
Trematodes (or Flukes).
The Roundworms (Nemathelminthes)

5. 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.

6. 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

7. 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

9. The SCOLEX or head, of Taenia solium

11. 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

14. Echinococcus granulosus
Grazing animals & humans carry larval form.
Dogs carry adult form – relatively harmless
Larvae damage muscles of liver & lungs.

15. 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.

16. 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

17. 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

18. 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.

20. WHIPWORM – Trichuris trichiura (a roundworm) causing Trichuriasis

21. Hook Worms, attached to intestinal mucosa

22. Wuchereria bancrofti (a roundworm that causes elephantiasis)

23. Diseases caused in humans
Ascariasis
Dracunculiasis
Elephantiasis
Lymphatic filariasis
Onchocerciasis
Schistosomiasis
Trichuriasis