Symbiosis Commensalism - one benefits and the other is not affected Mutualism - both benefit Parasitism - one benefits and the other is harmed

Phylum Nematoda Round worms, tapered ends; non- segmented No intermediate hosts in worms that infect humans Dioecious Most small - about 2 inches Have a complete digestive tract

Ascaris lumbricoides

Female is 8-12 inches long 25% of world infected – at least 1 million cases in U.S. Become infected through fecal/oral route Can re-infect self and infect others

Ascaris lumbricoides Life Cycle Ingest eggs – hatch in intestine Larvae burrow into lymph and blood Move to lungs; Cough up and swallow Move to intestine and grow into an adult Adults mate and produce eggs Excrete eggs in the feces

Ascaris lumbricoides Larva in lungs of host

Ascaris lumbricoides Symptoms Tissue damage from migration Pneumonia Blockage of intestinal tract, bile and pancreatic duct – can get as many as 1,000 worms clustered together

Ascaris lumbricoides Three “lips” Mass of worms

Ascaris lumbricoides Adult Ascaris wanders Organism can move out of the nose and mouth when people are asleep Organism is sensitive to anesthetics – will move out of nose and mouth after surgery

Roundworms in Animals Pigs infected with Ascaris also, but a different species – Ascaris suum. A. suum rarely found in humans. Dogs and cats infected with a different genus – Toxocara. -People get Toxocara from animals or from eating dirt or ingesting the eggs from dirt.

Ascaris ova Fertile egg Fertile egg

Necator americanus Hookworm infects 900,000,000 people Found in warm areas where people go barefoot and sanitation is not what it should be Get infected through unbroken skin

Necator americanus Hookworm Life Cycle Fecal contamination of ground Eggs hatch in soil and become larvae Larvae can penetrate the bottom of the foot and get into the lymph and blood system. Move to heart and lungs

Necator americanus Hookworm Life Cycle Causes irritation in lungs; cough up and swallow larvae Develop into adults that mate in the intestine and produce eggs Eggs passed in the intestine in feces

Necator americanus – “hookworm”

Adult worms have cutting plates (humans) or cutting teeth (dogs) Parasite cuts into tissue and lives off host’s blood and tissue fluids Some patient’s lose a unit of blood a week if heavily infected

Necator Ancylostoma Cutting plates in man Cutting “teeth” in dog

Ancylostoma

Necator americanus – “hookworm” Prevention Sanitation Education Teach people to wear shoes

Necator americanus Common name - “hookworm”

Enterobius vermicularis Extremely common worm Most children infected – don’t show any symptoms Some children do show reaction – usually in response to the worm leaving the body in the night

Enterobius vermicularis Organism lives in the large intestine Female migrates outside the body and lays eggs Eggs are sticky and itch; female irritates children and interrupts sleep Children can reinfect themselves by scratching and putting hands in mouth

Enterobius vermicularis

Diagnose by Graham’s Scotch Tape Technique Common Name – “pinworm”

Trichuris - “whipworm” Same life cycle as Ascaris Implants self in large intestine and lives off tissue fluids in man and animals (dogs, cats, humans – different species) May have no symptoms May have bloody diarrhea One quarter of the world infected

Trichuris suis – pig intestine Trichuris – “whipworm” Adult resembles buggy whip

Trichuris ova

Trichinella spiralis Not an intestinal parasite Found in muscle of pigs, bears, mountain lions Controlled in pigs by meat inspection Fewer than 100 cases in U.S./year due to hunters eating rare bear meat

Trichinella spiralis Life Cycle Ingest larvae in rare meat Larvae develop into worms in intestine Worms mate and produce more larvae Larvae get into lymph and go to muscle where they become cysts

Trichinella spiralis Symptoms – depends on where organism migrates Some people have no symptoms Encephalitis Pneumonia Tissue damage/pain

Trichinella spiralis Larvae cysts in muscle