Lecture 13: Phylum Nematoda, Part 2 Parasitic Life Histories Invertebrate Zoology Lecture 13: Phylum Nematoda, Part 2 Parasitic Life Histories

Parasitic Life Cycles 1: Single host with a free-living stage. Example: hookworms Overview Common intestinal parasites Affect 25% of the human population Primarily in the tropics Common in dogs, cats and other mammals Symptoms Severe anemia Skin infections

Hookworm life cycle *See additional details in text

Parasitic Life Cycles 2: Single host, direct host-host transmission Example: trichina worms (Trichinella spp.) Overview Humans infected by eating raw or undercooked pork. May be the reason for religious bans against pig products. Symptoms Excruciating pain and fever from larval burrowing into muscles

Trichina worm life cycle

Example: Onchocerca volvulus (river blindness) Parasitic Life Cycles 3: Filarial nematodes w/arthropod intermediate host Example: Onchocerca volvulus (river blindness) Overview Prevalent in Africa Symptoms Subcutaneous lesions, including lesions of the eye that cause blindness

Onchocerca volvulus life cycle