HELMINTHS

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. 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