River Blindness

• A patient infected suffering from river blindness.

• This elderly man shows nodules, skin changes and blindness, all manifestations of the disease.

• Cause: parasitic roundworm transferred by fly bites.

• Micro worms swarm through skin and eyes.

• Economic implications:– Increased disease frequency has resulted in

limited farm laborers who can grow and harvest crops.

                                                                                                                                                                

                           

Unsegmented Roundworms

Unsegmented Worms

Phylum Nematoda (round worms)-simplest animal to have a digestive system with TWO openings (mouth and anus advanced animal)

-found in soil, lakes, oceans, polar and tropical environments, hot springs (everywhere)

Ascaris the ones we will be dissecting

• Feeding:-most are free living carnivores/omnivores that

eat algae, fungi, animals, decaying matter -have a pharynx (suck in food)-some are parasitic (affect plants and animals)

• Respiration -Diffusion of gases through body walls• Excretion:-metabolic wastes through body walls via

diffusion and undigested wastes through anusNH3 CO2

O2

• Response: -simple nervous system-ganglia (group of nerve cells -not quite a brain)-sense organs and nerves that run down the body

(movement/chemical detection)• Reproduction:-sexual reproduction (separate sexes)-complex life cycle (2 to 3 different hosts/organs)

Four types of Nematoda

1. Ascaris-parasitic roundworm that lives in humans (and relatives in horses, dogs)Life Cycle

Intestine (human) → produces eggs → leaves in feces → enters mouth via food/contaminated water → hatch in new host(human) → small intestine → blood vessel → lungs → throat (cough)→ swallowed → back in intestine...cycle starts from beginning

2. Hook worm -serious human intestinal parasite common in Southern US/tropical countries (1/4 people are infected)

Life CycleEggs hatch outside of body and develop in soil → unprotected foot → sharp teeth/hook to burrow in the skin → enter blood stream → lungs → throat → back to intestine

3. Trichinosis/Trichonella-live and mate in the intestine-burrow eggs in intestine wall (1500 larvae)Life CycleIn a pig/rat: Larvae travel in blood vessels→ go

to organs → tissues where it forms a cyst (inactive)

-This inactive cysts is then eaten by humans (raw meat contains cyst, which becomes an active worm)

Dinner is Ready?

4. Filarial Wormsl-Tropical Asia/Africa-live in blood/lymph vessels of birds and

mammalsLife CycleHost (carrying worms)→ mosquito (now carrying

worms)→ releases worms and blocks passage of lymph vessels → swelling in vessels/tissues

**cause elephantiasis **The following pictures may be disturbing…

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